Leibniz and his Correspondents

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Leibniz and His Correspondents Unlike most of the other great philosophers, Leibniz never wrote a magnum opus. As a result, his philosophical correspondence is essential for an understanding of his views. This collection of new essays by leading figures in the field of Leibniz scholarship provides the most wide-ranging account of Leibniz’s philosophical correspondence available. It both illuminates Leibniz’s philosophical views and pays due attention to the dialectical context in which the relevant passages from the letters occur. The result is a book of enormous value to all serious students of early modern philosophy and the history of ideas. Paul Lodge is a Fellow of Mansfield College, Oxford, and University Lecturer in Early Modern Philosophy at the University of Oxford.

Leibniz and His Correspondents

Edited by PAUL LODGE Mansfield College, Oxford

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Contents

page vii ix

Contributors Abbreviations

xiii

Acknowledgments 1 Introduction Paul Lodge

1

2 Leibniz and His Master: The Correspondence with Jakob Thomasius Christia Mercer 3 A Philosophical Apprenticeship: Leibniz’s Correspondence with the Secretary of the Royal Society, Henry Oldenburg Philip Beeley 4 The Leibniz–Foucher Alliance and Its Philosophical Bases Stuart Brown 5 Leibniz to Arnauld: Platonic and Aristotelian Themes on Matter and Corporeal Substance Martha Brandt Bolton

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47 74

97

6 Leibniz and Fardella: Body, Substance, and Idealism Daniel Garber

123

7 Leibniz’s Exchange with the Jesuits in China Franklin Perkins

141

8 Leibniz’s Close Encounter with Cartesianism in the Correspondence with De Volder Paul Lodge v

162

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Contents

9 “All the time and everywhere everything’s the same as here”: The Principle of Uniformity in the Correspondence Between Leibniz and Lady Masham Pauline Phemister 10 Idealism Declined: Leibniz and Christian Wolff Donald Rutherford 11 On Substance and Relations in Leibniz’s Correspondence with Des Bosses Brandon Look 12 “[ . . . ] et je serai tousjours la mˆeme pour vous”: Personal, Political, and Philosophical Dimensions of the Leibniz–Caroline Correspondence Gregory Brown References Index

193 214

238

262 293 305

Contributors

Philip Beeley is Lecturer in History of Science at the University of Hamburg and editor of Leibniz’s philosophical papers at the LeibnizForschungsstelle, M¨unster. He is co-editor (with Christoph J. Scriba) of the Correspondence of John Wallis and author of numerous studies on the history of modern science and philosophy, including Kontinuit¨at und Mechanismus (1996). He is currently preparing a critical edition of Wallis’s Treatise of Logick. Martha Brandt Bolton is Professor of Philosophy at Rutgers University. She is the author of papers on a variety of figures and topics in seventeenthand eighteenth-century philosophy, including aspects of Leibniz’s theories of knowledge, perception, and thought. Gregory Brown is Professor in the Department of Philosophy at the University of Houston. He has published a number of articles on Leibniz and Descartes and is currently working on a book about the Leibniz– Caroline–Clarke correspondence. Stuart Brown was until his retirement Professor of Philosophy at the British Open University. He is author of Leibniz in the Philosophers in Context series (1984), editor of The Young Leibniz and His Philosophy: 1646–1676 (1999), and author of many papers on Leibniz and on other philosophers of the late seventeenth and early eighteenth centuries. Daniel Garber is Professor of Philosophy at Princeton University and Associated Faculty in the Program in the History of Science. Garber specializes in the history of philosophy and science in the early modern period, and he is interested also in issues in epistemology and the philosophy vii

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Contributors

of science. He is the author of Descartes’ Metaphysical Physics (1992) and Descartes Embodied (2001), and he is the co-editor (with Michael Ayers) of The Cambridge History of Seventeenth-Century Philosophy (1998). Paul Lodge is a Fellow of Mansfield College, Oxford, and Lecturer in Early Modern Philosophy at the University of Oxford. He is author of a number of articles on the philosophy of Leibniz and is currently working on an edition and translation of the Leibniz–De Volder correspondence for the Yale Leibniz series. Brandon Look is Associate Professor of Philosophy at the University of Kentucky. In addition to articles on early modern philosophy he has published Leibniz and the Vinculum Substantiale (1999) and has recently completed (with Donald Rutherford) an edition and translation of the Leibniz–Des Bosses correspondence, which will be published as part of the Yale Leibniz series. Christia Mercer is Professor of Philosophy at Columbia University. She is the author of Leibniz’s Metaphysics: Its Origins and Development (2001) and has written on early modern Platonism, Aristotelianism, and German philosophy. At present, she is working on a book entitled ‘Divine Madness’: Early Modern Views on Method, Mind, and Matter, in which Jakob Thomasius plays an important role. Franklin Perkins is Assistant Professor of Philosophy at DePaul University. He has published articles on early modern philosophy, Chinese philosophy, and comparative philosophy and is the author of Leibniz and China: A Commerce of Light (2004). Pauline Phemister is Lecturer in Philosophy at the University of Liverpool. She has published papers on Leibniz and Locke and currently is writing a book on Leibniz, passivity, and the natural world. She also has research interests in ecophilosophy and in the employment of historical ideas to shed new light on current concerns. Donald Rutherford is Professor of Philosophy at the University of California, San Diego. He is the author of Leibniz and the Rational Order of Nature (1995) and of many articles on the history of early modern philosophy. He has just completed (with Brandon Look) an edition and translation of the Leibniz–Des Bosses correspondence, which will be published as part of the Yale Leibniz series.

Abbreviations

A AG Ak

AT C Cosm

CPR

CSM

CWS

D

G. W. Leibniz. S¨amtliche Schriften und Briefe. Berlin: Akademie: Verlag 1923–. Cited by series, volume, and page. G. W. Leibniz. Philosophical Essays. Ed. and trans. by R. Ariew and D. Garber. Indianapolis, IN: Hackett 1989. Kant, I. Gesammelte Schriften. Ed. by Akademie der Wissenshaften. Berlin: Reimer, later DeGruyter 1910–. Cited by volume and page. Oeuvres de Descartes. Ed. by C. Adam and P. Tannery. Paris: J. Vrin 1964–74. Cited by volume and page. Opuscles et fragment in´edits de Leibniz. Ed. by L. Couturat. Paris: F´elix Alcan 1903. Reprinted Hildesheim: Georg Olms 1966. C. Wolff. Cosmologia Generalis [1731] in J. Ecole, ed., Christian Wolff, Gesammelte Werke, II. Abteilung, Band 4. Hildesheim: Georg Olms 1964. Cited by section number. Kant, I. Critique of Pure Reason. Ed. and trans. by P. Guyer and A. W. Wood. Cambridge, UK: Cambridge University Press 1997. Cited by page number in A and B editions. Descartes’ Philosophical Writings. Ed. and trans. by J. Cottingham, R. Stoodhoff, and D. Murdoch. Cambridge, UK: Cambridge University Press 1984–85. Cited by volume and page. The Collected Works of Spinoza. Ed. and trans. by E. Curley. Princeton, NJ: Princeton University Press 1985–. Cited by volume and page. Philosophical Works of Leibnitz. Ed. and trans. by G. M. Duncan. New Haven, CT: The Tuttle Moorehouse and Taylor Company 1908. ix

Abbreviations

x

DS Essay

Gb GM

GMet

GP

JLW K

L LA

LBr

LC LH

Leibnitz’s Deutsche Schriften. Ed. by G. E. Guhrauer. Berlin: Veit 1838. Cited by volume and page. John Locke. An Essay Concerning Human Understanding. Ed. by P. H. Nidditch. Oxford: Clarendon Press 1975. Cited by book, chapter, and section. Spinoza Opera. Ed. by C. Gebhardt. Heidelberg: Carl Winter 1925. G. W. Leibniz. Mathematische Schriften. Ed. by C. I. Gerhardt. Berlin 1849–55. Reprinted Hildesheim: Georg Olms 1962. Cited by volume and page. C. Wolff. Vern¨unfftige Gedancken von Gott, der Welt und der Seele des Menschen, auch allen Dingen u¨ berhaupt, in C. A. Corr, ed., Christian Wolff, Gesammelte Werke, I. Abteilung, Band 2. Hildesheim: Georg Olms 1983. Cited by section number. Die philosophischen Schriften von G. W. Leibniz. Ed. by C. I. Gerhardt. Berlin 1875–90. Reprinted Hildesheim: Georg Olms 1978. Cited by volume and page. The Works of John Locke. London: T. Tegg 1823. Cited by volume and page. Die Werke von Leibniz. Erste Reihe. Ed. by O. Klopp. Hannover: Klindwort 1864–84. Vols. 7–11 reprinted Hildesheim: Georg Olms 1970–73. Cited by volume and page. G. W. Leibniz. Philosophical Papers and Letters, 2nd ed. Ed. and trans. by L. E. Loemker. Dordrecht: Reidel 1969. The Leibniz-Arnauld Correspondence. Ed. and trans. by H. T. Mason, with an introduction by G. H. R. Parkinson. Manchester, UK: Manchester University Press 1967. Manuscripts of correspondence from the Leibniz Nachlass in Hannover. Cited by the numeration given in Der Briefwechsel des Gottfried Wilhelm Leibniz in der k¨oniglichen o¨ffentlichen Bibliothek zu Hannover. Ed. by E. Bodemann. Hannover: Hand’sche Buchhandlung 1889. Reprinted Hildesheim: Georg Olms 1966. The Leibniz-Clarke Correspondence. Ed. by H. G. Alexander. Manchester, UK: Manchester University Press 1956. Manuscripts other than correspondence from the Leibniz Nachlass in Hannover. Cited by the numeration given. Die Leibniz-Handschriften der k¨oniglichen o¨ffentlichen Bibliothek zu Hannover. Ed. by E. Bodemann. Hannover: Hand’sche Buchhandlung 1895. Reprinted Hildesheim: Georg Olms 1966.

Abbreviations LP LW

MD

MFNS

Mor

MP NE

NS

OCH

OL

Ont

Psy

SL ST

xi

Leibniz. Logical Papers. Ed. and trans. by G. H. R. Parkinson. Oxford: Clarendon Press 1966. Briefwechsel zwischen Leibniz und Christian Wolff. Ed. by C. I. Gerhardt. Halle: H. W. Schmidt 1860. Reprinted Hildesheim: Georg Olms 1963. Disputationes Metaphysicae, in Francisco Su´arez, Opera Omnia. Ed. by C. Berton, vols. 25–6. Paris: Viv`es 1866. Cited by disputation, chapter, and section. I. Kant. Metaphysical Foundations of Natural Science, in J. W. Ellington, trans., Immauel Kant, Philosophy of Material Nature. Indianapolis, IN: Hackett 1985. C. Wolff. Philosophia Moralis sive Ethica [1753], in W. Lenders, ed., Christian Wolff, Gesammelte Werke, II. Abteilung, Band 16. Hildesheim: Georg Olms 1973. Cited by section number. Leibniz Philosophical Writings. Ed. by G. H. R. Parkinson; trans. by M. Morris and G. H. R. Parkinson. London: J. M. Dent 1973. G. W. Leibniz. New Essays on Human Understanding, 2nd ed. Ed. and trans. by P. Remnant and J. Bennett. New York: Cambridge University Press 1996. G. W. Leibniz. Novissima Sinica. Original text in Nesselrath and Reinbothe 1979. English translation in WC. Cited by section number. The Correspondence of Henry Oldenburg. Ed. by A. R. Hall and M. Boas Hall. Madison, WI: University of Wisconsin Press; London: Mansell; London and Philadelphia: Taylor and Francis 1965–86. References to original text and translation are separated by a forward slash. Thomae Hobbes Malmesburiensis opera philosophica quae latine scripsit omnia. Ed. by W. Molesworth. London: Longman, Brown, Green 1839–45. ´ ed., C. Wolff. Philosophia Prima sive Ontologia [1730], in J. Ecole, Christian Wolff, Gesammelte Werke, II. Abteilung, Band 3. Hildesheim: Georg Olms 1962. Cited by section number. ´ C. Wolff. Psychologia Rationalis [1734], in J. Ecole, ed., Christian Wolff, Gesammelte Werke, II. Abteilung, Band 6. Hildesheim: Georg Olms 1972. Cited by section number. B. Spinoza. The Letters. Trans. by S. Shirley. Indianapolis, IN: Hackett 1995. St. Thomas Aquinas. Summa Theologiae. Madrid: Bibliotheca de Autores Christianos 1955–58. Cited by part, question, and article.

Abbreviations

xii

Sys Th

TIS

TSHT

W WC WF

Wid

Godfrey William von Leibniz, A System of Theology. Trans. by C. W. Russell. London: Burns and Lambert 1850. G. W. Leibniz. Theodicy: Essays on the Goodness of God, the Freedom of Man and the Origin of Evil. Ed. by A. Farrar; trans. by E. M. Huggard. La Salle, IL: Open Court 1985. R. Cudworth. The true intellectual system of the universe: the first part; wherein, all the reason and philosophy of atheism is confuted; and its impossibility demonstrated. London: Richard Royston 1678. Cited by volume, book, chapter, and article. The Correspondence of Isaac Newton. Ed. by H. W. Turnbull, J. P. Scott, A. R. Hall, and L. Tilling. Cambridge, UK: Cambridge University Press 1959–77. Leibniz Selections. Ed. by P. P. Wiener. New York: Scribners 1951. G. W. Leibniz. Writings on China. Ed. by D. Cook and H. Rosemont, Jr. Chicago: Open Court 1994. Leibniz’s ‘New System’ and Associated Contemporary Texts. Ed. and trans. by R. S. Woolhouse and R. Francks. Oxford: Clarendon Press 1997. G. W. Leibniz. Leibniz Korespondiert mit China. Ed. by R. Widmaier. Frankfurt: V. Klostermann 1990.

Acknowledgments

Leibniz and His Correspondents grew out of a conference of the same name which took place at Tulane University on March 16–18, 2001. This conference would not have been possible without the generous support of the following: The Center for Scholars of Tulane University’s Faculty of Liberal Arts and Sciences, The Philosophy Department at Tulane University, The D.A.A.D.–New York, The German Consulate General in Houston, Thoemmes Press, and Bahlsen. Many thanks also go to those who participated in the conference and helped to make it a great success, to Antonia LoLordo and the members of my Leibniz seminar in spring 2001 who provided much needed assistance during the conference, and, especially, to Caery Evangelist for her help and support throughout its preparation and execution.

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1 Introduction Paul Lodge

Leibniz never wrote a magnum opus. His books were generally limited in scope (e.g., the Dynamics and Theodicy), and the one exception (the New Essays) is shaped as much by Leibniz’s desire to show the inadequacies in Locke’s views as by his desire to provide an exposition of his own philosophy. Where Leibniz did present surveys of his philosophy, these took the form of essays which were published in the journals of the day or which lay hidden from public view until after his death. And these essays, even the most famous ones such as the Discourse on Metaphysics, the New System, and the Monadology, provide little more than brief, and often exasperating, sketches. Nowhere do we find the likes of Descartes’s Meditations, Spinoza’s Ethics, or Locke’s Essay. The task of understanding Leibniz’s philosophy would be a difficult one, to say the least, were it not for an additional fact. For Leibniz was unlike his contemporaries in another way, namely in the extent to which he was willing to engage in philosophical discussion through the medium of correspondence. To be sure, students of other major figures have letters available to them. For example, eighty-four letters between Spinoza and his correspondents have survived – although almost half of these were written to Spinoza rather than by him. And Descartes left a larger body of correspondence consisting of just over six hundred letters, around five hundred of which were written by Descartes himself. However, even Descartes’s output does not begin to compare with that of Leibniz. Leibniz was a prolific correspondent. His Nachlass contains over fifteen thousand letters from over one thousand correspondences (see LBr: Vorwort). Many of these are not directly concerned with philosophy; however, there are large numbers which do pertain to this subject. Even using 1

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a conservative estimate, the descriptions of Leibniz’s correspondences in Bodemann’s catalog (LBr: passim) suggest over one hundred which deal directly with philosophy. But it is not merely the volume of Leibniz’s epistolary output that is of importance here. For it is clear from even the most cursory readings that his discussions are often very detailed and, sometimes, extremely candid. The significance of Leibniz’s philosophical correspondence was recognized early. Leibniz himself suggested that his correspondence with Antoine Arnauld might be published (see GP I, 420 and Barber 1955: 258), and his correspondence with Samuel Clarke was published by Clarke in 1717, the year after Leibniz’s death (Clarke 1717), and again in French three years later (Desmaizeaux 1720). Editions of two more of Leibniz’s philosophical correspondences – with Johann Bernoulli (Anonymous 1745) and with Johann Schmid (Veesenmeyer 1788) – appeared before the end of the eighteenth century, and between 1734 and 1742 Christian Korholt published his four-volume collection Viri Illustriss. Godefridi Guil. Leibnitii EPISTOLAE AD DIVERSOS, which contains nearly five hundred of Leibniz’s letters (Korholt 1734–42).1 Material from Leibniz’s correspondences made its way into scholarly studies of his work early on. The pioneering works of commentators such as Foucher de Careil (1905), Russell (1937), Couturat (1901), and Cassirer (1902) are replete with references and discussion. This attention has continued to the present day. However, for the most part, discussion of material from Leibniz’s letters has taken place without serious concern for the surrounding correspondences. Usually, scholars draw attention just to individual passages which help support a thesis about Leibniz’s views on a given issue. Sometimes there is an account of the immediate context in which a point arises, but it is rare to find any serious attempt to examine its place within the correspondence from which it was taken. This kind of focus is only natural. Such attention to detail is likely to be inappropriate and a hindrance when an author has as his or her goal a general study or treatment of Leibniz’s views on a particular topic. However, the present volume is predicated on the idea that we have much to gain from taking a closer look at the correspondences themselves. Leibniz’s philosophical correspondences often provide us with detailed discussion of his views on a number of closely related issues. The selection of topics is given to us, and, if we focus on the correspondence as a whole, we find ourselves in the enviable position of knowing which issues were deemed relevant by Leibniz and his contemporaries for a proper understanding of the topics at hand. In addition, the existence

Introduction

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of a correspondent (generally with opposing views) to whom Leibniz must explain and justify his opinions often leads to a more thorough and detailed exposition than we find in his other writings. The chapters in this volume certainly are not the first to deal with Leibniz’s correspondences. Indeed, each of Leibniz’s two most famous correspondences has had an entire monograph devoted to it in recent years – see Robert Sleigh’s Leibniz and Arnauld (1990) and Ezio Vailati’s Leibniz and Clarke (1997). However, this approach is still comparatively rare. Sleigh’s book has been recognized widely as one of the most successful English language studies of Leibniz ever written. His closely contextualized reading of the Arnauld correspondence has revealed much that was previously unknown about the subtlety and complexity of Leibniz’s thought in the late 1680s. Furthermore, many of these discoveries are a direct consequence of the close attention that Sleigh pays to the dialectical structure of the correspondence. The to and fro between the philosophers is an essential key to understanding the views which Leibniz espouses. One could hardly ask for better advertisement for the fruitfulness of the study of Leibniz’s correspondences than Sleigh’s book. Sleigh and Vailati devote entire books to a single correspondence. The aims of this volume are, necessarily, more limited in scope. However, it is hoped that by drawing attention to the philosophical significance of a number of Leibniz’s correspondences, the chapters in this collection will stimulate further interest in the exploration of those that have not yet been studied in depth. Although one chapter (by Martha Bolton) revisits the Arnauld correspondence, the remainder draw our attention to discussions with contemporaries who are less well known (although most will be familiar to Leibniz scholars). The volume makes no pretense of offering anything close to an exhaustive coverage of the many interesting philosophical correspondences in which Leibniz engaged. Indeed, there is no chapter on the Clarke correspondence, arguably the most famous of them all. Although the aim is to provide a wide-ranging collection, the selection of correspondences was determined largely by the interests of the contributors. Seven of the eleven chapters in this volume are successors to papers that were presented at the conference Leibniz and His Correspondents, held at Tulane University in March 2001. The remaining chapters were solicited later. In each case, the contributor was asked to focus on a single correspondence and to present an original essay that illuminates Leibniz as a philosopher. The result is testimony to the different ways in which we may learn from these writings. Sometimes, the lessons are based on

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detailed analysis of the arguments of Leibniz and his correspondents in service of some tightly delineated claim. Other times, we learn more of the way in which Leibniz the philosopher moved through the Republic of Letters and other socio-political contexts while trying to establish himself and his views. Often we learn some of both. However, the reader should not expect to find much in the way of what Robert Sleigh has called “philosophical history” (1990: 2–3), where the aims of the author are to use the writings of a historical figure to illuminate a philosophical issue or discuss a topic “in the company” of such a figure. The primary goal of each of the chapters herein is to provide discussion which will allow the reader to understand the philosophy of Leibniz more adequately, whether this is through a detailed articulation of his philosophical views or by providing new information about the intellectual and socio-political contexts that shaped his philosophy. The chapters are arranged chronologically, based on the starting dates of the correspondences with which they are concerned. For the purposes of introducing the volume, I will illuminate some of the broader themes that link them together. To this end, I shall discuss the chapters in three groups. However, readers will discover many other points of comparison which would allow for different groupings. It should also be noted that many of the chapters impinge directly on our understanding of the work of other important philosophers of the seventeenth and eighteenth centuries, such as Locke, Kant, Arnauld, Wolff, and Foucher. Furthermore, the chapters which are concerned with the correspondences with lesser figures, such as Des Bosses and Princess Caroline, often address issues that are central to the relationship between Leibniz’s philosophy and major philosophical movements of the time, such as Jesuit Scholasticism and Newtonianism. The first group of chapters consists of writings by Stuart Brown, Christia Mercer, and myself. Each chapter provides a wide-ranging discussion based on an entire correspondence and investigates the philosophical themes which arise as Leibniz interacts with proponents of a major school of seventeenth-century philosophy. Stuart Brown considers the philosophical relationship between Leibniz and the skeptic Simon Foucher. Brown argues that this was underpinned by an alliance based on what Leibniz and Foucher believed was common philosophical ground and on the value they attached to what each thought the other aimed to accomplish in philosophy. He traces the alliance from its strong beginnings to its eventual dissolution. Leibniz was initially enthusiastic about Foucher’s skeptical posture, but this eventually gave way to the belief

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that his pre-occupation with the Academic Skeptics was an obstacle to Foucher’s declared aim of seeking truth and making progress in philosophy. Foucher, for his part, hoped for a constructive and demonstrated alternative to Cartesianism and was disappointed by what he saw as the hypothetical nature of Leibniz’s New System and its accommodation to a Cartesian problematic. The correspondence offers a fresh perspective on both philosophers as well as on the way in which Leibniz attempts to draw on the skeptical tradition in fine-tuning his own epistemology. Christia Mercer provides an account of the interchange between the German humanist Jakob Thomasius, who had been Leibniz’s teacher at Leipzig. According to Mercer, Leibniz acquired from Thomasius a commitment to a historically based “conciliatory eclecticism,” a belief in the soundness of the Aristotelian philosophy, and his familiarity with Platonism. By examining the whole correspondence, Mercer argues for two closely related points. (1) Despite his innovations, Leibniz’s philosophical goal was unremittingly conservative: He intended to borrow ideas from all the great philosophical schools to construct a true system that would effect intellectual peace. Furthermore, (2) despite his radical departure from Thomasius on some issues, he remained committed to the conservative philosophical goal inherited from his master. According to Mercer, once we take seriously the philosophical lessons that Thomasius bequeathed to his student, we can resolve the apparent tension between Leibniz’s innovation and his conservatism. In my chapter, I provide an overview of Leibniz’s criticisms of, and responses to, Cartesian metaphysics and epistemology as they appear in the correspondence with Burchard de Volder. I examine the ways in which the correspondence develops against the backdrop of De Volder’s version of the Cartesian philosophy and from his initial request for a naturalistic account of the causes of bodily motion. Along the way, Leibniz and De Volder lock horns over issues which include the appropriate methodology for determining the nature of body, the proper analysis of the nature of substance, and the extent to which Cartesianism is able to explain the phenomena which we associate with bodies. My chapter illustrates the ways in which De Volder’s lines of questioning and responses are a necessary condition for a proper understanding of Leibniz’s views. Furthermore, with this background in place, I raise a number of questions regarding the success of Leibniz’s critique. The chapters in the second group, which consists of essays by Philip Beeley, Franklin Perkins, and Gregory Brown, again provide accounts of a number of issues that arise within entire correspondences. They differ

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from the chapters of the first group in that each considers a correspondence in which Leibniz’s philosophical views are articulated within explicitly social and political contexts. Philip Beeley examines the nature of Leibniz’s relation to Henry Oldenburg, the Secretary of the Royal Society, as it emerges from their correspondence in the 1670s. Three central topics of their correspondence form the focal points of the investigation. The first two are the discussions between the two men about the Hypothesis physica nova and the Theoria motus abstracti – the publications through which Leibniz made his first appearance on the European stage. Beeley’s discussion of the correspondence uncovers the general aims and epistemological foundations of these works, as well as allowing for greater insight into the reasons for Leibniz’s acceptance by the English scientific community. The third topic of discussion on which Beeley focuses is the universal characteristic. The characteristic is much less prominent in the letters which passed between the two men, reflecting Leibniz’s general reticence at disclosing details of a project on which he had worked on and off since his eighteenth year. Nonetheless, important details emerge which are helpful in understanding conceptual developments within this project that took place in the 1670s. Franklin Perkins’s chapter is concerned with Leibniz’s correspondence with several of the Jesuits who were part of the mission to China. For Perkins, the correspondence exemplifies the way in which Leibniz’s philosophy, unlike the views of many of his contemporaries, provides a basis for comparative philosophy and cultural exchange. Indeed, Perkins claims that Leibniz stands alone among early modern philosophers in promoting an imperative not just to tolerate but to seek out and learn from other cultures. Perkins begins by analyzing the epistemological foundation for comparative philosophy, in particular Leibniz’s conception of the relationship between reason and experience. Then he investigates the role of these ideas in the correspondence with the Jesuits. Perkins argues that, side by side, each sheds light on the other and illuminates the ways in which Leibniz’s metaphysics and epistemology serve his practical, social concerns. Gregory Brown introduces the philosophical, personal, and political dimensions of the correspondence between Leibniz and Princess Caroline, Princess of Wales (and future Queen of England). The correspondence provides insight into Leibniz’s relations with the Newtonians in the last years of his life. Brown considers how the priority over the discovery of the calculus shaped the tone and substance of the correspondence between Leibniz and Caroline, and, ultimately, precipitated

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the famous, and much discussed, exchange between Leibniz and Clarke. In addition, he examines the way in which Leibniz’s arguments against atomism and the existence of the void lost their force over Caroline once she was living in England and the attendant failure of Leibniz to propagate his Theodicy in English translation. Brown’s chapter provides a fascinating glimpse into Leibniz’s philosophical personality and his relations with the courts in Hanover, England, and Vienna during the last years of his life. The third group of chapters consists of those by Martha Brandt Bolton, Brandon Look, Daniel Garber, Donald Rutherford, and Pauline Phemister. These chapters focus on philosophical issues that receive detailed discussion in a particular correspondence. Through careful consideration of the dialectical context, new light is shed on some familiar (in the case of Phemister, less familiar) topics. Within this third group, it is useful to note connections between some of the chapters. Martha Brandt Bolton and Brandon Look both consider the vexed question of the nature of corporeal substance in Leibniz’s philosophy by turning to two of the correspondences in which this is discussed in most detail. Bolton’s chapter tracks the part of Leibniz’s correspondence with Antoine Arnauld generated by Leibniz’s contention that in order that the body or matter not be a simple phenomenon, like the rainbow, nor an entity united by accident or by aggregation, like a heap of stones, it cannot consist of extension, and there must, necessarily, be something there which one calls substantial form and which corresponds in a way to what one calls the soul. Bolton draws on the details of the exchange that followed this claim to examine Leibniz’s position as a response to two questions that Arnauld posed: (1) why exactly Leibniz thought that what is extended, merely as such, cannot be a substance (or be real, in its own right); and (2) how Leibniz thought soul-like substantial forms could overcome this barrier to substantiality and reality. Through careful examination of Arnauld’s questioning, Bolton argues that Leibniz endorsed an ontology admitting nothing whatsoever except substances which come up to the highest standard of unity. In two short paragraphs in his last responsive letter, Leibniz indicated how he proposed to bring this off – although he did virtually nothing to explain his solution. Bolton argues that it yields a theory of composite (corporeal) substances that promises to come up to his standard of unity. Look’s chapter examines the correspondence with Jesuit Bartholomew Des Bosses. He shows how, in the course of this correspondence, Leibniz is pushed to show the relation and reconciliation, if possible, of his doctrine

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of monads with standard Scholastic and Catholic metaphysical doctrines. The best-known and most notorious outcome of the dialectic between Leibniz and Des Bosses is Leibniz’s putative concession of the existence of a “vinculum substantiale,” or substantial bond, which unites monads and which, ultimately, makes transubstantiation possible. However, Look argues that a closer examination of this correspondence makes manifest on a deeper level Leibniz’s struggle with and recognition of certain difficulties in his metaphysics. The chapter focuses on two related issues in the correspondence that have not received as much attention as they deserve: (1) Leibniz’s account of composite substance, focusing on his explanation of the nature of primitive active and passive powers; and (2) Leibniz’s account of relations within the Des Bosses correspondence and, in particular, an examination of the sense in which Leibniz appeals to a “more perfect” relation between monads made possible by the “vinculum substantiale.” Daniel Garber and Donald Rutherford investigate Leibniz’s commitment to idealism at different points in his career by investigating key interchanges. Garber deviates slightly from the rest of the contributors by considering the record of a direct interchange between Leibniz and Michelangelo Fardella. Although Fardella was one of Leibniz’s correspondents for many years, the focus of the chapter is a document that purports to represent some of the contents of their conversations from their first meeting in 1690. However, Garber also sets this discussion within the broader context of a discussion of the idiosyncratic Cartesian assumptions that Fardella brings to this interchange. The primary aim is to gauge the import of the document for debates about Leibniz’s idealism. Garber achieves this through a careful examination of the dialectical context. He contends, in contrast to previous scholars, that there may well be no evidence of idealism in Leibniz’s exchange with Fardella and, by extension, none in other writings from Leibniz’s “middle period.” Idealism is again at issue in Donald Rutherford’s discussion of the correspondence with Christian Wolff. Rutherford begins his chapter with the observation that Immanuel Kant regarded Leibniz’s monadology as at least a coherent attempt to reason about a supersensible reality of things in themselves. He believes that Kant’s reading of Leibniz’s monadology is largely correct, and he employs it in exploring what he sees as the central philosophical issue at stake in Leibniz’s correspondence with Christian Wolff. The thesis, simply put, is this: Leibniz is an idealist and Wolff is not. Through an examination of their correspondence, Rutherford shows that very early in his career Wolff was offered an entry into the inner recesses

Introduction

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of Leibniz’s philosophy and politely declined the invitation. Thereafter, in his mature writings, Wolff justified this refusal with a philosophical system which makes clear his differences with Leibniz. This is a piece of philosophical history interesting in its own right, but Rutherford also uses it to reinforce the thesis that Leibniz’s late philosophy is conceived properly as a version of metaphysical idealism, a reading on which he claims Kant as an ally. Finally, Pauline Phemister explores Leibniz’s use of the Principle of Uniformity in his correspondence with Lady Masham. She suggests that Leibniz’s appeal to the Principle and the underlying empiricism with its Lockean-sounding appeals to sensation and reflection are inspired by Leibniz’s desire to engage in philosophical debate with Locke (who was living in Masham’s household at the time). Phemister also argues that the application of the Principle produces highly suspect conclusions when the appeals to sensation and reflection are made in an essentially Lockean fashion. However, she claims that when Leibniz’s empiricism is understood as grounded ultimately in an ontological thesis that emphasizes the foundational reality of the living creature, comprising a mind, soul, or form theoretically capable of self-reflection, as well as a physical, sensing body, the arguments using the Principle of Uniformity are much more successful. Phemister argues that, in the end, the position advanced by Leibniz bears more resemblance to that of Ralph Cudworth, Lady Masham’s father, than it does to that of Locke. Note 1. Although the works mentioned here are the most important ones, other letters by Leibniz were published during the seventeenth and eighteenth centuries – see Ravier 1937: 115–301.

2 Leibniz and His Master The Correspondence with Jakob Thomasius Christia Mercer

In the spring of 1661, at the age of fourteen, Leibniz began his studies at the university in Leipzig where he came under the influence of Jakob Thomasius, a well-known German philosopher. Thomasius, who became the young man’s mentor and adviser, was born in Leipzig in 1622, attended university there, and eventually became Professor of Rhetoric, Dialectic, and Moral Philosophy.1 Before his death in 1684, he published in all the main areas of philosophy and directed dissertations on a wide range of topics. He was considered an “erudite” historian of philosophy, an important conciliator, and “a most recognized” philosopher (Sturm 1686: 72–3). Leibniz calls him “the most celebrated German Peripatetic” (A VI ii, 426) and refers to him as “our most famous Thomasius” (A VI i, 300). In April 1669, Leibniz wrote a letter to Thomasius in which he argues for the reconciliation of the Aristotelian and the mechanical philosophies, and for a conception of substance that would effect that reconciliation. He published the letter the next year, and it, thereby, became the young man’s first public presentation of his newly developed theory of substance.2 The title given to the letter is revealing: “Letter to a Man of the Most Refined Learning Concerning the Reconcilability of Aristotle and the Moderns.” In the remainder of Leibniz’s long life, he wrote thousands of letters to hundreds of people. Of all his correspondences, none is more important to an understanding of the sources and goals of his philosophical project than the one with his esteemed professor. I would like to thank the Herzog August Bibliothek of Wolfenbu¨ ttel, Germany for support during the research for this chapter.

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The Correspondence with Jakob Thomasius

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Between September 1663 and January 1672, Leibniz and Thomasius exchanged sixteen letters, five of which were written by Thomasius.3 The correspondence begins a few months after the defense of Leibniz’s B.A. thesis, De Principio Individui, written under the tutelage of Thomasius, and weeks after the young man’s seventeenth birthday. For the summer semester of 1663, Leibniz traveled to the nearby Lutheran university in Jena to study with Erhard Weigel (1625–99). The correspondence between Thomasius and Leibniz begins in September 1663, while Leibniz was living in Jena and just before he returned to Leipzig. It ends immediately before Leibniz leaves Germany for Paris in early 1672. That Leibniz’s correspondence with Thomasius is a thread that runs through radical changes in the young man’s life is clear from the following facts. By January 1671, Leibniz and Thomasius had exchanged fourteen of the sixteen letters that would pass between them, and Leibniz’s letter to Thomasius of January 1671 is the 37th in his extant philosophical correspondence. When Leibniz wrote his 11th (and final) letter to Thomasius a year later, it counted as the 100th in his philosophical correspondence. That is, between May 1671 and January 1672, the number of letters exchanged between Leibniz and other philosophers is greater than in all the preceding years of his life combined. Some of the most prominent contributors to seventeenth-century philosophy and science are included in this group: Spinoza, Otto von Guericke, Antoine Arnauld, Heinrich Oldenburg, Pierre de Carcavy, and Johann Comenius. Moreover, during the period of his epistolary exchange with Thomasius, the young philosopher managed to publish works in the areas of logic (Dissertation on the Combinatorial Art of 1666), jurisprudence (An Example of Philosophical Questions Concerning Law of 1664), theology (Confession of Nature against the Atheists of 1668), metaphysics (the letter to Thomasius, published in 1671), physics (Theory of Abstract Motion of 1671), and philosophical methodology (the entire preface to the text of Nizolio of 1671, which includes the letter to Thomasius of April 1669).4 He also began a large theological project (the Catholic Demonstrations) and composed a number of short essays on the topics of mind, body, and activity, which were not published (see A VI ii, 276–303). Between 1668 and early 1672, Leibniz wrote a series of theological essays and several notes on natural law, in which he articulates for the first time many of his core metaphysical assumptions. On the basis of an examination of these writings, I have shown elsewhere that Leibniz developed (at least some of) the core features of his metaphysics much earlier than formerly thought and that he

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is committed to a philosophical methodology that has previously gone unnoticed (see Mercer 2001: ch. 1). That the period of Leibniz’s correspondence with Thomasius is enormously fertile is obvious. Leibniz begins the correspondence as an eager and precocious young student. The epistolary exchange ends just as his international reputation is developing, and just before he leaves for Paris where he will assure that reputation. What makes the correspondence between the student and his mentor so singularly significant, however, is that it bears witness both to the influence that Thomasius’s own philosophical strategy had on the development of Leibniz’s thought and to the young man’s audacious divergence from his teacher. That is, we find here two features of Leibniz’s philosophical personality that stand in tension with one another. On the one hand, Leibniz is conservative and cautious: He follows his mentor in proclaiming the virtues of the past great philosophers, especially Aristotle; he suggests that most philosophical truths are to be found in the texts of the ancients, when those are properly read; and he insists on a philosophy that will reconcile the old philosophy with the new and, thereby, effect intellectual peace. On the other hand, he is rebellious and innovative: He rejects a major part of what his professor has taught him, embraces views that his master “disdains,” and sets out courageously on his own philosophical path. That these features of Leibniz’s philosophical personality stand in tension with one another has created hardships for his interpreters. It has been difficult to reconcile the modern side of his thought (the contributions in physics, logic, and mathematics) with the apparently traditional side (the commitment to Christian doctrines and to ancient authors).5 And this tension has helped to camouflage the genuine importance of Leibniz’s early works. Because scholars have been eager to see the great man as thoroughly innovative, they have ignored the conservatism underlying his approach, a conservatism bequeathed to him by Thomasius. But the neglect of Leibniz’s conservatism has come at a high price. Consider Leibniz’s (often quoted) description of his philosophical development in a letter to Remond of 1714: After finishing the Ecoles Triviales I fell upon the moderns, and I recall walking in a grove on the outskirts of Leipzig called the Rosental, at the age of fifteen, and deliberating whether I should keep the substantial forms [si je garderois les Formes Substantielles]. Mechanism finally prevailed and led me to apply myself to mathematics. (GP III, 606/L 655)

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Until recently, students of Leibniz have taken passages such as this to provide ample evidence of two things: his youthful rejection of the Aristotelian philosophy and anything else traditional, and his commitment to the physics of the mechanists (see, e.g., GP IV, 478/L 454).6 For many scholars, the only question that remained was one of influence.7 For others, Leibniz’s early period is one of “uncertainties and reversals” (Wilson 1989: 45). A few interpreters have noted that Leibniz’s early texts are strewn with references to Aristotle, but because of Leibniz’s apparent abuse of key features of the ancient philosophy, these references have been considered rhetorical.8 In the past decade, however, some scholars have begun to place the young Leibniz in his proper intellectual context and have, therefore, begun to discern other aspects of his thought. Thanks to the work of Philip Beeley, Maria Rosa Antognazza, Ursula Goldenbaum, Richard Bod´eu¨ s, Detlef D¨oring, Hubertus Busche, and others, the full richness of Leibniz’s early period has begun to emerge.9 In my book, Leibniz’s Metaphysics: Its Origins and Development (Mercer 2001), I show that the young Leibniz intended to borrow ideas from all the great philosophical schools in order to construct a true system that would effect intellectual peace, and that his grand metaphysics is the result of this recycling of philosophical doctrines. In the present chapter, I offer a fuller analysis of the inherent tension between a commitment to the old and an endorsement of the new in the young Leibniz’s thought. This tension is wonderfully apparent in the correspondence between Leibniz and his respected master. Based on a (brief) commentary on the Leibniz–Thomasius correspondence, we are able to discern a tension between the conservative and the innovative in two closely related ways. The first is that despite Leibniz’s endorsement of the new mechanical physics, he remained unremittingly committed to the truth of past ideas. This commitment led him to find a way to embed his mechanical physics within ancient ideas. The second is that despite the conciliatory methodology that he inherited from Thomasius, he was prepared to depart from his esteemed mentor on behalf of the truth. Once we take seriously the philosophical lessons that Thomasius bequeathed to his student and once we see the development of the young Leibniz’s ideas within this context, we are able both to identify these tensions and to witness Leibniz’s successful attempt to resolve them. In the end, the correspondence with Thomasius offers important lessons about Leibniz’s philosophical personality.

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Before turning to the correspondence, it will be helpful to situate the philosophical discussion between the master and student in its proper context.

1. historical and philosophical background In 1669, Leibniz prepared an edition of a text by the sixteenth-century humanist, Mario Nizolio, which he published in early 1670. Leibniz wrote a lengthy introduction to Nizolio’s book, On the True Principles and the True Method of Philosophy, Against the Pseudo-philosophers (1553). Both Nizolio’s text and Leibniz’s introduction discuss the proper way of philosophizing. Leibniz attached to his introduction a slightly revised version of his April 1669 letter to Thomasius, which he entitled “Letter to a Man of the Most Refined Learning Concerning the Reconcilability of Aristotle and the Moderns [recentioribus].” By such means, Leibniz calls dramatic attention both to his admiration for Thomasius and to the strategy of reconciliation that he had learned from his erudite teacher. In order to discern the philosophical and methodological lessons of this and the other letters to Thomasius, our own learning requires a bit of refinement. The philosophical proposals of both Leibniz and his master are understood best within the following philosophical traditions.

Humanism and Conciliatory Eclecticism For our purposes, we may bypass the complications involved in describing humanism as a method and tradition and move directly to the humanist assumptions particularly relevant to Thomasius.10 Many Renaissance and early modern humanists practiced and preached conciliatory eclecticism among the ancient schools, and some extended their eclectic scope to include more recent authors.11 Here, the underlying assumption was that the classical texts offered a treasure trove of truths that contemporary philosophers could combine to form the true philosophy. According to many humanists, the diverse philosophical traditions were not as incompatible as they appeared at first. The goal was to forge a reconciliation among the worthy schools, the result was a mixture of ancient and modern ideas; and the hope was that the proper synthesis would effect peace among contemporary philosophers. We can glean from Thomasius’s many publications the methodological lessons that he taught his students.12 Thomasius believed that the true philosophy could be constructed from the raw materials of apparently

The Correspondence with Jakob Thomasius

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diverse philosophical schools, but he insisted that those raw materials be chosen with great care. Thomasius complained bitterly about the propensity among his predecessors and colleagues to collect ideas without thorough analysis, to assume that all philosophical schools could be made to cohere, and then to force a synthesis among doctrines where there was none. He believed that ancient philosophers offered the primary raw materials for the proper conciliatory philosophy, but he was prepared neither to force their ideas into Christian doctrine nor to accept the mistaken interpretations of their ideas promulgated by the less discriminating humanists. He saw the need to take the texts of classical authors on their own terms (see e.g., Thomasius 1693: 466, 478ff.). The result of this historically informed analysis of ancient philosophy was to make the “true” views of the ancients available for careful scrutiny. Once the ancient doctrines were properly interpreted, they could be thoroughly evaluated. For example, Thomasius’s Exercitatio de Stoica mundi exustione (1676) is an extended comparison of the tenets proposed by leading Stoics, Platonists, Aristotelians, and Epicureans.13 In the process of identifying the heretical views and “many errors” of some of these past philosophers (especially the Stoics), Thomasius is eager both to identify and clarify those ancient doctrines that conform to Christian teachings. For Thomasius, the goal of proper historical analysis is to identify the real views of the ancient philosopher, to discriminate carefully between those views that are orthodox and those that are not, and then to construct the true philosophy. By such means, we will escape “the shadows of the pagans” and discover “the light of true doctrine” (1676: 3).

Aristotelianism In Thomasius’s opinion, the brightest light to be found among the ancient thinkers was that of Aristotle. Like so many humanist thinkers before him, Thomasius distinguished between Aristotle and his dim-witted followers and claimed that many of the “true” views of the ancients had been misunderstood (1658: 75).14 Although Thomasius had no doubt about the superiority of Aristotelian philosophy, he subjected that philosophy to the same scrutiny that he applied to other ancient sources. He writes in his Schediasma, for example: “For those people who repeat the same old song that the ancient Aristotle can be reconciled with sacred scripture, they should be met with derision” (1665: 22 – see also 13). Although it was an arduous task to uncover Aristotle’s real views, Thomasius insists that the philosophy of Aristotle, once properly understood, had enormous

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merit (1658: 72–82). In his Schediasma, Thomasius claims that “there has been abundant pouring forth of divine wisdom” in ancient philosophy and that the profundity of the Aristotelian philosophy is due to the fact that Aristotle, more than any other philosopher, understood that “God speaks through the book of nature” (1665: 479). Although Thomasius admits that there is much wisdom to be found in Plato and in the other ancient philosophers who used their intellect to discern God in nature, he announced that it was Aristotle who had the greatest insight. In the preface to his textbook on physics, Thomasius proclaims that “God himself” may be revealed through “the study of nature” once we make proper use of the philosophy of Aristotle. He concludes his preface by writing that: there is the most elegant nexus among things and the finest order [which acts] as a ladder for us with which to ascend to God. This [Aristotelian order] [ . . . ] reveals the glory of the supreme Craftsman [ . . . ]. Assuredly, whoever glimpses the single harmony and beauty of ends will therefore grasp [ . . . ] the Wisdom of the most Benevolent Architect. (1670: preface [9])15

Platonism Thomasius also depended on the philosophy of Platonism to help him ascend the ladder to God and the ultimate truths. That is, despite his very definite Aristotelian leanings, Leibniz’s master was thoroughly conversant with the details of Platonism and quite sympathetic to Platonist tenets. At least since the time of Porphyry (232–304 CE), it was common for philosophers to turn to the Platonic tradition for inspiration concerning divine matters and to Aristotelianism for insight concerning the mundane. Thomasius is no exception. For example, in his Exercitatio, he discusses at length the views of Platonist philosophers on this topic, and he concludes that Platonism is extremely valuable. Because Renaissance Platonists “have wrapped that [Platonic] philosophy in mystery and obscurity” (1676: 478 – see 1665: 52) it is especially important to distinguish between Platonist tenets that are sound and those that are heretical. But in the end, Thomasius admits that the Platonic tradition is an important source of truths, especially about God’s relation to the created world (1665: 13; 28; and 249–52). He agrees with the Platonists against the Stoics in their account of “the flowing of creatures from God” (1665: 249– 52). Although he accepts that the supreme being is “the fountain of features which flow into creatures” and although he agrees with Augustine that “God contains all things in himself,” he insists that this flowing or

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emanation be understood in the right way (ibid.). In brief, Thomasius is extremely knowledgeable about the whole history of Platonism, and he is keen to use that tradition once its orthodox tenets have been interpreted rightly.

Reformed Philosophy In his October 1668 letter to Leibniz, Thomasius accuses his former student of accepting the philosophical proposals of the Dutch Cartesian, Johannes de Raey. In his April 1669 letter to Thomasius, Leibniz calls himself “a reformed philosopher” and proudly announces the benefits of the reformed philosophy. In order to understand properly both Thomasius’s criticism of Leibniz’s proposals and the status of the proposals themselves, it will be helpful to display some of the features of reformed philosophy and to see De Raey’s thought in this context. Due to the anti-Aristotelianism of Luther and the early reformers, the scholastic philosophy of northern universities went through a radical transformation in the second half of the sixteenth century. The place of Aristotelianism had just become stable again when, in the first half of the seventeenth century, the intellectuals of northern Europe were confronted with the new natural philosophies of Galileo, Descartes, and Gassendi. By the middle of the century there had evolved throughout Europe, and especially in the Protestant areas of the north, a group of eclectics whose members sometimes referred to themselves as the reformers [reformatores] and their philosophy as reformed philosophy [philosophia reformata or philosophia emendata]. For Leibniz, any thinker who articulated a desire to accommodate the new mechanical physics within some version of Aristotelian metaphysics was a reformed philosopher.16 Reformers had very different recipes for mixing the old with the new. Each was prepared to say that when the Aristotelian philosophy was properly understood, it could comfortably accommodate the mechanical philosophy. Thus, at the very time that philosophers such as Descartes and Gassendi were crying for the demise of the Aristotelian philosophy, others were calling for its transformation. The reformers maintained that the Aristotelian philosophy did not need to be rejected, it just needed to be reformed (see Verbeek 1992: 8–9 and Mercer 1993: 41–3). Johannes de Raey (1622–1707) was a prominent philosopher at the university in Leiden. In his September 26/October 6, 1668 letter to Thomasius, Leibniz writes that in the same way that Thomasius had saved Aristotle “from the smoke of the Scholastics,” so De Raey in his

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Clavis philosophiae naturalis Aristotelico-Cartesiana (1654) “shows [ . . . ] that Aristotle conforms wonderfully to [the philosophy of] Galileo, Bacon, Gassendi, Hobbes, Descartes, and Digby” (A II i, 10).17 For our purposes, the Dedicatory Letter of the Clavis is especially interesting. De Raey explains there that because the Europeans “lost the works of Aristotle” and because the scholastics promulgated false views about the ancient’s thought, the true meaning of Aristotle’s writings have been lost. The great importance of the Cartesian philosophy, claims De Raey, is that it reveals the true meaning of Aristotle’s principles. However incompatible modern mechanism and Aristotelian physics may seem, the incompatibility is only apparent, an unfortunate result of an historical accident. In order to discover the correspondence between the Cartesian and Aristotelian philosophies, all one has to do, De Raey suggests, is to penetrate through the layers of misinterpretations to the real philosophy of Aristotle. Not surprisingly, De Raey thinks that he has accomplished this task. De Raey’s method in the remainder of his book is to describe what “the schoolmen” say about a crucial element in Aristotle’s philosophy (e.g., substance, substantial form, matter), to quote Aristotle (rendered in Latin) on the topic, and then to explain what Aristotle really meant. Although many of De Raey’s interpretative conclusions seem far-fetched, he does manage to construe intelligently and then put to interesting use genuine elements of Aristotle’s metaphysics in an honest attempt to reconcile the ancient’s thought with Cartesian mechanism (see Verbeek 1992: 8 and 72).

2. the early correspondence between leibniz and thomasius, 1663–68 Between September 1663 and October 1668, six letters passed between Leibniz and Thomasius. One philosophical topic is dominant: mechanism as a means to explain the features of the corporeal world in a manner consistent with the Aristotelian philosophy, as Leibniz interpreted it.

Leibniz’s Master In the introductory section to this chapter, I presented some of Leibniz’s autobiographical remarks about his youthful development, and I noted a tension between his endorsement of the new mechanical philosophy and his commitment to a methodology of reconciliation. In section 1, I offered the appropriate historical context within which to see Leibniz’s correspondence with Thomasius. Before turning to the correspondence,

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it will be helpful to consider comments about Leibniz’s development and, thereby, to place his relation to Thomasius in its proper light. Consider Leibniz’s description of the original impression made by “his master”: As soon as I arrived at the Academy, by a rare fortune I met, as a Master, the well known J. Thomasius who, although he did not accept my doubts and was very little disposed to let me do such a reform of the substantial, incorporeal forms of bodies, engaged me very strongly to read Aristotle, announcing to me that, when I would have read this great philosopher, I would have a wholly different opinion than that offered by his scholastic interpreters. I soon acknowledged the wisdom of this advice and saw that between Aristotle and the scholastics, there was the same difference as between a great man versed in the affairs of state and a monk dreaming in his cell. I therefore took of Aristotle’s philosophy another idea than the common one. I did not accept all of his hypotheses, but I accepted them as principles. Aristotle seemed to me to admit, more or less like Democritus or, in my time, like Descartes and Gassendi, that there is no body which can be moved by itself. (Foucher de Careil 1905: 5–7)18

Leibniz followed Thomasius in returning to the philosophy of Aristotle so as to distinguish between the ancient himself and his more incompetent followers. He also agreed with his master that the teachings of ancient philosophers such as Aristotle had much more to offer contemporary thinkers than was often thought. Nor did the lessons learned from Thomasius stop there. As we have seen, whether it was Aristotelianism, Platonism, or some other ancient philosophical tradition, the erudite historian encouraged his students to discriminate among interpretations of the ancient doctrines and to seek profound truths in classical texts. Consider another account that Leibniz offers of his youthful development. This time he is writing in the late 1670s and speaking of himself in the third person: “he fell first across the Ancients, in whom at the beginning he understood nothing, and then something, and at last as much as was needed [ . . . ]; he gained a sense not only of their language but of their thoughts.” Unlike more recent thinkers whose works are full of “swollen words” and “patchworks of borrowed opinions,” the thoughts of the ancients “stood out strenuous and commanding, and embraced as it were in a picture the whole field of human life; their diction was clear, natural, easy, and appropriate” (GP VII, 52).19 Following his master, Leibniz learned to find his own way in the ancient texts and to take ideas that were not entirely “common.” But this tendency toward innovative thinking also led the precocious young man to disagree with his teacher on important points. In the end, the student

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did not accept the master’s interpretation of substantial forms, and he was bold enough to make his own “reform” of this central notion. Thus, although it is true that Leibniz “despised the method of those who use only forms” to explain the features of nature and “was charmed by their [the mechanists’] beautiful ways of explaining nature mechanically,” it does not follow that he rejected the whole of the Aristotelian philosophy. Rather, he chose the physical explanations offered by the mechanical philosophers over those offered by traditional scholastic philosophers. As a fifteen-year-old, when mechanism “prevailed” over scholastic substantial forms and he applied himself “to mathematics,” the young man’s commitment was to get to the bottom of the new mechanical physics.20 But it is important to see Leibniz’s endorsement of the new philosophy within the context of his conservative methodology: Following the methodological example of Thomasius, he considers the main proposals of the mechanists consistent with those of ancient philosophers such as Democritus: “Aristotle seemed to me to admit, more or less like Democritus or, in my time, like Descartes and Gassendi, that there is no body that can be moved by itself.” For the young Leibniz, mechanical philosophers such as Descartes and Gassendi fall into the same philosophical camp as does Democritus, and, moreover, Aristotle agrees with them all concerning the movement of bodies. It was during the 1660s that Leibniz succeeded in forging a synthesis between Aristotelian metaphysics and mechanical physics. His letters to Thomasius indicate how and why he succeeded.

Leibniz’s Letter of September 1663 (A II i, N. 1) In the summer semester of 1663, Leibniz went to Jena to study with Erhard Weigel who, unlike Thomasius, endorsed the ideas of the “new” philosophers.21 While in Jena, Leibniz apparently became a member of an academic society, which was presided over by Weigel and which met weekly for discussion of old and new books (see Aiton 1985: 16). The first letter in Leibniz’s extant correspondence, and the first to Thomasius, was written toward the end of Leibniz’s stay in Jena. Leibniz describes a disputation on a political topic (specifically, on natural rights), which he must have considered of interest to his master. As Professor of Moral Philosophy, Thomasius was often engaged with political and moral matters. He was familiar with the work of Machiavelli, Hobbes, and other “recent” thinkers.22 In this letter of September 1663, Leibniz offers extremely brief observations on the political thought of Machiavelli,

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Hobbes, and others. For our purposes, the letter is important in two ways. First, Leibniz shows a keen interest in English philosophers such as Hobbes and Digby, both of whom are major proponents of the mechanical philosophy. Under the direction of Weigel, Leibniz had begun a more serious study of the “new” philosophy in general and of the mechanical physics in particular. Second, both Leibniz’s presence in Jena as a student of Weigel and his recommendation of the sorts of texts and issues being discussed in Jena make evident the young man’s desire to go beyond the philosophical culture of Leipzig. And yet, there is no suggestion of disdain for that more conservative culture. Rather, Leibniz suggests a genuine desire to involve his former master in conversation about the new philosophy, and he seems to have carefully chosen the topic so as to pique Thomasius’s interest. That is, from the beginning of his philosophical evolution, Leibniz is keen to forge intellectual peace.

Leibniz’s Letter of February 1666 (A II i, N. 3) Between 1666 and early 1672, Leibniz lived in Mainz where (among other things) he acted as lawyer and adviser to a distinguished German statesman, Baron Johann Christian von Boineburg. Under the encouragement of Boineburg, he began work on a large theological project entitled Catholic Demonstrations. Leibniz’s original metaphysical and physical principles emerge as the implicit premises and underlying assumptions of the texts that were written as part of the project. Between the time of Leibniz’s conversion to mechanical physics (about 1661) and the commencement of the Catholic Demonstrations in 1668, the young man had hit on what he considered to be the common denominator among the mechanical options of philosophers such as Gassendi, Hobbes, and Descartes. Although his account ignores important differences among the individual mechanists, it successfully identifies the explanatory model at the center of the mechanical physics. Among other things, the correspondence with Thomasius offers us a ringside seat on the struggle between Leibniz’s commitment to the mechanical physics and his attachment to Aristotelianism. The second letter of the correspondence, again written by Leibniz, is a fascinating little exercise on the paradox of the possibility of black snow. Although Leibniz mentions Hobbes at the outset of his discussion, he gives a Gassendian account of perception.23 Some scholars have taken this letter to be clear evidence that by February 1666, Leibniz has rejected his youthful Aristotelianism and accepted Gassendian atomism. But in

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fact, this is the only text of the period in which Leibniz does not combine his mechanical approach to physics with ideas from ancient sources, especially from Aristotle. The letter reads very much like an exercise that the student prepared for his former master. It consists, in its twenty-sixline entirety, of a solution to a paradox first proposed by Anaxagoras. Leibniz begins with the hypothesis that color is only an idea in the mind and not a quality in things. He then uses this hypothesis, along with some Gassendian principles, to solve the paradox (A II i, 4–5). There would be reason to take this position as somehow representative if Leibniz continued to make important use of these same principles. He does not; and there is little reason to believe that Leibniz was particularly wedded to Gassendi’s views on perception or to Gassendi’s philosophy, for that matter. Another reason for not generalizing from this one instance is that in the same year Leibniz published his Dissertation on the Combinatorial Art. Because this work uses the Aristotelian account of cause, analyzes the four Aristotelian primary qualities in mechanical terms, and presents Aristotle’s notion of the mean, there is little justification for thinking that Leibniz had given up combining ancient or historical ideas with modern ones in 1666. For us, however, the letter is noteworthy because it suggests that Leibniz hopes to interest Thomasius in the mechanical physics. Although we cannot be certain of Leibniz’s intentions, he apparently has constructed a clever trap: Given Thomasius’s vast familiarity with ancient thought (and hence with the paradox)24 and given his thorough familiarity with ancient atomism, the presentation of Gassendi’s version of Epicurean atomism as a solution to the problem would surely strike his fancy. That is, the young man seems to have wished to engage the elder philosopher with contemporary theories of perception. Thomasius did not take the bait.25

Leibniz’s Letter of September 26/October 6, 1668 (A II i, N. 9)26 If Leibniz’s intention was to entice Thomasius into a discussion about “new” ideas in general and the mechanical philosophy in particular, the fourth letter in the correspondence was a success. In this letter of September 26/October 6, Leibniz presents his original account of corporeal substance. In brief, he claims that (1) the prime matter of Aristotle is nothing but inert mass [moles] without motion and figura;27 (2) the origin of motion is God; (3) figura results from the potentiality of matter; (4) this figura “is the source of all the affections or sensible qualities which maintain themselves as a result of the form of this thing”; (5) we

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can call this “innermost figura of parts [intima partium figura]” substantial form because (a) it can be distinguished from matter, (b) it is prior to everything else concerning body, and (c) it is in terms of it that we explain all the appearances or qualities of the body (A II i,11). According to Leibniz, his understanding of substantial form has one great benefit over the account of the scholastics. If “we admit in bodies” substantial forms or “quasi-spiritual beings” whose power is supposed to make the rock fall and the plant grow, then “we prevent ourselves from the most apt way of demonstrating [the existence of] God and throw away that excellent principle of Aristotle: that whatever is moved has the cause of motion outside itself, which itself climbs the ladder to the prime mover” (ibid.). Leibniz’s rhetorical strategy here is clever. As the young man knew, his illustrious teacher was keen to argue that it was Aristotle (as opposed to Plato and other great ancient thinkers) who offered the most secure “ladder” with which to ascend from nature to God. Leibniz hopes to tempt Thomasius into reflecting on the mechanical philosophy by claiming that his own account of substantial form provides a better ladder and, hence, a more direct ascent. Leibniz argues as follows: there is nothing in body “other than matter and figure”; neither matter nor figure can act as the cause of the motion of body; therefore, “the cause of motion must be outside of body”; “there is nothing conceivable outside of body other than mind”; “mind without question is God.” That is, Leibniz attempts to use a mechanical notion of body as extended matter to ground his version of the cosmological argument. The argument itself is neither original nor (particularly) convincing. But it is interesting for what it reveals about Leibniz’s attempt to forge a synthesis between Aristotelian metaphysics and mechanical physics (see Bod´eus ¨ 1993: 58–70). Before we analyze Leibniz’s position in greater detail, it will be helpful to consider Thomasius’s response.

Thomasius’s Letter of October 1668 (A II i, N. 10) Leibniz’s proposal elicited an immediate response from Thomasius. The most striking thing about Thomasius’s letter of October 1668, the fifth letter in the correspondence and the first by Thomasius, is that it reveals charmingly his quiet disdain for the young man’s mechanical leanings and, thereby, explains why he is not keen to engage with his former student on the topic. His attitude seems one of bemused resignation. Although he makes it perfectly clear that he “spurns” much of the new

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philosophy (A II i, 13), he seems neither surprised that his precocious young friend has embraced it nor optimistic about dissuading the young man from the folly of his ways. Rather, the elder philosopher chides the younger: “excuse me, but you do not yet convince me” about the views of “Descartes and the other new philosophers” (A II i, 12). With what appears to be exasperation, he admits: “I make this protest to you, as I have been making them to others” (A II i, 13). Thomasius seems to understand the temptation that “this way of talking” has for eager young minds, but he continues to find it unhelpful and inaccurate. Thus, Leibniz’s master, despite his proclamations about the dangers of the new philosophy, was familiar with some of its representatives. He insists, for example, that the German Cartesian, Johann Clauberg, is clearer and “more pleasing” than Descartes. He is also quick to suspect that the proposals of his former student have been “suggested” by the “meditations” of Johannes de Raey, whose philosophical doctrines he knows “by report” from “the book sellers” and others (A II i, 12–13). It is at this point in the correspondence that we glimpse some of the appeal that Thomasius must have had for the brilliant young Leibniz. The master offers two different kinds of criticisms of the position proposed by Leibniz. The criticism that dominates the letter is, explains Thomasius, “a question of history” (A II i, 13). Although he endorses fully Leibniz’s goal of intellectual harmony, he warns his former student: Before there can be “any hope of harmony [among the philosophical schools], [ . . . ] we need to examine a bit more fully the mind of the philosopher [i.e., Aristotle].” Thomasius points out that the substantial form cannot be identical to accidental things such as the figuration and magnitude of parts “in whose agreement you seem to construct the harmony” (A II i, 12). Although he acknowledges that he is “aware of this manner of talking” and admits that others may accept this way of making “peace” (A II i, 13), he seems appalled by the historical inaccuracy of Leibniz’s proposal. Perhaps not surprisingly, Thomasius then offers a rather lengthy history lesson in which he shows that the “new philosophers” have much more in common with Epicurus than with Aristotle. In the end, Thomasius disapproves of any attempt to forge a synthesis of the mechanical philosophy with Aristotelian tenets that requires such a radical departure from the thought of Aristotle himself. Part of Thomasius’s point seems to be that because no self-respecting Aristotelian will condone this “reform” of substantial form, there is little hope of forging genuine peace between Aristotelians and mechanists. Moreover, it also follows that because no self-respecting Aristotelian will admit that there is nothing in body “other

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than matter and figure,” Leibniz’s argument for the existence of God begs the question and will not be taken seriously by any thoughtful student of Aristotle. In the middle of the history lecture, Thomasius makes two astute philosophical points. First, in response to the idea that the form of the body is merely an organized arrangement of parts, Thomasius asks whether or not this applies to the human form. “Must we deny,” wonders Thomasius, “that the substance [of a human being] is distinct from its figura?” Although Thomasius does not develop his criticism, the suggestion is that there is more to the substantial form of a human being than the organized arrangement of its matter. Thomasius’s second philosophical point is made in response to Leibniz’s claim that his mechanical conception of body offers a ladder with which to ascend to God. The master neatly shows the weakness in the young man’s position as presented in the letter. According to Leibniz, for any individual body, because we must go outside the body to explain its motion, it is supposed to follow that God exists as the source of motion. But, as Thomasius rightly points out, there is nothing in Leibniz’s position that blocks an infinite regress. Nor is that all. Thomasius is keen to note that because the young man has reformed the traditional account of substantial form, he has removed “the most beautiful ladder” by which Aristotle would have us ascend “to the prime mover.” In the end, insists Thomasius, we must revert to the proper understanding of a substantial form as “the principle of motion and rest” and, thereby, offer a firm account of motion without the threat of regress (A II i, 13 – see Bod´eu¨ s 1993: 75–96). Leibniz’s attempt to attract the attention of the former master was successful. But his mechanical rendition of the cosmological argument in the letter of October 1668 failed miserably as a means to enlist Thomasius’ support. In the end, Thomasius’s dislike of the new philosophy was not diminished, and his fears about the new tendency to “reform” Aristotle’s thought very likely were increased. Perhaps it is not surprising that he does not engage with the young man in any detail again on these topics. It seems likely, nonetheless, that his criticisms encouraged Leibniz to rethink his views. As we will see, already in 1668–69, the young man’s attempt to place a mechanical physics within an Aristotelian metaphysics becomes more clearly conceived. And by 1670, he has changed his notion of substance to accommodate the sorts of criticisms leveled by Thomasius. Before concluding this discussion, it is worth noting a more personal feature of the letter. From what Thomasius writes, it is clear that Leibniz

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has recommended his former teacher to his employer, and, moreover, that Thomasius has been asked to send Boineburg some of his philosophical works. “I am sending,” explains Thomasius, “the most illustrious Baron” those treatises and disputations that are readily available. Thomasius hopes that Leibniz has not “deceived” this great “patron of letters” either about Thomasius’ “achievements” or about “the excellence” of his writings (A II i, 12). It seems clear that the young man has recommended his former master and, thereby, tried to bring him into the range of Boineburg’s influence. There is something strikingly generous about this. When this generosity is set next to Leibniz’s attempt to convince Thomasius of the mechanical philosophy, it is reasonable to suppose that the young man yearned to include his former master in his own intellectual voyage and to share the wealth of its success.

The Early Correspondence Between Leibniz and Thomasius in Its Wider Context That Thomasius considered Leibniz’s philosophical proposal in his letter of October 1668 an utter failure seems clear. But the energetic young man was not discouraged, and it is now time to consider exactly why he was prepared to go so far beyond the teachings of his master. In order to evaluate Leibniz’s proposals in the correspondence of 1663–68, we need to examine more thoroughly exactly what motivated the young man to reject the metaphysical foundations of mechanism and how he intended to place a mechanical physics on Aristotelian foundations. From the beginning of his philosophical evolution, Leibniz intended to reform the Aristotelian notion of substantial form and, thereby, to create an Aristotelian notion of substance that could comfortably accommodate the mechanical physics. Leibniz’s reform involved the rejection of the traditional role of substantial form in the explanation of corporeal phenomena. Roughly speaking, for the scholastics, the substantial forms of bodies possessed innate powers that inclined those bodies to behave in characteristic ways: Fire, for example, contained the innate power to heat and to rise whereas rocks possessed the tendency to fall. The youthful Leibniz rejected this explanatory model, and he replaced it with a mechanical one. Between the time of Leibniz’s conversion to mechanical physics (about 1661) and the commencement of the Catholic Demonstrations in 1668, the young man attempted to discover the common denominator among the mechanical options of philosophers such as Gassendi, Hobbes, and Descartes. By the time Leibniz wrote to Thomasius in 1668,

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he had accomplished that task. For Leibniz, the mechanical position reduces to the following: There is some sort of matter or extended stuff [res extensa], which is (somehow) moved and whose arrangements both cause and explain the corporeal features of individual bodies; therefore, a body is organized res extensa and all corporeal features are reducible to the arrangements of such extended stuff.28 What struck Leibniz as right about the mechanical philosophy was the idea that the corporeal features of natural bodies were to be explained in terms of matter and motion, so that there was no need here for “mysterious” innate tendencies. Whether it was the shape of the shoe or the heat of a fire, the standard mechanist insisted that corporeal features were reducible to (some form of) res extensa and motion. But Leibniz differed from his contemporary mechanists in his rejection of the metaphysical foundations on which the mechanical explanations of corporeal phenomena were supposed to rest. Indeed, Leibniz never seems to have been satisfied with the metaphysics offered by the prominent proponents of the mechanical physics. One of his main goals in the mid-1660s was to reform the metaphysics of Aristotle to provide a stable foundation for the mechanical physics.29 By 1668, he had managed to reduce the mechanical notion of body to the status of prime matter, which he could then combine with his “reformed” theory of substantial form so as to construct a properly self-sufficient account of substance. For help in deciphering the deep motivation behind Leibniz’s reformation of the Aristotelian philosophy, let’s turn to another text of 1668, the Confession of Nature against the Atheists. In this essay, which is the first one written as part of the Catholic Demonstrations, Leibniz displays his underlying dissatisfaction with the mechanical philosophy. He explains that although the causes [rationes] of the ancients had referred either “to the Creator or some kind (I know not what) of incorporeal forms,” the mechanists had discovered that “the causes [rationes] of most things can be given in terms of the figure and motion of bodies, as it were mechanically” (A VI i, 489). Leibniz accepts this explanation of corporeal features. The disagreement that he has with the mechanists is in the inference they draw from this explanation. Before adequately considering the metaphysical foundations of their mechanical explanations, these philosophers proclaimed that natural reason offered no evidence of anything incorporeal (either of God or the soul) so that one had to find evidence for the incorporeal elsewhere. But, Leibniz asks: “what if I should demonstrate that the origin of these very primary qualities themselves cannot be found in the nature of body? Then, indeed, I hope that these naturalists will admit

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that body is not self-sufficient and cannot subsist without an incorporeal principle” (A VI i, 490).30 Of course, Leibniz is confused about what the mechanists’ position actually is. Although they do think that all corporeal features are explicable in terms of the fundamental features of body (they differ about what these are) without recourse to anything incorporeal, they do not believe that the fundamental features are themselves derivable wholly from the nature of body [res extensa] taken by itself.31 Leibniz’s mistaken interpretation of the mechanists rests on one of his most fundamental assumptions. Because the mechanists designate magnitude, figure, and motion as the fundamental features of body and because they take body to be extended stuff, Leibniz assumes that they must also believe that the cause and explanation of these features lie in the nature of body. He finds it unfathomable that someone would assign to an object fundamental features that themselves do not follow from the nature of the object. According to Leibniz, if the “origin of these very primary qualities themselves cannot be found in the nature of body,” then “body is not self-sufficient” (A VI i, 490). The underlying assumption here is that bodies are supposed to be self-sufficient entities that offer the cause and explanation of their features. In a related essay of the Catholic Demonstrations, Leibniz explains exactly how bodies come to be self-sufficient. In On Transubstantiation, which was written almost certainly after the September 26/October 6, 1668 letter, he writes: 1. Substance is a being that subsists per se. 2. Being that subsists per se is one that has a principle of action in se [ . . . ]. 3. Whatever has a principle of action within itself, if it is a body, has a principle of motion within itself [ . . . ]. 4. No Body apart from a concurrent mind has a principle of action in se. This has been demonstrated in Part I of the Catholic Demonstrations [that is, the Confession of Nature against the Atheists], where the existence of God is proved. 5. Therefore no body taken apart from the concurring mind is a Substance. (A VI i, 508–9)

Here the assumption is that to be substantial is to be self-sufficient, and, moreover, to be self-sufficient is to have a principle of activity. That substance is essentially what acts and, hence, is what has its own principle of activity is a view from which Leibniz never wavers. By such means On Transubstantiation goes beyond what was said in the Confession of Nature and explains exactly why corporeal nature needs an incorporeal principle: bodies cannot “subsist without an incorporeal principle” because it is

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from the latter that they attain a principle of activity that makes them properly self-sufficient. In other words, they need an incorporeal principle exactly because they need a principle of activity, and they need a principle of activity in order to cause, along with res extensa, their primary features. Without a source of activity to arrange the matter or extended stuff in some way, bodies would have no such features (A VI i, 511). It is striking that Leibniz presents neither explanation nor argumentation for his assumptions. They derive from the young man’s interpretation of the philosophy of Aristotle. As Leibniz understood the ancient’s thought, substance is both ontologically and explanatorily basic. It is the primary created thing, that on which all other created things depend and in terms of which everything else is explained. Despite the various conflicting interpretations and accounts of Aristotle’s metaphysics, Aristotelians generally did think of substance as that which causes and explains its essential features and, in this sense, as what is self-sufficient. Given the criticisms offered by Thomasius in his letter of October 2/12, it is not surprising that the young man insists on the self-sufficiency of substance in On Transubstantiation. That is, it seems likely that this shift in focus between the Confession of Nature against the Atheists and On Transubstantiation was motivated by Leibniz’s attempt to address Thomasius’s worries. With this said, it will be helpful to return to Leibniz’s letter of September 26/October 6, 1668. According to Leibniz, prior to all motion, what we think of as body is merely inert stuff everywhere the same, without division or distinction. This inert mass is what the Aristotelians call “prime matter” (point (1)). God acts on it through motion, so that combinations of matter in motion arise (point (2)). “The figura [,] arising from such a combination of motions, comprises this orderly arrangement of parts [figura a complexione motuum orta, ipsam partium dispositionem complectitur]” (A II i, 10). That is, the inert matter, once moved, becomes arrangements of parts of matter or figurae (point (3)). Because God is (in a sense yet to be explained) the principle of action and because there is a figura only if there is motion, it is clear that matter is first individuated and then maintained as a figura through the active principle in God. But even though God maintains the figura, the figura still has its own nature: It is the totality and arrangement of its parts. This implies, first, that figura is distinct from matter (point (5a)): It is, after all, an organized arrangement of matter. But it also implies that figura is the nature of body and can be said to be prior to everything else concerning body (point (5b)). Because all the features of bodies (e.g., squareness, heat) are reducible to and

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explained by the arrangement of their parts, it follows that the figura is that in terms of which we explain all the features of bodies (point (5c)). By insisting on the self-sufficiency of substance in his theological essays, Leibniz offers a response both to the historical and to the philosophical criticisms leveled against him by Thomasius in the letter of October 1668. Considering the historical criticism, namely, that Leibniz’s reinterpretation of substantial form was based on a misunderstanding of Aristotle, we can now see that Leibniz’s reformation of the Aristotelian notion is not quite as inept as it first seemed. According to Leibniz, God acts as the incorporeal principle in nature: this active principle combines with purely passive matter and, thereby, creates with it an organized corporeal nature. From this perspective, it does not seem so far-fetched to call figura “substantial form.” Even though God acts as its principle of activity, the figura does constitute the innermost nature of body (point (5)) and the source of its affections (point (4)). In other words, although the figura does not have the causal priority and self-sufficiency that Aristotle requires of substantial form, it has some of the other characteristics that Aristotle attributes to this fundamental principle. For example, figura so understood constitutes the nature of bodies and the source of its features. In this case, body has its own essence: it is essentially this organized arrangement of parts, this matter in motion. Nor is Leibniz’s rendition of the cosmological argument quite as bad as it seemed originally. Whether his position has developed in response to Thomasius’s criticism or was inadequately explained in the September 26/October 6, 1668 letter, by insisting on the self-sufficiency and activity of substance in On Transubstantiation, Leibniz offers a response to the criticism leveled against him. According to Thomasius, when Leibniz removes the cause of the motion of a body from inside the body to something outside it, he, thereby, opened himself up to a regress problem. But Leibniz’s more developed position contains a response to this criticism: Once we understand that God is supposed to act as the principle of activity which, along with matter, creates the substantial nature of a body, there will be no regress of causes.32 Moreover, Leibniz’s position in On Transubstantiation includes a response to Thomasius’s worry about the absence of a human substance in the figura of a person. In the essay, the young man distinguishes between human substances and all other sorts in that the former have their own mind. “Substance is union with mind,” explains Leibniz. “Thus the substance of a human body is union with the human mind; and the substance of bodies which lack reason is union with the universal mind, or God” (A VI i, 508/ L 116). There can

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be little doubt that Leibniz’s position is becoming more subtle at least partly in response to the criticisms of his master.

3. leibniz’s letter of april 1669 (a II i, n. 11) In the epistolary exchange with Thomasius, the letter of April 1669 is by far the most interesting.33 Its argument is long, obscure, and important. For our purposes here, a very brief summary will have to suffice. Three features of the letter are particularly relevant. The first is personal. It begins with grand claims about Thomasius’s erudition and insight, makes congratulatory comments about a recent publication, and suggests that it is the duty of Thomasius to forge philosophical peace. The most extraordinary thing about this part of the letter is that the young man attributes to the elder some of his own insights about how to effect such intellectual peace.34 On the one hand, this is slightly odd: Leibniz seems committed to taking Thomasius with him on his philosophical journey. On the other hand, the young man’s attitude is exceedingly generous: he appears to want to credit his former master with some of his own insights. He writes, for example: “it will be play for you, but fruitful for the public” to warn “our unseasoned youth” of the dangers of the new philosophy and the benefits of the old (A II i, 14–15). Although Thomasius does not do this in any systematic fashion in any of his publications, Leibniz performs this twofold task in the remainder of this letter. The second important feature of the letter is methodological. Leibniz makes it perfectly clear that he is a conciliatory eclectic who intends to forge a philosophy of peace out of Aristotelian metaphysics and mechanical physics. In the process of making this point, he offers a fascinating glimpse of the contemporary philosophical and methodological terrain and indicates where on the proposed map he stands. He insists “that it is wrong to give our renovators [novatores] credit either for everything or for nothing.” The best way to correct the wrongs of the new philosophers is to follow in the footsteps of his master and turn to the history of philosophy so as to grasp “profound reasons for the interconnections among doctrines” (A II i, 14/L 93). Concerning his own place on the contemporary philosophical map, Leibniz reveals precisely where he stands. Although he is “anything but a Cartesian,” he does “maintain the rule that is common to all these innovators [restauratores] of philosophy, [namely that] nothing ought to be explained in bodies except through magnitude, figure, and motion.” However, he approves “of more things in Aristotle’s books on physics

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than in the meditations of Descartes; so far am I from being a Cartesian” (ibid.). Leibniz makes it clear that he is not interested in the metaphysical underpinnings that the mechanists offer for their philosophy (and the various debates surrounding them) but only in mechanical explanations of corporeal features. Moreover, he is an enthusiastic reformer and believes that Aristotle’s physics can be permitted without violating the reformed philosophy. He goes on to explain a bit more about his attitude toward the philosophy of Aristotle: “For the most part, Aristotle’s reasoning about matter, form, privation, nature, place, infinity, time and motion is certain and demonstrated [ . . . ]. Who would disagree, for instance, with his theory of substantial form as that by which the substance of one body differs from that of another? Nothing is truer than his view of primary matter.” He continues: “The one question is whether Aristotle’s abstract theories of matter, form, and change should be explained by magnitude, figure, and motion. This is what the scholastics deny and the reformers [reformatores] affirm. The latter opinion seems to me to be not only the truer but also the more in agreement with Aristotle” (A II i, 15/L 94). Besides the recentiores (all of whom accept the stated rule), there is a group of reformatores who propose to explain Aristotle’s most basic physical principles in terms consistent with mechanism. Those principles, as interpreted by the scholastics, cannot be so explained. The pressing question is, therefore, whether the scholastics or the reformers are correct in their interpretation of Aristotle’s physical principles. Leibniz thinks that a reformed philosophy can be constructed that would fully “explain” the relevant principles and that such a philosophy would be more in agreement with Aristotle than are the opinions of the scholastics. Leibniz also suggests that were this reformed philosophy to explain successfully Aristotle’s abstract theories of matter, form, and change in terms of magnitude, figure, and motion, then most philosophers would accept the resulting Aristotelian views about (say) prime matter. After all, these views would be a synthesis of Aristotelian and mechanical principles and would appeal to the modern philosophers and to the Aristotelians, or so Leibniz seems to believe. Having clarified his general methodological strategy, Leibniz spends the remainder of the April 1669 letter arguing for his own version of the reformed philosophy. He introduces the conclusion for which he will argue by asserting that, as a variety of philosophers have noted, the scholastics perverted Aristotle’s meaning in metaphysics, logic, and law. Leibniz proposes to demonstrate that the schoolmen did this in physics as well. In other words, he will argue that the reformers and not the

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scholastics are correct about Aristotle’s physics. This, he says, can be done in two ways: It can be shown either that the Reformed Philosophy can be reconciled with Aristotle’s and does not conflict with it or in addition, that the one not only can but must be explained through the other, nay, that the very views which the moderns [recentiores] are putting forth so pompously flow [ fluere] from Aristotelian principles. By the former way, the possibility of the reconciliation is confirmed, by the latter, the necessity. But if the reconciliation is shown to be possible, it is by that fact accomplished. Even if the explanation [explicatio] of both Scholastics and moderns [recentiores] were possible, the clearer and more intelligible of two possible hypotheses must always be chosen, and without any doubt this is the hypothesis of the moderns, which conceives no incorporeal entities within bodies but assumes nothing beyond magnitude, figure, and motion. (A II i, 16/L 95)

Leibniz presents here, in his typically terse fashion, the assumptions and structure of his argument. The two crucial issues are, first, whether the scholastics or the reformers interpret Aristotle’s physics more properly and, second, whether the physical explanations offered by the scholastics or those offered by the reformers can be shown to be true. Making a frontal assault on Thomasius’s criticism of his earlier proposals (in the October 1668 letter), Leibniz asserts that the scholastics posit the existence of “a kind of immaterial being” which is “insensible” within bodies, namely, substantial form, in terms of which corporeal features are to be explained. But, cautions Leibniz, “Aristotle seems nowhere to have imagined any substantial forms” of this kind (A II i, 20/L 99). Because the reformers have properly understood the thought of Aristotle, they deny both the existence and intelligibility of any sort of immaterial form and maintain instead that all corporeal features are to be explained in terms of matter in motion. According to Leibniz, then, the reformers do not want to explain the features of (say) fire as the traditional scholastics had done, namely, in terms of some immaterial form in the fire. Rather, they agree with the mechanists that the heat in fire can be fully and intelligibly explained by simple reference to the movement of the matter that makes up the fire; there is no need to posit any other entity. It is important to understand that the context here is one of physical explanations and that, according to Leibniz, the reformers and the moderns offer one explanatory model whereas the scholastics offer another. Within this context, Leibniz wants to convince us (1) that the position of the reformers is consistent with the thought of Aristotle and, therefore, that the scholastics’ interpretation of Aristotle’s physics is incorrect; (2) that the reformers’ position in fact follows from the fundamental principles

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of Aristotle’s philosophy, once that philosophy is properly understood; and (3) that even if the physical explanations of corporeal phenomena offered by both the scholastics and reformers were “possible,” the former would have to be rejected because of its lesser intelligibility and because (as he goes on to say) of the “manifest truth” of the reformed philosophy. A final point to note about Leibniz’s strategy here is that although the discussion is presently focused on physical explanations, it is ultimately about the metaphysical foundations of physics. Leibniz asserts that “the views of the moderns” about physics “flow from Aristotelian principles,” that is, from the basic constituents of Aristotelian metaphysics. Having stated the conclusion for which he will argue and outlined his argumentative strategy, Leibniz turns his attention to the proof that the reformers and not the scholastics are correct about Aristotle’s physics. He writes: “I cannot better show this [ . . . ] than by asking for any principle of Aristotle which cannot be explained by magnitude, figure, and motion” (A VI ii, 435–6/L 95). He then proceeds to treat Aristotle’s principles of matter, form, and change in turn. In each case, he takes one of these fundamental principles and transforms Aristotle’s original notion into a mechanistic one.35 Not surprisingly, the crux of this reformation is his account of substantial form. Returning to the position of his September 26/ October 6, 1668 letter, he explains that the substantial form of a body is its figura, which is an “organized arrangement of parts” of matter produced by motion. He happily concludes that “there is obviously almost nothing in Aristotle’s physics which cannot be readily explained and made clear through the reformed philosophy” (A II i, 18/L 97). Thus far, Leibniz points out, he has only shown that “these positions can be reconciled; it still remains to show that they ought to be.” But Leibniz’s present task is not a very difficult one. The first part of his demonstration virtually accomplishes it: Because Leibniz has mechanized Aristotle’s basic principles of matter, form, and change and because Aristotle’s fundamental principles are the origins or sources of everything else in nature, the position shared by the reformers and moderns (namely, that all corporeal phenomena can be explained by matter in motion) will follow from those principles. Leibniz explains: For what does Aristotle discuss, in the eight books of the Physics, besides figure, magnitude, motion, place, and time? If the nature of body in general can be explained in terms of these, a particular body must be explained in terms of a particular figure, a particular magnitude, etc. In fact, he himself says in the Physics, Book iii, Section 24, that all natural science concerns magnitude (with

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which figure is, of course, associated), motion, and time [ . . . ]. Everything in nature must therefore be explained through these (A II i, 19/L 98).

By so neatly mechanizing the Aristotelian principles, he has shown that the physical explanations proposed by both the moderns and the reformers really do follow from Aristotelian principles. He concludes: “the Aristotelian Philosophy has been reconciled to the Reformed Philosophy” (A II i, 21/L 100).36 Leibniz is not yet satisfied. He now turns his attention to the final part of his demonstration and attempts to show “the manifest truth of the Reformed philosophy itself.” He maintains that nothing is needed to explain the phenomena of the world besides magnitude, figure, and motion. As a response to Thomasius, this is a very clever strategy because he had learned his respect for nominalism from the master himself.37 The young man now proposes to the elder philosopher: “there are no entities in the world except mind, space, matter, and motion and therefore that the hypotheses of those recent thinkers [recentiores], who use only these to explain phenomena, are the better ones. For it is a defect in hypotheses to assume what is unnecessary. For truly all things in the whole world can be explained by these things alone.” By such means, Leibniz has shown not only that the reformers interpret Aristotle’s physics more properly than do the “uncultured” scholastics, but also that they accept the insights of the nominalists. The materials are in place to formulate the “truth per se” (A II ii, 21–2 /L 100). In the remainder of his letter to Thomasius, Leibniz presents a theory of substance that is supposed to constitute the foundations of the proper reformed philosophy.38 The conception of substance presented in the April 1669 letter to Thomasius includes an account of prime matter, substantial form, and their relation. There is insufficient space for details here, but suffice it to say that Leibniz offers a slightly more complete account of the position outlined in his letter of September 26/October 6, 1668.39 Given our concerns, perhaps the most striking aspect of Leibniz’s account is that the young man ignores the warnings of his master and insists throughout that he is following the teachings of Aristotle. He writes, for example: “Aristotle seems nowhere to have imagined any substantial forms which would themselves be the cause of motion in bodies [ . . . ]. Therefore, it is not absurd that of the substantial forms only [divine] mind should be designated as the first principle of motion” (A II i, 20/L 99). Nor is Leibniz’s claim here entirely outlandish. He constructs an account of corporeal substance that is appropriately self-sufficient and

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properly Aristotelian by demoting res extensa to a mere constituent of substance and by distinguishing between a primary form and the form or figura in an individual substance. For Leibniz, prime matter is extended stuff that functions as the potential principle and, thereby, plays exactly the same role as Aristotle’s matter: It is that “from which all things are made” (A VI ii, 435/L 96). Although res extensa is not a substance by itself, Leibniz has neatly made it the passive element in substance: when res extensa is joined with the primary form that functions as its principle of activity, it becomes a constituent of a self-sufficient corporeal substance. Like the Aristotelian notion, Leibniz’s matter is indeterminate and must be made into an individual thing by its substantial form. As Leibniz writes: “For [divine] mind supplies motion to matter [ . . . ]. Matter is devoid of motion per se. Mind is the principle of all motion, as Aristotle rightly saw” (A II i, 20/L 99). It is significant that the individual substance here is composed of indeterminate matter and a determining form (namely, God) and that, once this “organized arrangement of parts” of matter (A II i, 17/L 96) or “secondary form” is created, it is itself a principle of motion. God may cause (and sustain) the organization of the parts of the substance, but once those parts are so organized, the secondary form is able to act as a cause of motion both in itself and in another body. If we understand this secondary form to be the arrangement or organization of primary matter, then it has some of the features of the Aristotelian notion: It constitutes the nature of the substance and the cause and explanation of its essential features. Although it remains perfectly clear that much of what Leibniz says about matter and (secondary) form in this letter is inconsistent with anything the ancient accepted, these unAristotelian elements fit neatly within a theory of substance that has the structure of Aristotle’s. For example, although God is the principle and cause of individuation and matter has a well-defined nature, the fact that they combine as active and passive elements to form a union that constitutes the cause and explanation for substantial properties is recognizably Aristotelian. With admirable finesse, Leibniz has situated a version of mechanical physics on an Aristotelian foundation.

4. the later correspondence between leibniz and thomasius, 1669–72 Between May 1669 and January 1672, ten letters passed between Thomasius and Leibniz. Given our concerns here, only two of these deserve sustained comment.

The Correspondence with Jakob Thomasius

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Thomasius’s Letter of May 1669 (A II i, N. 12) It is not surprising, perhaps, that Thomasius was rendered virtually speechless by Leibniz’s letter of April 1669. He had informed his former student only a few months previously that he was prepared to take seriously neither the young man’s reformulation of fundamental parts of Aristotelian metaphysics nor the mechanical physics that the reformulation was supposed to accommodate. In reaction to Thomasius’s considered opinion, Leibniz composed an extended response that began with grand pronouncements of his former master’s erudition and insight and ended with a lengthy argument for a position only slightly more subtle than the one that the elder philosopher had recently rejected. In his response to Leibniz’s very long letter, Thomasius seems both flattered and perplexed. On the one hand, he is “charmed” by the letter and even moved by its argument to reconsider his views: “For although the things that you discussed as I read them did not wholly drive out my earlier impression, they nevertheless seemed to cause it to totter and to prepare me substantially either for discarding my opinion or perhaps for uniting it with yours in some way.” On the other, the elder professor is inclined “to stay respectfully silent.” He explains that he does not have the requisite skills in “the mathematical sciences” to argue with the gifted young man, nor does he have the time to rise to “the same level” as Leibniz occupies in these matters. That is, he possesses neither the expertise necessary to respond adequately nor the free time to acquire the requisite knowledge. With what appears to be genuine kindness, he acknowledges that unlike his young friend who is prepared to “go into battle” for the sake of these matters, he is immersed in intellectual tasks that leave him neither the time nor the energy to take up the challenge. With striking honesty, Thomasius writes: “you are more fortunate than I [ . . . ] for your most flourishing period of life [vernantissima aetas]” comes at a time when such a “battle” can be fought “to the finish.” Having come of age in the difficult aftermath of the Thirty Years War, Thomasius admits: “on the other hand, all my youth was spent in those remnants of the savage age out of which I was able to rise up little by little, in whatever manner, to whatever kind of success of cultured knowledge.” Given his limited knowledge and the limitations of his time, the elder philosopher proposes that they “strike a bargain”: if he can find some “quiet time for thinking,” then he will respond to Leibniz (A II i, 25). Otherwise, the suggestion is, Leibniz should not again waste his energy, however abundant it may be.40

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Letters of Congratulation: September 1669–December 1672 (A II i, Ns. 13; 14; 17; 29; 30; 35; 37; 50; and 100) Leibniz never again attempts to engage his former master on the topic of the reformation of the Aristotelian philosophy. In September 1669, Leibniz writes to Thomasius announcing the preparation of the edition of the text by Mario Nizolio. He describes some of the goals of the undertaking and asks for Thomasius’s advice. In his reply of December, which is the ninth letter of their correspondence, Thomasius proclaims that he “loves” the project and offers some words of wisdom (e.g., he defends the scholastics in their use of technical language). He is particularly pleased that one of the main goals of the project is to discuss “the true method [ratio] of philosophizing” (A II i, 27). In the letters that exchange hands between April 1670 and January 1672, other congratulatory comments were made. In his letter of October 11/21, 1670, Thomasius praises Leibniz for the success of his edition of Nizolio’s book (A II i, 67). In his letter of December 1670, Leibniz applauds Thomasius’s new book on physics, namely, Physica, Perpetuo dialogo (1670).41 In the letter of January 1671, Thomasius acknowledges the good reception of the young man’s Schediasma, that is, the two-part work in physics published in 1671 and entitled New Physical Hypothesis and Theory of Abstract Motion (A II i, 75). Both the master and his illustrious former student seem to be committed to maintain a friendly communication, despite the very obvious divergence of philosophical paths. Thomasius incites difficulties, however, when in his letter of 11/21 October 1670, he claims that he will be “thankful” and not “displeased” if “you will demonstrate to me my errors,” that is, the errors in Thomasius’s new Physica, Perpetuo dialogo (A II i, 67).

Leibniz’s Letter of December 1670 (A II i, N. 35) Leibniz’s first response to Thomasius’s Physica is important. Although in their epistolary exchange thus far, the ancient philosopher most cited is Aristotle, Leibniz feels that it is appropriate here to bring in Plato. As noted in section 1, Thomasius himself was thoroughly acquainted with the history of Platonism. I have argued elsewhere that Thomasius bequeathed to his student a similar erudition and that Leibniz’s conception of God and the relation between God and the world develops out of this tradition. I also have argued that it was in late 1670 and early 1671 that Leibniz begins to develop his theory of preestablished harmony that

The Correspondence with Jakob Thomasius

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has its roots in this Platonism and that rejects the reality of passive matter. As I have shown, in an attempt to make created substances entirely self-sufficient, Leibniz gave each non-human substance its own mind or principle of activity. “For truly the instrument of God is Mind, unified with God by which means God acts on bodies other than by creating.” Moreover, explains Leibniz, individual minds act “constantly by a special reason [ratio]” (A VI i, 533–4). Given the present analysis of the correspondence with Thomasius, it seems likely that Leibniz was motivated to develop his theory of preestablished harmony at least partly in response to the criticisms leveled by his master.42 It is significant, therefore, that in the final days of 1670, Leibniz wrote a letter to Thomasius in which he discusses the philosophy of Plato, the nature of mind, and the importance of final causes. In the letter, the young man compares his illustrious teacher to Plato and displays some of his own most basic beliefs about the place of mind in nature. Leibniz proclaims that Thomasius and Plato share a goal and method. In the same grand way that Plato helped his contemporaries escape “from the shadows” of materialism by introducing them to final causes, so Thomasius has encouraged his contemporaries to avoid the dangers of that false philosophy by reminding them of the importance of such causes in physics. As Leibniz sees it, Plato had the courage to reject the views of his materialist predecessors and to turn instead to the “truly rational causes [rationes] of things, that is, the ends.” Where Democritus and some of his contemporaries mistakenly made matter the cause [ratio] of things, Plato correctly saw that there were “two principles, mind and matter.” Similarly, because Leibniz’s contemporaries rely too heavily on geometry “which lacks any reference to a final cause” and because in general “the cause [ratio] of the recent physics [ . . . ] [is] the material causes of things,” Thomasius struggles to return philosophy to its proper objects (A II i, 73). Leibniz encourages his teacher to follow Plato’s lead and prove the usefulness of mind to philosophy in general and to physics in particular. There is little doubt that Leibniz is sincere in his approbation of Thomasius. The master had bequeathed to his student a conception of the created world as an elaborately interconnected and divinely harmonized whole, in which the supreme being is immanent.43 Consistent with this idea, Leibniz writes in the December letter that God arranges things from the beginning and thereby “emanates in his work so arranged.” In his letter to Leibniz of October 1668, Thomasius had himself compared Plato’s account of “the ideas of things” with Aristotle’s view of substantial

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form (A II i, 13). But when Leibniz insists that philosophers must reclaim minds and final causes, he is prepared to exceed the pronouncements of his teacher in significant ways. I have argued elsewhere that, by December 1670, Leibniz is willing to reduce everything to the activity of mind-like substances whose behavior has been harmoniously arranged (see Mercer 2001: chs. 8–9). As he explains to Thomasius, the thinking of individual or “secondary” minds “comes from the first mind, i.e., from God” who “on account of his wisdom, has arranged things from the beginning” so that “all things follow as if by a certain necessity toward the greatest harmony of all things.” Leibniz explains that because of his discovery about the relation between primary and secondary minds, “I came to think of motion as the unique universal [ . . . ] cause [ . . . ] of all the phenomena in whose appearances we perceive many and marvelous things” (A II i, 73–4). Leibniz’s letter of December 1670 is neither as long nor as complicated as the one of April 1669, but it must have surprised Thomasius almost as much. Like the earlier letter, it begins with grand proclamations about Thomasius’s erudition and insight, makes congratulatory comments about a new publication, and then goes well beyond anything claimed explicitly by the author of the Physica. Moreover, Leibniz’s views themselves have evolved since the earlier presentation, at least partly in response to Thomasius’s comments. It is perhaps not surprising – though it is a disappointment – that Thomasius does not engage with Leibniz’s proposals. What he does, however, is to wonder aloud in his response of January 1671 as to whether or not the aether in his Physica has something in common with the aether assumed in Leibniz’s Schediasma (A II i, 75). In May 1671, Leibniz responds eagerly to this question about the possible similarity between their notions. In this, the thirteenth letter of their correspondence, Leibniz writes: “To me, my [account of] aether seems to differ neither from the Aristotelian one, nor greatly from your own” (A II i, 96). As he goes on to explain, the hypotheses of his Schediasma are consistent with those of Copernicus and Tycho and are wonderfully able to offer the cause [ratio] of the miracles of nature” (ibid.). Although Thomasius was probably amused at Leibniz’s attempt to be the great conciliator, the young man may have tried his master’s patience when he went on to announce: “to such a degree that you now consider” things from the largest perspective, is it not true that “it is possible to save all the phenomena of bodies by means of only magnitude, figure and motion, without the other qualities?” (ibid.).

The Correspondence with Jakob Thomasius

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Thomasius did not respond, and Leibniz wrote the final letter of their correspondence in January 1672, just before his departure for Paris. In the letter, the young man explains to his former master that he will soon travel to Paris for an extended stay. Thomasius would live another twelve years, would continue to publish well-received books, and would oversee a wide array of dissertations. Leibniz would continue to speak well of Thomasius and refer to his many books,44 but they would never engage directly again.

5. conclusion: leibniz, thomasius, and their innovative conservatism The correspondence between Leibniz and Thomasius was neither longlived nor argumentatively intense. But when situated in its proper historical context, it reveals a good deal about the sources and goals of Leibniz’s philosophical project, and it offers important insight into a curious tension at the heart of Leibniz’s philosophical personality. Like his master, the student valued erudition and engaged in thoughtful reconstruction of ancient philosophies. Like the older philosopher, the young man intended to forge a synthesis of the major philosophical schools while remaining consistent with Lutheran doctrine. But contrary to Thomasius, Leibniz was prepared to embrace the new physics in an attempt to construct the true philosophy. Partly as a result, the young man’s synthesis – unlike that of his master – is one of the most innovative philosophies in the history of philosophy. What the correspondence with Thomasius reveals is that Leibniz’s striking innovation was the result of a methodology of reconciliation. One of the overlooked aspects of Leibniz’s brilliance is his success in building such an original and sublime philosophical edifice out of recycled materials. But the correspondence with Thomasius also reveals the generosity and intellectual honesty at the core of Leibniz’s personality. I have argued elsewhere that Leibniz practices a “rhetoric of attraction,” according to which he attempts to engage the sectarian reader by using agreeable philosophical terminology and by extolling the virtues of the reader’s sect while attracting attention to the benefits of other philosophical schools. Ultimately, the goal of this rhetoric is to entice the reader to consider certain underlying assumptions, which Leibniz considers to be true and which he thinks will eventually lead the reader to philosophical enlightenment and intellectual peace (see Mercer 2001: ch. 1).45 In the correspondence with Thomasius, we witness the original use of this rhetoric of

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attraction as well as the underlying generosity that (partly) motivates it. That Leibniz wanted to include Thomasius in his philosophical journey is clear. Once Leibniz hit on “the truth” of the new philosophy, he was eager to persuade Thomasius of its value, and he attempted to do so in terms that would appeal to his elder. Although, ultimately, Leibniz failed to enlist Thomasius, his struggle to engage him on his own terms tells us a great deal about Leibniz’s underlying concerns. He intended to construct a true philosophy out of the materials of the past, and he hoped to convince everyone of its rightness. His loyalty to Thomasius is touching, as is his charmingly na¨ıve desire to carry his master along in the wake of his own intellectual achievements. Leibniz’s patience and magnanimity toward his former teacher reveal a genuine kindness that is more difficult to glimpse in the heady activities of his later life. In the end, we are left thinking that Leibniz was a decent person, who cared deeply for his master but even more deeply for the truth. Notes 1. It is odd that there has been so little written on Thomasius. Besides the fact that he trained Leibniz and was the father of Christian Thomasius, Guhrauer (the first great biographer of Leibniz) claimed that Thomasius had begun “the scientific study of the history of philosophy in Germany” (1842: 27–8) – see also Leinsle 1988: passim and Mercer 2001: passim. By far the most important work done on Thomasius is that of Bod´eu¨ s 1993, whose work on the correspondence between Leibniz and Thomasius is very helpful. 2. In earlier works, such as Dissertation on the Combinatorial Art Leibniz had discussed metaphysical topics and offered some suggestions about the proper elements of metaphysics (see A VI i, 170ff), but the published letter to Thomasius constitutes his first attempt to offer a fully articulated and original theory of substance. 3. The letters by Leibniz are A II i, Ns.1; 3; 8; 9; 11; 13; 17; 29; 35; 50; and 100. Those by Thomasius are Ns. 10; 12; 14; 30; and 35. 4. It is noteworthy that Leibniz managed to publish so much in these early years and published so little in the remaining decades. 5. Bertrand Russell famously reconciled these by attributing to Leibniz an underlying dishonesty (1937, vi). 6. For standard responses to Leibniz’s decision, see Kabitz 1909: 50–1, and Brown, S. 1984: 30. The latter has maintained that Aristotelianism and mechanism confronted Leibniz “as stark alternatives.” 7. Concerning Hobbes’s influence, see Bernstein 1980 and Beeley 1996a: passim. For the influence of Gassendi, see Kabitz 1909: 50–1; Moll 1978–96: passim; Brown S. 1984: 31; and Hannequin 1908: ch. 1. For recent discussion of the influence of Bisterfeld, see Antognazza 1999 and 2001. Each of these commentators has presented a plausible story for the primary influence of

The Correspondence with Jakob Thomasius

8. 9. 10. 11.

12.

13.

14.

15. 16. 17.

18.

19.

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one of these authors. Before we can properly evaluate the contribution of any single philosopher on the development of Leibniz’s thought, we need to understand his underlying concern to borrow ideas strewn throughout the history of philosophy and to turn those ideas into a conciliatory synthesis. For citation to other literature, see Mercer 2001: passim. See especially Moll 1978–96: vols. 1–2; Loemker 1973; Hochstetter 1966; Belaval 1962: ch. 2; and Foucher de Careil 1905: ch. 1. See, e.g., Beeley 1996; Antoganazza 1999 and 2001; Goldenbaum 1999; Bod´eu¨ s 1993; D¨oring 1996; and Busche 1997. For a recent collection of essays on humanism and for citations to previous literature, see Kraye 1996. I use the somewhat vague designation “conciliatory eclecticism” to refer to any eclecticism that attempts to combine the views of some group of apparently incompatible philosophies into a coherent system. It is not terminology used by Renaissance and early modern thinkers and so it is free of complicating connotations. My discussion is based primarily on Thomasius’s Origines historicae philosophiae & ecclesiasticae (1699); Exercitatio de Stoica mundi exustione (1676); and Dissertationes LXIII & varii argumenti magnam partem ad historiam & ecclesiasticam pertinentes (1693). For a more thorough discussion of these and other texts, see Mercer 2001: passim. The full title of the work is Exercitatio de Stoica mundi exustione: cui accesserunt argumenti varii, sed inprimis ad historiam Stoicae philosopohiae facientes, dissertationes XXI. As many humanists had done before him, he argued that the bad translations of Averroes and the misinterpretations of the scholastics had made the excavation of the real Aristotelian philosophy especially difficult. Preface pages are not numbered in the original. It is important to be clear about the fact that some of the thinkers whom Leibniz called reformers and whom I discuss here did not use the term itself. Nor was Leibniz unusual in his reaction to the Clavis – see, e.g., the contemporary of Leibniz, Johann Christoph Sturm, who considers De Raey to be “most learned” and the doctrines of his Clavis “most acute” (1686: 75–6). This passage is found among the notes that Foucher de Careil collected, published, and subsequently lost. According to Foucher de Careil, the passage cited here was written during the 1660s. The remainder of this passage is interesting: Leibniz compares the ancients to the moderns about whom he felt “disgust” and says that what he learned from the ancients, as opposed to the moderns, was “always to seek for clearness in words” (GP VII, 52). The picture he paints is rather different from those found in the later accounts of his development or even in the letter to Arnauld of 1671 (A II i, 169–81). The lesson here is important: We should not take any one of the various (and often inconsistent) accounts he gives of his philosophical development too seriously. When describing his intellectual history, as he does in the letters to Remond and in the New System of 1695, Leibniz often paints in broad strokes. The point of these stories is not so much to present the actual steps in his intellectual autobiography as

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21.

22. 23. 24.

25.

26.

27.

28.

29.

30.

Christia Mercer to give his reasons for accepting some philosophical doctrines and rejecting others. It is a mistake then to base one’s history of Leibniz’s philosophical development entirely on such accounts, as many commentators have done. In the mid-seventeenth century, there were other German philosophers who attempted to combine the new mechanical philosophy with the thought of Aristotle – see especially Johannes Clauberg, Disputationes Physicae (1664) and Johann C. Sturm, Philosophia Eclectica (1686). For a brief discussion of Clauberg and Sturm and for citation to other literature, see Mercer 2001: passim. For Weigel’s views, see especially his Analysis Aristotelica ex Euclide Restituta (1658). The degree to which he influenced the young Leibniz’s ideas about logic has been much discussed – see Moll 1978–96; Leinsle 1988; Mercer 1999 and 2001: passim. See Thomasius 1693: passim. On Hobbes, see Dissertatio XIX. Scholars of the period have made much of this letter. For a discussion of this point and for citation to the literature, see Mercer 2001: ch. 1. Bod´eu¨ s does a wonderful job of tracking down the various references in the correspondence between Thomasius and Leibniz. For his helpful notes on this letter and on the topic of black snow, see Bod´eu¨ s 1993: 46–7. We know that Thomasius and Leibniz remained on very friendly terms and, e.g., that Thomasius congratulated Leibniz on his promotion to doctor of jurisprudence in Altdorf in 1667 – see Bod´eu¨ s 1993: 11. The third letter of their correspondence, written by Leibniz on September 19/29, 1668, describes a political issue involving Boineburg and contains nothing of any philosophical significance – see A II i, N. 8; and Bod´eus ¨ 1993: 51–2. The Latin term figura has at least two rather different senses. It can mean, on the one hand, either form, shape, or figure and, on the other, nature, kind, or species. Because Leibniz here takes the nature of a body to be an arrangement of parts of matter, figura here is most appropriately understood as arrangement or organization. That this is what Leibniz has in mind will become clear in what follows. Nevertheless, it seems appropriate to stay as close to Leibniz’s original meaning as possible and not to translate the Latin figura. For more on this point, see Mercer 2001: 91. For the sake of simplicity and clarity, I will use the neutral term feature when talking about the qualities, accidents, affections, or properties of corporeal things. Although the overriding goal of the project was to solve some of the most intractable theological problems (e.g., incarnation, resurrection, transubstantiation) in a manner acceptable to Catholics and Lutherans, Leibniz intended to solve these problems by the careful construction of the true metaphysics. For more on this, see Mercer 2001, especially ch. 2. In fact, the proposals of the mechanical philosophers differ greatly and it is difficult to summarize accurately their basic assumptions. Leibniz’s discussion here is based on an over-simplification of their views, but it is one that I will follow in presenting his argument.

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31. Although Descartes and Gassendi have very different accounts of motion with respect to God’s agency, they both assume that God is required to account for the motion of body, and, in this sense, they deny that motion comes from the nature of body itself. Descartes maintains that God “preserves motion in matter,” whereas Gassendi thinks that God infuses motion into atoms at their creation. Descartes and Gassendi are perfectly happy to let God be the cause of the motion of bodies and see no problem in the fact that the full account of motion does not rest in the nature of body. For Descartes’s views about motion, see especially Part II, §§37ff. of the Principia philosophiae (AT VIIIA 62ff./CSM I, 240ff.). Like his ancient predecessors, Democritus and Epicurus, Gassendi takes motion to be intrinsic to matter, but unlike them he thought God put motion into atoms. He writes: “It may be supposed that individual atoms received from God [ . . . ] the requisite force for moving, and for imparting motions to others [ . . . ]. All this to the degree that he foresaw what would be necessary for every purpose he had destined them for” (Gassendi 1972: 400–1). 32. It is unclear when the Confession of Nature was written in 1668. But part of that text seems like a well-crafted response to Thomasius’s criticism. Leibniz writes: “But if they say that this body is being moved by another body contiguous to it and in motion, and this again by another, and so on without end, by no more have they presented the ratio why the first and second and third and any one whatever is moved as long as they do not present the ratio as to why the following one is moved and why all the antecedent ones are moved. For the ratio of a conclusion is not fully given as long as the ratio of the argument is not given [Ratio enim conclusionis tam diu plane reddita non est, quamdiu reddita non est ratio rationis], especially because the same doubt remains in the case without end” (A VI i, 491). 33. This discussion is taken from Mercer 2001: ch. 3. For citations to the other literature written on the letter, see that source and Bod´eu¨ s 1993. 34. For a more thorough discussion of this part of the letter, see Mercer 2001: 110–14 and Bod´eu¨ s 1993: 117–21. 35. Prime matter becomes continuous mass [massa] “which fills the world while all things are at rest” and “from which all things are produced by motion and into which they are reduced through rest.” As such, the “essence of matter or the very nature [ forma] of corporeity consists in antitypy or impenetrability” (A VI ii, 435). 36. See Kabitz 1909: 59–63 and Bod´eu¨ s 1993: 117–210. 37. For more on Leibniz’s views about nominalism, see A VI ii, 428–9/L 128. 38. This part of the letter is so obscure and Leibniz’s views so difficult to make out that commentators have taken Leibniz’s conception to be a version of mechanism merely translated into Aristotelian terminology. For further discussion of this point, and citations to other literature, see Mercer 2001: ch. 3. 39. Concerning substantial form, Leibniz again maintains that God, by acting on matter through motion, creates what there is in the world. He adds: “Forms must necessarily arise from motion [ . . . ]. For, the division [of prime matter] comes from motion, the boundaries of the parts [termini partium] come from division, their figurae come from the boundaries of parts, and

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Christia Mercer forms from figurae ; therefore forms come from figurae [ . . . ]. [Thus] forms arise from the potential of matter, not by producing something new, [ . . . ]. causing boundaries through the division of parts” (A II i, 17/L 96). In 1669, Thomasius became Rector of the university, and his life must have been extremely busy – see Bod´eu¨ s 1993: 11. For more details on this and related matters in these letters, see Bod´eu¨ s 1993: passim. For more about the development of this important theory as well as Leibniz’s mental monism, see Mercer 2001: chs. 4 and 6–8. For a discussion of Thomasius’s Platonism, see Mercer 2001: ch. 5, section 8. See, e.g., A VI iv, 436 and 678. Leibniz praises Thomasius in the Theodicy and continues to do so until the very end of his long life, e.g., in the letter to Bourguet of 1714: GP III, 563 – see Bod´eu¨ s 1993: 7–29. The rhetoric of attraction contradicts a view held by Leibniz scholars from Bertrand Russell to Robert Adams, namely, that Leibniz practiced a kind of philosophical Machiavellianism. As I see it, the correspondence with Thomasius confirms the underlying honesty of Leibniz’s character.

3 A Philosophical Apprenticeship Leibniz’s Correspondence with the Secretary of the Royal Society, Henry Oldenburg Philip Beeley

Still scarred by the ravages of war and politically disunited, Germany at the time of the young Leibniz was in danger of losing touch with philosophical and scientific developments elsewhere in Europe. In a letter written in August 1670 to the diplomat Johann Christian von Boineburg (1622–72) who since his reconciliation with Johann Philipp von Sch¨onborn (1605– 73) some two and a half years earlier was once more in the service of the Elector of Mainz, Henry Oldenburg (1618?–77) expresses his concerns over what he sees as the deplorable state of philosophy in the country of his birth: Would that those who excel in litigation and in the sciences in Germany make their contributions towards the restoration and perfection of philosophy with a better will than they have shown hitherto, and would eagerly imitate in this the example of England, France, and Italy herself in turning to experiments. What we are about is no task for one nation or another singly. It is needed that the resources, labors, and zeal of all regions, princes, and philosophers be united, so that this task of comprehending nature may be pressed forward by their care and industry. (OCH VII, 107–8/108–9)

Oldenburg’s concerns were not without justification. The new, mechanistic world picture had, after all, found only few adherents, most notably Erhard Weigel (1625–99) in Jena, and the creation of a focal point of scientific activity such as the Royal Society in London or the The author would like to express his thanks to Christoph J. Scriba (Hamburg) and Martin Schneider (Munster) ¨ for their comments on earlier drafts of this chapter. He dedicates it, with warm memories of formative years spent in Berlin, to his academic teacher Hans Poser on the occasion of his 65th birthday.

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Acad´emie Royale des Sciences in Paris was still a long way off. This is, undoubtedly, the reason why the promising young doctor of laws Gottfried Wilhelm Leibniz, who, about the same time as he was appointed revision counsel to the Higher Court of Appeal in Mainz in July 1670, set out in a letter to the secretary of the then most important scientific institution in Europe his aspirations in the field of natural philosophy, was to receive the support he did. Leibniz’s division of interests between law and natural philosophy evidently had the approval of his patron Boineburg, and it was almost certainly he who mediated the initial contact to Oldenburg. In this chapter, we shall take a closer look at the nature of Leibniz’s relation to the Secretary of the Royal Society, as it emerges, in particular, from their correspondence. I will show that Oldenburg’s support was decisive in Leibniz’s gaining admittance to that institution and, over and above this, in becoming established as a young scholar whose ideas were to be taken seriously. Without Oldenburg, Leibniz’s acceptance into the circle of the leading scientists of his day would certainly not have occurred so rapidly. On the other hand, it would soon become apparent to Oldenburg that Leibniz, more than any other man in Germany, was in a position to promote scientific activity in the spirit he envisaged. Three central topics of their correspondence form the focal points of our investigation. The Hypothesis physica nova and the Theoria motus abstracti, through which Leibniz made his first appearance on the European stage, both evolved their final forms during the course of his early exchanges with Oldenburg, who subsequently played a significant role in their being made known to scholars abroad. These two tracts were published at the same time and are, indeed, complementary to one another; but each has its own history and is, therefore, dealt with in separate sections of this chapter. The third topic focused on is universal character. Although this topic is much less prominent in the letters which passed between the two men, reflecting Leibniz’s general reticence at disclosing details of a project at which he worked on and off since his eighteenth year, important details emerge which are helpful in understanding conceptual developments which took place in the 1670s. But before considering these topics in more detail, we turn, first of all, to Oldenburg himself. In doing so, it will become clear that his intellectual background not only inclined him to provide the assistance he did but also supplied him with philosophical and scientific goals similar to those of Leibniz himself.

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1. oldenburg and the comenian ideal The role which Oldenburg played within the Royal Society as one of two secretaries – the other secretary was John Wilkins (1614–72) – was very much one of his own making. Although, already, Bacon had recognized that the advancement of learning required that scientific institutions engage in the mutual exchange of information, this is not something which was enshrined in either of the Society’s two charters (Boas Hall 1975: 179). Nevertheless, the second charter did at least provide for the Society to conduct correspondence of this nature either through the president or his deputy. The reception and communication of knowledge which in many ways was an essential part of the success of the Royal Society in the seventeenth century was not explicitly intended but rather came about through Oldenburg and his influential group of friends, most notably Robert Boyle (1627–91) and William Petty (1623–87), with whom he had been associated during his time in Oxford between 1654 and 1656. A German Protestant by birth, who had pursued his education abroad, Oldenburg first visited England in 1653 as a diplomatic representative of Bremen. There, he soon became a member of the circle of Lady Ranelagh (1614–91), her brother Robert Boyle, Samuel Hartlib (c. 1600– 62), and John Dury (1596–1680) (see Webster 1975: 501 and Stimson 1939: 316–18). His participation in Hartlib’s intelligence network, his journeys across Europe, particularly as tutor to Lady Ranelagh’s son, and the support of Boyle, are decisive aspects of his early career which prepared him for the role he subsequently created for himself in the Royal Society (see Avramov 1999: 190–1). He became, in many ways, the direct heir to Hartlib, and through him to Comenius (1592–1670), who, like Bacon, attached great importance to the creation of a network of correspondents as a means to promoting scientific activity on an international level. By the time of the foundation of the Royal Society in December 1660, he had effectively taken over from Hartlib the role of being the central figure in England engaged in correspondence with continental natural philosophers (see Hill 1965: 106 and Webster 1975: 501–2). In this respect, his strong affinity for mechanistic philosophy, in general, and his keen interest in physical problems, in particular, proved to be advantageous. Like Hartlib, he saw the ultimate goal of experimental science to be one of improving the conditio humana. This becomes apparent, for example, in his letter of February 28, 1663 to the Danzig astronomer Johannes Hevelius (1611–87), who had previously conducted his correspondence with English virtuosi through Hartlib.1 When Oldenburg

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comes to set out the aims of the new Society in London he does so in terms of advancing what is publicly good and, thus, very much in keeping with the humanitarian goals established in the Comenius–Hartlib tradition: For it is now our business, having already established under royal favor this form of assembly of philosophers who cultivate the world of arts and sciences by means of observation and experiment and who advance them in order to safeguard human life and make it more pleasant, to attract to the same purposes men from all parts of the world who are famous for their learning, and to exhort those already engaged upon them to unwearied efforts. (OCH II, 25–6/27)

In a letter written to Eccard Leichner (1612–90) in Erfurt later in 1663, on October 3, politely replying to a man whose views were clearly outside the framework of the new philosophy propagated by the Royal Society, Oldenburg described, once again, precisely where the interests of the Society lay: “the Royal Society says it is not its concern to have any knowledge of scholastic or theological matters, for it is its sole business to cultivate knowledge of nature and useful arts by means of observation and experiment, and to promote them for the safeguarding and convenience of human life” (OCH II, 110/111).2 But as Oldenburg recognized, this was not a task to be restricted to one nation alone. The cultivation of knowledge made sense only as an international project, involving the cooperation of men and women on a universal level. Thus, anticipating the remarks he would later make to Boineburg, Oldenburg expresses already in his letter to Hevelius of February 1663 the aim of uniting the efforts of scientists in Europe and beyond: “We also entertain a bright hope that France, Italy, and the Netherlands, and the people of other countries will be brought together in advancing and honoring this purpose with all their might” (OCH II, 26/28). Ultimately, Oldenburg’s network of correspondents became worldwide, stretching from the Orient to the American colonies. Nevertheless, in his efforts to cultivate the new science he encouraged, in particular – and, indeed, as one might expect – contacts between the Royal Society and German scientists. Especially noteworthy here are the numerous contacts with members of the Collegium curiosorum naturae, which later became the Caesarea Leopoldino–Carolina Naturae Curiosorum Academia and now bears the name Deutsche Akademie der Naturforscher Leopoldina.3 This early German scientific society, which had been founded by a number of medical physicians in Schweinfurt in 1652, reflected the political state of Germany: There was no permanent seat, members were spread

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out over a multitude of states, and activity was confined largely to correspondence, which, however, in the absence of a pivotal figure such as Oldenburg was essentially a scientific exchange between individuals. It was, thus, a considerable advance when in 1670 through the efforts of Philipp Jakob Sachs von L¨owenheim (?–1672) a biannual journal was founded with the intention not only of publishing results of investigations by German scientists but also of like-minded men abroad. Sachs, who was also a long-standing correspondent of Oldenburg, sent him a copy of the first volume in October of that year.4

2. hypothesis physica nova It is, then, not surprising that Leibniz was given such encouragement by Oldenburg right from the outset. All the more so because his philosophical interests evidently concerned topics at the focal point of activity in the Royal Society itself. In addition, it is apparent that his first letter accompanied one from Boineburg, who had clearly already been in correspondence with the Secretary of the Royal Society for some time. As appears from Oldenburg’s reply of August 20, 1670 (OCH VIII, 107/108), Boineburg used the opportunity to inquire about recent publications by Hobbes (1588–1679). But we can be fairly sure that he would also have written some lines introducing the young philosopher to whom he was bound by friendship and who also enjoyed his patronage,5 having been brought to Mainz at his recommendation. In the absence of Boineburg’s letter itself, we gain an impression of the esteem in which he held Leibniz from what he wrote about him to Herman Conring (1606–81) earlier the same year on April 22: He is a young man of twenty-four years from Leipzig, a doctor of law, and indeed more learned than either can be said or believed. He understands well all philosophy and happily excogitates on the old and the new. He is equipped with an ability to write of the highest level. He is mathematically very inclined and well versed in physics, medicine, and mechanics. (Gruber 1745: II, 1286–7)

It would have been a logical step for Boineburg, having brought about Leibniz’s contact with one of the leading law professors in Germany, to have promoted his interests in a similar way in the field of natural philosophy. But Leibniz, nevertheless, begins his first letter to Oldenburg (July 23, 1670) apologetically, describing himself as an unknown person writing to one who is not unknown – a means of approach which he employs towards a number of other new correspondents.6 He then touches

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on a theme close to Oldenburg’s heart, the situation of the sciences in Germany, and notes, in particular, that the political disunity of the country was hindering its advance: “Remarkable experiments are not wanting among us, but such is the state of politics now, on account of the open eagerness of one and hidden envy of another, that there can be no uniting into societies, nor is it easy for so many states to be combined into one nation” (A II i, 59; OCH VII, 64/66). It is, of course, a reflection of this state of affairs that already the young Leibniz devotes much of his scarce spare time to questions of the institutional organization of science.7 Plans such as those for a German Societ¨at der Wissenschaften, in which perceived deficiencies in existing scientific institutions such as those in London and Paris are to be overcome, are clearly motivated first and foremost by the awareness that the long-term improvement of living conditions required the coordination of activity in all fields of the experimental philosophy (see Fichant 1998: 168–70 and Poser 1999: 102).8 At the same time, they can be seen effectively to respond to Oldenburg’s exhortations to his correspondents abroad to enter into scientific discourse and, indeed, to unite their efforts with those of their counterparts in the Royal Society. There was no better way to do this – not least with a view to securing the interests of the countries involved – than on an institutional level. Apart from communicating general intelligence from the scientific world, including news of publications and inventions, which Leibniz always regarded as one of the great benefits of correspondence in general, he uses his first letter to Oldenburg simply to sketch projects he was working on, in particular, that of his new physical hypothesis, which evidently at the time was still in its inception. To do more than provide a glimpse of his promise and an indication of the breadth of his interests was not necessary at this stage. In view of Oldenburg’s concern to promote the growth of knowledge, it is not surprising that in his reply of August 20, 1670 he not only returns scientific intelligence which he had gathered himself but also encourages Leibniz to complete his hypothesis as soon as possible, suggesting that the young philosopher already in advance of this provide a more substantial summary of its content. Since it was the practice of the Royal Society to have letters on pertinent topics read at meetings – and for those deemed worthy of the honor also to be copied into the Letter Books – Oldenburg no doubt had this option in mind for presenting Leibniz’s theory to that qualified forum: “You will prove yourself to be a true philosopher if you bring a project of such importance to completion, and you will perform

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an act most welcome to the Royal Society if you will take the trouble to explain the gist and foundation of that hypothesis” (A II i, 61; OCH VII, 110/112). Correctly suspecting that Leibniz was well aware of the increasing number of disputes over issues of priority which were plaguing the R´epublique des Lettres – something to which the emergence of academic journals and the institutionalization of science in general had evidently contributed9 – Oldenburg almost seeks to reassure the young philosopher that no harm to his discoveries would come about through divulging such information in advance of publication. To this end, he quotes the case of Christiaan Huygens (1629–95). The Dutch mathematician had, he notes, following the example of others, submitted to the Royal Society his then still unpublished laws of motion. Together with other contributors, who were likewise “worthy of immortality,” Huygens would be “assured undying fame” by the preservation of his results in the archives of the Royal Society, where “each is certain of his due.” This said, Oldenburg then adds the appropriately encouraging remark to Leibniz: “the same may befall your own reflections and discoveries if you will but prove yourself ready and sensible by communicating and explaining them” (A II i, 61; OCH VII, 110/112). Quoting the case of Huygens was in fact a skillful ploy. In the then recent dispute between him and Christopher Wren (1632–1723) over priority in discovering their essentially identical laws of motion, the Dutch mathematician – a fellow of the Royal Society since 1663 – had publicly voiced his anger at being disadvantaged by not having his results published in the Philosophical Transactions at the same time as those of his opposite party. This had created the impression that despite calls for cooperation on an international level, the work of scientists in England was to be decidedly favored. Oldenburg’s remarks were thus apparently intended to overcome any misgivings on the part of Leibniz at revealing too much too soon. The aspiring young philosopher did not disappoint his new correspondent. In a series of letters sent over the next seven months, Leibniz went to great pains to provide adequate summaries of the work he was completing. But he had good reason for this as well. Just as Oldenburg was keen to encourage activity in the spirit of the new science in the country of his birth both as something useful in itself and as part of general efforts to improve the human condition, Leibniz too pursued a clear strategy. He recognized the importance of having his work assessed by members of the leading scientific institution of his day first and foremost as a means

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to gaining acceptance among their number. But even this was in effect part of a broader goal which consisted not only in the improvement of his own ideas but also, just like Oldenburg, in the creation of the material means for improving human life itself – something which he described in 1671 as being the sole end of philosophizing.10 Here was a fundamental point of agreement between the two men. In view of Leibniz’s apparent aim of entering a fruitful dialogue with fellows of the Royal Society and, ultimately, of himself being accepted into that institution, it is striking that his letter to Oldenburg on September 28 is devoted mainly to central themes of the tract which under the title Theoria motus abstracti he would later dedicate to the Acad´emie Royale des Sciences. Notwithstanding the fact that this tract is complementary to his hypothesis, the reason for the disproportionate treatment in the letter, as he makes little effort to disguise, is that his hypothesis at this time was still to be completed. In fact, he describes the summary of his hypothesis which he produces towards the end as being only in a “brief and crude form,” but says of the whole that “with a few changes and many excisions it can be made perfect in every respect” (A II i, 65; OCH VII, 165/169). We have already mentioned the communication of intelligence as being one of the benefits of correspondence in Leibniz’s view. Another of its values, as Leibniz later remarks to Duke Johann Friedrich (1625–79) in January 1677, is that it often throws light on aspects of an author’s work which are generally not recorded in print. Alongside news of new books, letters often provide information on “their motives, critiques and the circumstances of their being written, of which the journals and catalogues say nothing” (A I ii, 17). His letter to Oldenburg of September 28 is a case in point. Even if the young philosopher does not provide anything more than a summary of his new physical hypothesis, he is, nevertheless, able to point out that the circumstances of his addressing the concept of motion in the first place were directly related to discussions which had taken place in the Royal Society. As he recalls, while accompanying Boineburg in 1669 during his stay at the spa town of Bad Schwalbach – which already in the sixteenth century had become famous as a place where learned men, divines, and politicians would meet during the summer months (see DS I, 105) – he had been introduced to Erich Mauritius (1631–91), professor of law at the University of Kiel and a close friend of his patron. Mauritius, who claimed to be in correspondence with the Royal Society (or at least with one of its members) and who, undoubtedly, possessed a strong interest for the new philosophy, showed Leibniz

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copies of the Philosophical Transactions containing articles by Wallis (1616– 1703), Wren, and Huygens on the laws of motion, a topic very much at the focal point of interest in the R´epublique des Lettres at the time. From these articles he learned of the dispute which had arisen after Oldenburg had published the contributions of the two Englishmen (see Wallis 1669 and Wren 1669) but not that of the Dutch mathematician, arguing that his laws were largely identical to those of Wren. Huygens, aware that the public, on seeing his results appear after the others, would suspect that he had committed plagiary, found himself forced to print a French version of his paper in the Journal des Sc¸avans with an explanation on the background of the dispute (see 1669a).11 It was only following this that Huygens’s results, accompanied by an account of the circumstances of the delay written by Oldenburg, were published in the Philosophical Transactions (see Huygens 1669b).12 Because of this experience, Huygens submitted the proposal to the Royal Society that future contributors to discussions be able to send in cipher results which they had not yet fully worked out.13 In this way scientific discourse could take place without fear of plagiarism, since in the event of such disputes the question of rightful authorship could be established impartially. For Leibniz, however, the dispute on the true laws of motion was, from a scientific point of view, largely irrelevant as the laws proposed were based, on his opinion, on mistaken premises. As he writes to Oldenburg, he found on considering closely the laws of Huygens and Wren that they do not, in fact, constitute what they purport to be – such laws on his view would only obtain under ideal conditions – but instead are contingent on the conditions present in the created world, as conceived by him in the framework of his new physical hypothesis. Moreover, it was precisely his recognition of this which led him to draw up his theory of abstract motion, the first draft of which he apparently completed while still at Schwalbach.14 A re-worked and polished version of that draft which he gave to Mauritius to be conveyed to Oldenburg did not go further than the hands of Martin Fogel in Hamburg (see Mauritius to Leibniz, January 17, 1671: A II i, 75). Fogel, a professor of mathematics, held the work back, due to his own disagreements with it. This, however, turned out to be fortunate, as Leibniz himself soon became aware of weaknesses in the argumentation. On hearing later of the whereabouts of his draft, Leibniz urged Fogel not to send it on (To Fogel, February 13, 1671: A II i, 82–3). Quite apart from those aspects which he now rejected, the experimental orientation of the Royal Society clearly spoke against its being submitted – at least in the first instance. It was not by

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accident that Leibniz made his mark in that institution through his new physical hypothesis and not through consideration of motion under ideal conditions. As mentioned already, Leibniz in his letter of September 28 barely does more than sketch the structure of his hypothesis, noting only that it supposes there to be a circulation of ether with light or by itself about the earth, contrary to the earth’s rotation, and that from this he is able to deduce gravity, expansion, and magnetism. Only in the following letter of March 11, 1671 and after being pressed by Oldenburg to send his whole hypothesis – and not just the already promised abstract principles of motion – does Leibniz go into more detail. Not only is the account now more precise, indicating that much had only been written since his earlier letter, but it was also sent accompanied by a substantial part of the printed Hypothesis physica nova itself. As he explains, his original intention had been to send the whole hypothesis, but this had been frustrated due to mistakes committed by the printer (A II i, 88; OCH VII, 485/488). Clearly recognizing that he might be stretching the patience of members of the Royal Society too far and at the same time keen to receive their views, he chose to send what had then been adequately typeset rather than wait for the completion of the whole. One of the most apparent differences from the earlier sketch is that Leibniz now states quite explicitly in the accompanying letter (A II i, 88; OCH VII, 485/489)15 that in his model two basic explanatory principles are deduced from the reverse circulation of ether about the earth, namely gravity and elasticity, and that from these all other observable phenomena can be explained. He claims, for example, that his model is able to provide explanations for chemical reactions, the springing back of catapults, the vibration of springs, and the oscillation of pendulums. It would also account for most, if not all, magnetic phenomena. In fact, Leibniz’s correspondence at the time, especially that with Oldenburg, reveals a remarkable interest on his part for the topic of magnetism.16 Here, as in other aspects of his hypothesis, he was keen to take account of contemporary scientific results, regretting, thereby, that lack of resources prevented him from carrying out experiments of his own (A II i, 89; OCH VII, 486/489).17 We have no grounds for suspecting that Leibniz’s story of the printer’s errors is untrue. Nevertheless, the time which elapsed before he sent Oldenburg the rest of the Hypothesis physica nova clearly allowed him to consider in more depth at least one major point in the tract as it was originally conceived. For although in his letter of March 11 he postulates

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two explanatory principles, by the time he sent the rest of his hypothesis, namely at the end of April, he had added as a third principle that of magnetism (see Hypothesis physica nova §58: A VI ii, 249). It was possible for him to effect this change without contradiction because the question of principles is only taken up in the latter part of the tract. And it is, of course, a further reflection of the importance he attached to the topic of magnetism at the time. By now assured of Oldenburg’s support and desirous of the critical assessment of his hypothesis by some of the leading scientists of his day, Leibniz points out towards the end of his letter that he has dedicated the work to the Royal Society (A II i, 91; OCH VII, 488/491). In view of his apparent aim of being received into the illustrious circle of fellows this was not only a shrewd step to take but also one which was well justified. The Hypothesis physica nova is, considered as a whole, an impressive work, coming as it did from the pen of a twenty-five-year-old philosopher. Not only did it seek to produce explanations for all natural phenomena, but it sought also to show that the model put forward for doing this can be perfectly reconciled with the results of contemporary experimental science as well as with the world systems of Nicholas Copernicus and Tycho Brahe. More than anything else, it is the ability of his hypothesis to accommodate important discoveries of his time which Leibniz emphasizes in his correspondence with Oldenburg. Unable to carry out experiments of his own, Leibniz sees his contribution to contemporary scientific discussion as being principally one of providing a model of nature which agrees with the experimental evidence of others.18 But this also has, at the same time, a lot to do with his conception of truth. It is fundamental to Leibniz’s understanding of the growth of knowledge, to which he sees his philosophical and scientific theories as contributing, that the veracity of these theories is greater according to the degree of agreement with the sum of human learning, that is to say, with the ideas and discoveries of the ancients just as with those of the moderns. As he writes in his Hypothesis physica nova, the explanatory model he proposes “appears to combine and harmonize the various hypotheses of others” (A VI ii, 257). Oldenburg emphasizes particularly this aspect in his later advertisement of the work which he published in the Philosophical Transactions.19 But this is not to say that other theories are simply taken on board. Rather, they are supplemented where they are deemed deficient, extended where they are deemed to stop short, and rendered intelligible where they are deemed to be obscure and their meaning hidden.20 The result is a hypothesis which is a good way along the road to true knowledge, then, as he notes,

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“it is no small indicator of the truth of our hypothesis, that it agrees with all” (A VI ii, 252). This is, at least, the way things are presented. In fact, it can be shown that Leibniz drew heavily on the results of the experimental scientists of his day in framing his hypotheses.21 Precisely for this reason he is able to claim the agreement he does. Not only the discoveries of microscopists such as Hooke and Borel but also those of chemists such as Tachen played a significant role in the development of the architectonics of Leibniz’s explanatory model. This allows him later to formulate principles such as Naturam cognosci per analogiam or the law of continuity both in an explanatory and in a heuristic context. Effectively, agreement with such principles just as with scientific results is already built into the system.22 In his following letter to Oldenburg of May 9, where, suspecting that that of March 11 had not arrived, he again summarizes his two tracts on motion, Leibniz suggests that so long as we have not penetrated all of nature’s secrets we are dependent on hypotheses and that the approximation of these to the truth is proportionate to their clarity, simplicity, elegance, and, above all, their ability to agree with phenomena. In neither of the two letters, however, does the young philosopher go into the more speculative side of his theory, namely into its material basis. Not only does he not mention the four elements which he postulates in the then traditional manner – ether, air, water, and earth – he also remains silent on his reduction of these to the purely theoretical concept of bubbles [bullae], which themselves contain ether in different quantities and densities. Although the bullae concept plays a fundamental role in his hypothesis and indeed provides the structural foundation for its agreement with the discoveries of microscopists such as Hooke and Borel, Leibniz evidently felt it unnecessary – and probably unhelpful – to touch on the more metaphysical side of his position. Even if Leibniz had good reasons for sending his hypothesis in an incomplete state, this was, nevertheless, in view of the dedication to the Royal Society a bold step to take. The printed text he included with his letter of March 11 contained a little more than half his Hypothesis physica nova (up to and including §49).23 At the end of the letter he promised to send the rest soon. However, on account of the somewhat misleading way he explained this, pointing out that he would add his theory of abstract motion to the last pages of his hypothesis, Oldenburg understood Leibniz to mean that the missing part was none other than the abstract theory itself. This, in turn, led him to believe that the Theoria motus abstracti was

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an integral part of the Hypothesis physica nova and not, as Leibniz had conceived it, a theory complementary to it. It was no doubt because of this misunderstanding that Oldenburg produced the as yet incomplete Hypothesis physica nova before the Royal Society at the first opportunity after its arrival in London. At this meeting, which took place on April 2, 1671, Boyle, Hooke, Wallis, and Wren were requested to examine the work and to report on it.24 In fact, only Hooke, Pell (1611–85), and Wallis actually seem to have received the Hypothesis for perusal. While nothing is known of Pell’s views, Hooke’s judgment was short and dismissive. Wallis, on the other hand, produced an extensive account, in which he pointed out the substantial agreement between his views and those of the young German philosopher. This report, which Oldenburg later communicated to Leibniz together with Wallis’s rather more compact opinion on the Theoria motus abstracti, without doubt played a decisive role in his being admitted later as fellow of the Royal Society.25 It also had significant consequences with regard to the republication of the tract itself.

3. theoria motus abstracti Wallis did not fail to recognize the incomplete nature of the hypothesis as it had been presented to him. It was, however, not until the end of April that Leibniz sent Oldenburg the missing sheets together with a copy of his Theoria motus abstracti. On being received, the long-awaited tract was given to Hooke for consideration. Only after he had provided a disappointing report to the Society on June 4 was the copy of the Theoria motus abstracti sent to Wallis.26 This time the Savilian professor restricted himself to just a few remarks on Leibniz’s model of cohesion, indicating that lack of time had prevented him from considering the work in any depth. As Leibniz had already explained to Oldenburg in his letter of September 28, 1670, the true laws of motion were, on his view, quite different from those published by Huygens and Wren. Having given his account of phenomena in the Hypothesis physica nova, he uses the complementary tract, Theoria motus abstracti, as a vehicle for presenting laws which can be deduced from pure concepts and which do not involve contingent properties of bodies in the created world. At root, this distinction was already well recognized. It had been explicitly part of the brief of the Society to the participants in the original discussion in 1668–69 that they concern themselves with the physical causes and principles of motion rather than

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investigate the mathematical rules by which it is governed (see Wallis to Oldenburg December 15, 1668: OCH V, 221).27 Leibniz effectively sought to place this distinction on a new foundation, but one unfortunately conceived to a large extent on a false understanding of the nature of elastic collision.28 Although two years had elapsed since the original publication of Huygens’s and Wren’s laws in the Philosophical Transactions, Leibniz was, nevertheless, able to profit from continued interest in the topic. But the Theoria motus abstracti was altogether more ambitious than simply being an account of what Leibniz regarded as the true laws of motion. In his letters to Oldenburg between September 1670 and June 1671 he refers repeatedly to what he sees as the major achievements of the work, emphasizing in particular his solution to the then highly controversial problem of cohesion. After remarking that the mechanistic models of Descartes and Gassendi failed to provide reasons why material particles should stick together and that Hobbes had assumed the property to be a kind of irrational fact, he indicates already in his letter to Oldenburg of September 28 that he has found a theoretical solution based on his concepts of point and conatus, “from which spring many miraculous ideas about the nature of things” (A II i, 64; OCH VII, 164/168). He then proceeds to give a concise explanation: “Whenever things so move that one seeks to enter into the place of another, these cohere, so long as that endeavor lasts. For this endeavor (as Hobbes rightly observed) is the beginning of motion, or stands in the same relation to motion as a point to a line” (A II i, 64; OCH VII, 164/168). Later on, he gives Oldenburg a first indication of the complexity of his concept of point, which allows for the penetration of boundaries in the required sense: “Truly wonderful is the nature of point, for although the point is not divisible into separate parts (parts placed outside parts), still it is divisible into parts not formerly separated one from another, or into points that were previously inter-penetrating” (A II i, 64; OCH VII, 164/168). Oldenburg remained to be convinced. In his reply of December 18, 1670, he made no effort to hide his doubts regarding the philosophical stringency of Leibniz’s concept: “Meanwhile your subtle disquisition on the nature of points and their inter-penetration, and their divisibility into parts not previously inter-penetrating, seems to require greater enlightenment and a firmer foundation on which to rest” (A II i, 70; OCH VII, 309/312). Pressed in this way to be more forthcoming, Leibniz returned to the theme in subsequent letters, seeking to convince Oldenburg that his

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concepts of point and conatus, continuum, and motion only at first sight appeared paradoxical. In addition, he now lets it be known that he sees his concept of point not only as the means to overcoming the labyrinth of the continuum, but also as the foundation of the method of Cavalieri, which he had clearly learned about through secondary sources – principally through Hobbes’s Examinatio et emendatio mathematicae hodiernae, Dialogue 5 (OL IV, 174–6) and Thomas White’s first preface to the Latin translation of Digby’s Two Treatises (Praefatio ad Tractatus I, §3 – in Digby 1651). Perhaps most remarkable, however, are the conclusions which he is able to draw in respect of the nature of mind and body. Conatus, he suggests, might open the door to understanding the distinction between mental and corporeal activity because whereas in the mind a plurality of endeavors can remain indefinitely – this he postulates as the basis of memory and consciousness – two endeavors cannot persist in body for more than an instant (A II i, 65; OCH VII, 165/169). He then proceeds to give Oldenburg what he calls “a brief hint” of his position: “that every body is a momentary mind, and hence without consciousness, sensation, or memory” (To Oldenburg, 11 March 1671: A II i, 90; OCH VII, 487/490). There can be little doubt of the intention of this characterization. Although Leibniz had spoken approvingly of Hobbes’s concept of conatus – which was in many ways the source of his own – it was necessary for Leibniz to distinguish clearly his position from that of the English philosopher, whose apparent materialism along with his antagonistic attitude towards the universities had placed him at odds with a large part of the political and intellectual establishment in that country.29 But this was something which Leibniz apparently only came to recognize during the course of his correspondence with Oldenburg and probably through reading Hobbes’s belligerent attack on Wallis in the Examinato et emendatio – just one of numerous writings produced by both sides of the conflict during the long drawn out war between the philosopher and the Savilian professor. In his first letter to the Secretary of the Royal Society, he had enclosed a letter to Hobbes of the same date, July 23, 1670 (A II i, 56–9), clearly indicating that Oldenburg should forward it to the aging author of Leviathan. At the time, not only Leibniz himself but also Boineburg displayed a marked interest in Hobbes’s work (see Oldenburg to Boineburg, August 20, 1670: OCH VII, 107–8/108–9). But although Oldenburg in a postscript to his reply to Leibniz of August 20, 1670 wrote that he had sent the letter “to Mr Hobbes in the country” (A II i, 62; OCH VII, 112/114), all the evidence suggests that he did not, in fact, do this.30 In the dispute

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between Hobbes and Wallis there was no middle ground, and both men had shown themselves prepared to rally their supporters in order to attack the views of the other. Had an exchange of letters between Leibniz and Hobbes come about, it is inconceivable that Wallis and other leading figures in the Royal Society would have wanted anything more to do with him. Oldenburg would have been acutely aware that it would not have served Leibniz’s interests had contact with Hobbes been established. As things turned out, the orientation towards the Royal Society proved fortuitous. It was precisely Wallis – with Oldenburg pulling the strings in the background – who played an important role in launching Leibniz’s career. Nowhere is this more clearly demonstrated than in the reprinting of Leibniz’s two tracts on motion in England in 1671. Already in his letter to Oldenburg of March 11 of that year, Leibniz had expressed the wish that his hypothesis – he refers to it modestly as a “Schediasma” – be printed in Philosophical Transactions. Oldenburg, as owner and editor of the journal consented immediately to do this (see Boas Hall 1975: 185). “I shall strive without delay,” he writes on April 24, “to make your whole hypothesis an ornament of the Philosophical Transactions” (A II i, 93; OCH VII, 571/572). Due to his misunderstanding of Leibniz, he, thereby, considers the “whole hypothesis” to consist of a concrete and an abstract part. Thus, only ten days later on May 4, he writes again, urging Leibniz to send “the second part on the abstract laws of motion” as soon as possible (A II i, 101; OCH VIII, 10–11/11). Conscious of the need to have his work more widely distributed, Leibniz was happy with this arrangement. However, after Wallis had provided favorable reports on both tracts – and possibly also on account of their combined length exceeding what could easily be accommodated in the journal – Oldenburg decided instead to have Leibniz’s work reprinted by John Martyn, the printer to the Royal Society. He announced this at the end of his letter of June 22, which also contained the relevant passages of Wallis’s reports. Himself referring to the need for wider distribution of Leibniz’s writings, Oldenburg also noted the benefits to be gained by gathering the opinions of others, “from whom some light might be forthcoming where you so far have seen but darkly” (A II i, 134; OCH VIII, 102/103–4). His aim was quite clearly one of helping Leibniz to make a name for himself among the leading scientific figures in Europe and at the same time of enabling him to profit from their criticism of his work. As a consequence of Oldenburg’s original misunderstanding of Leibniz, the title of the London edition31 of the two tracts differs from

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that of the former Mainz edition32 and suggests a composite nature of the new hypothesis and the theory of abstract motion. Soon after its appearance from the press, Oldenburg sent a copy to Gaston Pardies (1636–73) in France, thus exemplifying further his continued efforts to promote the young philosopher’s interests abroad. Indeed, he now indicates that Leibniz’s views on motion merit comparison with those of leading scientists of his day. After citing first of all the grounds for reprinting as being “because of a shortage of copies, and because the subject seemed to merit consideration by scientists everywhere,” he expresses his desire that Pardies himself form an opinion on the work: Since this author gives us his ideas about both abstract and concrete motion (the subject which at present occupies the philosophers of Europe), we believe it is necessary to examine everything written on this subject, so important for all philosophy; it was this, Sir, that made me judge that you would be very glad to compare this work with yours, and with those of Mersenne, Wallis, Wren, and Huygens. (To Pardies, August 20, 1671: OCH VIII, 191–2/193–4)

4. ars characteristica There can be little doubt that an important part of the reason why Oldenburg felt so highly of Leibniz was the evident diversity of his interests. The young philosopher himself had been keen to demonstrate this right from the outset. Thus, alongside general remarks on his theory of motion, Leibniz also refers in his first letter to Oldenburg to his scheme to reduce jurisprudence to more or less demonstrable principles “such as may satisfy any rigorous philosopher” (To Oldenburg, July 23, 1670: A II i, 59; OCH VII, 64–5/66). Later on in the correspondence, he engages Oldenburg, and through him Wallis, in investigations on ancient manuscripts.33 There are frequent exchanges between the two men on developments and discoveries in the fields of technology and natural philosophy. From 1673 onwards, Oldenburg plays an important role in conveying mathematical intelligence – on the English side mainly from John Collins (1625–83) – between London and Paris, where Leibniz was now residing. But without doubt the philosophically most significant part of their literary commerce apart from the discussions on the theory of motion is the topic of universal character. Again, Leibniz touched on this topic already in his first letter to Oldenburg, where he refers to John Wilkins’s efforts towards creating a real character for philosophical purposes as well as to the work of Athanasius Kircher in developing a universal language (To Oldenburg,

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July 23, 1670: A II i, 60; OCH VII, 65–6/67). At this time he had apparently only been informed of Wilkins’s work by Marcus Hesenthaler, professor of law at the University of T¨ubingen and a close friend of Jan Amos Comenius. It was not until May 9, 1671 that Leibniz was able to announce to Oldenburg that he had read the Essay towards a real character and at the same time express the wish that it be translated into Latin (A II i, 104; OCH VIII, 24–5/28).34 Leibniz’s first visit to England at the beginning of 1673 took place shortly after the death of Wilkins and we know that against the background of this loss, artificial language was a topic of conversation at meetings between him and both Oldenburg and Boyle.35 Leibniz made a careful study of George Dalgarno’s Ars signorum36 at this time, and, on his return to Paris, he re-iterated his desire to see Wilkins’s Essay translated (To Oldenburg, 26 April 1673: A III i, 87; OCH IX, 595/599). Nevertheless, the existent correspondence of the two men suggests that Leibniz throughout this time did not provide Oldenburg with written evidence of his own work on universal character. This changes only at the beginning of 1676. In a letter written to Oldenburg from Paris, Leibniz recalls that he had for a long time been concerned to treat the science of mind by means of geometrical demonstrations. It was, of course, this goal that lay at the root of the model of mental activity which he had developed earlier in the Theoria motus abstracti. But now, as he writes, he has in mind an altogether different approach – one which in many ways can be traced back to his earlier work on combinatorics, the Dissertatio de arte combinatoria from 1666 (A VI i, 162–230). After describing as “sophistry” both scholastic and Cartesian accounts of the concepts of mind and of being, he indicates that his universal character would provide a criterion of truth “which is fixed, visible and (so to speak) irresistible, as though by mechanical reasoning” (To Oldenburg, January 7, 1676: A III i, 331; OCH XII, 97). Algebra, which represents a focal point of Leibniz’s mathematical activity in Paris and which is also an increasingly important topic in the correspondence with Oldenburg, is considered to be “only a part of that general system” (A III i, 331; OCH XII, 97). In other words, it is subsumed under the higher science of combinatorics or universal character, whose excellence consists precisely in the fact that in employing it, as he writes, “we cannot err even if we wished to, and that truth is as it were delineated for us on paper, as though with the aid of a sketching machine” (A III i, 331; OCH XII, 97).37 We have here already an expression of the concept of calculus ratiocinator, in which the combinatoric art combined with universal character presents the possibility of reducing human thought,

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and in particular scientific argument, to a process of manipulating signs according to certain pre-determined rules. As he writes in a contemporary draft on the same topic, by finding signs which are able to express adequately all our ideas, we would be able to carry out “all matters which are subject to reason” just as in arithmetic and geometry (A VI iv, 6).38 Leibniz voices the hope of sometime being able to write more fully on what he calls “the marvellous strength and power of this science” (To Oldenburg, December 28, 1675: A III i, 331; OCH XII, 98), but, nevertheless, he makes clear in his succinct remarks that universal character will not only serve to ascertain the truth or falsity of existing knowledge, but also to make new discoveries: This, however, I dare to say, that nothing can easily be conceived which is more effective for the perfection of the human mind; and once this theory of philosophizing has been accepted, the time will come, and come soon, when we shall have no less certainty about God and the mind than about figures and numbers, and when the invention of machines will be no more difficult than the construction of geometrical problems. (A III i, 331; OCH XII, 98)39

There is no evidence that Leibniz ever actually provided the Secretary of the Royal Society with a detailed presentation of his Ars characterisica. However, among his papers in Hannover (LH IV. 5. 6, Bl. 20–1) we find the heavily re-worked draft of a letter to Oldenburg on this topic which without doubt was written sometime between the end of 1675 and the end of 1676,40 and which, therefore, possibly represents the basis of the account he at least intended to produce. The central question which he addresses in the draft is the difference between his Ars characteristica – to use just one of the names he employs – and other artificial language schemes such as those of Dalgarno and Wilkins, which at first glance appear to be of a similar nature. As Leibniz points out, their aims are altogether more restricted: to produce a philosophical language free from ambiguity or a symbolic language able to serve as the basis of universal communication. His Ars characteristica, too, would fulfill these needs, but he describes this as being the least important side of its value.41 The true significance of his Ars characteristica lies namely elsewhere: in its heuristic potential or, in his words, its ability “to increase one’s power of invention and to guide one’s thoughts.”42 Noting that he had begun his work on the Ars characteristica at the age of eighteen – in effect the earliest fruit was therefore the Dissertatio de arte combinatoria43 – he makes clear in the draft that on his view the perfection of mental activity depends on the perfection of language.

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By inventing a suitable system of symbols and determining the rules for their employment, we would, in effect, be creating the philosophical counterpart to instruments used in astronomy and the physical sciences: “let us construct a new telescope for the mind itself, which will not only bring the stars but also our own minds closer to us, which will not only represent the surface of things, but also disclose their inward form” (To Oldenburg, 1675/6: A II i, 241; OCH XIII, 371/375).44 But if this is his aim, the details remain rather vague. This is, however, not surprising. We know that he only later comes to recognize the need to combine the principles for demonstrating existing knowledge, and discovering new, into the universal science or scientia generalis and to conceive Ars characteristica fundamentally as the verum organon of this science. It is the declared goal of the scientia generalis, thereby, to contribute to a demonstrable and systematic presentation of all human knowledge.45 The requirement of an encyclopedic ordering of knowledge as something which goes hand in hand with the scientia generalis is only alluded to in the draft, and it is likely that at the time Leibniz had not yet worked out the role of Ars characteristica in respect of this (see Ma characteristique demande une encyclopedie nouvelle, A VI iv, 161). But Leibniz does dwell on two important aspects. He describes, first, how names in the universal language are discovered by means of analysis and that they in turn serve as a key to all which can be known “in rational and orderly terms” about whatever is denoted (To Oldenburg, 1675/6: A II i, 240; OCH XIII, 370/374). On account of this order into which the language is organized – which effectively reflects the encyclopedic ordering of knowledge and over and above this the order of nature – Leibniz contends that whoever learns the language cannot forget it, “or if he does forget it, he will easily be able to recall the necessary terms” (A II i, 240; OCH XIII, 370/373). His approach, thereby, is similar to that which he employs in the creation of his physical hypotheses: The order of nature, partly already discovered, partly remaining to be so, provides the theoretical basis for conclusions concerning the cognitive potential of individuals. A cognitive potential, which in this case rests on the assumption that complex concepts on their resolution through analysis to more simple concepts are always intimately related to the things they designate. The second aspect he focuses on is closely connected to this. The symbolic system of the Ars characteristica will, he suggests, be difficult to create – as indeed his own experience had shown – but easy to learn. The language would in effect have to prove adequate to the task of

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designation. But, once the language was created, different educational possibilities would emerge: even if broad apprehension of it required corresponding aptitude on the part of the individual, a core which would serve day-to-day needs could be gathered by all. The greatest benefit, however, would accrue clearly to he who was able to achieve mastery of the language. For he who achieved this would, as Leibniz explains, at the same time become the master of an encyclopedia “which will be the true gate to all things” (A II i, 240; OCH XIII, 370/374).46 It is clearly no accident but, nevertheless, remarkable that Leibniz uses here the expression “Janua rerum.” In doing so, he refers directly to the work of Comenius and, thus, to a man in whose spirit of universal cultivation and dissemination of knowledge Oldenburg rightly considered himself to be working.47 Leibniz reports being shown a copy of the rare 1649 edition of Janua rerum by Tschirnhaus (1651–1708) on the latter’s ¨ Gespr¨ache mit Tschirnhaus, return from London in autumn 1675 (see Uber Matthion und Justel. A VI iii, 382). It is likely that his reading of passages in the book where Comenius articulates his own ideas on universal language and its relation to the encyclopedic knowledge concept of the pansophia prompted his remark in the Oldenburg draft. But the significance would appear to go deeper than this. Comenius had a profound influence on the discussion on universal languages in England. There can be little doubt that the schemes of Cave Beck (1623–1706?), Dalgarno (1626?–87), and Wilkins were at least partly motivated by Comenius’s visit to England in 1641 or that Oldenburg’s own interest in universal language came about through his contacts both with Comenius himself and with his supporters in the circle around Samuel Hartlib.48 In many ways, therefore, Comenius can be seen to represent an important part of the background to Leibniz’s early philosophical development. Despite clear differences in their conceptions of lingua universalis, Leibniz was able to benefit from the tradition of Comenius in universal language and learning which continued to exert a powerful influence on intellectual life in seventeenth-century England.

5. conclusion It was first and foremost as a natural philosopher that Leibniz took his place among the learned men of Europe. But he did not achieve this by his own means alone. As we have seen, Leibniz’s early philosophical and scientific career was decisively promoted through the efforts of Henry Oldenburg. Motivated by considerations of international scientific

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cooperation in the spirit of Comenius and Hartlib and with particular concern for the development of experimental philosophy in the country of his birth, the Secretary of the Royal Society soon became the most important correspondent of the young philosopher. He not only engaged him in the exchange of scientific intelligence but also supplied him with careful advice in the course of preparing his two tracts on motion of 1671. In many ways, the role Oldenburg took on was similar to that of Leibniz’s patron Boineburg. He effectively introduced Leibniz to the Royal Society and was, thus, instrumental in making him known to the leading scientific figures in England at the time, including Wallis and Boyle. Nor does Oldenburg’s significance end there. It was he, too, who first informed Christiaan Huygens of the promising young German scholar “of no ordinary intelligence,” noting in his letter of April 7, 1671 that Leibniz had “examined minutely what great men, both ancient and modern, have to say about nature, and finding plenty of difficulties that remain, has set to work to resolve them” (OCH VII, 537/539). To back up his judgment, Oldenburg sent Huygens a copy of Leibniz’s Hypothesis physica nova, just as he later sent Pardies, another leading contributor to the discussion on the laws of motion, a copy of the Theoria motus abstracti. The fact that England became the starting point of his career in this way effectively reflects the endurance of the spirit of Comenius and Hartlib, to whom Oldenburg may in many respects be regarded as the rightful heir. It was through him that Leibniz came to receive the official recognition which he correctly saw as important for achieving his broader philosophical and political goals. For this reason, he also sought to be received into the Acad´emie Royale des Sciences in Paris (see Fichant, 1996: 344–6). But there, precisely on account of the absence a figure such as Oldenburg, his initial attempts did not meet with success. Not only was his Theoria motus abstracti, which he submitted together with his Hypothesis physica nova, from the outset unlikely to have found the wholehearted acclaim of the members,49 but also he made his approach without the necessary backing within the institution itself.50 A further attempt in 1676/7 was to involve an incomparably more substantial work, his De quadratura arithmetica circuli. But the unfortunate loss of the manuscript meant that this, like the earlier attempt, was also frustrated. It was not until 1700 that he was finally accepted into the Acad´emie as a foreign member. Leibniz gladly accepted the support which Oldenburg offered him. Through his correspondence with the Secretary of the leading scientific institution of his day, he hoped to receive – and indeed did – constructive criticism on his theory of abstract and concrete motion. He was aware,

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too, of the shared interest in universal language, a topic very much close to his heart. The favorable response by Wallis particularly to his Hypothesis physica nova prepared the ground for his successful first visit to London at the beginning of 1673, where at the meeting of the Royal Society on January 29 he demonstrated the capabilities of his then still imperfect calculating machine. Due to the positive reception of his work, he was persuaded to seek admittance to the Royal Society. Immediately before embarking on his journey back to Paris he submitted his request enclosed in a letter to Oldenburg of February 20, 1670 (A III i, 32–4).51 Without delay, he was proposed a candidate by Robert Moray (1608–73) and was duly elected together with Edward Bernard (1638–96) on April 19 of that year (see Birch 1756–7: III, 82).52 Fittingly, Oldenburg passed on the good news. But he did not do so without reminding Leibniz of his obligation to continue to pursue the exchange of intelligence: “it is now for you to prove yourself a true alumnus of the philosophical society, and to bring before the public those matters which either you shall have yourself pursued by reflection and experience in physics or mechanics, or others in Germany shall have thought out on the same philosophical topics” (To Leibniz, April 20, 1673: A III i, 79; OCH IX, 582/583). In effect, his career had been successfully launched. But Leibniz was not to forget the circumstances which had brought this about. Notes 1. See Beeley and Scriba 2003 for examples of Hartlib’s role, particularly in the early correspondence between Wallis and Hevelius. 2. See also his letter to Peter van Dam of February 2, 1663 (OCH II, 12–14/ 14–15). Except where otherwise stated, all dates are given new style, that is, according to the Gregorian calendar. 3. For a detailed discussion of Oldenburg’s relation to the Collegium curiosorum naturae see Scriba 1987. 4. See Sachs to Oldenburg, October 10, 1670 (OCH VII, 194–6/196–8) and Paisen to Oldenburg, mid-July 1670 (OCH VII, 82–3/83–4). Also see Leibniz to Oldenburg, March 10, 1671 (A II i, 90; OCH VII, 487/490) and Nietzsche’s letter to Leibniz of November 15, 1670 (A II i, 68). References to both A and OCH, separated by a semicolon, are provided for Leibniz’s correspondence with Oldenburg. 5. On Boineburg’s relation to Leibniz see DS I, 12–14 and Aiton 1985: 23–6. 6. See Leibniz to Lambert van Velthuysen, April 16, 1670 (A II i, 39); Leibniz to Martin Fogel, January 24(?), 1671 (A II i, 77); Leibniz to Antoine Arnauld, beginning of November 1671 (A II i, 169); Leibniz to Johann Andreas Bose, October 5, 1669 (A I i, 77) and Leibniz to Gottlieb Spitzel, December 22, 1669 (A I i, 80). Also see his letter to Thomas Hobbes of 1674 (?) (A II i, 244).

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7. See, for example, Grundriß eines Bedenkens von Aufrichtung einer Societ¨at (A IV i, 530–43) and Bedenken von Aufrichtung einer Akademie oder Societ¨at (A IV i, 543– 52). The second of these memoranda, both of which were probably written in 1671, begins with a passage deploring German inability to match skill in discovery with the advancement of sciences: “It is no credit to us Germans that we have been largely the first in making discoveries in mechanics, technology, and other arts and sciences, but are now, when it comes to increasing and improving them, the last.” See also his letter to Jakob Thomasius of October 6, 1668 (A II i, 10). 8. As Poser notes, “the real goal is that theory without practice and practice without theory should be mutually fruitful” (1999: 102). 9. See Beeley 2002 for a detailed discussion of the background to the growth of controversies in seventeenth-century science. 10. Hypothesis physica nova, concl.: “and finally in the application of discoveries in order to improve life and to increase the power and happiness of mankind, which clearly we must consider to be the sole end of philosophy” (A VI ii, 257). 11. At the end of his account, Huygens explicitly claimed priority to the laws: “I could point out to you that I have long had knowledge of these laws of nature, if I did not perceive that this would give you all the more reason for criticizing me for having taken so much time to communicate them” (1669: 24). 12. On this episode also see Boas Hall 1975: 188. 13. See Huygens’s letter to Oldenburg of 6 February 1669 (OCH V, 360–2), in which he also suggested that he might send newly discovered theorems on the same topic in this way. Oldenburg replied in his letter of February 14, 1669 that the Society had approved of Huygens’s suggestion. It is noteworthy that Oldenburg encouraged Huygens to send first a summary of his latest results for publication in the Philosophical Transactions. 14. Leibniz evidently found his visits to Bad Schwalbach conducive to creative work. The following year, working together with Boineburg, he produced the Securitas publica (see Aiton 1985: 36–7). 15. See also his letter to Conring of February 8, 1671 (A II i, 80). 16. See, for example, his letters to Oldenburg of March 11, 1671 (A II i, 89; OCH VII 486/489); May 9, 1671 (A II i, 103–4; OCH VIII 24–5/27–8); and June 18, 1671 (A II i, 123/OCH VIII 77/80) – see also his letter to Hevelius of May 3, 1671 (A II i, 99–100) and Kochanski’s letter to Leibniz of November 18, 1671 (A II i, 188–92). 17. See also La vraie methode: “But the unfortunate thing is that experiments in physics are difficult and cost a lot of money [ . . . ]” (A VI iv, 4). 18. Leibniz was keen to discover the opinion of those contemporaries whose results he had cited as being in agreement with his theory. See for example his letter to the chemist Otto Tachenius of May 4, 1671 (A II i, 100–1), with which he enclosed copies of the Hypothesis physica nova and the Theoria motus abstracti. Other copies were sent to Martin Fogel (A II i, 99), to Honorato Fabri (A II i, 185–6), and to Johannes Hevelius (A II i, 99–100).

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19. “What he hath therein [sc. natural philosophy] performed, he imparts in this Hypothesis to the Learned world [ . . . ] he maketh it his business to shew, that by the help of it the Causes of most of the phaenomena of Nature may be rendred from one single and universal Motion, suppos’d in our Globe, neither crossing the Copernican nor Tychonian Hypothesis; the Author having so managed the whole, as that all Sects may bear and admit what he here produceth, without a prejudice to their own Opinions” (Oldenburg 1671: 2213). 20. See Hypothesis physica nova, concl. (A VI ii, 257). For a more detailed treatment of this topic see Beeley 1996: 217–27. 21. See Duchesneau 1993: 192, where he distinguishes in this respect validit´e heuristique and validit´e d´emonstrative – also see Duchesneau 1994: 74–89. 22. For a discussion on such in-built principles see Beeley 1999. 23. This emerges from a note appended to the version of Wallis’s letter to Oldenburg of April 17, 1671 published in Wallis 1671: 2229: “In the first place the author has apparently only sent by letter the first part of this Hypothesis, namely up to page 48, without the Theoria motus abstracti.” In the body of the letter itself, Wallis says that he has seen neither the Theoria motus abstracti, “from which he takes the foundation for his hypothesis,” nor the sections subsequent to those delivered to him, to which there were occasionally references. 24. See Birch 1756–7: II, 475; Boas Hall 2002: 225; and Boas Hall 1978: 173. 25. The importance which Leibniz accorded to Wallis’s judgment can be gauged from remarks he made in his letter to Fogel of October 5, 1671: “Without doubt, the celebrated M. Wallis in his opinion conveyed to me has judged it [sc. Hypothesis physica nova] in a generous manner and, indeed this opinion having been written by a man so eminently learned in these matters, I could have read none that would have satisfied me more” (A II i, 154). 26. “[Hooke] acquainted the society, that he had perused and considered Monsr. Leibnitz’s Theoria motus abstracti, but was of opinion, that he had not hit right” (Birch 1756–7: II, 482). 27. See also Oldenburg’s letter to Downes of May 14, 1669: “The Society is at present chiefly employed in considering the Principles and Laws of motion, and therein they have been presented by Dr Wallis, Dr Wren, M. Wm. Neile and Mr Hugenius with their several meditations and Theories which are now under the examination of experiments” (OCH V, 512). 28. On Leibniz’s early concept of elasticity see Bertoloni Meli 1993: 50–4 and Breger 1984: 113–16. 29. On the background to this conflict see Jesseph 1999 and Probst 1997. 30. Not only is the letter to be found among Oldenburg’s papers in the British Library (Add. MS. 4294, fol. 64r–66v) but also no reply is known to have been sent. See Leibniz’s later letter to Hobbes, probably written in 1674 (A II i, 244–5). 31. Hypothesis Physica Nova, Qua Phaenomenorum Naturae plerorumque causae ab unico quodam universali motu, in globo nostro supposito, neque Tychonicis, neque Copernicanis aspernando, repetuntur. Nec non Theoria Motus Abstracti. Autore G. G. L. L. Londini: J. Martyn 1671.

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32. Hypothesis Physica Nova, Qua Phaenomenorum Naturae plerorumque causae ab unico quodam universali motu, in globo nostro supposito, neque Tychonicis, neque Copernicanis aspernando, repetuntur, Autore G. G. L. L. Moguntiae: Chr. Kuchler ¨ 1671; Theoria motus abstracti seu Rationes Motuum universales, a sensu et Phaenomenis independentes. Autore G. G. L. L. [Mainz 1671]. 33. Thus, Leibniz passed on P. D. Huet’s request for information on manuscripts of the second-century astrologer Vettius Valens to Oldenburg who, in turn, asked Wallis to see what he could find in Oxford. The Savilian professor sent the results of his investigations to Oldenburg; they eventually reached Huet after first being forwarded to Leibniz (see Huet’s reply to Oldenburg of April 5, 1673: OCH IX, 538/538–9). In a postscript to his letter to Oldenburg of November 28, 1676, Leibniz asks the Secretary of the Royal Society to inform him of the existence of Apollonios manuscripts in England and suggests that he employ the assistance of Wallis in Oxford (see British Library Add. MS 4429, fol. 8r–8v). In the direct correspondence between the two men at the end of the century, Leibniz calls on Wallis’s assistance in investigating a book by Adam Bohoriz (1520–1600) – see Leibniz to Wallis, May 28, 1697 (GM IV, 29) and Wallis to Leibniz, August 9, 1697 (GM IV, 39) and Wallis to Leibniz, February to April 1699 (LBr 974, Bl. 37a). 34. See the similar wish expressed by Hevelius in a letter to Oldenburg on the topic of magnetism: “Would to God, that those Excellent Books that are publish’t in English, were, for the benefit of the whole Learned World, made Latin; All Learned men would be exceedingly obliged to you for it” (Hevelius 1670, 2059). About the time of his letter to Oldenburg, Leibniz wrote preliminary studies on universal characteristic based on the table of definitions contained in Wilkins’s Essay (A VI ii, 487–510). 35. See Zur Ars signorum von George Dalgarno (A VI iii, 170) and Leibniz to Haak, February 1680 (A III iii, 83–4). 36. Zur Ars signorum von George Dalgarno (A VI iii, 169–98). On Leibniz’s relation to Dalgarno see Cram and Maat 2001: 64–5. 37. See also La vraie methode: “Those who write in this language will not err, so long as they avoid errors of calculation, barbarisms, solecisms, and other faults of grammar and linguistic construction” (A VI iv, 7). 38. Also see Leibniz’s letter to Duke Johann Friedrich, October 1671 (A II i, 160). 39. Again, he writes similarly in La vraie methode: “For all investigations which depend on reasoning can be carried out by the transposing of these characters and by a sort of calculus; which will render the discovery of wonderful things quite easy” (A VI iv, 6). 40. This letter has never been successfully dated previously. It is possible that Oldenburg reminded Leibniz during his second visit to London in 1676 of the promise he had made earlier. A year later he points out to Gallois that while on board boat on the Thames in October 1676, waiting for favorable conditions for the passage to Holland he had above all thought about his “old design for a rational language or script” (A III ii, 228–9). 41. Leibniz to Oldenburg, 1675/6: “For nothing can ever befall mankind of more advantage than the perfection of mental function: yet a rational

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43. 44.

45. 46.

47.

48. 49. 50.

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symbolization, I repeat, will be a most powerful instrument, and one should suppose that the least part of its usefulness will be communication between people divided by language [ . . . ]” (A II i, 239; OCH XII, 369/372). He voices a similar idea in a letter to Gallois written in September 1677: “I thought about my old design for a rational language or script, whose least importance would be universality and communication between different nations. Its true usage would not be speech [ . . . ] but thought, and to speak to the understanding rather than to the eyes” (A III ii, 228–9) – see also Pombo 1987: 79–81. Leibniz to Oldenburg, 1675/6: “For some symbolizations have been discovered either merely for the sake of mental brevity, or of commerce, or even of secrecy, while others increase one’s power of invention and guide one’s thoughts” (A II i, 239; OCH XII, 369/373) – see also Leibniz to Haak, January 6, 1681 (A III iii, 313–14). Leibniz refers to the same distinction years later in his letter to Remond of January 10, 1714 (GP III, 605) – see Dascal 1987: 47–8. On the combinatory predecessors to the Ars characteristica see Pombo 1987, 86–91. See Zur Ars signorum von George Dalgarno: “But the true real character, such as it is conceived by me, must be considered to belong to the most suitable instruments of the human mind, and will namely possess an invincible power of invention, memory, and judgment” (A VI iii, 170) – also see Leibniz to Duke Ernst-August, 1685–87 (A I iv, 316). See Schneider 1994, 214–15 and H. Schepers’s introduction to A VI iv (A VI iv, l–lxii). Leibniz later appears to relativize this somewhat in his letter to Cluver of September 10, 1680, where he notes that “it would be ridiculous to expect Pansophia from some kind of character, and equally so from some kind of analysis, since many things are recognized only by experience” (A III iii, 264). See Oldenburg to Comenius, June 15, 1668, “What you advocate and pledge yourself to is most arduous, though sought by the efforts of certain good men; that is, the universal cultivation and dissemination of truth, and of the fructiferous sciences. Not undeservedly, you may judge our England to be a station excelling others on the globe as a seat for carrying on this commerce” (OCH IV, 449–50/450). See Hill 1965, 106–7 and Pˇr´ıvratsk´a and Pˇr´ıvratsk´y 1994, 171–2. See, for example, the decidedly cool response from Pierre de Carcavy in his letter to Leibniz of July 10, 1671 (A II i, 139). Leibniz stood in contact to a number of members of the Acad´emie, including Gallois, who was in the exceptional position of being able to exert influence on Colbert. But this was still to no avail. See J. E. Hofmann’s introduction to A III i (A III i, lxvi–lxxii). Leibniz’s letter to the Royal Society was read at the meeting on March 1, 1673 – see Birch 1756–7: III, 76 and Boas Hall 1978: 175. Unfortunately, first tensions between Leibniz and the Royal Society arose immediately afterwards (see Hofmann 1974: 34–5).

4 The Leibniz–Foucher Alliance and Its Philosophical Bases Stuart Brown

To those who think of Leibniz as a dogmatic philosopher, his close association with a sceptic such as Simon Foucher may come as a surprise. Thus, in a characteristically ground-breaking article, Richard Popkin remarks that it was “strange but nevertheless a fact that Leibniz was a warm and close friend of the three leading French sceptics of his time, the abb´e Simon Foucher, Bishop Pierre-Daniel Huet and Pierre Bayle” (1966: 228). Popkin’s investigation into how such an accord could be maintained between such apparently contrary types of philosopher led him to acknowledge that Leibniz, after all, was not as far from the sceptics as is commonly supposed. And on this point, on which I will have more to say, I agree with him. But, at least as far as Foucher goes, another part of the explanation is that someone may call himself a sceptic because he is committed to the search after truth and not, as Popkin supposes, because of an inclination to doubt everything. In fact, or so I will argue, Foucher and Leibniz agreed about a good deal and, for a while, thought they agreed even more, about philosophical matters. There was, as the title of my chapter claims, an alliance between them. And this alliance had, or appeared to each of them to have, substantial philosophical bases.

1. simon foucher Simon Foucher was two years older than Leibniz. His home town was Dijon, where he became an honorary canon of the Sainte Chapel, but he moved to Paris, where he became the chaplain to a religious house. He had attended lectures on physics given by the Cartesian Jacques Rohault in the late 1660s, and he had published a book on hygrometers.1 But 74

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philosophy was his main interest. He thought of himself as an Academic Sceptic “after the manner of Plato” (GP I, 388). He was not a wholly destructive sceptic since, for instance, he allowed the demonstration of some cardinal truths of religion. As Foucher presented it, Academic Scepticism was just a more rigorous methodology for searching after truth, not a counsel of despair. His scepticism did, of course, have a destructive side to it, in relation to dogmatic metaphysics, especially that of the Cartesians. He had a nose for seeking out unproven assumptions of their metaphysics and in this way sought to bring into question the conclusions they sought to draw. Foucher’s first philosophical book was printed in 1673, for private circulation.2 Like some of his other books, it had two titles: a generic title, in this case, Dissertations sur la recherche de la verit´e, and a more distinctive alternative title, in this case, Sur la logique des academiciens (Foucher 1673). Foucher himself usually referred to his philosophical books by their second titles or even by abbreviations. Thus, he referred to this early work simply as his Logic. The first volume of Malebranche’s Recherche de la verit´e seemed to contain a critical reference to the Logic and gave Foucher the excuse to write his Critique de la recherche de la verit´e (1675). Malebranche replied in the second volume of his Recherche, and this gave Foucher the opportunity to write a further rejoinder (Foucher 1676). There was also a reply from the Cartesian, Dom Robert Desgabets, to which Foucher wrote a further R´eponse (1679). Foucher later wrote two further dissertations on the search after truth, which he usually referred to as the Defence of the Academics (Apologie des Academiciens), published in 1687, and the Philosophy of the Academics (La Philosophie des Academiciens), which appeared in stages in the early 1690s (see Foucher 1693).

2. the leibniz–foucher correspondence Foucher was introduced to Leibniz during the latter’s stay in Paris, probably by one or both of the Dijon councillors to the national parliament, Jean-Baptiste Lantin and Philibert de La Mare. Leibniz seems to have met Lantin soon after his arrival in Paris and quickly established a rapprochement with him on philosophical matters. Lantin knew of Leibniz’s early writings on physics and was, as Leibniz acknowledged, one of the first to encourage him to apply his “dynamical meditations” to metaphysics.3 It is not certain when Leibniz met Foucher, though by 1676 he considered that he had known the abb´e from Dijon “for a long time” (LBr 339 – see Muller ¨ & Kr¨onert 1969: 41). They seem to have had extensive discussions

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on topics that ranged from the measurement of changes in the air to the problems of Descartes’s philosophy as well as, of course, the virtues of Academic Scepticism.4 Although they never met again after Leibniz went to Hanover, their letters frequently repeat the hope that one day Leibniz would return to Paris – a hope that was, in the event, frustrated by political and other circumstances. Their correspondence continued, sometimes sporadically, for about twenty years, overlapping, but not entirely including, the published exchanges between the two men that appeared in the Journal des savants in the 1690s. It ended abruptly with the death of Foucher in Paris on April 26, 1696. The correspondence was not extensive, by Leibniz’s standards. There are thirteen extant letters or copies or extracts of letters from Leibniz to Foucher and fifteen from Foucher to Leibniz. All but one of these are published in Gerhardt (GP I, 369–427).5 In addition there were at least seven letters written by Leibniz that did not survive in any form but whose existence and part of whose contents may be inferred from the rest of the correspondence. There were also at least two further letters from Foucher. The letters overlap with but do not entirely include the published exchanges between the two men that appeared in the Journal des savants in the 1690s. In addition, Leibniz’s notes on Foucher’s reply to Desgabets have survived (A VI iii, 311–26),6 as well as notes on Foucher’s objections to his own New System (GP IV, 490–3/WF 45–7). The correspondence is a rich one and would repay study from a number of different points of view. Here I focus on an overview that brings out the philosophical alliance between Foucher and Leibniz. The two friends agreed on quite a number of specific points of doctrine, especially on a whole raft of objections to Descartes. Many of these – for instance their rejection of the distinction between primary and secondary qualities, of the Cartesian doctrine of the essence of matter, or of Descartes’s arguments for the existence of God – deserve more attention than I give them here. But, for the purposes of their alliance it was sufficient that they agreed about the broad conclusion, that Descartes’s project in the Meditations failed at most of the key points. They did not argue over the different reasons they often had for coming to the same conclusion. And so, interesting as those differences are, I do not explore them here. More fundamental are the points where they agreed with one another about how one should proceed in philosophy. On some matters they disagreed strongly with Descartes and his followers. On others they could almost make common cause with them. At one point in their

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correspondence, as I bring out, they seem to have thought they were almost in complete accord as to what was required in metaphysics. Foucher, moreover, repeatedly expressed his optimism that Leibniz would produce a metaphysics that was free of the deficiencies he found in the writings of dogmatic metaphysicians such as Descartes and Malebranche. The high hopes Foucher had of Leibniz are evident throughout and the lapses in the correspondence never seem to have been his fault. Twice in the early stages, Leibniz’s pre-occupation with other matters meant that Foucher’s letters went unanswered. The correspondence was largely continuous between 1684 and 1693, though there are two large gaps during this period, mostly due to Leibniz’s travels. Then, owing to a misunderstanding on his part, Leibniz thought Foucher wished to curtail the correspondence. There were, therefore, five breaks, and these provide some basis for dividing up the correspondence into six phases. In treating each phase I first offer a brief survey and then look at the state of the philosophical alliance. I conclude by considering the aftermath of the correspondence in Leibniz’s references to Foucher and his changing attitude towards scepticism. I argue that the alliance between Foucher and Leibniz was based on philosophical convictions that the two men either really did share or thought they shared. In the first category is their common commitment to the revival of ancient philosophy and their principled opposition to Cartesianism. In the second category is the belief they thought they shared in Academic Scepticism as a philosophical methodology. The alliance proved to be a fragile one in that it became clear in the course of the correspondence that each understood this commitment in a different way. Thus, Leibniz alternated between claiming to have been a better Academic Sceptic than Foucher and distancing himself from Academic Scepticism altogether. The correspondence, it is argued, reveals an important shift in Leibniz’s thinking about the possibility of a demonstrative metaphysics.

3. early communications (1675–76) The first phase relates to the latter part of Leibniz’s Paris period, or shortly thereafter, when he was beginning to position himself in relation to Malebranche, Foucher, and the new perspectives he was being offered on Descartes. All that survives from this period are his fairly extensive notes on Foucher’s reply to Desgabets (A VI iii, 311–26) and the longest of his letters to Foucher (A II i, 245–9/AG l–5).

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The Alliance (1675–76) It is clear from the letter Leibniz wrote to Foucher in 1675 that, in their discussions, the two men had already established a good deal of common philosophical ground. Three points in particular stand out, on Leibniz’s side. He agreed with Foucher on the methodological principle they broadly shared with Descartes, that it is important to examine all our assumptions, at least once, to establish something solid (A II i, 245/AG 1). He also agreed that the existence of an external world, pace Descartes, cannot be demonstrated (A II i, 248/AG 3–4). Foucher was, therefore, right to renew the criticisms of the ancient Academy of Plato. In wishing Foucher well with his meditations, Leibniz expressed his own views about their value: in teaching us that our knowledge of the material world must always be confused; and in confirming the distinction between body and soul, since we can doubt the former but not the latter. He also hinted at what, from his point of view, was to remain a divisive issue between them – the need, as he saw it, to gain ground and make progress in philosophy. One of the broadest, but by no means the least important, cementing points for the alliance between Leibniz and Foucher was their commitment to ancient philosophy and its revival.7 Leibniz had himself produced abridgements of Latin translations of the Phaedo and the Theaetetus while he was in Paris, which were probably intended for the use of the Dauphin (see A VI iii, N. 20). Moreover, he had high hopes that Foucher would make available selections in French translations of Plato and the Academics. He was especially keen to encourage selections from Plato, in whose writings, he claimed, were to be found “things [ . . . ] more beautiful and solid than is commonly thought” (A II i, 249).8 But both agreed that more was needed than a return to the ancients. They were modern philosophers who thought the new philosophy had surpassed that of the ancients. So the revival of ancient philosophy had to be, in Foucher’s phrase, “to the purpose.” Its relevance had to be made clear.

4. malebranche and scepticism (1678–79) The Correspondence (1678–79) It seems that Leibniz, as he settled into his new life in Hanover, largely forgot about Foucher and left it to his French friend, who was more flattered than he was by the connection, to revive the correspondence. Though no version of his reply survives, Leibniz evidently promised to

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send Foucher a copy of a letter he had written to Princess Elizabeth – the one in which he discussed Descartes’s arguments for the existence of God (A II i, 433–8/AG 234–40). In this lost letter Leibniz seems to have urged Foucher once again to offer the public translations from Plato and to cast his propositions in the form of theorems from geometry. Foucher replied, agreeing that translations could be done in due course, but clearly procrastinating. As to producing his philosophy in the form of theorems from geometry, he declined, referring Leibniz to Descartes’s reply to Mersenne on the same point (GP I, 376)9 and to remarks he himself had made in conversation with Leibniz. He reminded Leibniz that he had not yet received the promised letter to Princess Elizabeth. The letter would also be shown, he promised, to other friends such as Lantin, who were anxious to see what Leibniz had written. It is likely that Leibniz did eventually send a copy of his letter to Princess Elizabeth. Generally, however, Leibniz did not, for whatever reason, give much priority to Foucher at this stage, and the correspondence seems to have been dropped for several years.

The Alliance (1678–79) In spite of the rather occasional nature of their correspondence at this time, the two philosophers seem to have extended their area of critical agreement to Malebranche. They appear to have agreed that Malebranche, in the third volume of his Recherche, had largely capitulated to scepticism, in that he now denied that we have a clear idea of the nature of our soul or that we could know through our senses that there are bodies outside us. There are some notes from around 1684 on Malebranche’s Treatise of Nature and of Grace in which Leibniz reports: “Malebranche says that we have no certainty about bodies except through faith, since they are not known by means of the senses. One of my friends has told me that, in effect, Malebranche does not believe in the reality of bodies” (A VI iv, 2640).10 It seems likely that this friend was Foucher. Implicit in this passage is a point on which Leibniz and Foucher appear to have agreed, that fideism generally is a form of virtual unbelief.11 Bayle, by contrast, celebrated fideism at this and at other points, especially in his article on Zeno, in which he tells the same story about Malebranche believing that “faith alone can truly convince us of the existence of bodies” (1697: XV, 52/Popkin 1991: 377).12 Foucher and Leibniz thought that a moderate scepticism like Foucher’s was an antidote to dogmatic rationalism in

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metaphysics and in religion. In this way it supported a reasonable faith. But they neither thought, nor professed to think, that total scepticism was conducive to religious belief.

5. leibniz as academic sceptic (1684–87) The Correspondence (1684–87) Foucher again attempted to revive the correspondence at the end of 1684, reporting on the controversy between Malebranche and Arnauld concerning the nature of ideas and on his own publishing ventures, as well as enclosing some verses he had written. Once again he expressed the wish that Leibniz himself would write a book (GP I, 378). The occasion for the letter was the death of the Abb´e Edm´e Mariotte, who had performed some services for Leibniz in Paris, which Foucher now offered to take over. Leibniz wrote back, apparently without keeping a copy of his letter, to accept this offer. He also referred to his Meditations on Knowledge, Truth and Ideas, which had been recently published in the Leipzig Acta eruditorum (A VI iv, 585–91/AG23–7). Foucher replied, complaining about the difficulty of getting access to foreign journals in Paris and offering some more gossip and commentary on the Malebranche–Arnauld controversy, as well as news of their mutual friend Lantin. He also sent Leibniz a copy of his printed reply to Desgabets and a commentary on the first fifty-two verses of his Wisdom of the Ancients.13 This time, perhaps because in 1686 Leibniz was full of philosophical ideas, he replied at some length. He praised Foucher’s work on the wisdom of the ancients and encouraged him once again to restore the true teaching of Plato, which he contrasted implicitly with the false Platonism of Ficino and Patrizzi (GP I, 380). He also commented in some detail on the printed reply to Desgabets, which he had seen in an earlier form when he was still in Paris. Foucher’s scepticism about mind-body interaction provided Leibniz with one of his earliest opportunities to air his own opinion, recently articulated, as we know now, in what he called his “little discourse of metaphysics.” He suggested to Foucher that “every individual substance expresses the entire universe in its manner and that its next state is a consequence [ . . . ] of its previous state, as if there were only God and it in the world” (GP I, 382). The lengthy extract of this letter that has survived deals mostly with philosophical matters. The letter sent, however, evidently dealt also with more personal matters, perhaps relating to Foucher’s offer effectively to act in some ways as his agent in

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Paris. Foucher proposed to make copies of the letter available to Lantin and other interested “friends.” He assured Leibniz that he would circulate to others only “what concerns the sciences,” implying that the letter he had received contained personal matters. Foucher promised to urge readers not to come to a final judgement on “the system you propose” (GP I, 385). He excused himself from offering a philosophical response to Leibniz’s system on the ground that it might some day be printed, when he promised Leibniz he would “reply fully and in a manner that will not be disagreeable to you” (ibid.). In a missing letter of early 1687, Leibniz outlined to Foucher the argument of his Brevis demonstratio against Descartes’s laws of motion (A VI iv, 2027–9/L 296–8). He seems also to have called to Foucher’s mind his criticisms of Descartes’s ontological argument. Foucher agreed on both points. In his reply, he said that he did not think the existence of God could be better demonstrated than “on the principles of Plato” (GP I, 390).14 Foucher had at a number of points expressed the wish that Leibniz could be persuaded to return to Paris and in a veiled postscript Leibniz came up with a scheme that would allow him to visit Paris without having to resign his position in Hanover (GP I, 393–4). The suggestion was that he might be some kind of expert correspondent on matters relating to mines and minerals. He would come to Paris, from time to time, to report to the Academy. It is apparent that Foucher played a part in advancing this scheme, though it is not clear, from the extant correspondence, what exactly that was. Their plan was, as it turned out, overtaken by events. Leibniz was planning an extensive tour in 1688 to research the history of the house of Hanover. His intention had been to include France and Holland in the tour but his employer put his foot down. As Leibniz succinctly informed Foucher, “my instructions did not permit me” (GP I, 396).

The Alliance (1684–87) This phase of the exchanges between Leibniz and Foucher represents the high point of the alliance between them. At one stage in 1687 Leibniz went so far as to appear to embrace Academic Scepticism. When Foucher had sent him the second part of his Reply to Desgabets,15 which consisted of a discussion of Augustine’s opinion of the Academics, Leibniz wrote back: “I have read it with much pleasure and I tell you without flattery that I have found it entirely to my liking. The laws of the Academics which

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you have expressed in the words of St. Augustine are those of the true logic” (GP I, 390). This seems a very strong statement indeed and raises two questions: (1) What exactly was it that Leibniz appears to have been endorsing? (2) How far can his endorsement have been considered and sincere? (1) Foucher argued that Augustine, in spite of having written a book called Contra Academicos, was really himself one of the Academics, indeed, their leader.16 Foucher claimed to have extracted from Augustine’s writings a set of methodological principles, which he called “the laws of the Academics.” These take the form of five precepts: 1. Be guided only by demonstration in the business of philosophy. 2. Do not engage in controversies that are clearly not decidable. 3. Admit what you do not know and of which you are, in effect, ignorant. 4. Distinguish what is known from what is not known. 5. Always search for new knowledge. (Foucher 1686: 44–5) I do not know how widespread this perception of Augustine as an Academic Sceptic was. Leibniz may have accepted Foucher’s account of the matter without much thought. At the same time his own frequent references to Augustine suggest he had read a good deal even though he may have skimmed over much of it. In a paper of 1686 on the general science, he had quoted a passage from Augustine that seemed to make the same call for rigour in doing philosophy that he himself wished to make: “Do not allow yourself to suppose that you have discovered the truth in philosophy unless you can explain the step we take in putting together one, two, three and four to make ten” (A VI iv, 705/W 37). So far as Leibniz was concerned, the search for demonstrations was important even for truths that we accept as obvious. When he was in Paris, he recalled, the geometer Gilles de Roberval was laughed at by some members of the Royal Academy of the Sciences for proposing that an attempt be made to demonstrate the axioms of Euclid. Leibniz himself had not mocked, he assured Foucher, and, indeed, the project had been thought of long before by Proclus and Appolonius (GP I, 402). It was part of the value of scepticism, in his view, that it made us go back to first principles in this way. (2) That Leibniz could agree that the laws of the Academics were those of “the true logic” will come as no surprise to those who think of him as a “rationalist” philosopher who believed in constructing a deductive system founded on the indubitable truths of reason. That, indeed, is what perfect

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knowledge or scientia would be like, for Leibniz. There is no doubt that Leibniz accepted this ideal as an ideal. It is the kind of knowledge of the world that an angel might be supposed to possess.17 What is less clear is how far, if at all, he thought humans could reach it. Certainly he did not think we could reach it completely, in this life. He thought it was part of what, in the language of Catholic theology, is called the “beatific vision,” granted to the blessed who see God face to face. Leibniz appropriated this phrase for the purposes of his epistemology: to attain the beatific vision is, at least in part, to arrive at a perfected and completed science. It is this ideal state that he invokes, for instance, in the early letter to Foucher, in which he has conceded that we have at best a strong moral assurance of the existence of things outside us: it will only be moral assurance until someone discovers the a priori origin of the world we see and pursues the question as to why things are the way they are back to the ground in essence. For, having done that, he will have demonstrated that what appears to us is a reality and that it is impossible that we will ever be deceived by it again. But I believe this would nearly approach the beatific vision and that it is difficult for us to aspire to this in our present state. (A VI i, 249/AG 4)

It is in discussing the beatific vision that Leibniz best expresses his rationalist ideal of a purely a priori view of the world. In his Examination of the Christian Religion, he offers a purely philosophical defence of the Catholic doctrine: For, as God is the ultimate reason of all things, it follows, as a consequence, that when our knowledge will be a priori, through the cause of causes, we shall certainly see God: insasmuch as our demonstrations will then require neither hypotheses nor experiments, and we shall be able to give reasons, even to the primitive truths themselves. (A VI iv, 2452/Sys 162)

Such knowledge would be completely a priori. At the same time, accepting a particular view of the nature of perfect knowledge and even believing that some may attain it in an afterlife is consistent with total scepticism about the prospects of mere mortals doing so. It is also consistent with believing that some mortals might achieve such knowledge in part. Where, exactly, did Leibniz stand? I think that, at least in this phase of the correspondence with Foucher, Leibniz was optimistic that he was making progress towards and that he was, perhaps, even close to achieving this perfect knowledge, at least on some central points of metaphysics. But he did not think he had actually achieved it. He added a qualification to his remark that the precepts of the Academics are those of the true logic: namely, that, in practising them, we must not only reject what is poorly

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established, as Foucher rightly did, but seek to establish solid truths bit by bit. This seems to be the same qualification as Leibniz had made in his “grande letter” of 1686, in which he praises the Academic Sceptics for exposing the weaknesses of our reason when it comes to fundamental principles. He there went on to say: But in questions to do with the human sciences we must try to advance and, even if the only way of doing so were by establishing many things on a few suppositions, that would remain useful: for at least we should then know that all that remained to reach a full demonstration was to prove these few suppositions and escape from the confusion of disputes. This is the method of the Geometers. (GP I, 381)18

The point that we do not need infallible starting-points to resolve controversies and make progress became a recurring feature of Leibniz’s philosophy.19 It is not insignificant that around this time he engaged in an important correspondence with Paul Pellisson-Fontanier with a view to exploring the bases of a possible reconciliation of the Lutheran and Catholic Churches. Pellisson took the view that, without infallibility, it would be impossible to resolve controversies in religion and that this infallibility existed only in the Roman Church. Leibniz rejected the first premise, arguing that it was sufficient that people “believed the truth concerning some necessary points” (K VII, 91). His hope of producing (and claims to have produced) a method that would make it possible to escape the confusion that characterised metaphysical and theological disputes is a not infrequent topic of his more programmatic papers. For instance, in On the true method of philosophy and theology, in which he preaches proper mathematical rigor and claims to have found the true concept of substance, he stresses the importance of his results for “peace among the Churches” (A VI ii, 59/W 65). Leibniz wished to apply his geometric method widely to the resolution of controversies. It was, of course, directly relevant to metaphysical disputes. Leibniz claimed that many things could be established by this method in metaphysics if we make use of axioms such as the principle of contradiction and the inesse principle (GP I, 382). This is consistent with continuing to search for a demonstration of axioms, as some geometers were rightly doing for the axioms of Euclid. So Leibniz had time for Foucher’s project. But, in the meantime, it would be possible “put an end to the disputes” and “make some ground” (GP I, 382). In fact, however, there are problems about interpreting the precepts of Academic Scepticism as stated by Foucher. Indeed, there is a problem of priorities when it comes to following them, especially between

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precepts (1) and (5). Here a crack appeared in the alliance between the two philosophers, with each choosing different priorities. Foucher paid more than lip service to the search for new knowledge but prioritized the demand for full demonstration. Leibniz, for his part, paid more than lip service to the search for full demonstration but prioritized the search after truth.

6. foucher and metaphysics (1688–91) The Correspondence (1688–91) Leibniz wrote to Foucher in late 1688 giving some details of his tour of southern Germany and Austria. He seems to have written again in 1689, mentioning that he was going to Italy, for Foucher replied with advice to visit the libraries, especially the one in Florence. It is clear from Foucher’s 1689 letter that the war Louis XIV had declared that year made correspondence difficult and had prevented access to Dutch and German journals. The correspondence was also disrupted by Leibniz’s travels. There are no other extant letters from Leibniz in this period, though it is clear that at least three further letters were written by him around 1690–91 because Foucher acknowledges receipt of three in his letter of May 1691 (GP I, 397). His replies indicate some of the matters raised in Leibniz’s missing letters. One of them would have been at least a covering note for the piece on Whether the essence of body consists in extension, which was published in the Journal des savants on June 18, 1691. It is probably in relation to this piece that Foucher reported the unwillingness of the editor (Cousin) to publish Leibniz’s contributions anonymously, using only initials, as was Leibniz’s preference and his practise20 with the articles he wrote for the Acta eruditorum of Leipzig and the Nouvelles de la R´epublique des Lettres.

The Alliance (1688–91) The letter by Foucher of 26 May, 1689, which Gerhardt missed and which remains unpublished, is quite important for the light it throws on Foucher as more than a merely sceptical philosopher. It contains his first critical comment on Leibniz’s system: Your hypothesis of concomitant causes needs a fuller explanation. It is a system that has its beauties and, above all, it contains much penetration and intelligence.

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Yet it does not seem entirely free from difficulty. God may be the cause of all finite forms and of all powers. But creatures have their individual action that determines the general impression God continually gives them to proceed to their ends.21

Here it is evident that he thought “the hypothesis of concomitant causes” committed Leibniz to fatalism and so was inconsistent with a doctrine of free will, which it seems Foucher wished to embrace.22 Moreover, in this letter, Foucher drew attention to Part IV of his Defence of the Academics, in which he makes clear that the doubt of the Academics about the senses does not prevent them accepting dogmas and from recognising substantial truths like the existence and unity of God, his providence, and the immortality of the soul. Academic Scepticism did not, in short, “throw the baby out with the bathwater.” One could reject the pretensions of Cartesian metaphysics to demonstrate a large range of dogmas without, at the same time, undermining the rational foundations of religious belief. Though Foucher subscribed to the highest standards of demonstrative rigor in metaphysics and was quick to identify points at which other philosophers failed to achieve them, he did not live up to those standards himself when trying to support his own philosophical intuitions, for instance, about free will and interaction. Though this may have been philosophical weakness rather than bad faith on his part, Foucher failed to practise what he preached, as Leibniz was later to point out. He seems, for instance, to have accepted the view that we cannot know the essence of the human soul and so, presumably, we do not know the soul is an immaterial substance. On this issue Foucher believed less than Descartes. However, he did think we know the soul has unity as one of its essential features and from this he supposed we can infer that the soul is immortal. So, on this issue, he believed more, since Descartes allowed that God could have given the soul such a nature that it disappeared at death and that the most we can claim is that there are no processes we know of by which this could happen.23 In this case it seems that Descartes was more careful than Foucher in not claiming more than he could demonstrate. Leibniz, for his part, accepted the Platonic argument from unity to natural immortality but realised that the conclusion that could properly be drawn was a long way short of the immortality people aspire to, since that involves memories and continuing personal identity. The German philosopher thought that the Platonic argument proved the indestructibility of all living things and this was how he understood “natural immortality.” This “natural immortality,” though much less than full immortality, provided some sort of analogue of it and, in the face of certain kinds of materialism, gave some credibility to religious teachings about

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an afterlife. But, at the end of the day, on Leibniz’s view, continuing personal identity for humans after death depends on Providence, and belief in it is a matter of faith, that is, goes beyond what reason can establish (see Brown, S. 1998).24 Foucher was not, of course, alone in thinking immortality could be demonstrated. Much the same argument was trotted out by other philosophers of the period as if it were conclusive.25 It is a matter on which Descartes was much more cautious than some of the Cartesians. What is salient about Foucher is, however, not that he is original but that, on this matter, as well as on several others, he proves himself to be more than a merely critical philosopher. Moreover he is, at this point, more dogmatic and less critical than Leibniz.

7. exchanges in the journal des savants (1691–93) The Correspondence (1691–93) Leibniz wrote to Foucher several times in 1691 and, though these letters do not survive, some of their contents can be inferred from Foucher’s replies.26 But, even disregarding the missing ones, there are eleven letters or extracts of letters surviving from this period, including four that were published in the Journal des savants. The topics covered by these letters extend widely and reflect the wide scientific interests of the correspondents, Foucher’s extensive knowledge of what was happening among the savants in Paris and Leibniz’s varied projects. Foucher reported on the latest books, such as the massive Syst`eme de philosophie (1690) of the Cartesian Pierre-Sylvain R´egis and the seven-volume Theologia speculatrix et practica (1690–91) of their mutual friend, Jean-Baptiste Duhamel. Foucher also reported on what was happening at the Academy of Sciences and his discussions with other savants, such as Malebranche, with whom he discussed philosophical matters raised in his correspondence with Leibniz. Foucher, enouraged by their mutual friend the Royal Librarian Thevenot, wanted to know what was happening about Leibniz’s Dynamics, which he had left in Italy. Leibniz, for his part, shared his concern that one of his important mathematical papers had been plagiarized by Jacques Ozanam, though he was prepared to concede that Ozanam was a good enough mathematician to have arrived at the result independently. Their letters, as well as treating such matters and others, often focused on a philosophical topic. Foucher sent Leibniz part of his Philosophy of

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the Academics on the last day of 1691, and Leibniz wrote back in very positive terms, urging his French friend to acknowledge the importance of axioms in the sciences (such as that Nature never acts by leaps) and to produce demonstrations of some of the accepted ones. Foucher took the liberty of submitting an extract from this letter (GP I, 402–3)27 to the Journal des savants on the pretext that many of Leibniz’s friends in Paris wished to have copies. No doubt Foucher would also have been pleased to have his own Academic Scepticism given favourable attention in the Journal. He first replied privately, referring to three axioms he had attributed to the Academics in the third part of his Apology. But, in the following year he decided to reply publicly and sent an extract of a letter for Leibniz (GP I, 410–14)28 to the Journal in which he advertised the latest part of his Philosophy of the Academics, defended his interpretation of the Greek sceptics, and made some critical comments on some of the axioms Leibniz had mentioned with approval. Foucher mentioned in flattering terms Leibniz’s youthful treatises on motion, and Leibniz, in his reply, was critical of his juvenilia whilst conceding that there “must be something good about them since you, sir, as well as others, judge it so” (GP I, 415).29 Leibniz also sketched his account of indivisibles and his solution to the paradox of Achilles and the Tortoise. This phase concludes with a letter from Foucher reporting that Leibniz’s last reply in their published exchanges had been published. Foucher’s letter is undated but it is likely to have been August 1693. In it he complains of restrictions on their correspondence because of the war: “Neither you nor I speak of politics or religion, and yet we don’t have all the freedom of conversation we could wish. We have to make a few concessions to the times: silent leges inter arma” (GP I, 420). Leibniz seems to have misunderstood Foucher’s meaning in using this Latin aphorism and to have supposed he was effectively breaking off their correspondence. This may be one reason why, when he decided to publish a version of his New System in 1694, he thought of turning to Bossuet as an intermediary who would get the editor of the Journal des savants to accept the piece (A I x, 133/WF 35).30 It seems he was on the brink of dealing directly with the editor himself.31

The Alliance (1691–93) At the end of 1691, Foucher sent Leibniz the second book of his Philosophy of the Academics and Leibniz replied, expressing his pleasure on reading it. Leibniz, characteristically, offered a favourable gloss on Academic

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Scepticism whilst not losing sight of the points at issue between Foucher and himself: I am of your opinion that it would be good to look for proofs of all the truths that can be proved. It is not that this is absolutely necessary, nor that we should stop until we can prove all the principles from the first ones. For if the Geometers had tried to postpone the solutions of problems and the demonstrations of theorems until they had demonstrated their axioms and demands or postulates, they would have done poorly and deprived themselves of the advantages that Geometry has brought us. Nevertheless, it is good that there should be some minds who are trying to make good what we have left behind for the sake of making progress. And if your reasonings on the art of doubting are taken in this light, then nothing is more reasonable. But it would be good if you were to explain distinctly that this was your intention, so that those who do not sufficiently understand may not baselessly imagine that the Academy is opposed to progress in the sciences. (GP I, 402)

Leibniz is saying in this letter that demonstrations from first truths are very desirable but not “absolutement necessaire.” Embedded in Foucher’s letter is a quite opposed position. There is nothing wrong with people doing as Leibniz says they should and deriving secondary truths from principles that themselves still need to be demonstrated. He dismissed this as something people could do as much as they wished. But, he insisted, this “does not avoid the necessity of once at least going from the last principles to the first, and vice versa” (GP I, 409). By this stage the difference between the two friends as to philosophical priorities must have been quite clear to them both.

8. leibniz’s new system and foucher’s critique (1695–96) The Correspondence (1695–96) In April 1695 Leibniz wrote a tentative letter to Foucher, inquiring after his health and the progress of his meditations. He also mentioned his intention to publish his “system of the communication of substances” (GP I, 420). Foucher replied promptly that he was “extremely happy” that Leibniz was about to get his “system of concomitance” out (GP I, 422). It was Foucher who placed Leibniz’s manuscript with the editor of the Journal des savants, and it was Foucher who, as he had promised to do, wrote the first reply to the New System when it appeared. Two things about Leibniz’s New System particularly disappointed him. Leibniz, despite all he had been saying in his letters about the method of geometry, had

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decided on a “popular” rather than a systematic presentation.32 The New System is couched in the accessible format of an intellectual autobiography and fails, from Foucher’s point of view, to present propositions “in order.” Worse, the autobiographical account falsely advertises Leibniz as someone working within a Cartesian mind-body problematic. Foucher’s disappointment is encapsulated in these remarks, directed against the systems of Descartes, Malebranche, and Leibniz: is it not clear that [ . . . ] all these systems are only invented after the fact, in order to defend certain preconceived principles? Thus the Cartesians, having assumed that there was nothing in common between spiritual and corporeal substances, cannot explain how each operates on the other, and so are reduced to saying what they say. But you, sir, who could have got out of it in various other ways, astonish me by entangling yourself in their difficulties. (GP I, 426)

Leibniz, in his reply, made no apology for his system being invented “after the fact” since, he claimed, all systems are constructed “in order to save the phenomena or appearances.” And he wished to defend as “a priori” what Foucher dismissed as “preconceived”: “It is usually enough that a theory should be proved a posteriori by its fitting the phenomena: but when there are also other reasons for it, and these are a priori, then so much the better” (GP I, 496/WF 50). The nub of the issue between the two was obviously whether Leibniz could substantiate his claim that his system was based on demonstrable a priori truths or whether Foucher was right in saying that they were no more than prejudices. At this intriguing point, however, the correspondence was brought to an abrupt end by Foucher’s death on April 27, 1696.

The Alliance (1695–96) Though Foucher kept his promise to reply to Leibniz’s system when it was published, he did not, perhaps because he was not able to, keep it in full. For he had promised to reply in a manner that would not displease his German friend. In the event, his tone is very different from that of their previous deferential exchanges in the Journal des savants. It is severe, hostile, and even dismissive. Leibniz must have thought Foucher had treated him very badly, since he had outlined his views in his letters to Foucher, and, apart from a brief mention of a problem about free will, Foucher had put off commenting until Leibniz published his views and explained them more fully. In his reply Leibniz gently reproved Foucher for not coming out with his objections before and went on to answer him point by point in the most civilised way, praising Foucher as “an able

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Academic” who wishes to go into things more deeply. Foucher concluded his critique by saying, in effect, that it all goes to show that we should observe the rules of the Academics. To this Leibniz replied: “I am not sure that your Academics have practised what is good in their method more rigorously or effectively than I have” (GP I, 497/MP 129).33 He himself, he pointed out, had often attempted to produce demonstrations from first principles. This, he implied, was more than Foucher had done.

9. the aftermath Leibniz’s reply to Foucher’s critique of his New System was published in April, 1696, the very month that Foucher had died. Leibniz did not learn of his friend’s death for a long time, though Foucher’s failure to reply made him worried. Nearly ten months later he wrote to Nicaise: “Is the Abb´e Foucher dead or alive? He has said nothing about my reply in the Journal. When he wrote against my philosophical thoughts, he believed they were no more than hypotheses. But, on reflection, he found that they were demonstrations” (GP II, 563). Foucher had, of course, found no such thing. Leibniz was assuming here, perhaps, that his friend had managed to read, absorb, and acknowledge the justice of his reply, in which he had pointed out that his theory of pre-established harmony followed from his view of unities. In a much later account of the same episode, in his New Essays, Leibniz made no such assumption and complained against Foucher rather that: He was always urging that one should beware of preconceptions and cultivate great accuracy: but besides not taking trouble to practice what he preached – for which he can largely be excused – he seemed to me not to notice when someone else practiced it, no doubt taking it for granted that no-one ever would. (NE 374)

Leibniz was here reverting to the same point he made against Foucher in his reply to the critique of his New System, that he himself had practised what is good in the method of the Academics better than the self-styled Academics themselves. And this confirms the view that Leibniz had been sincere in his acceptance of the “laws of the Academics,” at least as he understood them. He would not, of course, have been happy to declare himself publicly to be an Academic Sceptic because of his unwillingness to be identified as a member of a sect. Indeed, while he continued to praise Foucher as a “learned and shrewd” man whose books had given him a good reputation,

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he criticised him for “being a little too taken with his Academics” and with wanting to revive a sect (A VI vi, 373). That was one of the cracks in their alliance that Leibniz and Foucher had largely managed to “paper over.” They were less successful in papering over their differences over whether demonstrative rigor should, if necessary, have priority over making progress. And, in later references to Foucher, Leibniz referred back to this, claiming to have often reminded his sceptical friend that one must not doubt for the sake of doubting but that “doubts must serve us as a gangway to the truth” (GP VI, 324–5/Th 336–7). These were real points of division between the two. Leibniz tended to stress such points in his later writings. No doubt, it was partly because he thought Foucher had in the end let him down that he later tended to stress their differences and underplay what they had previously had in common. But another, more philosophically interesting reason may be suggested. It is that there was a gradual shift in Leibniz’s epistemology towards a more positive view of moral certainty and a correspondingly less positive view of the value of scepticism. For instance, Leibniz and Foucher had lamented the lack of demonstrative rigour in Descartes’s ontological argument for the existence of God. In particular, Leibniz was worried by the assumption that Descartes made but had not proved, that the concept of God was free of contradictions. During his visit to Spinoza in 1676, he produced an extraordinary argument to demonstrate that there was no contradiction in the concept of God and so plug the gap in Descartes’s argument (see A II i, 271–2/L 167–8).34 But it seems that he was later unconvinced by his work of repair and assumed instead that it was not possible. In the New Essays, he suggests that the onus of proof lies with anyone who maintains there is a contradiction in the idea of God and is content to claim that the argument gives moral certainty.35 Another example of Leibniz’s change to a more positive view of moral certainty is to be found in his remarks about the Cartesian life-as-onelong-dream scenario. Leibniz continued to take the view that the coherence of our experiences is the basis for our belief that they are real. But, in his 1675 letter to Foucher, he had emphasised that this was no more than a moral assurance and that it was part of the value of Academic Scepticism to bring this out. The implication was that it is only if we were to be granted a beatific vision or something like it, and so have a true a priori knowledge of the state of the world, that we could really be certain and so would really know one way or the other. Nearly thirty years or so later, however, in his New Essays, Leibniz’s memory of his exchanges with Foucher was rather different. He claimed to have

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shown Foucher that “the truth about sensible things consists only of the linking together of phenomena” (NE 374). He concedes that, metaphysically speaking, it is not impossible for life to be one long dream. But the moral certainty he continued to profess about the external world ceased to be mere moral certainty. On the contrary, the onelong-dream hypothesis is dismissed as just as “contrary to reason” as it would be to imagine a book resulting from jumbling together a printer’s pieces of type (NE 375). It is not clear when, or even whether, Leibniz ever made such a point to Foucher. But the thought seems to be of a piece with one he made in his “Critical Remarks on Descartes’ Principles of Philosophy,” which were written in the early 1690s (GP IV, 354–92/L 383–412). In the Principles Part I, §4, Descartes had given reasons for scepticism about the objects of the senses (AT VIIIA 5–6/CSM I, 193–4). Leibniz comments as follows: About sensible things we can know nothing more, nor ought we to desire more, than they are consistent with each other as well as with rational principles that cannot be doubted, and hence that future events can to some extent be foreseen from past. To seek any other truth or reality than what this contains is vain, and sceptics ought not to demand any other, nor dogmatists promise it. (GP IV, 356/L 384)

These remarks show that Leibniz had come to the view that Descartes and the sceptics had made the same mistake. Leibniz seems to have grasped the insight that sceptics and dogmatists create business for one another and that the right way to avoid both dogmatism and scepticism was to deny what they had in common. This common assumption is that we do not really know something unless certain stringent conditions are met, for instance, unless it is either self-evident or can be demonstrated from truths already known to be self-evident. Leibniz’s strategy, as he makes clear in the discussion of Foucher in the New Essays, is to introduce another sense of knowledge, what he calls “la connoissance de vraisemblable” (NE 373). In this different but appropriate sense, I do know that life is not one long dream. In his 1675 letter to Foucher he seems to accept a metaphysical paradigm of knowledge and at least implies that we would only really know that life is not one long dream if we were to enjoy something like the beatific vision and see a priori how everything had to be the way it is. It seems, then, that at this fundamental point, Leibniz moved away during the period of his correspondence with Foucher from his earlier position of at least partial support for Academic Scepticism. The negative tone of his later references to Foucher does not, therefore, only

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reflect his eventual disappointment in his Paris friend but a shift in his own philosophical position.

Notes 1. For a fuller acount of Foucher’s life and works see Watson 1987: ch. 3. 2. Foucher wrote to Leibniz that it had not been for sale (GP I, 390) and that he had only had a small number of copies printed for communication to the “savants” (GP I, 378/A II i, 378). He could never find a spare copy to send Leibniz. In his letter of December 8, 1684 (GP I, 378/A II i, 248) he said that he had only one copy left. In the letter of of May 30, 1691 he inconsistently implied he had “hardly any copies” (GP I, 399). 3. He told Foucher in July 1695 about a letter written “twenty four years ago or thereabouts” in which, according to Leibniz, Lantin encouraged him to apply some of his “dynamical meditations” to metaphysics (GP I, 423). 4. Muller ¨ & Kr¨onert note a discussion of measurement in April 1675 (1969: 38). Their philosophical discussions are reflected in a letter Leibniz wrote to Foucher in the same year, of which an autograph draft survives (A II i, 245–9/AG 1–5). 5. The letter missed by Gerhardt, but noted by Bodemann, is one from Foucher dated May 1689. It has been transcribed by R. N. D. Martin and others, though it has not yet been published. 6. An extract of the notes on Foucher’s reply to Desgabets is included in L 154–5. 7. Here they, as well as Lantin, were opposed to the Cartesians. 8. The excerpt Leibniz planned to include from the Phaedo in his Discourse on Metaphysics §20 seems to be a good example of the kind of selection from Plato he was encouraging Foucher to make (see A VI iv, 1562–3). 9. The reference is presumably to the Second Set of Replies that Descartes had published with his Meditations (AT VII, 160–70/CSM II, 113–20). 10. The Akademie editors suggest that Foucher was the source. This is certainly plausible, though it is not confirmed by Foucher’s remarks in any of the extant letters. 11. For some account of Leibniz’s critique of fideism, see Brown, S. 1990: 207–87. 12. I assume that Bayle was a sincere fideist, though it is not difficult to understand why he has been so often taken as a sceptic at heart, as Leibniz probably thought. 13. The first of these is his Nouvelle dissertation (Foucher 1679). The second were printed pages from his De la sagesse des anciens (Foucher 1682). 14. Foucher referred Leibniz to his Logic. 15. This had been delayed because of difficulties in getting it published (GP I, 387). Foucher seems to have re-used it in his Defence of the Academics. 16. He was, according to Foucher, the “Chef d’Academie” (1693, 67). 17. God’s knowledge of the world is even better than this since, on Leibniz’s conception, he does not need to calculate. Angels are intermediate in their

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20. 21.

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23. 24.

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capabilities between God and humans and, as such, are used in Leibniz’s epistemology to illustrate a superior knowledge of the world that is less than God’s but beyond what humans can attain – see, for instance, GP VII, 265/L 173. Leibniz uses almost identical wording in a paper entitled Recommandation pour instituer la science g´en´erale (A VI iv, 692–713), which also dates from early 1686 and throws a good deal of light on this letter. Similar phrases occur in this chapter, e.g. la vraye Logique (A VI iv, 711/W 44) and la confusion des disputes (A VI iv, 704/W 36), and there is also a reference to the Roberval project of demonstrating the axioms of Euclid (A VI iv, 704/W 35). I am grateful to Franklin Perkins for perceptive comments on my paper when presented at the conference Leibniz and His Correspondents, and, in particular, for his suggestion that I should consider the wider implications of the phrase “confusion of disputes.” The suggestion is worth pursuing much further than I have found possible in this context. For the full titles of Leibniz’s articles in learned journals see Ravier 1937: ch. 2. “vostre hypothese de la concomitance des causes demendroit une explication plus ample cest un systeme qui a ses beautez et qui renferme surtout bien de la penetration et bien de l’esprit, mais il ne paroit pas estre entieremt . exemte de difficult´e. Dieu est la cause de toutes les formes finites et de toutes les puissances mais les creatures ont leur action particuliere et determinative de l’impression generale que Dieu leur donne continuellemet . pour se porter a leur fin” (LBr 278). Curiously, Foucher did not return to this line of criticism in his reply to the New System itself, perhaps because he knew that Leibniz had chosen to refrain from developing his views on this topic until there was a popular demand for a fuller account of his system. In such a fuller account, he wrote Foucher in July 1695, he would offer, inter alia, his way of resolving “the difficulties de fato et contingentia” (GP I, 423). The mind is immortal, for Descartes, “in so far as it can be known by natural philosophy” (AT VII, 154/CSM II, 109). Leibniz came to see that the traditional a priori argument, such as that claimed for Descartes by some of his disciples, failed to establish continuity of personality and memories (A II i, 502/AG 242–3). By the time of the New System he thought it was a matter of God’s providence that the “moral qualities of their personality” were preserved in rational souls (GP IV, 481/WF 14–15) – also see Theodicy §89 (GP VI, 151–2/Th 171–2). Berkeley’s use of the argument, in his Principles of Human Knowledge (1710: §141), was probably more Platonic than Cartesian in inspiration. But others developed the argument on Cartesian principles. For instance, it is used by the English Cartesian (and Malebranche translator) Richard Sault in his Conference betwixt a modern Atheist and his Friend (1693). For instance, it is clear that Leibniz had, in a missing letter, expressed the wish to have a table of the books referred to in the Journal des savants. Foucher replied that the Journal did not provide such a table and sent him instead a table of contents.

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27. The letter was sent in January 1992 and was published as “Extrait d’une lettre de M. Leibniz a` M. Foucher, Chanoine de Dijon, sur quelques axioms de Philosophie” in the Journal des savants for June 2, 1692: 247–8. 28. This letter, sent to Leibniz with a more conciliatory tail-piece, was published in the Journal des savants for March 12, 1693. 29. Leibniz’s reply was published in the Journal des savants for August 3, 1693: 355–6. 30. Bossuet was sent at least one paper for publication by Leibniz (the French version of his 1694 paper on the reform of metaphysics) but did not submit it to the Journal des savants as Leibniz had wished. 31. See the editorial note on A I x, 133. 32. Leibniz’s reasons for adopting a “popular” presentation rather than presenting himself in a more rigorous form are discussed in Brown, S. (1996) and Rutherford (1996). 33. This comment was probably directed against Descartes as well as Foucher. 34. A II i, 271–2/L 167–8. I do not mean to imply that the later Leibniz thought there were no fully demonstrative arguments for the existence of God. See, for instance, NE 440. 35. “We are entitled to assume the possibility of any being, and above all of God, until someone proves the contrary: and so the foregoing metaphysical argument does yield a demonstrated moral conclusion” (NE 428).

5 Leibniz to Arnauld Platonic and Aristotelian Themes on Matter and Corporeal Substance Martha Brandt Bolton

In many essays over a large number of years, Leibniz attacked the Cartesian doctrine that extension constitutes the essence of a substance. In some of these essays, he, nonetheless, advocated a doctrine of corporeal substance, although, perhaps, his enthusiasm for it flagged as the years went on. In the letters he wrote to Arnauld, between 1686 and 1690, both the critical attack and Leibniz’s own account of bodily substance are prominent. At this stage, he was presenting this theory of substance to a truly formidable critic, perhaps for the first time. He did not insist that it is true, but he did set himself up to explain what the theory is: given that no substance could be merely extended, what would be required for a substance to be corporeal? Substantial forms, in a word. Arnauld immediately raised a couple of central questions. As the correspondence proceeded, he learned more about Leibniz’s proposal, but he kept coming back to these two central points. The strategy of this chapter is to exploit the fact that Leibniz’s responses occur in the context of this ongoing dialogue. Each letter of Leibniz can – I would say, must – be understood in light of the ground covered in previous letters. The mutual understanding built up between the two is directly relevant to an appreciation of the force of Arnauld’s final queries and the demands they make on his I want to thank members of the Descartes–Leibniz seminar taught by Roger Woolhouse and myself at Rutgers in spring 1997 for thought-provoking discussion; Roger Woolhouse, Paul Lodge, Glenn Hartz, and Don Baxter for helpful comments on earlier versions of this chapter; Bob Sleigh for generously providing transcripts of unpublished drafts; participants in the lively conference on Leibniz and his Correspondents held at Tulane, spring 2001, including my commentator Alison Simmons; and Paul Lodge for suggesting improvements on the most recent versions.

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correspondent. Any extended exchange between philosophers uniquely creates this sort of interpretive resource. In this case, the accumulation of shared understanding and expectation is all the more significant because of the penetrating intelligence and mutual good will of the parties. The immediate aim of this chapter is to bring this interpretive strategy to the texts. Owing to Arnauld’s acuteness, the questions to which he kept returning bear directly on issues much discussed in recent secondary literature. There are two such issues: (1) whether Leibniz held, in this exchange, that the aspect of corporeal substance that is extended, modified by figure, size, motion, and so forth, is independent of mental operations such as perception, abstraction, and imagination1 ; and (2) whether the fact that a corporeal substance consists of infinitely many substances is strictly consistent with Leibniz’s doctrine that substances are true unities. I will urge that the answer to (1) is given in his response to two final questions of Arnauld. Also I will suggest briefly that the letters set up several standards of substantial unity and create a particular difficulty for the claim that bodily substance meets all of them. This correspondence has been studied carefully in a variety of ways by other scholars. Their work is invaluable. My reason for revisiting the texts is to use an interpretive strategy that leads to somewhat different results.

1. the hypothesis The question of the substantiality of bodies is debated with some precision through six letters, three from each correspondent. Altogether Arnauld wrote four letters to Leibniz, and the topic of bodily substance came to the fore in the second of these. When the correspondence first began, Arnauld had received, from an intermediary, summaries of each section of Leibniz’s Discourse on Metaphysics. He did not see the entire work. But he learned that Leibniz propounded the complete-concept definition of individual substance and claimed to derive his main metaphysical doctrines from that (see Discourse §8: A VI iv, 1539–41/AG 40–1). Arnauld’s initial letter raised objections to the definition, which he believed to have unacceptable implications.2 Most of Leibniz’s first reply addressed those objections, but at the close of this letter (long letter, July 4/14, 1686), he picked up the thread of his argument in the Discourse. He briefly mentioned a few consequences of his definition of substance, specifically regarding mind and body (GP II, 57–9).3 When Arnauld answered (his second letter, Sept 28, 1686), he sought clarification on two of these doctrines: the theory of harmony proposed to explain the union

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of soul and body, which is not my main concern here, and the reality of bodies. Arnauld wrote quoting Leibniz: The second matter on which I would like enlightenment is the following remark: “that in order that the body or matter not be a simple phenomenon, like the rainbow, nor an entity united by accident or by aggregation like a heap of stones, it cannot consist of extension, and there must necessarily be something there that one calls substantial form and which corresponds in a way to what one calls the soul.” There are many things to ask about that. (GP II, 65–6)

Seven questions followed. Arnauld assumed bodies are more than rainbows and heaps, and he even inclined to regard them as substances. Yet he recognized at once that the structure of extension might be thought to compromise the substantiality of something whose essence is to be extended. He was interested in learning how Leibniz purported to overcome the difficulty, but he was unable to see how either souls or substantial forms could do it. There are two central related questions that he persisted in exploring throughout the ensuing exchange: (1) why exactly did Leibniz think that what is extended, merely as such, cannot be substance; and (2) how can soul-like substantial forms overcome whatever it is that bars being that is merely extended from substantiality. The discussion of these two questions is tracked in the following sections of this chapter. But more needs to be said about the hypothesis that attracted Arnauld’s interest. In effect, Leibniz posed a disjunction: either bodies are on a par with rainbows and heaps, or they are not wholly constituted by extension and have something like substantial forms. The first downgrades the reality of body in such a way that only immaterial substances exist, and it identifies those substances as spirits, immaterial rational souls – roughly Cartesian thinking substances. The second disjunct involves a much more extensive ontology although this is not fully apparent in the initial statement. The hypothetical ontology could have been regarded as controversial, even dangerous to morality and religion, and this might suffice to explain why Leibniz hesitated to commit himself to it. Even in his last communication, he did not insist on it, acknowledging that some might find it difficult to accept (GP II, 127). According to the hypothesis, there are not only rational souls, but also immaterial soul-like forms in all animals (GP II, 75); indeed, there are analogous forms in all living things (GP II, 76–7; 92; and 127). Since Leibniz held that all of these forms are indivisible and naturally indestructible, he had to be prepared to explain how the moral attributes of

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rational souls differ from those of lesser forms (GP II, 100 and 124–5). There was also the question of what happens to the indestructible soul-like forms of living things when they die: transfiguration is Leibniz’s answer (GP II, 99; 116–17; and 124). Further, the hypothesis implies that there are swarms of living creatures that stand to be discovered, for instance by microscope, but also vastly more than could ever be confirmed empirically. For every inanimate body is said to be composed of animate bodies and every animate body, composed of endlessly many other animate bodies (e.g., GP II, 99–100). Thus, every body, whether it has a soul-like form or not, is composed of bodies that have such forms. Leibniz said that if bodies are more than simple phenomena, like rainbows, or united accidentally, like heaps, then there are substantial forms in them. Rainbows are perceptual appearances, and heaps have no definite enumeration or diachronic identity, except by fiat.4 How did Leibniz think the reality of bodies would be enhanced beyond that of visual appearances and vague entities, if there are substantial forms? His choice of the term substantial form unmistakably refers to the Aristotelian theory that a material substance is a composite unity; that is, a substantial union of matter and form, the reality of which is in no way dependent on perceptual appearance or arbitrary decision. But Aristotle supposed that even matter that lacks substantial form – mud, for example – exists in a similarly mind-independent way. A decidedly Platonic note is sounded by Leibniz’s presumptive doubt about the reality of what is extended, his declaration that what is extended is in danger of being no more real than a rainbow or a heap.5 It is not clear, from the start, what aspects of the two ancient doctrines Leibniz approves, nor how he purports to make his Aristotelianism consistent with his Platonic tendencies.

2. arnauld’s first take on the problem Arnauld was told next to nothing about why Leibniz thought bodies might be nothing more than rainbows and heaps. He came up with his own explanation: “For it is the divisibility of extension into an infinite number of parts that gives one trouble in conceiving of its unity” (GP II, 66). He could see Leibniz was not urging the atomistic solution to the composition of matter; but he was completely unable to see what he was urging instead. In one way or another, each of his seven questions asks: how can substantial forms possibly impart unity to infinitely divisible stuff? To begin, Arnauld argued, along Cartesian lines, that the rational soul could not serve as substantial form of the body because the soul is a substance really distinct from the body, whereas substantial forms were

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said to be naturally inseparable from matter. Besides, bodies in general do not have rational souls; so if the rational soul is the model of substantial form, very few bodies would be more than rainbows or heaps. He went on to observe that the non-rational substantial forms invoked by scholastics are divisible and, therefore, unable to introduce unity into divisible extended stuff. Arnauld was well informed about all of this. Scholastics sometimes said that a rational soul is wholly present in the whole body and wholly present in all its parts and, thus, is not destroyed by any division of parts. In contrast, lesser substantial forms are wholly present in the whole and partly in the parts and, thus, destructible by separation of bodily parts (see Adams, M. 1987: i, 244; ii, 645; and ii, 659–60). Next, Arnauld wondered whether perhaps Leibniz was proposing a general “form of corporeity.” Scotus posited a form by this name in order that matter without substantial form should, nevertheless, have a certain actual being; for prime matter, altogether without form, would have no actual being but only being in potency (see Adams, M. 1987: ii, 633–70 and Robinet 1986: 50–1). None of this apparatus solved the problem of infinite divisibility, as far as Arnauld could see. He was right that Leibniz took the divisibility of what is extended to be a barrier to its unity, which in turn compromised its mind-independent reality. A deeper account of why Arnauld found the reality of what is merely extended problematic came out in his reply (November 28/December 8, 1686): if there are no bodily substances such as I can accept, it follows that bodies will be no more than true phenomena like the rainbow; for the continuum is not only infinitely divisible, but every part of matter is in fact divided into other parts as different one from another as the two diamonds mentioned above; and since it continues endlessly in this way, one will never arrive at a thing of which it may be said: ‘Here really is an entity’, except when one finds animate machines whose soul or substantial form creates substantial unity independent of the external union of contiguity. (GP II, 77 – emphasis added)6

Arnauld correctly surmised that Leibniz thought the reality of what is merely extended is compromised by the infinite divisibility of the continuum. Still, a good deal of unexplained theorizing about the continuum lies behind these remarks. They distinguish between infinite divisibility and an actual infinite division. Leibniz agrees with Arnauld that the continuum is endlessly divisible but adds that every bit of matter is actually divided into different parts. In effect, he contrasts the potential divisibility of strictly continuous abstract geometrical extension and the actual discrete division of matter. The former can be divided at will, whereas the latter is actually divided, as we say, into denumerably

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many parts.7 The view that this sort of compositional structure is found in matter – as distinct from the abstract continuum – was assumed by Leibniz throughout the correspondence. Arnauld never explicitly challenged it. It frames the problem that substantial forms are supposed to solve. If forms exist, then the parts into which every bit of matter is divided are “animate machines” – with unity “independent of the external unity of contiguity,” which is the only unity mere extension affords. Arnauld’s next question (of the seven) brought up the notorious obscurity of substantial forms. Extension is no less obscure, Leibniz retorted, returning to the “strange problems over the composition of the continuum.” He added with emphasis: “and it can even be said that there is no fixed and precise shape in bodies because of the actual subdivision of the parts. With the result that bodies would undoubtedly be merely imaginary and apparent, if there existed nothing but matter and its modifications” (GP II, 77). One can wonder whether Leibniz means that matter is infinitely divided and lacks determinate shape, even if there are substantial forms; we might be tempted to think otherwise – that forms prevent the actual subdivision that makes shape indeterminate, so that bodies are neither imaginary nor mere appearance. But this seems not to be correct. Arnauld’s final question conjectured that Leibniz did not endorse Cordemoy’s thesis that the division of matter terminates in extended, indivisible atoms, from which all other extended things are composed. In his reply, Leibniz confirmed this surmise (GP II, 78). So even assuming there are substantial forms, every bit of extended matter is endlessly divided and, for that reason, bodies have no determinate shapes (also see GP II, 98–9; 119; and Discourse §12: A VI iv, 1545/AG 44).8 The conclusion is that bodies are all the more surely “merely imaginary and apparent” if they consist of nothing but extension and its modifications. This second letter seems to say that forms give to bodies a dimension of reality compatible with their having no precise extensional boundaries. To Arnauld, this underscores the difficulty. Although substantial forms are supposed to endow what is extended with true unity, they seem not to eliminate the factor that prevents what is merely extended from being a true unity – its endless division and vague boundaries.

3. more on the problem about the reality of what is merely extended In this same letter (November 28/December 8, 1686), Leibniz did resolve one of Arnauld’s questions about substantial forms. He asked whether a

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substantial form is supposed to make one entity of a marble tile and, if so, what happens to the form when the tile breaks. For Leibniz, a tile is a paradigm of body that has no substantial form. He replied that because its parts have only the unity of contiguity, a tile is what is called “one by accident [unum per accidens]”; a substance has unity of an altogether different type: There is as much difference between a substance and such an entity as there is between a man and a community, such as a people, army, society or college, which are moral entities, where there is something imaginary and dependent on the fabrication [la fiction] of our minds. Substantial unity requires a complete, indivisible and naturally indestructible entity, since its concept embraces everything that is to happen to it. [ . . . ] which [can be found] in a soul or substantial form after the example of what one calls self. (GP II, 76)

Precisely because a tile can be broken into parts, it is not a substance, for Leibniz. Substances are indivisible and without parts. After reading Leibniz’s letter, Arnauld remained puzzled (letter of March 4, 1687). He now understood that Leibniz’s substantial forms have the indivisibility and indestructibility ascribed by scholastics to the rational soul and by Descartes to a thinking substance. At this point, Arnauld did not repeat his question about how such a form confers unity on matter that is infinitely divided, but he raised a related question. Since Leibniz did not assign soul-like forms to many material things, such as marble tiles, how did he purport to secure reality for extended things in general? He also pressed for more information about what the problem is supposed to be, the first of his two central questions. Leibniz indicated, in a passage quoted earlier, that his objection to the substantiality of what is merely extended was based on his definition of substance, on which a substance has a concept that determines, once and for all, everything that is to happen to the substance. Arnauld reported, in his second letter, that Leibniz had satisfied his initial objections to this doctrine in regard to human beings (GP II, 64). But now he questioned its adequacy as a definition of substance. Leibniz had cited Plato, who denigrated sensible things to a mere imitation of substances, in support of his contention that extension is not enough for a substance (GP II, 76). Arnauld counters with Augustine, who held that matter is a substance despite lacking unity. Suppose it is the essence of matter not to have true unity because of its infinite divisibility. That just means that bodies are substances of a sort inferior to souls, Arnauld argued (GP II, 86–7).

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In place of Leibniz’s thesis that substance is a true unity, Arnauld proposed a definition of substance he claimed to be equally good: substance is “that which is not modality or state.” Since a block of marble is neither the mode nor the state of a substance (as he assumed), it is a substance by this definition. One might say the hunk of marble is not a single substance but rather many substances mechanically joined; why is that a reason to deny its substantiality? Arnauld declared that he found nothing amiss in saying that “in the whole of corporeal nature there are only [ . . . ] ‘machines’ or ‘aggregates’ of substances, because of none of these parts can one say, accurately, that it is a single [une seule] substance” (GP II, 86–7). So there are extended composite substances, but all of them are composed of other such substances.

4. the aggregate and modal arguments Arnauld was directly challenging a central thesis of Leibniz’s metaphysics (see GP II, 57–9). It was undoubtedly important to him to rebut the challenge convincingly. He began his response (letter of April 30, 1687) by returning to the difference between aggregates and substances. His strategy is to classify things that are merely extended as entities of a more general type, aggregates, and to reason about aggregates. I believe that where there are only entities through aggregation, there will not even be real entities; for every entity through aggregation presupposes entities endowed with a true unity, because it obtains its reality from nowhere but that of its constituents, so that it will have no reality at all if each constituent entity is still an entity through aggregation; or one must yet seek another basis of its reality, which in this way, if one must constantly go on searching, can never be found. (GP II, 96)9

This much is indisputable: there is an aggregate of F s only if there are Fs that are constituents of the aggregate. Arnauld’s position in no way denies this. An extended substance is a compound (he never referred to it as aggregate), and its components, too, are compound substances.10 Precisely because there is an endless regress of such compounds, the indisputable formula is always satisfied. If Leibniz’s reasoning has any force against Arnauld, it depends on a different principle.11 In fact his contention is that aggregates are real (mental fabrications) only if there are true unities, that is, substances as Leibniz defines them. His argument is: anything that is merely extended is an aggregate; an aggregate is real only if there are true unities on which its reality depends;

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therefore, corporeal, or extended things, are real only if there are true unities on which their reality depends. In light of its importance for Leibniz, this argument seems disappointing; it suffers from two related defects. Assuming that Arnauld accepted the first premise (as mentioned, he never explicitly did), nothing is said to persuade him to accept the second one. On the contrary, he proposed openly that every extended thing is a multiplicity of other extended things and nonetheless real and substantial. Leibniz said nothing to indicate why an infinite regress of non-unitary constituents is vicious.12 Nor did he say how extended things are supposed to depend on true unities, which might shed light on why he thought that they do, if they have a certain reality. It is natural to suppose the dependence is like that of a whole on its parts – compositional. This is suggested by the examples of aggregates: an army, college, machine. And the composition of matter was in question from the start. Leibniz went on immediately to canvass the entities that, as Arnauld agreed, cannot possibly compose the extension of bodies (atoms, points), concluding that if any reality “can be found in bodies,” there are substances in them (GP II, 96). Extension is real, he suggested, only if it is composed of extended parts that are true unities. But this is exactly what Arnauld found incomprehensible – extended true unities. Leibniz’s soullike substantial forms are genuine unities, but not extended. The unities on which an extended thing depends, as a whole on its parts, must already be extended. Extended true unities cannot be composed of substantial forms, as a whole is composed of parts or an aggregate, of constituents. If forms yield extended true unities, Leibniz said nothing to explain how they do it.13 Yet this is precisely what Leibniz was obliged to explain. He contended that the reality of what is extended is compromised because extension alone affords no principle of unity, and he claimed that his hypothesis secures unity for bodies, nevertheless. Arnauld understood the problem and, not seeing a solution, made a move to avoid it. So far, Leibniz had offered nothing to persuade Arnauld that the problem cannot be avoided by his definition of substance, nor had he indicated how the problem can be solved by substantial forms. If he can do no better, Arnauld might justifiably conclude that his theory of corporeal substance was a bluff. Leibniz continued with the “modal argument,” which does at least address the new definition of substance. On Arnauld’s proposal, a substance is something that exists and is not a state or a mode of something else.

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Leibniz denied that things that are merely extended are substances on that definition: It seems too that what makes the essence [ fait l’essence] of an entity through aggregation is only a state of being of its constituent entities; for example, what makes the essence of an army is only a state of being of the constituent men. This state of being therefore presupposes a substance, whose essence is not a state of being of another substance. (GP II, 96–7)

Things merely extended are classed as aggregates by Leibniz. It is the essence of an aggregate to be a mode or state, he contends. Therefore, things merely extended are not substances, on Arnauld’s definition. To avoid this result, Arnauld might defend his implicit claim that although a body comprises other bodies, it is not a mode or state of those other bodies (see GP II, 86–7). It is clear that if one body comprises many bodies, then there is some dependence relation between the former and the latter. To defend his proposal, Arnauld might urge that it is, not the mode-substance relation, but something else instead.14 In his next (final) letter, he did not defend his contention that what is merely extended is substance, but neither did he retract it. Waiving the question whether merely extended things are properly classed as aggregates (or modes), there are two things Leibniz engaged to show: (1) that if an aggregate is composed of nothing but other aggregates, it is not real and (2) that if an aggregate has constituents that are substances, by Leibniz’s lights, then the aggregate is real. Here is the argument he offered: what makes the essence of a being by aggregation is nothing but a state of being of its constituents; therefore, the state of being of an aggregate presupposes a substance, whose essence is not a state of being of another substance (GP II, 96–7). The premise means, I think, that an army, for instance, is defined in terms of men in certain “states of being” – men with certain training, various dispositions to act, organizational ties, and so on.15 Why is it supposed to follow that a real aggregate, such as an army, depends on constituents that are not, themselves, aggregates? What’s wrong with Arnauld’s infinite regress of compound substances made of other compound substances? The problem, in Leibniz’s view, is that an aggregate is not an entity to which states or modes properly belong. He said in previous letters that an aggregate’s being an entity at all is due to imagination (see especially GP II, 76 – also see GP II, 100–2). Elaborating the modal argument, he stresses this: “the unity of [entities through aggregation] exists only in our mind, which bases itself upon

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the connexions or modes of genuine substances” (GP II, 97). Although the soldiers in an army are real, the army is a convenient construct of our minds. Leibniz’s doctrine is that an aggregate, that is, a unitary entity, is a fiction – its unity is supplied by a mind; in reality, there are just substances. Accordingly, an army strictly has no states of being, even though it may be said to have such states on the basis of the modes or states of its personnel. An endless series of aggregates of aggregates consists of fictitious entities (unities) all the way through. Nothing in the series has states or modes in its own right, so nothing has states or modes at all – so Leibniz argued. Now, if Arnauld were to agree to the premise that an extended thing is an aggregate and, thus, a mode or state of something else, then this argument might well bring him to agree that the infinite regress of aggregates is vicious. Surely Arnauld’s definition of substance implies that if a mode exists, it depends on substance, which is not itself a mode. That is, for Arnauld, substances and modes are in different categories, and the latter cannot exist without the former. But suppose Arnauld were not to grant the premise, and were to urge a non-modal account of the relation between a substance and the substances that compose it. Then, as we have said, he might still maintain that bodies are substances, on his definition.16 In his final letter, he did not return to these issues. Meanwhile Leibniz had, at best, established only the first of the two claims he was engaged to show. The second claim is that an extended thing is real if its constituents are true unities. In context of the modal argument, what is needed are extended things that are ultimate bearers of states or modes. That is, things that have extension but do not inherit their states or modes from their extended parts. A substance, as Leibniz said in an earlier letter and in the Discourse, has a concept from which all predicates of the substance can be derived; evidently he takes this to imply that a substance is, intrinsically, a subject of modes. It has modes due to it, in itself. One can see that if there are corporeal substances of the sort Leibniz posits, it would be advantageous to logic, the theory of truth, theory of action, and moral accountability. But Leibniz did not indicate how anything extended can have this sort of unity, assuming substantial forms. To summarize, the modal argument claims to show that merely extended things are not substances, on Arnauld’s definition. Arnauld could resist this, and defend this stance by urging that the dependence relation between one extended substance and the substances that compose it, on his view, is not the relation of mode to substance. But if Leibniz’s claim that extended things, as such, are modes of their extended parts is granted,

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then his argument does seem to show that body, consisting only of extension, is an infinite series of modes, which never arrives at substance – a result Arnauld could hardly accept. Arnauld may well have understood all of this, and he may have seen the attractions of Leibniz’s demanding notion of substance. But he could hardly be expected to acquiesce to the argument or the definition without understanding how Leibniz proposed to make out that extended things can be made into true unities. The modal argument does not discharge Leibniz’s primary obligation. In his last letter, Arnauld steadfastly pursued the question he raised at the start, how substantial forms can confer true unity on what is extended.

5. the indeterminacy of figure, size, and motion In this same letter (April 30, 1687), Leibniz returned to the claim that the extensional qualities of things are imprecise: There is no fixed, precise shape in bodies because of the actual subdivision of the continuum to infinity; and [ . . . ] motion, in so far as it is only a modification of extension and change of surroundings, embraces something imaginary; with the effect that one cannot decide to what subject it belongs among those that change, without recourse to the force which is the cause of the motion, and which exists in bodily substance. (GP II, 98)

It is apparent here, perhaps more so than in the previous letter, that the presence of substantial forms does not prevent bodies from lacking precise shape.17 For here the situation in which bodies have no determinate shape is also the situation in which motion can be assigned a definite subject, which Leibniz holds to require substantial forms. If there are bodily substances, then physical forces “exist in” them and determine the assignment of motion to individual bodies.18 These remarks about physical forces raise a number of questions about how forces are grounded in substantial forms yet distributed among bodies, but Arnauld did not raise them. On the natural reading, the existence of bodily substances is still posited when Leibniz returns again to the indeterminacy of extension and its qualities: “Furthermore, in nature there is [no extension that is determinate]; everything is strictly indefinite where extension is concerned, and what extension we ascribe to bodies is merely phenomena and abstractions; [ . . . ]. One is [ . . . ] mistaken in imagining extension as a basic concept without imagining the true concept of substance and action” (GP II, 99). This seems to say that even assuming substantial forms

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endow what is extended with true unity, they do not make unities of their extensions. In nature, there is no body whose extension is not phenomenal and abstract.19 To be sure, it strains understanding to see how bodies can be objectively “one,” if their extension, size, and shape are mental abstractions and phenomena.

6. extended true unities? Arnauld (in his next and final letter, August 28, 1687) did not challenge the aggregate or modal arguments, but was puzzled about what Leibniz hoped to gain by using them. As he correctly observed, the reasoning depends on the principle, “there cannot be many entities, where there is not one entity” (GP II, 106). He did not think Leibniz could eliminate the intrinsic multiplicity of what is extended. Because there are many bodies that can hardly be supposed to have soul-like forms, for example, a marble tile, he did not see how Leibniz could avoid recognizing extended things that lack genuine unity. This brought him back to his original question. How are Leibniz’s substantial forms supposed to eliminate the feature that prevents what is extended from being real on his showing? I do not see how your substantial forms can cope with this problem. For the attribute of the entity that is called one considered as you consider it with metaphysical rigor, must be essential and intrinsic to what is called one entity. Therefore if a particle of matter is not one entity, but many entities, I do not conceive how a substantial form (which, as it is really distinct from it, can only confer on it an extrinsic denomination) is capable of causing it to cease to be many entities and to become one entity through an intrinsic denomination. (GP II, 107 – point (2) in the letter)

Forms cannot change the essential structure of matter; instead all they can do is change what matter is in relation to forms. They cannot change the infinite division that bars mere extended matter from reality, according to Leibniz. This is an acute statement of his original query. Arnauld went on to make a similar point. Because all animate bodies are organic, they consist of many parts: “So far from your substantial forms preventing the bodies to which they are joined being many entities, the bodies must be many entities in order to be joined to them” (GP II, 107). The focus here is on the extension of matter that forms a body united with a soul. Since that matter is many extended things, Leibniz’s form fails to secure reality for the interior regions of the body (GP II, 107–8 – point (3) in the letter).

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Leibniz expressed irritation at this response, complaining that Arnauld raised no objection to his arguments but still refused to accept their conclusion (GP II, 118). It seems unlikely that Leibniz supposed Arnauld had no resources for challenging these arguments; we have seen that there is a way he might have done so. Rather it is likely Leibniz had hoped to enlist Arnauld’s agreement, in effect, that extended things, merely as such, are imaginary, mere appearances before explaining how substantial forms give them more reality than that. If Arnauld accepted this threat to bodily reality, he might be favorably disposed to Leibniz’s explanation when he got it – or so Leibniz may well have thought. But Arnauld insisted on the opposite way of proceeding. He demanded an explanation of the scheme for making extended things into real unities before taking a stand on Leibniz’s contention that there is minimal reality without substantial unity. Withholding comment on the modal argument, he asked instead how the hypothesis of substantial forms was supposed to work, in the first place. Leibniz’s answer, at this point, was a test of his credibility as philosopher and correspondent. Responding to the first objection (letter of October 9, 1687), he began with a clarification. It is not the matter that is a substantial unity, but rather “it is the animate substance to which this matter belongs which is truly an entity” (GP II, 118). This does not correct a careless error on Arnauld’s part, and it is hard to see how Leibniz could have thought that it did.20 The question identifies precisely the problem his hypothesis needs to solve in order to live up to his claims for it. Arnauld had raised this question initially, sought clarification, and received in reply nothing that answers this query. Leibniz responded with this: I answer that it is the animate substance to which this matter belongs that is truly an entity, and the matter considered as the mass in itself is only a pure phenomenon or a well-founded appearance, as also are space and time. It has not even precise, fixed qualities which can give it the appearance of a specific entity, as I have already hinted in my previous letter. (GP II, 118–19)

He mentioned this earlier, and now it takes center stage. The letter goes on to give a long, detailed account of why “shape, which is of the essence of a finite extended mass” is never determinate in nature. Considerations offered in the previous letter are repeated: “shape, far from being constitutive of bodies, is not even a wholly real and specific quality outside of thought.” Leibniz generalized: “And I can say the same about magnitude and motion, namely that these qualities or predicates partake of the phenomenal” (GP II, 119).

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Leibniz must surely be talking about extended matter as it figures in his theory of bodily substance. To speak here of extended mass on the assumption that there are no substantial forms would be wholly impertinent to the question – and Leibniz is under the gun to give a cogent reply to this question. Arnauld asked how soul-like forms change the essential, reality-barring multiplicity of the extension of matter, and Leibniz replied that it doesn’t. Assuming forms exist, extension and its qualities, figure, motion, and space, are “only a pure phenomenon.” Forms do not alter that.21 But Arnauld wanted to know what substantial forms do in relation to extended matter, and accordingly Leibniz continued: consequently, extended mass considered without the substantial forms,22 consisting only of these qualities, is not bodily substance, but an entirely pure phenomenon like the rainbow, therefore philosophers have recognized that it is form which gives determinate being to matter, and those who do not pay attention to that will never emerge from the maze of the composition of the continuum, if they once enter it. Only indivisible substances and their different states are absolutely real. This is what Parmenides and Plato and other ancients have indeed recognized. (GP II, 119)

Once again, what does “extended mass considered without the substantial forms” refer to? Either it refers to mass considered on assumption that the hypothesis of forms is false or considered in abstraction from forms assumed to be there. The former has no relevance to the question Leibniz was heavily obliged to answer, so we can presume he intended the latter. To find extended mass, which is what Arnauld asked about, one has to consider an aspect of bodily substance in abstraction from the rest. But if extended mass is a way of considering corporeal substance without regard to substantial forms (which are there), how do those forms bring “determinate being” to this abstract conception? There is no straightforward explanation here. Yet it is significant that Leibniz refers here to Plato and Parmenides, not to Aristotle. Plato is commended for holding that substances are indestructible (also see GP II, 76). Indeed, this sets him apart from Aristotle, whose material substances are divisible, generated, and corrupted; a man can be destroyed by cutting him up, on this view. It is Plato’s theory of indestructible souls that Leibniz invokes to indicate how souls endow extended mass with “determinate being.” According to Plato, a soul brings life to a body – especially perception.23 The allusion suggests that forms underwrite, perhaps not a precise division of extended mass, but a semblance of differentiation because the life functions of soul-like forms are

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carried on in the mass. No precise figure can be assigned to a body, but still perhaps operations such as perception can be ascribed to it. Yet how can this work, if the mass is an abstract way of conceiving corporeal substance? After this Platonic reference, the letter proceeds directly to the second objection.24 It raises precisely the right question: how can Leibniz account for the reality of the organs that compose an animate body, which are many but not many unities. There is some obscurity about Leibniz’s response. But there is so much pressure on him to clarify how substantial forms yield corporeal unities that it seems unlikely he completely evaded the question. Let us suppose that his reply addresses the issue: [you say that] since all organic bodies are many entities, forms or souls, far from making one entity of them, rather require in consequence many entities so that the bodies may be animate. I reply that assuming there is a soul or substantial form in animals or other bodily substances, one must argue from it on this point as we all argue from man who is an entity endowed with a genuine unity conferred on him by his soul, notwithstanding the fact that the mass of his body is divided into organs [ . . . ] and the parts are undoubtedly full of an infinite number of other bodily substances endowed with their own substantial forms. As this [ . . . ] objection is substantially in keeping with the previous one, that solution will serve here too. (GP II, 120)

Arnauld asked about the parts of an animate body. Leibniz said that the mass of an animate body is divided into organs which are “full of” bodies, each with its own substantial form. In this way, he proposes, the bodily mass is divided into parts each of which is one (a unity). As we argue from the soul of a man, that the man, to which the soul belongs, is a genuine substance; so we are to argue from each substantial form, that it belongs to an animate substance. A man is a bodily substance, then, consisting of a soul and a body composed of other bodily substances. These lesser animate bodies have the same structure: a soul-like form and a body composed of yet lesser animate bodily substances. In the make-up of a human substance, endlessly many substances repeat the pattern. So Arnauld mistook in supposing that there are regions internal to a human body that lack substantial unity, on Leibniz’s hypothesis. But Leibniz was under pressure to say how substantial forms bring reality to extended mass – in his example, the mass associated with the body of a man. We consider this mass to have functional parts, he said; but he could hardly maintain that organs such as eyes, lungs, heart are real parts of a human body because they are not animate. For Leibniz, what gives reality to a human body is not its functional parts but the

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animated bodies (unities) that compose it. What account of the reality – the unity – of extended mass does he offer, then? Where does extended stuff fit into the composition of a man? Leibniz brought his previous answer into play: “that solution will serve here too.”25 The foregoing solution is that extended mass “considered without substantial forms is a pure phenomenon, like the rainbow.”26 As we saw, to consider mass without substantial forms is not to negate forms but rather to ignore them – otherwise Leibniz’s first answer is impertinent. The mental act of considering extended mass in abstraction from forms, which are really there, plays a part in Leibniz’s second reply, too. He first considered the body of a man abstractly – as a mass divided into functional parts (which are not strictly real, since they lack forms). Then the body of a man is considered more concretely – as a collection of bodies animated (unified) by forms. The former ignores what gives reality to the body, for Leibniz, namely, the soul-like forms, whereas the latter takes them into account. Arnauld’s repeated question about the reality of extended mass received an answer here, but a complicated one: on Leibniz’s hypothesis, extended mass is not a constituent of an animate substance; no such substance is composed of a soul and extended mass. An animal can be regarded as having a body that is an extended mass, but, in fact, its body is composed of lesser animate bodies. In sense perception, the bodies of animals appear to be extended masses that have functional parts – eyes, ears, and so forth. For Leibniz, attending to the sensory appearances of an animal is a way of abstracting from the real animate components of its body. Abstraction can occur at any level of bodily composition – under the microscope or in thought about animate bodies much too small to be perceived. All sensory presentation and abstraction aside, however, nothing remains of extended mass. If we could attend all at once to the endlessly many soul-like forms really comprised by a man, extended mass would disappear.27 According to Plato, immaterial souls are the only substances. Souls bring life to bodies, but vitally functioning bodies are not substances, nor does a soul in conjunction with such a body constitute a substantial unity. The proper activity of souls is not dependent on the life functions of bodies. A rather similar theme can be found in Leibniz’s doctrine: souls and soul-like forms are said to “animate” bodies, but bodies consisting of organs that carry on the life functions associated with a soul are merely phenomenal and abstract. Souls and functional bodies do not constitute substantial unities, and to this extent Leibniz sounds a Platonic note.

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7. are bodily substances true unities? Had Arnauld replied to the letter we just discussed, he might well have focused his repeated question – how do substantial forms overcome the multiplicity that is supposed to bar what is extended from substantiality – on Leibniz’s claim that an animate substance, as described in this letter, is a substantial unity.28 On several occasions, Leibniz claimed that if there are substantial forms, as he proposed, then there are “bodily substances endowed with true unity” (GP II, 97 – also see Discourse §34: A VI iv, 1583–4/AG 65–6; GP II, 118 and 126). Having understood that an animate substance comprises a soul and endlessly many other animate substances, Arnauld might have asked what counts as a true, substantial unity, for Leibniz and how he meant to defend the claim that an animate substance is such a unity. In the context of their exchange, these questions pose a peculiar difficulty for Leibniz. We have said that a Platonic theme emerges when he is pressed to say how soul-like forms bring reality to extended mass. Yet several points in his doctrine sound an Aristotelian theme. The thesis that a substance is a composite being, which has substantial unity primarily in virtue of one of its constituents – its “form” or “soul,” echoes Aristotle’s theory of animate substance. The two themes suggest opposite views of the dependence relation between souls and living bodies and opposite answers to the question whether a soul-body composite has substantial unity. What is Leibniz’s standard for true unity, in these letters? It is clearly necessary for an entity to have true unity that it be incapable of being divided or destroyed by any change in the mutual relation of its parts (GP II, 75–6 and 116–17). Leibniz can show easily that an animate body meets this condition, on his hypothesis. As he explained: “although it is possible that a soul has a body made up of parts animated by separate souls, the soul or form of the whole is not on that account made up of the souls or forms of the parts” (GP II, 100). Suppose a worm is cut in two. Its soul will remain in one of the severed parts, given Leibniz’s view. The portion animated by the soul, after the cut, is identical to the worm animated by that soul, before the cut. The identity of the animate body is determined by the identity of its soul, and the soul always remains in some part of the body, no matter how the body is manipulated. But although an entity’s having this sort of indestructibility is necessary for it to be a substantial unity and is perhaps, even sufficient, Leibniz characterized true unity in other ways, too. This prompts one to ask whether bodily

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substances have all the characteristics he ascribes to a being that is truly “one.” Leibniz’s main arguments regarding substantiality invoke the substance-aggregate contrast: a substance is a true unity and an aggregate, not. Although aggregate is never defined in the letters, the discussion suggests that there is a necessary condition for the unity of an aggregate that Leibniz surely wanted to deny is necessary for the “unity” of a substance.29 Taking this to be a distinguishing mark of true unity, Arnauld might have asked: what is it in virtue of which a composite substance has this distinguishing mark? For Leibniz, an aggregate is “one” entity in an essentially arbitrary, mind-dependent way: “the unity of these [aggregates] exists only in our mind, which bases itself upon the connexions or modes of genuine substances” (GP II, 97). He agreed with Arnauld that some aggregates have more unity than others, a machine has more than a society; “but then all these unities are made complete only by thoughts and appearances.” Because they are constructs, they have no intrinsic states or modes: “Our mind notices [ . . . ] certain genuine substances which have modes [ . . . ] [that] embrace relationships with other substances, from which the mind takes the opportunity to link them together in thought and to enter into the account one name for all these things together, which makes for convenience in reasoning” (GP II, 101). Accordingly, the existence of the right substances is not sufficient to make them an aggregate. Rather, Leibniz indicates three conditions jointly necessary, and perhaps sufficient, for a “real” aggregate; roughly put: (1) there are several substances; (2) a mind distinguishes them from other substances, perhaps imprecisely, on the basis of sensory appearance, a stated rule, a practice, and so forth; (3) this mind regards the substances, so distinguished, as constituting one entity for convenience of speech or thought. So a number of people related as teachers and students are not a school. It is true that they may be related in any number of ways that might serve as a rule, even a precise rule, for distinguishing members of a school – level of achievement, doctrine taught, a mutual financial agreement. But according to Leibniz, there is a school only if a mind takes some rule to delimit its members and regards them as forming one entity. The “oneness” of a substance is different in kind, and Leibniz is surely committed to saying that a corporeal substance has this higher sort of unity. Provided only that a human soul and the endlessly many corporeal substances that are comprised by a human exist, a composite substantial unity exists – the Aristotelian theme. Like an aggregate, a

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bodily substance exists only if numerous (other) substances exist. But for the bodily substance, nothing more is required – above all, no arbitrary, efficiency-making mental act of taking them to be an entity. A man supervenes on its soul and the particular corporeal substances comprised in its body; an aggregate does not supervene on its substantial members. There is nothing incoherent in Leibniz’s thesis that some composite entities differ from others in this way.30 But it is not clear how he meant to defend his Aristotelian claim. There are, of course, respects in which the constituents of a bodily substance differ from those of aggregates; by virtue of its unique combination of elements, a bodily substance is vital, living, animate. But why should this make it a genuine unity, or, again, a subject of intrinsic (unborrowed) modes? It is difficult to see, from the letters, that Leibniz had a clear line of response. In fact, he sometimes relied on the plausibility of the general Aristotelian thesis that souls, or forms, bring unity to composites to which they belong while promoting his specific account of the ingredients of the composite. More than once, he asserted that a man is a substance unified by a soul, most notably at the crux of his reply to Arnauld’s query about the unity of the parts of an animate body: “assuming there is a soul [ . . . ] in bodily substances, one must argue from it on this point as we all argue from man who is an entity endowed with a genuine unity conferred on him by his soul” (GP II, 120 – also see GP II, 98 and 77). This familiar doctrine is used to illustrate how the soul of every bodily substance unifies the peculiar inventory of entities that substance comprises, according to Leibniz. Perhaps Leibniz built upon the familiar thesis because the Church prescribed that the soul confers unity on a man (GP II, 58 and 75).31 But it also seems likely he was under the sway of the compelling Aristotelian tradition regarding the unity of material substances. Some indication of this comes from a short study contemporary with the letters given the title Notationes generales. It investigates the difference between the “unity and reality” of an aggregate, like an army, and that of a man. Here Leibniz said that the distinctive feature of an army is, roughly, that predications that have the logical subject, army, can be expressed as predications of the individuals in the army without mentioning the entity, army, at all; for instance, the proposition, that the army is in the fields of Marathon, can be expressed by propositions to the effect that each soldier is in those fields. “But as for the fact that in a man, there are parts that make a unity, this unified entity has an attribute that cannot be expressed without this bond [vinculum], namely, the faculty of sensing

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and desiring” (A VI iv, 556 – see note 19) These psychological activities, in particular, are said to be attributes ascribed to a man that cannot be expressed in terms of propositions about the components of the man. Precisely this is said to show that a man has unity different from that of an aggregate. The spirit is Peripatetic. According to Aristotle, vital functions like perception must be carried on in a unitary, but composite, substance because those functions have inseparable physical and psychological aspects. Vision requires eyes, for example, which are bodily organs. It also requires that the animal be ready to see when its eyes perform their proper function, and the readiness to perform cognitive acts pertains to the soul (an organization ready to perform specifically psychological functions). But the animal must be a unitary composite of physical and psychological principles. When a cat sees a mouse, it is not as if the eyes perform one operation and the soul another. Instead, what the eyes do could not be done just by the eyes, nor could the soul’s part in seeing be done by it alone. For this reason, Aristotle maintained that an animal must be a unified, but composite, substance (e.g., see De Anima I, 4 and De Sensu I). Now Leibniz did not say why a man’s ability to sense and desire cannot be expressed in terms of operations of various parts of the man. But the natural explanation is that he supposed the exercise of these abilities is a single, integral operation ascribed to the man but dependent on his soul and sensory organs. Leibniz may, then, have been influenced by this Aristotelian picture. But right from the start, some revision of it was implied by his unwillingness to accept certain aspects of Aristotle’s theory of material substance – he denied that substantial forms are divisible, and he mistrusted the reality of what is extended, merely as such. It is not clear that the Aristotelian argument for composite unity retains its force in the context of the theory of bodily substance Leibniz had in view, or that he had an alternative way to motivate his claim that a corporeal substance, on his theory, is unified by its soul. A problem comes directly from the account of extended mass given to Arnauld: the organic parts of an animate body are mind-dependent abstractions. Leibniz’s bodily substance has determinate real parts, but they are not functional. We conceive a cat’s body to have eyes, nerves, brain, and other bodily organs that sustain feline life. But the cat’s sensory system is the product of a mental act of abstracting from, or neglecting, the real parts that compose a cat’s body, on Leibniz’s view. Indeed, this makes it is difficult to see why Leibniz should think that a soul needs a body in order to sense – or

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to execute its role in sensing. The bodily parts it would seem to need are not really there, and the parts that are don’t do the work of sensory organs. Then what claim does an animal have to be a composite unified by its soul, a natural composite that supervenes on its soul and the components of its body? Leibniz may have had something to say in response, as he hinted at least once in his letters to Arnauld.32 A cogent answer would require a radical revision of Aristotelian theory of sense perception, a theory of perception capable of providing a radically new ground of the unity conferred on a composite substance by its soul or soul-like form. The mutual functional dependence of physical and psychological elements in a substance is undercut by the hypothesis finally presented to Arnauld. What the Platonic theme gives Leibniz, to give a dimension of reality to extended mass, works against the Aristotelian notion of composite substantial unity.

Notes 1. Some recent scholars who hold that, in the Discourse on Metaphysics and the Arnauld correspondence, Leibniz subscribed to the theory that the extended matter that pertains to a bodily substance has reality independent of (corresponding to) the perceptual states of souls and soul-like entities include Brown 1984: 136–43; Garber 1985: 27–130; Hartz 1992; and Woolhouse 1993: 54–74. Those who claim that Leibniz held in this period that extended matter is nothing more than coordinated perceptual content of souls include Adams, R. M. 1994: 217–307 and Rutherford 1995: 218–26. Others maintain that in this period Leibniz vacillated between the two positions: Robinet 1986; Wilson 1989; and Hartz 1998. A variant is urged by Sleigh 1990: 110–15. 2. After receiving Leibniz’s explanation, Arnauld reported himself satisfied the definition (GP II, 63). 3. The definitive edition of Leibniz’s correspondence and related material is Finster 1997. Leibniz’s copies of the letters along with his draft for one letter are published in GP II, 1–138 and are translated in LA. The marginal pagination in LA correlates with GP II. For ease of reference, in this chapter citations will be given only to GP II. Translations quoted here are LAs with minor changes. Three known extant drafts of letters by Leibniz are not included in this material (see Finster 1997 and Sleigh 1990: Appendices). For information about the history of the exchange, see the introductory material in LA, Finster, Gerhardt, and Sleigh. Details of the drafting process are provided by Robinet 1986. The copies of letters received by Arnauld are not identical to the copies Leibniz retained. The former are in Lewis 1952. 4. In fact, for Leibniz, heaps are “mental fabrications,” just as all aggregates are; so both rainbows and heaps are, at least to some degree, mind-dependent entities. Still, if there are substantial forms as Leibniz proposes, then even

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rainbows and heaps acquire some dimension of reality; in contrast, if there are no such substantial forms, then rainbows, heaps, and extended matter are “lacking all reality as would a coherent dream” and “wholly imaginary” (GP II, 97). Brown, S. 1984: 137–42, identifies Aristotelian and Platonist problems in the Discourse and letters to Arnauld. The passage continues: “And if there are none [substantial unities], it follows that apart from man there is apparently nothing substantial in the visible world” (GP II, 77). It is far from clear how a man could be a substance on the hypothesis that the only substances are rational souls and what is merely extended has no more reality than the rainbow. Scholars who hold that Leibniz sometimes endorsed this hypothesis or that he favored it have not explained this. On the background in Leibniz’s earlier thinking about the continuum, force, cohesion, and the composition of bodies, see Robinet 1986: chs. 3–4; Arthur 1989 and 1997; Beeley 1996a and 1996b; and Levey 1998. Other contemporary writings indicate unambiguously that the existence of substantial forms does not eliminate the imprecision of the extensional qualities of bodies: Specimen inventorum (GP VII, 314/MP 81–2), on the date, see Robinet 1986: 34 n.20; letter to Simon Foucher (GP I, 391–2), which Robinet 1986, 22 dates from the period of the Arnauld correspondence; also see GP IV, 436/L 307. Also see later passages (GP II, 100–1) and the draft of the previous letter (GP II, 88). The terms aggregate and constituent suggest that the former depend on the latter, whereas Arnauld said nothing to indicate just how he construes the relation between an extended substance and those it comprises. Part of Leibniz’s reply reads: “Entity is one thing, entities another; but the plural presupposes the singular, and where there is no entity, still less will there be many entities” (GP II, 97). If this expresses the thesis that there cannot be many Fs unless there are Fs that are not many Fs, but rather one and only one F, then it begs the question. It is true that Arnauld’s proposal implies that any material thing can equally well be regarded as one substance or several substances, but in effect, his challenge to Leibniz is to say what is wrong with that. This account of the aggregate and modal arguments has a good deal in common with the analysis in Sleigh 1990: 119–23, from which I have learned a lot. In the copy Leibniz retained, he wrote that aggregates of substances depend on substances “from which the aggregates result [dont les aggreg´es resultent].” He typically used the term result for a dependence relation with some similarity to supervenience: things of one sort result from things of another just in case a mind that apprehends the latter, thereby, understands the former – see Rutherford 1995: 221. In the letter Arnauld received, the corresponding passage reads: “dont tous les aggreg´es soient faits” (Lewis 1952: 68). That could mean there are unities from which aggregates are either composed or made in some non-compositional way.

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14. Descartes’s theory of extended substance posits the same “compositional structure” among material substances – see Principles I, §60: AT VIIIA, 28– 9/CSM I, 213. 15. Sleigh 1990: 213; 129; and 132 helpfully cites this from an essay of the period of the correspondence: “It is worth investigating in what way an entity through aggregation, such as an army or even a disorganized multitude of men, is one; and in what way its unity and reality differ from the unity and reality of a man. It seems that the chief difference is to be observed in their attributes and operations. Some attributes are said equally of the whole as of its parts, as, for example, that the army is located in the fields of Marathon, which is true of each individual soldier. Other attributes can be said only of the whole, as, for example, that the army is 30,000 strong, and that it is disposes in a lunar-shaped battle line. Nevertheless, all these things can be stated and expressed even if the multitude is not viewed as a single entity. Thus, I can say that 30,000 soldiers are present and that one soldier is situated with respect to another just as the battle line mentioned requires, so that certain ones are distanced from a fixed point by so much, others by so much. But as for the fact that in a man, there are parts that make up a unity, this unified entity has an attribute that cannot be expressed without this bond [vinculo], namely, the faculty of sensing and desiring” (Notationes generales: A VI iv, 555–6). 16. Descartes indicates as much in Principles I, §60. 17. Advocates of the view that the extended matter endowed with substantial form has reality comparable to that of material things in Aristotelian hylomorphic theory seem to me to take insufficient account of Leibniz’s repeated arguments that the qualities ascribed to extension are imprecise – see Sleigh 1990: 110–15. 18. Garber 1996 maintains that the main motivation for corporeal substance is to account for the presence of physical forces in bodies with mind-independent extension – also see Garber 1985. 19. Evidently the presence of substantial forms in bodies somehow endows the bodies with predicates other than size, shape, and the other modifications of extension. But Leibniz had not indicated what those predicates might be, nor could Arnauld be expected to figure it out. 20. Sleigh 1990: 107–9 and 125–7 supposes Leibniz did not pursue the question Arnauld asked, namely, how substantial forms confer unity on extended mass. Instead Leibniz assumed Arnauld intended to ask a different question, namely, how forms confer unity on a substance that has extended mass. By noting that “it is the animate substance that is a true unity,” Leibniz was stating the doctrine he assumed Arnauld wanted explained, and so he proceeded to explain it. In brief, this explanation consists in the thesis that the soul-like form determines the diachronic identity of the composite of extended mass and form. Sleigh finds reference to this doctrine in the answer to Arnauld’s second question, but he says it is explained more fully elsewhere. This does not seem to be the most plausible reading of the text (GP II, 119– 20). It is unclear why Leibniz should have thought Arnauld failed to ask the question he meant. Leibniz’s contention that infinite divisibility precludes

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substantiality encourages the question he did ask, and it was raised by his initial list of seven questions. Further, because Sleigh supposes Leibniz is not addressing a query about the metaphysical status of extended mass (as opposed to a substance in which extended mass is a component), it is unclear what he can make of the portion of the reply in which Leibniz reiterates that extension and its qualities are indeterminate and says “the mass itself is a pure phenomenon.” Because Leibniz is clearly not concerned, here, with what extended mass would be in the absence of soul-like forms, it is unclear why these remarks should be relevant to the question Leibniz undertakes to answer, according to Sleigh. His dismissal of this passage may help to explain why he understands Leibniz to be presenting to Arnauld the doctrine that the extension of bodies with soul-like forms is neither phenomenal nor abstract but rather entirely mind-independent. In the corresponding portion of the draft of this letter, the point is more explicit: “I agree that a particle of matter in itself will never become a true being, whatever soul is given to it, but also, in the manner in which you take it. That is, an extended mass composed of parts where there is only mass and extension does not enter into the substance and is only a pure phenomenon rather like space, time, and motion. One can also judge the smallness of the reality of this mass from the fact that the extension demands a certain figure, and I hold that there is no figure in nature that is precise and determinate, as I noted in my previous letter. Moreover every part is actually divided into others so that one cannot assign a determinate surface to any of them, as one could if there were atoms” (Finster 1997: 300 – translation partly based on Sleigh 1990: 108). LA and GP II have “entelechies,” following Leibniz’s copy, but the term “substantial forms” appears in the letter received by Arnauld – see Lewis 1952: 86. On Plato’s view, a soul is a substance, or very substance-like (see e.g., Phaedo 78d–79e). On soul bringing life to the animal body, see Phaedo 105e–106e. But Plato does not consider the living body to be a substance (see Timeus 41d– 42d and 49d–50) and there is no indication that the construct of human body and soul is a substance. Since Leibniz maintains that the animate body, comprising a soul and something bodily, is a substance, Plato is evidently commended for taking souls to ground a second-rate reality on the part of something corporeal – also see Brown, S. 1984: 136– 43. GP II and LA insert text, which Gerhardt reports was written in the margin of the manuscript letter and not sent to Arnauld, between Leibniz’s answer to the first question and his reply to the second (GP II, 119–20). This material is enclosed in parentheses, but included in the text of this letter in Finster 1997: 300. It is very similar to a corresponding passage in the draft of this letter (Finster 1997: 328). It is entirely consistent with the position Leibniz urges in the letter he sent to Arnauld, as interpreted here. But I regret the disruption of the flow of Leibniz’s reply, because it dilutes the impact of his statement that the same reply answers both questions. In the unstruck part of the draft letter (Finster 1997: 300), Arnauld’s two questions are given only one answer.

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26. In addition to portions of the answers to the first and second queries, discussed earlier, consider this remark from the close of this same letter: “As for bodily substances, I maintain that mass, when one considers only what is divisible [sic], is a pure phenomena” (GP II, 126). 27. Leibniz did not say that the attribute of being extended, associated with a bodily substance, is “phenomenal and abstract,” nor, of course, did Arnauld raise precisely this question. Still, if all phenomena and abstraction were put aside, as discussed earlier, the vestige of extension that would remain is the discrete series of soul-like forms ordered over the volume of, say, the body of a man. But even a spatial ordering of forms is questionable because Leibniz’s doctrine that the figures and sizes of (even animate) bodies are indeterminate might seem to frustrate the attempt to assign a determinate spatial ordering to the soul-like forms that animate bodies. But it would be going too far to say that Leibniz explicitly had this in mind. 28. Some recent commentators urge that the claim that corporeal substances have substantial unity is dubious, if not false (see especially Adams, R. M. 1994: 292–4 and Rutherford 1995: 266–73). 29. For a useful discussion of Leibniz’s notion of aggregate, see Lodge 2001a. 30. Adams, R. M. 1994: 25–6 ascribes to Leibniz the following connected theses about aggregates. (1) A real aggregate is reduced to its substantial constituents, i.e., they are necessary and sufficient for the reality of the aggregate. (2) The unity of an aggregate is constituted by a relation among its constituents. But (1) and (2) conflict with a point Leibniz stressed in letters to Arnauld, that an aggregate is “one,” a singular subject of modes or predicates, and its “oneness” is constructed by a mental act – also see Rutherford 1995: 266–71. To characterize aggregates in this way is, in effect, to beg the question against Leibniz’s contention that a composite substance has a unity different from that of an aggregate as it took shape in the correspondence. 31. In as much as this doctrine implies that there is a human body, the issue over the reality of extended stuff must have had special urgency for both correspondents. 32. Leibniz wrote that the perfect correspondence between a soul and its body is due entirely to the harmony of their respective operations: “The soul, however, is nevertheless the form of its body, because it is an expression of the phenomena of all other bodies in accordance with the relationship to its own” (GP II, 58). This undercuts the basis of Aristotelian unity, but it also suggests that a soul’s perceptual activity requires that it have an immediate perception of its own body and, through it, of other things. In this capacity, the extensional aspects of body are needed, precisely to provide the representative content of perceptual states.

6 Leibniz and Fardella Body, Substance, and Idealism Daniel Garber

In the last number of years, there has been a remarkable interest in Leibniz’s account of the physical world, and, in particular, his account of corporeal substance. Much of the discussion has focused around the question of Leibniz’s idealism. In particular, the question has been whether even in the so-called middle period, the 1680s and 1690s, when discussions of corporeal substance seem to be most visible, Leibniz’s position included the same kind of idealism with respect to the physical world that occupied him in his later, more obviously monadological, writings, or whether he understood the physical world in a more realistic way. In this essay I suggest that this may not be the right question to be asking about Leibniz’s philosophy during this period. I arrive at this reorientation of our thinking about the texts of this period by looking at one text of particular clarity and interest. The text I intend to examine was written in March of 1690, while Leibniz was in Italy. It seems to be notes connected with a conversation Leibniz had with the Italian philosopher Michelangelo Fardella. Written shortly after the main bulk of his correspondence with Antoine Arnauld and in the same month as his very last letter to Arnauld, the notes state with stark clarity some of the themes that were suggested somewhat more obliquely in those other letters. Leibniz’s interchange with Fardella is a central document for our understanding of the evolution of Leibniz’s views on the nature of body and of his ontology more generally, and for the evolution of his idealistic metaphysics. The text itself is difficult to understand and has yielded conflicting interpretations from scholars. In fact, the complexity and ambiguity of the text is probably such that it cannot stand on its own and be interpreted in isolation of its larger context. 123

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What we need is a better sense of the dialectical context in which it was written and a better sense of what Fardella brings to the conversation. When we read the text as a conversation between two different philosophers, each of whom brings a point of view to the discussion, it becomes possibile to see the text in a clearer light.

1. michelangelo fardella Michelangelo Fardella was born in 1650 in Trapani, Sicily, four years after Leibniz was born. We can presume that he was given a standard scholastic education, though early on in his studies he seems to have turned toward Augustine, if his own later reflections can be trusted.1 Fardella became a priest in 1672 at the age of 22. In that same year, in 1672, he met the great Italian scientist and mathematician Giovanni Borelli at Messina, where Fardella was studying and Borelli was teaching. In 1676, Fardella left Messina for the attractions of Rome. It is in Rome where he probably first came across Cartesianism, most likely through the Cartesian NicolasJoseph Poisson, who was then visiting in Rome (see Femiano 1979: 32ff.). A desire to deepen his knowledge of the Cartesian philosophy and science led the young Fardella to Paris in 1678, six years later but at almost exactly the same age that Leibniz first visited Paris. Fardella spent three years in Paris, where he met Malebranche, Arnauld, R´egis, Bernard Lamy, and others in the large and active circle of Cartesians. Fardella was especially taken by Malebranche’s Search and with the Port Royal Logic, which, as he noted later in life, led him to the Cartesian philosophy, to the proper method and order for philosophizing, and to “a clear and profound understanding of the most hidden mysteries of nature” (Femiano 1986: 32).2 Fardella returned to Rome in 1680, deeply enthusiastic about the new philosophy and science that he had been exposed to in Paris. In Rome he received his degree in scholastic theology and began teaching. He also started an academy for experimental science on the model of Rohault’s and R´egis’s academies that he had attended while in Paris (see Femiano 1979: 54ff.). A bright young man, with up-to-date knowledge of scientific circles, Fardella was soon attracted away from Rome to Modena at the invitation of the Duke, who was obviously impressed by him. In Modena he taught mathematics, logic, physics, and metaphysics from 1681 to 1684. While in Modena he published his Restitutae ac methodicae philosophiae et matheseos praecipuae et utiliores assertiones (1683), a collection of “assertiones” that shows very nicely his Cartesian credentials.3 In that

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work, Fardella comes out clearly against the scholastic forms and qualities, for the Cartesian views that the real cause of motion is God’s continual conservation of the same quantity of motion in the world (1683: 188f ), that a body in motion always remains in motion unless interfered with by an external body, that a body tends to move in a straight line (1683: 180), that mind is unextended substance that exists outside of all spatiality, that its essence is understanding [“cum tota essentia spiritualis sabstantiae [sic] sit in intellegendo [ . . . ]”](1683: 199), and that mind is better known than the body (1683: 193–4 and 199), and so on. But disputes in Modena between Fardella and more conservative elements unhappy with his anti-Scholasticism and his embrace of new ideas led him to seek a more comfortable place. This eventually led him to Venice, perhaps by way of Capodistria (Femiano 1979: 60). Fardella was in Venice possibly as early as 1684, but perhaps as late as 1687. In any case, he was certainly in Venice in February and March of 1690 when the emissary of the House of Brunswick, the eminent Gottfried Wilhelm von Leibniz, passed through. Leibniz, who had been named the Historiographer of the House of Brunswick in autumn of 1687, was on a trip to Italy and Austria to retrieve documents for his history. However, while he was there he took the opportunity to meet Italian philosophers, mathematicians, theologians, and scientists and to generally scope out the scene.4 In his very last letter to Antoine Arnauld, written in March 1690 while he was in Venice, Leibniz talked a bit about his Italian trip. He wrote: As this journey has served in part to rest my mind from ordinary pursuits, I have had the satisfaction of conversing with many able people on sciences and erudition, and I have told some of them of my private thoughts, which you know, in order to profit from their doubts and difficulties; and some of them, who were not satisfied with common doctrines, have found extraordinary satisfaction in certain of my views. (GP II, 135/LA 170)

One of the people with whom Leibniz met in Venice, probably just weeks or days before writing these words, was Michelangelo Fardella. It is not at all surprising that the two should have found one another. Interested in physics and mathematics, logic and metaphysics, like Leibniz himself, Fardella had the reputation in northern Italy for being a very talented thinker and a passionate advocate of the new philosophy. As we shall see when we look at the document connected with their meeting, Leibniz’s words to Arnauld describe exactly what seems to have passed between the two: Leibniz presented condensed versions of some of his views, and

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Fardella replied with his objections, which Leibniz, in turn, attempted to answer. These exchanges between the two marked the beginning of a long relationship. But before discussing their relationship, let me return briefly to Fardella. Venice wasn’t altogether comfortable for Fardella either. Among other problems, Fardella was investigated by the Inquisition on suspicion of sympathies for Lutheranism. The fact that the authorities were correct to suspect him in this regard didn’t make things any more comfortable. Fardella was to pass from Venice to Padua in 1693, from there to Barcelona in 1709, and then from there to Naples in 1712. He died in Naples in 1718.5 Fardella and Leibniz stayed in epistolary contact from 1690 through 1714.6 In addition to philosophical exchanges, Fardella was important to Leibniz in helping to get his new calculus established institutionally in Italy through the appointment of his allies in Padua (see Robinet 1991). Furthermore, the letters also contain discussions of Fardella’s sympathies for Lutheranism, a question of passionate interest to Leibniz, who was always eager to find ways and means for reuniting the Protestant and Catholic churches. At this point, I would like to turn to some of Fardella’s ideas. As I noted earlier, Fardella was quite definitely a sympathizer with Cartesian ideas, with Descartes’s method, metaphysics, and physics. We saw this earlier in connection with the Restitutae ac methodicae philosophiae et matheseos praecipuae et utiliores assertiones of 1683. This is also quite clear in an important response to an attack on Descartes’s philosophy by one Matteo Giorgi.7 Giorgi had attacked Descartes’s conception of body and space, arguing against the claim that extension is the essence of body, the identification of space and material extension, and the infinity extension of space. In a series of letters published in the journal La Galleria di Minerva starting in 1697, Fardella answered these criticisms and attempted to establish the Cartesian doctrine of body, extension, and space. However, Fardella’s Descartes was much augustinianized. As the historian of Cartesianism, Francisque Bouillier put it, Fardella hoped to pass to the philosophy of Descartes and Malebranche through the philosophy of St. Augustine (1868: 2, 525–6). Fardella’s best-known and most popular work was entitled Animae humanae natura ab Augustino detecta (1698). The work took the form of a direct commentary on certain texts of St. Augustine. But in it, he used Augustine’s words to prove characteristically Cartesian doctrines about the existence and nature of the soul, the fact that it is incorporeal and immortal and completely distinct from

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body. In one passage, which Fardella entitled “The Augustinian investigation of the nature of the human mind in Book X of de Trinitate, set out in a different way, [ . . . ]” we find what amounts to a direct paraphrase of Descartes’s discussion of mind in Meditation II in the guise of an interpretation of Augustine, culminating in the observation that “if I understand, I am, I exist, I live [si intelligo, sum, existo, vivo]” (Fardella 1698: 213 – the entire passage runs 210–16). There is a very interesting difference, though, between Fardella and the Cartesian tradition, a difference that attracted a good bit of attention. In 1691, shortly after his meeting with Leibniz, Fardella published a work called Universae Philosophiae Systema. In quo nova quadam, et extricata Methodo, Naturalis Scientiae et Moralis fundamenta explanantur. Tomus Primus. Rationalis et emendatae Dialecticae specimen tradens [ . . . ] (1691a). This was obviously supposed to be the first volume of a much longer and more complete treatise on the whole of philosophy that Fardella had planned but never actually executed. This first volume was a logic, modeled on the Port Royal Logic, which he had been acquainted with in France. But in an appendix, Fardella included a rather surprising doctrine. In Meditation VI, Descartes, of course, proves the existence of the external world through the veracity of God. This proof, though, was not accepted by all. Malebranche, for example, claimed that Descartes’s argument did not establish the existence of body with genuine certainty, but that Descartes had only made it probable that bodies exist. In the end, Malebranche argued, the existence of body can be established with certainty only as a matter of faith, through biblical testimony. Insofar as the Bible says that God created heaven and earth, we must believe in a world of bodies.8 In the appendix to the Universae philosophiae systema, Fardella takes this a step farther. He argues that Descartes’s arguments don’t even make the existence of body probable. Furthermore, he argues that biblical testimony is insufficient. Arguing that the Bible often speaks the language not of true science but of the common man, Fardella argues that nothing in the Bible can be taken to require the existence of an external world of bodies (Fardella 1691a: 518–9).9 The skeptic Pierre Bayle and the immaterialist George Berkeley (probably through Bayle) took notice of this remarkable observation.10 For this reason, Fardella is sometimes cited as an early, if somewhat ambiguous, immaterialist and idealist. But this may be reading too much into Fardella’s position here. Good Cartesian and Augustinian that he was, Fardella saw mind as better known than body, and of greater perfection; there can be no question about that. But for all that, Fardella didn’t

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necessarily want to reduce body to mind-like monads as Leibniz was later to do, or to collections of ideas existing in minds, as Berkeley was later to do. In one of his replies to Giorgi, he wrote: “it does not matter for the examination and discovery of its principle attribute or nature whether the existence of body be real, apparently certain or doubtful” (Lauria 1974: 138 left column).11 It is true that Fardella might turn out to be an idealist in the sense that all there really is for him is mind. But if he is an idealist, it is because bodies properly understood might not exist at all, and not that bodies might in some sense be reducible to minds or to ideas in minds. His view is that even if bodies don’t actually exist, their nature is what Descartes says it is. Fardella’s position is, thus, very different than Berkeley’s immaterialism, with which he is sometimes associated, or with Leibniz’s brand of idealism in the Monadology.

2. fardella and leibniz With this background, I would like to turn to the text at hand, the exchange between Leibniz and Fardella. The recently published volumes of the Akademie Edition VI iv collects four texts under (their) title Communicata ex disputationibus cum Fardella, which they date to March 1690(?) (A VI iv, 1666–74). The first text is certainly directly connected with a meeting with Fardella, and is dated by Leibniz to March 1690. It begins with the following paragraph: I communicated several of my metaphysical thoughts to the Reverend Father Michel Angelo Fardella of the Order of Friars Minor, because I saw that he combined meditation on intellectual things with an understanding of mathematics, and because he pursued truth with great ardor. And so, after he grasped my views, he wrote out certain propositions at home to remember them in order to master what he heard from me, along with objections, which, it so happens, he sent to me for my examination. (A VI iv, 1666/AG 101)

What follows then are three propositions, presumably Fardella’s rendering of views he understood Leibniz to hold. The first proposition is about foreknowledge and predetermination, the second about harmony, and the third about body and corporeal substance. In the first and third case the propositions are followed by Fardella’s objections, with Leibniz’s “clarification” [declaratio]. The second, third, and fourth texts grouped together are remarks apparently connected with the third proposition. The manuscripts of the second and third texts, also about body and corporeal substance, are bound in with the manuscript of the first in the

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copy in Hanover and, obviously, are connected to it by theme and terminology. The fourth text is an excerpt from Fardella’s Universae usualis mathematicae theoria (1691b), a demonstration that the part is less than the whole, which Fardella claimed Leibniz had shown him in Venice. I will concentrate on the first text. The others are interesting, to be sure, but don’t really add anything to my story. Let me begin with a discussion of the first text and its three propositions. In the first proposition, Fardella summarizes what he takes to be Leibniz’s view on how God determines at the moment of creation everything that is to happen in the world, including the free actions of his creatures. In his objection to Leibniz’s view, Fardella complains that “I don’t understand well enough how this sort of divine foreknowledge and predetermination can be reconciled with the freedom of the human mind” (A VI iv, 1667/AG 102). Leibniz answers by distinguishing between God’s foreknowledge and predetermination, and the contingency of what God knows and determines. In the second proposition, Fardella summarizes what he takes Leibniz’s position on the harmony of creatures in the world to be: “The infinitely many series of things and of changes so correspond to one another and are connected with such symmetry that any given one agrees perfectly with all the others, and conversely” (A VI iv, 1668/AG 103). Since Fardella makes no objection, Leibniz makes no response. But it is the third proposition, Fardella’s critique and Leibniz’s response that are the most interesting. This is an abbreviated version of proposition 3: A body is not a substance but an aggregate of substances, since it is always further divisible, and any given part always has another part, to infinity. Hence, it is contradictory to hold that a body is a single substance, since it necessarily contains in itself an infinite multitude, or an infinity of bodies, each of which, in turn, contains an infinite number of substances. Therefore, over and above a body or bodies, there must be substances, to which true unity belongs. For indeed, if there are many substances, then it is necessary that there be one true substance. Or, to put the same thing another way, if there are many created things it is necessary that there be some created thing that is truly one. For a plurality of things can neither be understood nor can exist unless one first understands the thing that is one, that to which the multitude necessarily reduces [referatur]. Hence, unless there are certain indivisible substances, bodies would not be real, but would only be appearances or phenomena (like the rainbow), having eliminated every basis from which they can be composed. However, from this, one must not infer that the indivisible substance enters into the composition of body as a part, but rather as an essential, internal requisite, just as one grants that a point is not a part that makes up a line, but rather

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something of a different sort which is, nevertheless, necessarily required for the line to be, and to be understood. Hence, since I am truly a single indivisible substance, unresolvable into many others, the permanent and constant subject of my actions and passions, it is necessary that there be a persisting individual substance over and above the organic body. This persisting individual substance is completely different from the nature of body, which, assuming that it is in a state of continual flux of parts, never remains permanent, but is perpetually changed. And so, there must be some incorporeal, immortal substance in man, over and above the body, something, indeed, incapable of being resolved into parts [ . . . ]. Hence, it seems probable that animals, which are indeed analogous to us, and similarly plants, which correspond to animals in many ways, are not composed of body alone, but also of soul, by which the animal or plant, the single indivisible substance, the permanent subject of its actions, is controlled. This is well understood by the mind, though the imagination cannot grasp it. Souls of this sort never perish, but when they seem to perish, they remain hidden in some inconspicuous part of a fragmented mixture. (A VI iv, 1668–70 AG 103–4)

To the penultimate paragraph, Leibniz added the following marginal comment: “I judge that it is probable that plants and animals are animate, though I cannot say anything with confidence about any body in particular except the human body with which I am intimately acquainted. However, I do venture to assert that they contain animate bodies or bodies analogous to animate bodies, that is, substances” (A VI iv, 1669/ AG 148 n.). Proposition 3 is, presumably, Fardella’s version of Leibniz’s proposal, what he wrote out “at home [ . . . ] to master what he heard from” the visiting dignitary from Hanover. I assume that the marginal note is Leibniz’s later comment on the matters at hand. Here, then, is Fardella’s objection: When dealing with a multitude of stones ABC, either stone A or B or C must be understood first. But it is not the same with a soul which, with other souls, does not constitute body. And it seems that there is some difficulty in the argument that, given that there are bodies composed of substances in the world, there must necessarily be something which is a single indivisible substance. Now, this can legitimately be inferred if the unity, as a part of the same sort, intrinsically composed the aggregate. But the substantial unity in question does not intrinsically constitute the aggregate, and is not a portion of it, but is understood to be essentially altogether different from it. How, then, is it required in order for this aggregate to subsist? (A VI iv, 1670/AG 104)

What is Fardella worried about here? As I read this passage, Fardella has problems both with Leibniz’s position, as he understands it, and

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with the argument Leibniz offers for it. He takes Leibniz to be arguing from the fact that bodies are divisible and, thus, aggregates of smaller parts, to the fact that they must contain indivisible substances. It seems to me that the assumption he makes here is that the indivisible substances that Leibniz has in mind in the initial passage are something like Cartesian souls, an assumption that isn’t surprising given Fardella’s own Cartesian background. This is the position he attributes to Leibniz, something not unlike what Leibniz will later hold in the classical monadological writings, and something not unlike what many later commentators have read into others of Leibniz’s writings in the period. (In 1690, of course, Leibniz has yet to use the word monad in this connection). Fardella wants to disagree with Leibniz about this position: souls taken together don’t make up bodies. Secondly, he wants to argue that the argument Leibniz uses here, the argument from the existence of an aggregate to the existence of unities that ground the existence of that aggregate, doesn’t work here. As I am reading this passage, Fardella argues that from the fact that a body is an aggregate of smaller parts, one cannot infer the existence of an indivisible substance (a mind or soul, Fardella thinks Leibniz intends) which is altogether different in kind from a body. From the fact that body is a multiplicity, we can infer only the necessity of bodily parts, parts of the same kind as the aggregate; we cannot infer the existence of parts of an altogether different sort. Here is Leibniz’s clarification: I do not say that the body is composed of souls, nor that body is constituted by an aggregate of souls, but that it is constituted by an aggregate of substances. Moreover, the soul, properly and accurately speaking, is not a substance, but a substantial form, or the primitive form existing in substances, the first act, the first active faculty. (A VI iv, 1670/AG 105)

Leibniz here is commenting on Fardella’s understanding of the argument in question. He is clarifying what he takes to be a misinterpretation of his position. And what he seems to be holding is that bodies are not collections of souls, as Fardella seems to have interpreted Leibniz as holding. He then goes on to say that, strictly speaking, souls aren’t substances. Instead, he asserts, souls are the substantial forms of substances. I don’t want to pause over the fact that this is inconsistent with what Leibniz (or Fardella’s version of Leibniz) says in the proposition that proceeds, and what he will go on to say later in the clarification. Nor is there an argument for the view given here. But Leibniz feels it is necessary first of all to clarify his view: bodies are made up of corporeal substances that are not themselves

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souls but which have souls. Leibniz continues: “Moreover, the force of the argument consists in this, that body is not a substance, but substances or an aggregate of substances. Therefore either there is no substance, and therefore there are no substances, or, there is something other than body” (A VI iv, 1670–1/AG 105). This is not an analysis of the argument itself, but of the conclusion of the argument: the force of the argument, what the argument is intending to establish, is that body itself, understood in the Cartesian way as extension, is not itself a substance. Leibniz continues with some thoughts on the relation between body and the substances it contains: “Further, although the aggregate of these substances constitutes body, they do not constitute it as parts, just as points are not parts of lines, since a part is always of the same sort as the whole” (A VI iv, 1671/AG 105). Note the first analogy here: substances are in body as points in a line. Leibniz goes on to introduce a second analogy: However, the organic bodies of substances included in any mass of matter are parts of that mass. So in a fish pond there are many fishes and the liquid in each fish is, in turn, a certain kind of fish pond which contains, as it were, other fishes or animals of their own kinds; and so on to infinity. (ibid.)

On this analogy, substances (or, at least, their organic bodies) are in body in the way in which fish are in a pond, little animals in the fluid of the fish, and so forth, to infinity. Leibniz then returns to the first analogy: And therefore there are substances everywhere in matter, just as points are everywhere in a line. And just as there is no portion of a line in which there are not an infinite number of points, there is no portion of matter which does not contain an infinite number of substances. But just as a point is not a part of a line, but a line in which there is a point is such a part, so also a soul is not a part of matter, but a body in which there is a soul is such a part of matter. (ibid.)

Here seems to end the explication of the analogies. What follows appears to be further rumination, somewhat hesitant and confused, about the point that Fardella raised about the heterogeneity of the body and the corporeal substances it contains, a heterogeneity that would seem to undermine the argument that Leibniz is trying to offer. He begins by introducing some questions that need further consideration: We must consider [considerandum] whether we can say that an animal is a part of matter, as a fish is part of a fish pond, or cattle are a part of a herd. And indeed, if the animal is conceived of as a thing having parts, that is, as a body divisible and destructible, endowed with a soul, then it must be conceded that the animal is part of matter, since every part of matter has parts. But it cannot then be conceded

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that it is a substance or an indestructible thing. And it is the same for man. For if a man is the I [Ego] itself, then he cannot be divided, nor can he perish, nor is he a homogeneous part of matter. But if by the name “man” one understands that which perishes, then a man would be part of matter, whereas that which is truly indestructible would be called “soul,” “mind,” or “I,” which would not be a part of matter. (ibid.)

Unfortunately, Leibniz’s clarification isn’t all that clear. The text becomes a bit murky as Leibniz struggles with making his argument work in the face of Fardella’s objection. Leibniz is here struggling to understand how substances he posits in bodies are related to the aggregates that he thinks bodies are. The first analogy he uses is that of points in a line. Points are everywhere in a line as the boundaries of possible finite line segments. However, they are not parts of the line, strictly speaking, since the line is not made up of them. But very quickly he introduces another, very different analogy, that of the fish in the fish pond, or an animal in a herd of animals. These are clearly very different ways of thinking of the aggregate, and it is reasonably clear that Leibniz is not able to choose between them. The remainder of the paragraph seems to be Leibniz thinking on his feet, trying to think about the relation of the line to the point, the cow to the herd, trying to figure out the ways in which they are homogeneous and the ways in which they are heterogeneous. That is to say, I think that Fardella hit something of a raw nerve in Leibniz, who is, in this text, coming to realize that the argument that he had used so confidently in the Arnauld correspondence may not work. The inner struggle over the argument continues first in a marginal note he appends to his supposed clarification and in at least the second and third texts that the editors of the Akademie Edition have appended.12 (The fourth and last text the Akademie edition appends, the excerpt from Fardella’s Universae usualis mathematicae theoria, is not relevant to this question.) However clear he seems to be about the position he wants to take, the aggregate argument, the argument from the existence of the aggregate to the existence of a simple that makes up that aggregate seems to have become somewhat problematic in the light of Fardella’s objections.

3. corporeal substance: realism versus idealism Now that we have this interesting text before us, I would like to reflect a bit on what it may or may not mean for some of the larger issues of interest to recent commentators. But before doing this, let me clarify some of the terminology. What do we mean when we call (or decline to

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call) Leibniz an idealist? For the purposes of this chapter, let me borrow an account from Robert Adams in his book, Leibniz: Determinist, Theist, Idealist (1994). Adams believes that Leibniz was an idealist throughout his mature career, including in the period in which this note was written. By idealism Adams means the following thesis: The most fundamental principle of Leibniz’s metaphysics is that “there is nothing in things except simple substances, and in them perception and appetite.” It implies that bodies, which are not simple substances, can only be constructed out of simple substances and their properties of perception and appetition [ . . . ]. A construction of the whole of reality out of perceiving substances and their perceptions and appetites exemplifies a broadly idealist approach to metaphysics. (Adams, R. M. 1994: 217)

To deny idealism is to deny this thesis.13 There may be a number of different ways of denying Leibnizian idealism. One might argue that there is something in the world over and above the monads that is necessary to understand the world. For example, one might argue that in addition to mind-like and purely non-extended monads we need something like matter, understood as something distinct from monads, for the world of bodies to be real. This is what might be called strong realism. Alternatively, one might argue that while there is nothing over and above monads in the world, certain organized collections of monads (corporeal substances, for example) have a kind of reality that is of the same order as the reality of monads, and that the reality of the world requires these entities as well, even if there is a sense in which these collections can be reduced to monads. This is what I shall call weak realism. It is not surprising why one might find the text that we have been examining strong evidence for a non-monadological and realist Leibniz. Fardella seems to present Leibniz with the perfect opportunity to admit to his idealism in Adams’s sense and to say that there is a strong sense in which body is made up ultimately of elements that are mind-like and that there is nothing else in the world. But he didn’t. In fact he explicitly denied it. Instead, he says, bodies are made up of substances, and souls are not themselves substances, but, instead, just the substantial forms of substances. The focus seems to be on corporeal substances, conceived as unities of form and matter. It would look as if Leibniz’s world in March 1690 cannot be the idealist world that it undeniably is in other, mostly later, texts. Not that it is easy to say what exactly Leibniz’s positive view was here. In an earlier paper, where I argued that Leibniz was a kind of realist in these years, I struggled to articulate what exactly the difference

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was. I argued that there were two important differences between the picture in the correspondence with Arnauld and the Fardella memo and the later monadology. In the earlier period, I argued, the primary focus of Leibniz’s attention was on corporeal substances, while in the later it was on the non-extended monad. Secondly, I argued, that in the earlier period, Leibniz accepted something like primary matter, non-mental and distinct from form, while in the later period, even matter is reinterpreted mentalistically. That is, I argued for what I earlier called a strong realist position (Garber 1985: 62–5). Later, after reading Robert Adams’s attack on that view in his book Leibniz, I came to doubt whether Leibniz held anything like Aristotelian primary matter (see Garber 1996). However, I continue to think that Leibniz did believe in the reality of corporeal substance (and, thus, the reality of the extended world) in that earlier period in a way in which he seemed to give up later. This is what I called a weak realist position. In his book, Adams offers a different reading of the Fardella notes, one that makes it at the very least consistent with an idealist interpretation. Let us focus for a moment on what I take to be the most striking line of the text, “the soul, properly and accurately speaking, is not a substance, but a substantial form [ . . . ].” Adams writes: One might certainly be tempted to take the statement that the soul is not a substance, strictly speaking, because it is a substantial form, as expressing the Aristotelian one-substance theory, in which a corporeal substance has its organic body as a constituent and does not have a simpler substance as a constituent. The statement does not compel us to this interpretation, however. In saying that the soul is not a substance Leibniz certainly has in mind that it is only an aspect of, or abstraction from, a concrete substance. The question is, What is that concrete substance of which it is an aspect? Is it a substance of which the organic body is a constituent, as in the Aristotelian one-substance conception? Or is it an unextended monad, as in the qualified monad and two-substance conceptions? (1994: 275)

Adams’s reading calls for a bit of background, in particular, what he means by the qualified monad, one-substance and two-substance interpretations. The two-substance conception is the view that there are two kinds of substance, the simple substance (or monad, as Leibniz was later to call it) and the composite or corporeal substance (Adams, R. M. 1994: 265–7). The one-substance interpretation seems to come in two flavors for Adams. First, there is the standard Aristotelian conception of substance, form and matter, where the matter in question is an organic body and the form is not itself a substance but simply a constituent of substance.

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Second, there is what Adams calls the “qualified monad conception.” On this conception, there is just one kind of substance in the world, the non-extended monad. But within the monad itself, we can distinguish between its matter (that is, its passivity) and its form (that is, its activity) (Adams, R. M. 1994: 267–9). What Adams is claiming here is that the Fardella notes can be read as any of these conceptions of substance. He goes on to discuss the rest of the text, and he argues that Leibniz’s discussion of parts and wholes, homogeneity and heterogeneity, and lines and points suggest strongly that he does not have in mind the more orthodox kind of Aristotelian conception of substance that I am inclined to see in this text, at least initially. What are we to make of this conflict? How can we settle the debate between idealistic and realistic readings of the text and of others like it? My suggestion is that, perhaps, we should look at the context, look back at who Leibniz was talking with, and read the text as part of a conversation between Leibniz and that person, Fardella. Fardella was a Cartesian scientist, mathematician, and philosopher, educated originally in scholastic Aristotelianism. Now, when Leibniz says to such a person that “the soul, properly and accurately speaking, is not a substance, but a substantial form, or the primitive form existing in substances, the first act, the first active faculty,” this is going to be understood most naturally in terms of a traditionally Aristotelian conception of substance. It is a virtual paraphrase of what one could read in any Aristotelian textbook.14 I don’t doubt that it could be read in a more idiosyncratically Leibnizian way as Adams does, as referring, for example, to the active aspect of a Leibnizian monad. But if so, one would suppose that Leibniz would have explained it to Fardella in a somewhat different way. After all, what would the point have been for Leibniz to have said a string of words to Fardella that he knew would be interpreted in one way, an Aristotelian way, when what he really meant was something altogether different? How would that have constituted a conversation? Furthermore, in Fardella he had what was probably as sympathetic an audience as he was likely to find for a monadological idealism, if that is what he really believed. Remember that Fardella himself was an Augustinian who was inclined toward giving greater weight and dignity to the mind over body, someone who had serious doubts about whether there was an external world of bodies. As I suggested earlier, this is not to say that he himself was an idealist in the Leibnizian or Berkelean senses. But when in his objection to Leibniz’s proposition Fardella introduced the view that bodies were aggregates of souls, it gave Leibniz the perfect opportunity to say that there was a real

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sense in which that was his view. If, that is, it was indeed his view. The fact that he didn’t take the opportunity to say that suggests to me that this kind of idealism wasn’t what was on his mind. Which is to say that Leibniz’s reply to Fardella’s objection strongly suggests to me the view that body is made up of something very like Aristotelian substances, souls connected with organic bodies, and that these corporeal substances are basic constituents of his world at that point. (Note here that I am careful not to say that they are the basic constituents of his world). But that isn’t to say that Leibniz wasn’t an idealist at this time, as I have argued on the basis of this and other texts from the period. I think that both Adams and I (and probably a number of other commentators) have made a basic error in reading these texts. It is, I think, wrong to force these texts into an idealist mold. But, I am now inclined to believe, it is equally wrong to see in them a denial of the idealist position that he was later to hold. Let me explain. Let us again return to Fardella and the dialogue he was having with Leibniz. Basic to Fardella’s Cartesianism was his commitment to Descartes’s conception of body as extension. While there were many disagreements among Cartesians in the period, including those whom Fardella met during his Parisian sojourn, the Cartesian analysis of body as extension alone, capable of divisibility without end, was a fundamental doctrine that was held virtually without dissent.15 It was to be at the center of Fardella’s exchange with Giorgi a few years later. Nor did Fardella’s interesting views about the existence of the external world undermine his Cartesian conception of body: even if there were in reality no bodies, the essence of body was still extension for Fardella. And this, I claim, was what the debate was really about, the nature of body. What is at issue, I claim, is not idealism versus some kind of realist metaphysics, but the Cartesian analysis of body versus an alternative that Leibniz was trying very hard at that moment to articulate and argue for. The question is not whether or not everything is reducible to mind-like things, but what exactly is the nature and structure of body. Leibniz is proposing an alternative to Descartes’s view, and, thus, addressing directly the view that Fardella held. On this view, body isn’t simply extension, it isn’t indefinitely divisible but, instead, it is actually divided into an infinite number of discrete and intercontaining constituents. Furthermore, a body can never be for Leibniz, as it was for the Cartesians, a single substance. Instead, a body is an aggregate of substances, of corporeal substances. The question of idealism is a somewhat different question, how corporeal substances are related to the soul-like entities that Leibniz recognizes

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clearly at this point as well, though he seems to be somewhat uncertain as to whether or not to call them substances. Fardella, in a way, put the question of idealism on the table by raising the possibility that bodies are just aggregates of souls. Leibniz explicitly took it off the table. Does that mean that Leibniz rejected idealism of the sort that Adams wants to attribute to him at this time? Maybe. But then, maybe not. One can read Leibniz’s response to Fardella as a straightforward denial of idealism (see Garber 1985: 48–50). But one can read it in a very different way. If we understand Leibniz’s interest here to be just the Cartesian conception of body as opposed to his own view of bodies as collections of corporeal substances, then the question of the ultimate makeup of corporeal substance may just not be of interest to him at this moment. Indeed, in this debate (as in the debate with Arnauld), it seems very possible to me that Leibniz simply didn’t have a position on the issue of idealism. Or, at least, he did not have a stable position. There is no question about Leibniz’s later interest in idealism. An important part of Leibniz’s later metaphysics was to establish that in a straightforward sense, all there are in the world is mind-like entities. But it may be very misleading to read Leibniz’s later interests (or our later interests) in idealism into this earlier conversation. It just may not have been on the agenda. What was on the agenda was the Cartesian analysis of body and Leibniz’s proposed alternative, that bodies are made up of corporeal substances. That is certainly something very much on both Leibniz’s and Fardella’s minds. My claim is that this is what the issue was.

4. conclusions A troubling aspect about the debate in the Leibniz literature about idealism versus realism is the apparent inability commentators have had in coming to agreement. In the so-called middle period, about which there has been so much debate, the same text can be read in different ways, either as showing Leibniz’s idealism or as showing his realism about body. Maybe (and I stress, maybe) the reason for this is because the issue just isn’t there, not in the texts and not in Leibniz’s mind. Notes 1. In the preface to the work for which he was best known, his Animae humanae natura ab Augustino detecta (1698: i–ii), Fardella gave what amounts to a small intellectual autobiography, on the model, perhaps, of the intellectual

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3. 4. 5. 6. 7.

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9. 10. 11. 12.

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autobiography that Descartes gave in the Discourse on the Method. He talks of looking in his youth for illumination in Epicurus, Empedicles, Democritus, Anaxagorus, and even Aristotle and Plato, finding only empty words and obfuscation, until finally he hit on the works of St. Augustine, where he finally found the illumination he looked for – also see Boullier 1868: 2, 524 and Femiano 1979: 20ff. The quote is take from Fardella’s Pensieri scientifici (1713). The Pensieri scientifici remained unpublished during Fardella’s lifetime. On the dating, Femiano 1986: 18. More generally, see Femiano 1979: 35ff. Fardella’s Restitutae is published as an appendix in Femiano 1979: 133–221. Page numbers given in the text refer to that edition. On Leibniz’s trip to Italy, see Robinet 1988. The trip to Venice is discussed in ch. 9. See Femiano 1979: I.3 for an account of Fardella’s later years. For an account of the letters, almost all of which remain unpublished, see Femiano 1982. Fardella’s contribution to the debate is reprinted in facsimile in Lauria 1974: 107–70. For accounts of the affair, see Bouillier 1868: 2, 528f., and Femiano 1979: 109ff. For Malebranche’s views on our knowledge of the existence of the external ´ world, see, e.g., VIe Eclaircissement (1678) to his La recherche de la v´erit´e (1674– 75). I am deeply indebted to Marta Fattori, who helped me obtain a copy of this exceedingly rare book. See Bayle’s article Zenon d’El´ee, note H in his Dictionnaire (1697: XV, 49– 52/Popkin 373–7) and Berkeley’s Philosophical Commentaries (1944: §79). Thanks to Vincent Bertolini for advice on the somewhat difficult Italian in this brief quotation. Interestingly enough, the marginal note to proposition 3 of the first text begins with a close paraphrase of the words at the beginning of the third proposition, “A body is not one substance but substances or an aggregate of substances [ . . . ]” (A VI iv, 1670?) This suggests that Leibniz was contemplating his own draft of the original proposition as drafted by Fardella to clarify matters in the face of Fardella’s objection. The second text (A VI iv, 1672) begins identically with proposition 3 of the first text: “A body is not a substance but an aggregate of substances.” Again, this suggests another attempt to draft proposition 3. There are, of course, other conceptions of idealism. The Leibnizian idealism at issue here is different from Berkeley’s idealism, and from the kind of idealistic position I discussed earlier in connection with Fardella. It is also different from two different kinds of phenomenalism that are associated with Leibniz’s views in the 1670s and 1680s. In the correspondence with Arnauld, for example, Leibniz says a number of times that bodies considered as collections of corporeal substances are phenomenal insofar as they lack substantial forms, and insofar as their unity is supplied by the mind – see, e.g., GP II 100–2. While this is certainly mentioned in connection with the exchange between Leibniz and Fardella, it is something quite separate from the kind

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of idealism that Adams wants to argue that Leibniz held in this period. In that period, Leibniz also toyed with a kind of Berkelean phenomenalism where the reality of the world is simply grounded in the orderliness of the perceptions of the conscious mind. On this, see, e.g., On the Method of Distinguishing Real from Imaginary Phenomena (A VI iv, 1500–4/L 363–5), currently dated at summer 1683 to winter 1685/6. This variety of phenomenalism is quite different from the kind that Adams wants to insist on in connection with Leibniz, and it doesn’t come up at all in connection with the exchange between Leibniz and Fardella. For a discussion of these themes, see, e.g., Adams, R. M. 1994: 235–40 and 244–7. 14. Eustachius a Sancto Paulo, e.g., characterizes the substantial form as “the primary and principal principle of acting [agendi principium [ . . . ] primarium ac principale]” (1648: Part III, 125). 15. I say here virtually without dissent because of the Cartesian atomist Cordemoy, whom contemporary Cartesians found puzzling in the extreme and whose views attracted Leibniz in the mid-1680s – see, e.g., the references to Cordemoy in Leibniz’s letters to Arnauld (GP II 78; 96; and 118) and the reading notes on Cordemoy (A VI iv, 1797–1801); the latter are discussed in Garber 1996. But even though Cordemoy was on Leibniz’s mind during these years, I see no reason to think that Cordemoy was at issue in the discussions with Fardella.

7 Leibniz’s Exchange with the Jesuits in China Franklin Perkins

On December 2, 1697, Leibniz wrote to the Jesuit missionary Antoine Verjus that he would like more information regarding China, Where I take such a part, because I judge that this mission is the greatest affair of our time, as much for the glory of God and the propagation of the Christian religion as for the general good of men and the growth of the arts and sciences, among us as well as among the Chinese. For this is a commerce of light, which could give to us at once their work of thousands of years and render ours to them, and double so to speak our true wealth for one and the other. This is something greater than one imagines. (Wid 55)

This “commerce of light” is a guiding principle throughout Leibniz’s relationship with China, from his earliest encounter with the Jesuit mission, through the publication of the Novissima Sinica, to the founding of the Berlin Society of Sciences. Leibniz pursues this broader goal through a series of particular exchanges and negotiations, the most significant of which is between Leibniz and the Jesuits involved with the mission in China. “Commerce of light” is not a careless phrase but one directed specifically against the two forces then driving globalization and European expansion. The most powerful force was the valuable commerce of goods already connecting Europe with Asia, Africa, and the Americas. From an early age, Leibniz was well aware of the economic forces behind European expansion. In the “Egyptian Expedition,” he For this chapter, I am indebted to guidance and suggestions from Emily Grosholz and Paul Lodge, and to Rita Widmaier and Herbert Breger for their assistance at the Leibniz Archive. A fellowship from the Deutscher Akademischer Austauschdienst, a grant from the Institute for Arts and Humanistic Studies at the Pennsylvania State University, and a Vassar College Faculty Research Grant all made this research possible.

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gives details of the trade between Europe and the rest of the world, and he even describes trade and monetary policy between Asian nations (A IV i, 246 and 252).1 His main argument in those texts is that Louis XIV could more effectively harm the Dutch by attacking their overseas trade links than through direct invasion. As Leibniz matured, however, he showed surprisingly little interest in trade, advocating instead the exchange of knowledge, leading to mutual enlightenment. The “commerce of light” also challenges the other force driving European expansion, the missionaries. The missionaries were concerned with light, but only with giving it away, as the light of revelation and, at least for the Jesuits, the light of European science. An intercultural commerce of light places Leibniz even more at odds with other philosophers of his time, standing in contrast to two prominent approaches. For one, which might be called Rationalist, the sufficiency of reason left little use for other cultures. The purpose of doubt for Descartes is precisely to free himself from cultural limitations, so as to reach transcultural truths through reason alone. Spinoza expresses this tendency well in a letter to Albert Burgh. Burgh writes to Spinoza: How do you know that your philosophy is the best out of all those that have ever have been taught in this world, are at present being taught, or will ever be taught in the future? To say nothing of possible future philosophies, have you examined all those philosophies, both ancient and modern, which are taught here, and in India, and everywhere through the whole world? (SL 303)

Spinoza responds: I do not presume that I have found the best philosophy, but I know I understand the true philosophy. If you ask me how I know this, I reply that I know it in the same way that you know that the three angles of a triangle are equal to two right angles [ . . . ]. For truth is an index of itself and the false. (SL 342)2

The other prominent early modern approach showed interest in other cultures but only as illustrations of the diversity of human opinions and customs. The best example is Montaigne’s “On Cannibals,” and, although he is not a skeptic like Montaigne, Locke, in his argument against innate principles, uses cultures in a similar way to argue against universal consent in matters of religion and morality. Leibniz stands alone among early modern philosophers in promoting an imperative not just to tolerate but also to seek out and learn from other cultures. I believe this political or social imperative is not arbitrary but expresses deeper currents in his philosophy. These same currents are expressed in Leibniz’s other social plans, such as reconciling factions of the church and promoting learned

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societies. In this chapter, I briefly show how Leibniz’s philosophy provides a basis for comparative philosophy and cultural exchange, and I then focus on how this foundation is expressed in Leibniz’s main attempt at cultural exchange, in his correspondence with the Jesuits in China. My hope is that by focusing on this philosophical foundation and its application in correspondence side by side light will be shed on both, emphasizing in particular how Leibniz’s metaphysics and epistemology serve his practical, social concerns. Before turning to these issues, it is necessary to describe briefly Leibniz’s engagement with China, as it remains unfamiliar to many. The importance of China to Leibniz is affirmed by its place within his body of writings. Leibniz mentioned China as early as 1666, in his De Arte Combinatoria, where he writes that the Chinese language is pictographic rather than phonetic (A IV i, 270). A few years later, in the plans for the Egyptian Expedition, China ranks with Egypt as the mother of sciences and is recommended as the “most cultivated nation,” over Europe itself (A IV i, 379). One of the few books Leibniz published in his lifetime, the Novissima Sinica, was a collection of writings on China that he edited, introduced, and published in 1697 (Nesselrath and Reinbothe 1979/WC 45–59). At the end of his life in 1716, we still find Leibniz concerned with China – his most extensive writing on Chinese philosophy was the Discourse on the Natural Theology of the Chinese, an essay written for Nicholas R´emond, which was left unfinished at his death (Loosen and Vonessen 1968: 39–132/WC 75–138). Beside this essay and the preface to the Novissima Sinica, Leibniz wrote two other essays directly on China, both sent along with correspondence to Jesuits – the first to Antoine Verjus on January 1, 1700 (Wid 112–14/WC 61–5) and the second to Bartholomaeus des Bosses on August 12, 1709 (GP II, 380–4/WC 67–74). The practical focus of Leibniz’s engagement with China was always on missions. Almost every mention of China in his correspondence has some political goal in the background, shaped selectively to the interests and motives of the particular correspondent. Three goals are central. The first is for the Jesuit position of accommodation in the Rites Controversy. The Rites Controversy was a conflict between factions within the Catholic Church, focusing on whether converts in China could continue to practice traditional rituals honoring ancestors and Confucius, and whether traditional Chinese terms could be used to translate the word God. Leibniz and the Jesuits took the position of “accommodation,” allowing the rituals and using the Chinese terms. The second political goal is the creation of a Protestant missionary effort.3 To this end, Leibniz sometimes employs

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criticisms of the Jesuit mission, but his goal is to encourage everyone toward exchange, Protestant or Jesuit. If part of encouraging them is playing them against one another, he is not above doing so. The third prominent goal is the opening of a land route to China through Russia.4 Leibniz became acutely aware of the difficulties of reaching China through his relationship with the Jesuit missionary Grimaldi. Soon after the two met in Rome, Grimaldi set out to return to China through Russia. Grimaldi first failed to cross through Russia, then failed to cross through Persia, and was eventually forced to travel by the standard sea route, from Lisbon through the Portuguese colonies of Goa and Macao and then into China. Access to China was thus controlled either by the Portuguese or by the Spanish, who came the long way across the Pacific. This control caused trouble even for other Catholics, but Leibniz’s hopes for a Protestant mission depended on a different route of access, and Russia was the best hope. All three of these goals were pursued primarily through correspondence but also publicly through his preface to the Novissima Sinica and through his plans for learned societies, where he repeats the motto – Propagatio fidei per scientias. From the time of his first contact with the Jesuit mission in 1687, Leibniz promoted exchange and acted as an agent of exchange, writing almost constantly of China in his correspondence. Most interesting is the breadth of Leibniz’s interest in China, and his role as a conduit for information. Leibniz writes something to someone about all of the main controversies in China – polygamy, the discovery of an ancient Nestorian monument, the conflicts between Biblical chronology and Chinese historical records, the rumors that a Jewish community existed in China. In 1697, Leibniz wrote to Sophie Charlotte of Brandenburg, I will thus have a sign placed at my door, with these words: bureau of address for China, because everyone knows that one has only to address me in order to learn some news. And if you wish to know about the great philosopher Confucius, or about the ancient Chinese Kings quite close to the Deluge, and consequently the first descendants of Noah, or about the drink of immortality which is the philosopher’s stone of that country, or about some things which are a little more certain, you have but to order it. (A I xiv, 869)5

Leibniz remained a “bureau of address for China,” gathering information from his Jesuit sources and answering questions addressed to him. I will give one illustration, a letter from John Toland of February 22, 1710 (LBr 933, Bl. 17–18), to which Leibniz briefly responded in an undated letter (LBr 933, Bl. 33). Toland complains that the Jesuits always write

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that Chinese is so difficult, yet he recently heard from an Augustinian monk that it is fairly easy. He suspects that the Jesuits exaggerate the difficulty of the language so that they can dismiss the judgments that their opponents make about Chinese culture on the grounds that they do not understand the Chinese properly. Toland asks Leibniz’s opinion. What makes this letter interesting is that he wrote it to Leibniz in the first place. Toland had confidence that Leibniz could answer his concerns, and Leibniz’s response was right – the Jesuits are correct in saying that the written characters are difficult, but the spoken language is not. In many letters, Leibniz sought and sent specific scientific information. He forwarded medical questions from the physician Lucas Schr¨ock to China and Batavia (now Jakarta). He sent geographical information from the Jesuits to Nicholas Witsen, who published a well-known world map. With the linguist Hiob Ludolf, he discussed news of Chinese and Tartar words. The diagrams of the Yi Jing (Book of Changes), which Leibniz thought to be an ancient binary arithmetic, were discussed with several mathematicians and intellectuals, including Cesar Caze, Wilhelm Tentzel, and Louis Bourget.6 He sent sun spot observations from China to Gottfried Kirch, the official astronomer for the Berlin Society of Sciences.7 Leibniz even forwarded extracts of a letter from China to Peter the Great.8 The spring from which all of this activity flowed was the Jesuits and Leibniz’s correspondence with them.

1. foundations for cultural exchange What founds Leibniz’s interest in cultural exchange is the balance or harmonization of diversity and order on one side and the intersection of reason and experience on the other. One problem in engaging foreign thought is balancing similarities and differences. Without similarities, we have no point of access into the thought of the other; without differences, we have nothing to learn. The problem is that similarity and difference seem opposed. For Leibniz, however, they are not opposed, as his wellknown criterion of perfection is “the most variety, with the greatest order” (GP VI, 603/AG 210). Leibniz’s philosophy is an attempt to explain the world as exactly that maximum combination of order and diversity that would inspire cultural exchange. This tension between similarity and difference becomes clearer in the practice of comparative philosophy. If we focus exclusively on differences, denying underlying similarities, then we have no transcultural principles or framework by which to evaluate the thought of the other or to incorporate it into our own views. At

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its extreme, this approach is cultural relativism – all cultures are equal because there are no transcultural standards by which to judge them. On the other side, if all cultures hold something in common, we have no reason to look to another culture to learn it. We already have it. What is needed between cultures, then, is a foundation simultaneously common and diverse. This is exactly what Leibniz offers with his doctrine of expression and perspective. Leibniz writes: Just as the same city viewed from different directions appears entirely different, and, as it were, multiplied perspectivally, in just the same way it happens that, because of the infinite multitude of simple substances, there are, as it were, just as many different universes, which are, nevertheless, only perspectives on a single one, corresponding to the different points of view of each monad. (GP VI, 607/ AG 220)

As a different perspective, every monad has at least a slightly different view of the world, thus allowing and even requiring differences. At the same time, each monad is a perspective on the same thing, thus providing an underlying criterion for evaluation. Leibniz’s metaphor is quite general, but it indicates that nothing is identical between different monads, yet everything is grounded in some common foundation. The metaphor is further complicated because intelligent monads access necessary truths through their relationship with God, but even in this general form, we can extend the metaphor to relationships between cultures. Spinoza, as Descartes, tends to see everything important as common and available through reflection. Others, like Montaigne, see cultural differences as a kind of senseless diversity, useful to fuel skepticism or satisfy idle curiosity. For Leibniz, monads from different “cultures” or places have different and complementary perspectives on the same universe, and the progress of knowledge will lie in bringing together diverse perspectives. The bridge between cultural exchange and the maximization of variety and order comes through the intersection of reason and experience. The more reason yields truths free of the culturally conditioned limits of experience, the less cause we have to seek truths of reason in other cultures. That is, if reason is expressed in each culture, we should compare its various expressions, but if reason is given culture-free, cultural exchange remains only for what is beyond reason. Cultural differences in the use of reason become attributed not to the necessary intersection of reason and experience but to the poor use of reason by non-Europeans. No doubt Leibniz sometimes falls into this trap, assuming that the use of reason is free from culture and that Europeans use it better than others

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(and Leibniz best of all)! Nonetheless, for Leibniz, reason is limited by cultural limits of experience, and these limits lead Leibniz to China and his correspondence with the Jesuits. By reason, I mean that by which we acquire knowledge of relationships between ideas, in contrast to knowledge of particular existing things. In the New Essays, Leibniz explains that truth consists in the relationships between ideas, and these relationships are common to God, angels, and us: “When God displays a truth to us, we come to possess the truth which is in his understanding, for although his ideas are infinitely more perfect and extensive than ours they still have the same relationship that ours do” (NE 396). These necessary truths of reason can never come from experience, as we only experience particular possibles. Necessary truths are grounded in the understanding of God and are knowable by us only because rational monads express both God and the created universe. The difference between reason and experience suggests two points about the intersection of reason and experience. First, the ability to grasp necessary truths could be a threat to cultural exchange. Our access to existing things is limited and perspectival, and regarding knowledge of contingent existences we have much to learn from other cultures, which see this universe from different sides. Regarding knowledge of necessary truths, however, we all have access to the mind of God. If our access to the mind of God is not limited and perspectival, then we have little to learn regarding necessary truths from other cultures, and there is no difficulty in using these truths to judge the beliefs of other cultures. In some ways, this view is Leibniz’s, but a second point weakens it. Although we express two distinct ontological realms – that of ideas and that of the world – these expressions come together in one lived experience. This unity means that reason always conditions experience, but it also means that experience always conditions reason. The latter is crucial for cultural exchange and should be examined briefly. Our expression of ideas is not qualitatively limited, but it is quantitatively limited. That is, when we know necessary truths clearly and distinctly, we know them with certainty, but our finitude means we can bring into apperception only a limited number of truths. Leibniz writes, “All reasonings are eminent in God, and they preserve an order among themselves in his understanding as well as in ours; but for him this is just an order and a priority of nature, whereas for us there is a priority of time” (GP VI, 230/Th 247). It takes time to apperceive truths, so that what we can apperceive is always limited by what we have time for. Thus, we cannot have a priori knowledge of contingent truths because contingent truths depend

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on the consideration of infinite factors, which would require infinite time and would be incompletable in principle. Almost all of our knowledge, then, depends on experience. Even necessary truths, however, take time and must follow an order of discovery, depending on our circumstances. In a sense, Leibniz says, all people have an idea of God, “But if ‘notion’ signifies an idea which involves actual thinking, then it is a proposition of fact, belonging to the natural history of mankind” (NE 430). “Natural history of mankind” could just as well be “culture.” Given this effect, we would expect different cultures to have different bodies of necessary truths. A second form of conditioning that should be mentioned is the most intimate, the dependence of thought on signs.9 On the one hand, we rarely grasp ideas completely, since most have too many component parts. On the other hand, we can handle only a small chain of reasoning at once, so that we cannot follow complex chains. We are limited both in our ability to comprehend a present complex idea and in our ability to connect ideas over time. In both cases, our knowledge is symbolic, depending on signs. What signs are available to us is a question of experience, our concrete placement in the universe, and, thus, of culture. By emphasizing our dependence on signs, Leibniz lays the foundation for the claim that language limits the use of reason, although he does not explicitly draw this conclusion. He does think that different cultures have different systems of signs, and that we could possibly improve our sign systems – and our ability to use necessary truths – through cultural exchange. The greatest way that our expression of the universe conditions our expression of ideas, however, affects the attempt to bring necessary truths to bear on existing things. Necessary truths are based on identities, or truths about what is necessarily contained in a particular idea. That a simple substance cannot be naturally destroyed is a necessary truth because indestructibility is a necessary consequence of being a simple substance, and the opposite would be a contradiction. As Leibniz puts it, the idea “simple substance” contains the idea “indestructible.” Such necessary truths can be known without any particular experience, and, in theory, anyone in any culture has equal access to them. These ideas on which we base necessary truths, however, are abstract and different from ideas of particular existing things. The idea of any particular thing is infinitely complex and, thus, ungraspable by finite beings. Consequently, the use of necessary truth in experience depends on matching the abstract necessary truth to the particular existing thing. Leibniz suggests this when he says that all necessary truths when applied in experience

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are conditional: “As for eternal truths, it must be understood that fundamentally they are all conditional; they say, in effect: given so and so, such and such is the case” (NE 446). Leibniz then gives an example – the necessary truth, that every three-sided figure has three angles, says only, if there exists a figure with three sides, then that same figure also has three angles (NE 446–7). The application of necessary truths requires bridging between relations of ideas and existing things, and it is the most powerful way we depend on experience. An example can show how crucial this step is. According to Leibniz, “substance” contains the idea “indestructible,” so that I know that if I am a substance, then I am immortal. But how could I know that I am indeed a substance? Only by observation and experience. All necessary truths are similarly dependent for their use on experience, and this experience is multiplied through cultural exchange.

2. exchange with the jesuits – what leibniz offered With this foundation in place, we can now turn to Leibniz’s exchange with his correspondents in the China mission. Almost all of Leibniz’s information came directly or indirectly from the Jesuit missionaries in China, and although he hoped to open Protestant channels of information, his greatest political efforts were directed to sustaining his Jesuit sources. Leibniz discussed China with numerous Jesuits: Daniel Papebroch, Claudio Grimaldi, Joachim Bouvet, Antoine Verjus, Adam Kochanski, Bartholomaeus des Bosses, Ferdinand Orban, and Ren´eJosephe Tournemine are some of the more significant. Leibniz’s transition from an avid but passive recipient of knowledge to an active participant in the Jesuit missionary effort came in Rome in 1689, when he met the Jesuit Claudio Filippo Grimaldi. Grimaldi had been living in Beijing and was soon to return as head of the imperial bureau of mathematics. Through this meeting with Grimaldi, Leibniz struck up a correspondence with several other Jesuits in the mission. Leibniz’s connection to the Jesuit missionaries and its central themes can be traced further back to his first correspondence with Daniel Papebroch. In January of 1687, Papebroch writes to Leibniz telling him of a translation of Confucius by his fellow Jesuit, Phillipe Couplet (A I iv, 612–13). Leibniz responds, suggesting that the translation be published in an interlinear version with Chinese characters and that the Jesuits send more information from China (A I iv, 622). Papebroch replies, describing overworked missionaries with more

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important duties than gathering information for European intellectuals (A I iv, 630–1). Leibniz responds in turn, by describing the work some of the missionaries have been able to do without damaging their success as agents of the Church. He also tries to convince Papebroch that the search for knowledge assists the mission (A I iv, 655–6). Two letters, one to Grimaldi and one to Giovanni Laureati, another Jesuit about to leave for China, give us an idea of Leibniz’s vision of the mission and China at that time. The most significant aspect of these letters is that while Leibniz lavishes praise on the missionaries, it is always for their role in promoting exchange. He thus writes to Laureati, I hope “you will remember the great business that has been given to you, promoting commerce between two such widely separated spheres. A commerce, I say, of doctrine and mutual light” (A I v, 484). The missionaries have been chosen to fill great and weighty roles, not as spreaders of European truth, but as agents of this new “commerce of light.” Throughout his involvement with the mission in China, Leibniz pushes his vision of the mission as an agent for learning as well as teaching. In both letters, Leibniz expresses great confidence that the Chinese have much of value to teach. Even in these early letters, Leibniz wished to contribute to the success of the mission. He writes to Verjus in 1698, “This Mission seems to me so important for the good of the faith and of humankind, that it interests me extremely, and I often think on that which could serve it” (Wid 87). His most important contribution was through his consistent defense of accommodation in the Rites Controversy, which may have been the main reason the Jesuits maintained their exchange with him. Leibniz’s assistance is part of an attempt to simultaneously aid and influence the mission. Even his help with the Rites Controversy was meant to encourage a more respectful and receptive attitude toward the Chinese. Leibniz offers to promote two goals. The first is to help the Jesuits learn more from China. The second is to introduce Christianity to the Chinese through reason and philosophy. Leibniz’s position on both may now seem obvious, but his stance was rare at the time. What both positions assume is a balance between difference and similarity, coupled with the relative equality of the two cultures. He assumes enough differences to make cultural exchange rewarding, but enough common ground to allow communication and judgment. We have already seen how Leibniz from the beginning characterized the mission as one of exchange. Leibniz offered various arguments for learning from China, appealing to a duty to Europe and to fears that giving the Chinese knowledge without learning from them might put the

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missionaries in a vulnerable position. Most of all, Leibniz argued that only by understanding Chinese culture could the missionaries know how best to convert them. Leibniz contributes also through specific suggestions. He urges the missionaries to publish more, and himself published some of their writings in the Novissima Sinica. Sometimes he gives brief suggestions, such as the recommendation that some Chinese be brought to Europe to serve as “nomenclateurs vivans” (Wid 57). Other times, Leibniz offers developed plans, such as the creation of a dictionary or encyclopedia of Chinese knowledge. He had heard that a great Manchurian – Chinese dictionary was being compiled, as the imperial court of the newly founded Qing Dynasty still used Manchu as its mother tongue. Leibniz proposed having this dictionary translated into a European language at the same time, and expanding it to include figures, illustrations, and knowledge of specialized professions. “This dictionary would be the key to everything,” he writes to Bouvet (Wid 218). Leibniz – ever a diplomat – even suggests how the emperor might be convinced to fund the translation. Bouvet could propose to him the advantages of a dictionary of all Chinese knowledge and explain that the best way to make it would be with European expertise. They would be glad to help. Of course, to do that, the whole thing would have to be translated into a European language (Wid 217–18). Part of the Jesuit success in China was due to their expertise in science and mathematics. This knowledge made them valuable to the Chinese government and created interest in whatever they had to teach. Much of the assistance Leibniz gave the Jesuits was through news from the world of letters. In his letter to Bouvet from February 15, 1701, he begins by describing his new analysis of infinitesimals, a newly discovered “spiritum igneum,” and the use of a barometer to forecast weather (Wid 134–5). Sometimes, he sends his own philosophical ideas or discoveries. A good example is his binary arithmetic, which he sent first to Grimaldi and then later to Bouvet, who were both in China at that time.10 He says that he hopes it may carry great weight with the Chinese philosophers and even the emperor himself as an illustration and confirmation of creation ex nihilo, in that it shows how an infinite variety (the numbers) can be formed from being and nothingness (1 and 0). He adds that the missionaries may benefit from the emperor’s good will if he learns that the inventor is a friend of Bouvet, and he has sent it from Europe expressly as a gift for the emperor (Wid 138–9). These suggestions from Leibniz contributed to the indirect use of science for the missionaries, but of more philosophical interest is the direct

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use of science and philosophy in converting the Chinese. It was on this more general level that Leibniz thought he could best contribute, as he explains in a letter to Verjus. He would like to help the mission, but he is afraid all he can do is contribute through his work in general: “principally in two things which are, in the first place, the advancement of an art of invention (which is the art of arts), both by new methods and by selections of some consequence, and in the second place, the establishment of a solid philosophy, in which piety and truth are equally accounted” (Wid 55–6). These would contribute through their role in developing and refining a natural theology. Leibniz’s theory of natural theology is too complex to describe here, but it is based on the balance between similarity and order and reason and experience that we have already seen. Every rational monad has vague intimations of God through experience of the wonders of nature and through reasoning about the causes of nature (NE 76). Leibniz hoped to contribute to both sides of this process in China. The growth of science illuminates the perfection of the world. In a letter to Bouvet, Leibniz praises the accomplishments of the missions “by the propagation of the Christian religion and by growth of solid sciences, which gives us means to admire the advantages of wisdom and the power of the author of things, and to better assist mankind” (Wid 64–5). At the same time that experience and science help us admire the creator, reasoning about experience leads to God. Leibniz repeatedly emphasized his philosophy for its success in uniting science and theology: I believe I have rehabilitated the philosophy of the ancients or the schools in which Theology is surely so useful, without at all departing from modern discoveries nor mechanical explanations, because mechanics even supposes the consideration of force and nothing is more proper than force in the phenomena of bodies to give an opening for the consideration of spiritual causes. (Wid 64 – see Wid 56)

Leibniz’s confidence in the ability of reason to lead China to religion comes from a basic commonality, in that the Chinese are assumed to have made some progress along both sides of the path already. Both Europeans and Chinese have perspectives on the same universe, so the goal of the missionaries is to help clarify the Chinese perspective. We should note that in this case, the Chinese are meant to learn some necessary truths from the Europeans, indicating that their access to necessary truths has been culturally limited, and that their experience with the missionaries could help them overcome these limitations.

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3. exchange with the jesuits – what leibniz wanted None of the help Leibniz offered the Jesuits was innocent of his attempts to shape the mission. Sometimes his motives are clear, as when he suggests they publish more. Other times, they are more subtle, as when his suggestion that the Jesuits begin by introducing science encouraged the order to send missionaries with scientific curiosity and training. Besides this general influence, Leibniz hoped his correspondence would be a direct source of information he could tailor to his own needs. Underlying his exchange with the Jesuits is a faith that the Europeans had much to learn from the Chinese, which corresponds to his faith that the Chinese had much to learn from Europe. His expectations are illustrated in a letter to Bouvet from December 12, 1697. He gives Bouvet a list of information he would like and writes: I come to physique and I understand presently under this name all the experimental notices of corporeal things for which one still cannot give the reason by geometrical principle or mechanics. Therefore these cannot at all be obtained by reason and a priori, but only by experience and tradition; and I do not at all doubt that the Chinese surpass us much on this point, because their experience is longer and their tradition less interrupted and more polished than ours. (Wid 62–3)

By “physique” Leibniz means knowledge based on experiential truths, as opposed to those coming from necessary truths alone. Earlier in the same letter, Leibniz writes that he expects the Chinese to have many inventions that Europeans lack, even though the latter use better principles, because such inventions depend not only on principles but also on chance occasions, from which consequences and inventions can be drawn (Wid 62). Given the perspectival nature of experience, diversified according to our worldly embodiment, we would expect any different civilization to be a rich source of knowledge, but Leibniz considers China particularly excellent in that area which is most useful for cultural exchange – the accumulation of experiential truths. The reason for this particular excellence is given in the letter to Bouvet. The Chinese have an exceptionally long history, relatively unbroken and well recorded. In a letter to Grimaldi, Leibniz notes that the Chinese have managed to preserve ancient traditions lost in Europe through the migrations of peoples (Wid 3). This excellence among the Chinese leads to a particular complementarity between Chinese and European cultures. In the practices of everyday life, the two are about equal and both have much to learn from the other.

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In theoretical disciplines, including logic, geometry, metaphysics, and astronomy, Europe is the winner, but in observations of experiential truths, the Chinese are the victors (NS §2/WC 46). They also win in “practical philosophy, that is, in the precepts of ethics and politics adapted to the present life and use of mortals” (NS §3/WC 46–7). Based on his comparison, Leibniz claims that an expert in the excellences of peoples would judge the Chinese as better, if not for Europe’s possession of the Christian religion (NS §17/WC 55). Such complementarity is just what we would expect from Leibniz, given that each perspective is limited, that limitations are specified by place in the world, and that the Chinese were placed as far from Europe as possible. The Chinese have practical precepts and observations, but Europeans have geometry and first philosophy. Does Leibniz really think this is an even division, or is this mere rhetoric, meant to criticize Europe and inspire exchange? The earnestness of Leibniz’s efforts to foster exchange with China suggests the sincerity of his praise. What we have seen in examining Leibniz’s epistemology is the interdependence of necessary truths and existential truths. Without knowing that this thing is A, knowing the necessary truth that A is certainly B (the A contains B) is of little help, and we can only know that this is A from experience. Chinese culture is particularly rich in that kind of experience. Excellence in necessary truths, without the experience to apply these truths, is fruitless, and Leibniz thought this fruitlessness was reflected in the moral poverty of Europe in his time. Of course the Chinese had just as much, or more, to learn. The accumulation of experience, without the clarity and structure of logic, is confused and stunted, which is how Leibniz would have described Chinese philosophy and science. How this exchange of complementary strengths would work can be extrapolated from Leibniz’s comment to Bouvet about inventions. In that passage, he says that inventions depend on chance occasions, but also on reason, because from these chance discoveries, one can “draw forth a thousand beautiful consequences and find a thousand inventions” (Wid 62). Imagine the rewards then, if the chance occasions recorded by the Chinese were submitted to European reasoning, which is just the “commerce of light” that Leibniz had in mind. Following his evaluation of the complementarity of European and Chinese knowledge, Leibniz does not directly seek necessary truths from China, but rather seeks bits of data. We can get a survey of his goals by looking at a list of questions he wrote to Grimaldi in 1689 (Wid 3–4). These

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questions were answered by Grimaldi in conversation, although Leibniz recorded some of the responses (Wid 7–10). The questions cover a wide range of topics, but the majority relate to useful tools or processes, such as the making of porcelain, glass, and paper, and the use of artificial fire. Others ask about natural resources, for example, if the Chinese have any useful plants that could be transported to Europe. Leibniz’s questions reflect thoughtful knowledge of the information then available, and many of the questions are meant to fill in gaps or verify information found in works then current in Europe.11 What is notable is that Leibniz seeks no necessary truths from the Chinese – he never asks if their geometry has developed anything unknown to Europe – and he never asks about systematic knowledge that we might call science. His focus is on raw data, as best seen in two of his main concerns – astronomical observations and historical records. In these cases, Leibniz seeks simple truths of phenomenal observation, such as “in this certain year, I saw the sun and the moon in these positions.” Nonetheless, all knowledge takes place at some intersection of reason and experience, so it seems better to see the division between the knowledge of China and Europe as within science. Between the mere recording of facts and a deductive science, there is the body of systematic, probable knowledge. Where does Chinese knowledge fit in? Leibniz treats this question in a letter to Jean Baptiste Colbert from 1679 (A III ii, 918–19). He begins by saying that the Chinese best us in knowledge of experiments, but since we exceed them in knowledge of necessary truths, we can give a better description of the earth and the movement of the sky, and our machines are more miraculous than theirs. This division carries through to a division between Chinese strength in the practice of life and in observation and European strength in military power and geometry. He notes that “on both sides a certain severe rigor is demanded.” This last sentence suggests that there is more to the Chinese knowledge than recording of observations, as is clear in the “practice of life,” which could not be accomplished by recorded experiences alone. Leibniz’s previous sentence does not undermine this claim, for it implies that the Chinese not only have a mass of data but also have a description of the earth and celestial movement; these descriptions are just not as good as those of the Europeans. Thus, we might say that both have a kind of science, and both use observation and reason in developing it. Within these sciences, the Chinese are particularly good on the observation side, and the Europeans are particularly good on the reasoning side. This might mean

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that in the sciences in which principles dominate, such as astronomy, Europeans excel, and in the sciences in which data dominates, such as pharmacology, the Chinese excel; but the two need not divide so neatly. In any case, in learning from one another, both would learn some mix of data and reasoning, even if what each side benefited from most was different. One exception to Leibniz’s focus on data may be medicine. Leibniz’s praise for Chinese medicine must be coupled with his disdain for medicine in Europe. Leibniz conceives this relationship early, writing in 1671, “As foolish and paradoxical as the Chinese rules in medicine appear, they are however much better than ours” (A IV i, 552). A year later, Leibniz wrote to the orientalist Gottlieb Spitzel that the most promising thing to come from China is its medicine (A I i, 192). As Leibniz developed his knowledge of China, his concern for Chinese medicine also developed, and he sometimes says that besides the conversion of the Chinese, the most important thing the missionaries can do is to learn Chinese medicine (Wid 86). Partly, Leibniz wants observations, but he also suggests that he wants a science of medicine from the Chinese. He writes to Bouvet that he desire notices “with regard to some extraordinary experiences of physics or specific proofs of medicine” (Wid 139). This phrase suggests that when it comes to medicine, Leibniz intends something beyond extraordinary observations. This conception of medicine is reinforced in another letter to Bouvet, in which Leibniz writes: I do not at all doubt that there are still with them some very considerable things to be learned above all in medicine, which is the most necessary of the natural sciences. [ . . . ] But all the physical sciences and even medicine have as final end the glory of God, and the supreme good of men; for in preserving it they give the means of working for the glory of God. (Wid 63)

In this passage, Chinese medicine appears as a natural science and part of the projection of science toward God.12 As far as I know, Leibniz did not work on learning Chinese medicine himself, but he did encourage the doctor Lucas Schr¨ock to do so, forwarding a set of twelve questions from Schr¨ock to Bouvet and to Andreas Cleyer, a doctor living in Batavia.13 In his writings on China, Leibniz has two concerns that go particularly beyond physique. Both are complex, and I will only suggest the nature of his interest. The first is in the Chinese language and the hexagrams of the Yi Jing (Book of Changes). Throughout his writings on China, Chinese language is one of Leibniz’s main concerns, and in the time before his meeting with Grimaldi it is almost his sole concern.14 This interest aligns

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with a broader interest in comparative linguistics, projected in the New Essays: When there are no more ancient books to examine, their place will be taken by mankind’s most ancient monument – languages. Eventually every language in the universe will be recorded, and contained in dictionaries and grammars; and comparisons will be made amongst them. [ . . . ] [This study] will be extremely useful for the knowledge of things, since their properties are often reflected in their names (as can be seen from the names of plants among different nations), as well as for the knowledge of our mind and of the marvelous variety of its operations. (NE 336–7)

On this level, his interest is still data, but Chinese was not just another language for Leibniz, as he connected it to the development of a “universal characteristic.”15 Leibniz thought Chinese might help for several reasons. He believed that Chinese characters were ideographic and writes to Bouvet that he doubts any connection between Egyptian hieroglyphics and Chinese characters because the latter “are perhaps more philosophical and seem based on more intellectual considerations, such as giving numbers, orders, and relations; thus there are some detached traits which do not support any resemblance with some kind of body” (Wid 188). Thus, Leibniz knew the characters were not arbitrarily connected to their objects, and that they represented ideas directly rather than through speech. He also learned that Chinese characters were read in Japan and Korea, so that they were a kind of universal script. All of these were traits Leibniz hoped his characteristic would have. A final point that led Leibniz to look to China for his characteristic was the antiquity and preservation of the Chinese language. Leibniz had good reason to believe the original “Adamic” language would have left more traces in Chinese than in more recent, changeable languages (see Widmaier 1983: 35). As we have seen, one way experience limits our access to necessary truths is through our dependence on language. In this case, Leibniz hoped to use the Chinese language and cultural exchange to improve European access to necessary truths. The second area in which Leibniz shows an interest beyond collected data from experience is his praise for the morality of the Chinese and his conclusion that Europe needs to learn from China. The claim is most clearly expressed in the Novissima Sinica. We believe ourselves to be so cultivated, he begins, but now we find that we are surpassed by the Chinese in comprehending the practical precepts of life. He explains, “certainly they surpass us (though it is almost shameful to confess this) in practical philosophy, that is, in the precepts of ethics and politics adapted to the

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present life and use of mortals” (NS §3/WC 46–7). Among the Chinese, laws are beautifully directed toward the greatest tranquility and order. Because of their mutual respect, the Chinese rarely show any hatred, anger, or excitement. Leibniz concludes in favor of exchange: But it is desirable that they in turn teach us those things which are especially in our interest: the greatest use of practical philosophy and a more perfect manner of living, to say nothing now of their arts. Certainly the condition of our affairs, slipping as we are into ever greater corruption, seems to be such that we need missionaries from the Chinese who might teach us the use and practice of natural religion (NS §10/WC 51)

The recognition that the Chinese have better practical philosophy raises complex problems for Leibniz.16 It means that, though Europeans have a well articulated belief in God, better knowledge of necessary truths, and extensive science, their morals are not as good as those of the Chinese. The problems for the Church are even worse, since it means that the Chinese behave better without knowledge of Christ or Church hierarchy. In spite of these difficulties, I believe Leibniz’s praise is sincere, as it is repeated and expanded several times in his correspondence.17 We can make some sense of this claim using the foundation established thus far. Both Europeans and Chinese have perspectives and limitations in their views of natural theology. In Europe, theology is clearly articulated in proofs and arguments, but it is also obscured by mysteries and factional disputes. In China, this natural theology is less developed but also less obscured, giving it a more direct impact on action. Chinese missionaries would come to Europe to remind them of the basic, necessary truths of natural theology.

4. the significance of the exchange Leibniz’s correspondence with the Jesuits in the China mission raises curious stories and examples of Leibniz as diplomat, but why is it significant? The correspondence should be important to us because it was so important to Leibniz himself, as the source of one of his main practical endeavors, alongside his concerns with logic and symbolization, harmony within the Church, and the promotion of learned societies. Leibniz was engaged with China and the Jesuits throughout his adult life, in all stages of his philosophical development, and the correspondence intersects such concerns as the universal characteristic, binary arithmetic, and natural theology. Philosophers now recognize the dangers of imposing our disciplinary

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boundaries on thinkers of the past, and most acknowledge that a study of Leibniz’s philosophy should not ignore his work in mathematics and science. In the same way, a study of Leibniz’s thought must account for his political theory and social plans. The latter have been especially neglected, even in treatments of Leibniz’s political thought, yet according to the life Leibniz chose, they should be most central. Above all, Leibniz was a public promoter of harmony, communication, and exchange. To ignore this aspect of his thought is not only to get an incomplete view but to risk misinterpreting his philosophy, just as ignoring his physics would do. So, for example, the vision that develops in his correspondence with the Jesuits is clearly an expression of themes from his philosophy: what it means to be a limited perspective on a whole, the relationship between diversity and order, the relationship between reason and experience. Even if his social action derives from rather than drives this metaphysical and epistemological level, it is reasonable to believe that practical concerns influence which metaphysical themes he chose to develop and promote. Leibniz’s correspondence with the Jesuits and his writings on China are important, though, beyond the study of the philosophy of Leibniz. Our time is commonly characterized by multi-culturalism and the need to confront and accommodate cultural difference. If this is such a time, it is a late stage of a time that began with increased pressure and contact with the Islamic world in the twelfth century, which drove attempts to develop a sea route to Asia, which in turn led to the European “discovery” of the Americas. Leibniz stands near the beginning of this time, when the discourses of colonialism were only beginning to crystallize, and he remains arguably the most prominent European thinker to show serious interest in the thought of another culture. Thus, Leibniz’s exchange with the Jesuits is important for understanding the history of Europe’s encounter with other cultures and in suggesting alternatives to what became the dominant discourses. Although aspects of what has become known as “Orientalism” appear in his writings, his vision of cultural exchange remains remarkably progressive and is yet to be realized. A “commerce of light” sounds a bit silly now, but Leibniz’s point remains astonishingly relevant. The force driving globalization remains the commerce of goods, and where the exchange of ideas happens, it still tends to be one sided. We need look no further than academic philosophy. Academic philosophers around the world know Plato, Aristotle, and Kant, yet few European or North American philosophers could even name three non-Western philosophers. It remains very common for a new Ph.D. in philosophy to have studied nothing of the thought of any other culture.

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The reasons for this condition are more historical than philosophical. We live in the legacy of the rejection of Leibniz’s “commerce of light” and of the incorporation of racism and ethnocentrism into the heart of European philosophy.18 Nonetheless, contemporary ignorance of nonWestern thought is bound with real philosophical issues, particularly issues of relativism and the balance between similarity and difference with which this essay began. My hope is that Leibniz might be of value not simply for the progressive vision he offers but also for the philosophy that generates it.

Notes 1. The “Egyptian Expedition” is a group of texts that Leibniz wrote under the patronage of Boineburg in 1672. The plan was intended for Louis XIV, to convince him to invade Egypt rather than Holland. Louis XIV invaded Holland too quickly, and Leibniz never finished the plan. 2. Translation modified. Shirley leaves out the specific reference to India, which obscures the fact that Burgh raises explicitly the problem of comparative philosophy, and that he is aware that other parts of the world have philosophy. 3. This aspect of Leibniz’s writings are covered in Merkel 1920. Lach also has an extensive discussion of Leibniz’s missionary efforts as they relate to the German political scene and to Brandenburg in particular – see Lach 1957: 39–55. 4. For a more detailed discussion of the relationship between Russia and Leibniz’s missionary plans for China, see Merkel 1920: 151–6. Lach also gives an excellent overview of the need for a land route through Russia (1957: 5–20). For a broader discussion of Leibniz’s goals in connection with Russia, see Baruzi 1907. 5. Leibniz sends the same motto to Thomas Burnett of Kemney in January 1696 (A I xii, 370). 6. These writings are collected in Zacher 1973. 7. Leibniz’s letter is missing, but Kirch thanks him for the information in a letter from August 25, 1705 (LBr 472, Bl. 4). 8. Leibniz mentions that he is sending an extract from China in a letter to Peter dated January 16, 1712 – see Guerrier 1975: 205–8. 9. The connection between signs and necessary truths is well covered in Dascal 1978. 10. To Grimaldi in mid-January to early February 1697 (Wid 33–43) and to Bouvet on February 15, 1701 (Wid 134–143). 11. Widmaier gives the sources for many of these questions (Wid 6–7). 12. Leibniz’s view of Chinese medicine is difficult to determine conclusively because he sometimes contradicts himself, as in a letter to Kurf¨urstin Sophie from August 1697 (A I xiv, 12) in which he writes that he believes the Chinese do not know of the circulation of the blood, and that “Father Grimaldi, who is now a Mandarin, told me in Rome that their medicine does not seem to be

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a great thing.” Facing contradictory statements, it is probably best to look at Leibniz’s actions, in which case, we can see that he actively sought knowledge of Chinese medicine well after his meeting with Grimaldi in Rome. Widmaier gives a brief description of these questions (Wid 71). The questions themselves are in LBr 838, Bl. 2–3. His list of questions for Andreas M¨uller, for example, from 1679, focus solely on the use of Chinese for his universal characteristic (A I ii, 491–2). These connections have been well treated in Widmaier 1983. For a more detailed treatment, see Perkins 2002. See in particular, Leibniz to Electress Sophie, September 10, 1697: A I xiv, 72; and April 1709: K ix, 300–3; and Leibniz to Ren´e-Henri De Crux De Monceaux, October 4, 1697: A I xiv, 608–9. For an excellent study of this movement, see Eze 1997.

8 Leibniz’s Close Encounter with Cartesianism in the Correspondence with De Volder Paul Lodge

Much of Leibniz’s philosophy can be seen as a direct response to the views of Descartes. Sadly, there was no interaction between these two giants. Leibniz was only three years old when Descartes died, and even he had not begun to court the favor of luminaries from the Republic of Letters at this tender age. However, two of the most important of Leibniz’s correspondences, with Antoine Arnauld and with Burchard de Volder, allow us to gain some insight into how he might have interacted with the master. The latter correspondence will be my concern here. Scholars have long recognized the importance of Leibniz’s correspondence with De Volder and have drawn frequently on passages from Leibniz’s letters, both in book-length studies1 and in recent debates over the precise nature of his mature ontology.2 However, De Volder’s contribution to the correspondence has received little attention, despite the fact that an understanding of the views which both correspondents bring to the discussion is essential for a proper interpretation of Leibniz’s pronouncements.3 The main role which De Volder plays in his correspondence with Leibniz is that of apologist for a particular brand of Cartesianism. De Volder’s abilities as a disputant, and his genuine perplexity concerning the nature of the material world, force Leibniz to illuminate his own views in opposition to Cartesian doctrines on substance, matter, and motion. And De Volder’s relentless questioning over a period of eight years yields Many thanks to the following people for their helpful comments on earlier versions of the material in this chapter: Martha Bolton, Gregory Brown, Caery Evangelist, Antonia LoLordo, Tad Schmaltz, and Roger Woolhouse.

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responses with a clarity and depth which are to be found nowhere else in Leibniz’s surviving work. De Volder was introduced to Leibniz, by his friend Johann Bernoulli, as one who admired Leibniz’s work.4 Bernoulli regarded De Volder as someone ripe for conversion to Leibniz’s philosophy, and there was a job to be done. If Leibniz could convince De Volder of his views, and also publish a version of his dynamics, they could spread his new philosophy – the badly needed synthesis of traditional and modern – in the lecture halls of Leiden and throughout Holland (see GM III, 558). Despite De Volder’s initial enthusiasm, he was never satisfied with Leibniz’s explanations. A number of reasons for this failure can be found (see Lodge 1998a). In this chapter I examine one of the main stumbling blocks in some detail. More precisely, I consider a number of Cartesian theses which De Volder brings to the discussion, and I consider the extent to which Leibniz is successful in overturning them. It is my contention that the essentials of De Volder’s position remain largely unscathed by the actual arguments which Leibniz gives. In some ways this is a disappointing conclusion. However, the discussion provides essential background for the reexamination of familiar passages and for more nuanced readings of the views which Leibniz articulates. In addition, it sheds further light on a somewhat neglected question, namely the issue of why Leibniz’s philosophy never had anything like the widespread acceptance of the Cartesianism which he thought he had so thoroughly discredited.

1. de volder’s cartesianism Burchard de Volder (1643–1709) was a leading figure in Dutch intellectual life during the last quarter of the seventeenth century.5 After traditional courses of study in philosophy and medicine in Amsterdam and Utrecht, he worked under Francis de le Bo¨e Sylvius in Leiden and received his doctorate in medicine in 1664. It was under Sylvius’s tutelage that he came to abandon Scholastic Aristotelianism in favor of Cartesianism. After gaining his doctorate, De Volder practiced medicine in Amsterdam, but he did not lose his more academic interests in mathematics and philosophy. His reputation in these areas was such that, in 1670, he was offered a vacant chair at Leiden. Initially, De Volder discharged his official duties in a traditional way, teaching the logic of Franco Burgersdijk. However, he soon began to teach the philosophy of Descartes, both in public and in private. De Volder’s name became indelibly linked with that of Descartes in the mid-1670s when, along with his colleagues Christoph

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Wittichius and Abraham Heidanus, he published a pamphlet responding to attempts by the curators of the university to suppress Cartesianism through a promulgation of 21 propositions as outlawed from consideration at Leiden (Heidanus 1676). Although the aged Heidanus lost his academic position in the fallout, the ultimate upshot of the condemnation was a weakening of the conservative power base. Indeed, shortly after Heidanus’s expulsion Cartesianism began to be taught again openly and was not subject to further suppression. De Volder’s encounter with Leibniz was more than 20 years later, by which time he was a major figure within Dutch academia, ultimately holding the position of rector at Leiden. By this stage in his life, De Volder’s view of Cartesianism was far from slavish. He had come to Leibniz’s notice primarily as the author of a collection of Exercitationes academicae dating from 1690 to 1693 in which Descartes is systematically defended against the criticisms of Huet (De Volder 1695).6 However, by the time Bernoulli met De Volder in 1698, he was clearly disenchanted with at least some aspects of Cartesianism.7 Bernoulli reported to Leibniz that De Volder admitted that he found the “Cartesian principles largely inadequate and many false” (GM III, 558–9). And in his letter to Leibniz of November 12, 1699, it is clear that he was anxious to distance himself from at least some of the views of Descartes, since he complained that Leibniz had been unfairly labeling him as a disciple (see GP II, 198). Indeed, one of the main driving forces behind De Volder’s interest in corresponding with Leibniz in the first place was his belief that the Cartesian view was unable to explain the activity of bodies by appeal to an extended substance which was thought to constitute the corporeal world.8 Although De Volder was a disenchanted Cartesian by the time he corresponded with Leibniz, a number of central Cartesian commitments form the platform from which he argued. Even where he is doubtful about their adequacy, the views are often presented as default positions which Leibniz must overcome if he is to be taken seriously. In what follows I shall consider the view of the material world which De Volder brings to the correspondence along with arguments that Leibniz employed to try to disabuse him of this position.

2. de volder’s cartesian conception of the material world De Volder’s first letter to Leibniz was concerned primarily with issues in natural philosophy, in particular, the public debate in which Leibniz had

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been engaged over the question of whether the motive force of bodies should be measured by their quantity of motion, as the Cartesians had claimed. Although some interesting issues arose in the discussion which followed, they turn largely on empirical considerations and have little bearing on the remainder of the correspondence. For this reason, I shall pass them over here.9 In addition to following the disputes over the measure of motive force, De Volder had also taken an interest in Leibniz’s views concerning the nature of substance.10 In the initial letter to Leibniz he observes that many problems could be solved “if we had an a priori demonstration that every substance is active,” including the problem of the “cause of motion in bodies” (GP II, 151).11 De Volder was no friend of occasionalism, and, in Leibniz, he thought he saw someone who could provide an account of body which obviated the need to resort to this doctrine (see GP II, 242 and 254).12 This first letter fixes the basic agenda for the remainder of the correspondence. Although a number of other issues arose between the two men, De Volder’s mission remained steadfast throughout. He was hopeful that Leibniz had an account of substance which was sufficient to explain bodily change, and he was eager to learn more. De Volder’s search for an answer to this question was set against the background of his somewhat reluctant commitment to Cartesian views about the nature of substance and body. At the heart of his philosophy was a commitment to the Cartesian criterion of clear and distinct perception which led him to adopt an account of body as extended substance.13 De Volder invokes the criterion explicitly in his discussions with Leibniz. However, it is evidenced throughout his earlier works (see De Volder 1685: 20; 1695: I, 46–93; and 1698: 29). Following Descartes, De Volder admits an innate repertoire of ideas which may be uncovered through careful reflection and thereafter provide the categories for proper thinking. The most important of these ideas within the context of correspondence with Leibniz is the idea or concept of substance, which he explains in the letter of October 18, 1700. De Volder begins by claiming that consideration of his concepts reveals that they are all one of two kinds. Either they are per se conceivable, that is, representations of one thing, which is simple and cannot be broken down any further, or they represent two things, one, and only one, of which can be conceived independently of the other. The former are concepts of substances, and the latter are concepts of modes (GP II, 215).14 De Volder insists that these categories are meant to be exhaustive, claiming that “all our concepts are covered by

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this distinction” (ibid.). But he does not take himself to be claiming anything novel, given that it “is generally acknowledged that whatever things are or are conceived to be, they are in fact either substances or modes” (ibid.). He goes on to suggest that his notion of substance “agrees very well with the common, if rather obscure, definitions of substance” given that substance in this sense “will exist through itself, that is, it will require no subject in which to exist, [ . . . ] will sustain accidents, and, except for an efficient cause, [ . . . ] will need nothing else in order to exist.” Indeed, De Volder goes a step further and claims that “It is like Descartes’s view” (GP II, 217). It is an interesting question just how similar all this is to Descartes’s view. However, I shall not address this here, other than to note one clear difference. Unlike Descartes, De Volder insists that the concept of substance has a being of reason as its object, namely per se conceivability. Descartes clearly recognized the existence of such a criterion by which substances might be picked out (see AT VII 132/CSM II, 95). But these considerations do not find there way into Descartes’s account of the concept of substance itself (see AT VIIIA, 24/CSM I, 210 and AT VII 161/CSM II, 114).15 With his account of the substance in place, De Volder has a quick argument to the conclusion that extension is a substantial nature as Descartes had famously argued. In his letter of February 18, 1699, De Volder observes: “You seem to me to deny that extension is a substance, when that, if anything, is conceived per se” (GP II, 166).16 We can express this argument, which I label Ex. Sub., more formally: (1) Anything that is conceived per se is a substance. (2) Extension is conceived per se. Therefore, (3) Extension is a substance. The first premise in this argument is simply a reiteration of the concept of substance. Thus, there is no reason to repeat the support which De Volder offers for this claim. However, it is worth considering briefly why he thinks extension is conceived per se. Again we turn to the letter of October 18, 1700: “when I conceive of extension, one thing is represented to me; I can indeed conceive of it as greater or less, but whatever the magnitude, I conceive of extension of one kind, of which I either conceive the whole of it or none of it, as one might say” (GP II, 216). To conceive of extension is to conceive of a single thing. It may be represented as having different

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magnitudes, but nothing can be taken away without the representation losing all content. This, De Volder claims, is what it is to be a substance. We should note that the conclusion of this argument is not the claim that some extended substance exists. De Volder is merely establishing the possibility of extended substance, or that extension is a substantial nature. However, in the Exercitationes academicae, where De Volder offers the same argument, it is accompanied by an a posteriori argument which is supposed to show that the bodies that we sense are extended substance (see 1695: II, 36–52).17 One consequence of this view, which is important for De Volder’s account of the material world, is more apparent in the Exercitationes than anywhere in the correspondence with Leibniz. Here De Volder claims that there is no real distinction between being “extended or hav[ing] parts that are distinct from parts” (1695: II, 55). De Volder goes on to make it clear that he does not mean that the parts of extended things are “really separated from one another by division and divided” but rather that to be extended is to have “parts [ . . . ] that could be divided” (ibid.). But although De Volder thinks that being possibly divided into separate parts “is to be extended and vice versa” (ibid.), this does not mean that it should appear in the definition of extended substance. Rather it is a proprium of anything which is extended. De Volder follows Descartes in thinking that the material world is extended substance in some sense. However, important questions remain about his view. In particular, we might wonder just how many extended things De Volder admits into his account. Descartes’s own view on this issue is far from clear (see Woolhouse 1993: 22–3), and De Volder never presents a definitive statement of his view on this issue. However, he does suggest to Leibniz that “perhaps this whole corporeal universe is only one substance” (GP II, 255), and it is this view that he defends throughout the correspondence.18 Assuming that the world is a single extended substance, De Volder is obliged to give some explanation of the nature of individual bodies. Again he remains somewhat noncommittal. The closest he comes to endorsing a view is in the letter of July 25, 1702, where he observes: “Those who say that the substance of all corporeal things is one, do indeed want bodies themselves to be divided up among each other by modes of extension alone. Surely they are allowing that this corporeal universe is composed of one substance affected by an infinite number of modes” (GP II, 272).19 This passage provides us with an account of bodies which De Volder associates with the view that the material world is a single extended substance,

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namely that they are the result of the modification of this extended substance. Thus, according to the view in question, the corporeal world is a single substance which has infinite modes. And, it is in virtue of these same modes that the world is generally thought to consist of numerous bodies, rather than a single unified thing. Although he is not explicit here, De Volder grounds the individuation of bodies in their motion. We shall return to this later. In his discussion of these issues, De Volder appears careful not to present the view stated earlier as one which he confidently embraces. As we have seen, he qualifies his statements with words like “perhaps,” as well as presenting the ideas as those held by Cartesians and others. I think these passages reveal a genuine perplexity on De Volder’s part. As we have seen, De Volder was a committed Cartesian earlier in life, but by the time he corresponded with Leibniz he was anxious to distance himself from at least some of Descartes’s views. In particular, De Volder was concerned that the Cartesian view of the material world as extended substance was unable to explain the activity of bodies. But at the same time, he remained at least partly in the grip of his Cartesian upbringing. The argument from the clear and distinct conception of substance to the coherence of the notion of extended substance left De Volder reluctant to give up on his old views.

3. leibniz’s response to de volder’s cartesianism It was De Volder’s hope that Leibniz would be able to provide him with a plausible alternative to the position that he tentatively adopted. De Volder’s aspirations are revealed more clearly in the letter of February 18, 1699, where he tells Leibniz: “If you would like us to agree with you without any worries, I believe it will be necessary to descend to the notion of substance and demonstrate that it is necessarily active from its nature” (GP II, 166). Recognizing the passivity of extension, De Volder hoped that his own account of substance might be replaced by one which allowed us to see a priori that the material world qua substance is naturally active. De Volder never puts it quite this way, but it seems that he expected Leibniz would retain the Cartesian category of extended substance, but augment the notion of substance in such a way that the threat of occasionalism could be avoided. In response to De Volder’s request, Leibniz devoted the bulk of his time to two things: First, he attacked various elements of De Volder’s Cartesian metaphysic of body and the arguments presented in favor of

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them. Second, he provided a series of discussions of his own conception of the nature of substance and material reality. None of the positive discussion proceeded in the demonstrative form which De Volder had requested, and for this reason (as well as others) he remained unconvinced by Leibniz’s views throughout the correspondence.20 In section 4 I turn to another way in which De Volder’s Cartesian upbringing prevented him from accepting Leibniz’s positive views. However, in the remainder of this section I want to look at some of the more important elements of Leibniz’s attack on De Volder’s account of body. The first two parts of this discussion will be concerned with Leibniz’s attempt to refute Ex. Sub. The third will consider his response to De Volder’s claim that the actual material world is a single extended substance.

The Attack on De Volder’s Conception of Substance Leibniz raises a number of objections to De Volder’s notion of substance, which is the first premise in Ex. Sub. The most fundamental concern that he raises appears in the letter of December 31, 1700: I get stuck when you say “The concept of a substance is that which represents a single thing in such a way that nothing which is represented can be removed from it”.21 For you seem to describe the thing in another way presently, so that substance is that which can be conceived separately. [But] this definition does not seem to coincide with the previous one. (GP II, 220–1)

Leibniz claims that De Volder unwittingly offers two distinct accounts of the concept of substance rather than one. His concern is that De Volder slides between talk about the kinds of concepts which substances have, namely concepts which are simple and unanalyzable, and the way in which the substances themselves can be conceived, namely without anything else being conceived at the same time. I shall refer to the first of the two accounts as the conceptually simple account, or CS for short, and to the second as the independent conceivability account, or IC (see GP II, 178 and 222).22 De Volder tries to defend himself against the charge of ambiguity in his letter of February 13, 1701, claiming that while it is true that having a simple concept is not the same thing as representing a thing which can exist independently, the two are necessarily coextensive (GP II, 222). However, to understand the objections which Leibniz raises it will be useful to retain the distinction within De Volder’s account.

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There is not space here to discuss all of the objections which Leibniz raises to De Volder’s CS or IC accounts of substance. I shall focus on two of the most interesting from the perspective of De Volder’s Cartesianism, one for each account.23 In his letter of July 6, 1701, Leibniz raises the following concern in connection with CS: it is not clear how it would be possible for modes to arise on your notion of them. For a substance such as you define, or which is one simple thing in representation or of one attribute, will only have one mode. Indeed the source of diversity is not apparent, since only one comes from one; whence the mode will be invariable, contrary to the hypothesis. But furthermore, because of this the thing will not even have a mode, since it is not even clear how a mode might arise that was different from the attribute. (GP II, 226/L 525)

Leibniz suggests that CS commits De Volder to the view that each substance has one and only one attribute, on the grounds that, according to CS, it is a single attribute which must be the “one thing” represented by the simple concept from which nothing can be removed.24 Leibniz then proceeds to claim that such a “single attribute view” of substance is unable to account for the undeniable fact that modes do arise in substances. It is unclear whether this is meant to be a conceptual argument or one which derives its force from the actual existence of modes. However, De Volder is surely vulnerable to either version. There are two steps in the argument: Leibniz begins by suggesting that, since only one thing can come from one other, there can at best be one mode for each attribute; but he then proceeds to deny the possibility of even one mode, on the grounds that an attribute could not cause anything different from itself. Thus, Leibniz concludes that what was previously supposed to be a single mode would really be identical with the attribute from which it arose and not a mode at all. De Volder’s reply to these charges is to be found in the letter of October 7, 1701: Next you say that no modes will arise with my notion of substance. I do not deny this. Indeed this is why I asked so eagerly for a demonstration by which it might be shown that every substance is active from its nature. Certainly it is evident that every such substance, which is subject to a variety of modes, involves action and active force, either in itself or in that substance which produces the variety. (GP II, 230–1)

Here De Volder seems to accept Leibniz’s criticism unreservedly. Does this mean then that De Volder is prepared to give up CS and the single attribute view which it entails? The answer to this question is quite clearly “no,” as can be seen from the letter of April 13, 1702. During a

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discussion of Leibniz’s claim that it can be shown that modes arise from everything which exists,25 De Volder says: “Of course I agree with you through experience that it is certain, and by no means that bodies are devoid of all force, but I seek a demonstration of this thing which is recognized through experience, derived from the nature of substance itself” (GP II, 238). In fact, the only thing which Leibniz has really achieved with this objection is to draw attention to the very worry which precipitated the discussion of the nature of body in the first place. De Volder accepts, on a posteriori grounds, that there is some cause or other which enables modes to arise in extended substance. But without an a priori demonstration he refuses to accept that this cause is something natural. Consequently, he does not accept the inadequacy of CS simply because it cannot explain how and why substances change. Although De Volder is no fan of occasionalism, the possibility still exists that all causes of change may be supernatural. And should this turn out to be the case, there would be no incompatibility between CS and the conclusion of Leibniz’s argument. For this reason then, De Volder rests the burden of proof with Leibniz and demands that he give a demonstrative argument which proves that this does not obtain, if he intends deny the viability of CS. Leibniz did have an account of body which was supposed to provide a natural basis for the production and explanation of modifications. However, as I noted earlier, he never provided an a priori demonstration of how they arise, and De Volder remained unconvinced (see Lodge 1998a: 48–51). Thus, the objection we have been considering had little force in De Volder’s eyes. All this is testimony to the force of De Volder’s commitment to the concept of substance which he took himself to have established on a priori grounds on the basis of clear and distinct ideas. The only way in which he was willing to give up on this was if Leibniz could show that he was wrong in the same a priori fashion. Empirical evidence of a mismatch between what is derivable from his concept of extended substance and the way the actual world appears did not suffice. The most important objection which Leibniz raises to De Volder’s account construed as IC first appears in the letter of December 31, 1700: “except for the first substance nothing (so I believe) can be conceived per se. But I believe that you recognize that this is not the only substance, or rather that the word ‘substance’ has been taken by men in such a way that there are many substances in the universe” (GP II, 221). Leibniz gives De Volder two reasons to be concerned about the fact that his notion of

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substance applies only to God. On the one hand, he claims it would leave De Volder maintaining inconsistently that there is only one substance and that there is more than one. On the other, Leibniz offers a more direct argument, namely that it would leave De Volder with a concept which does not accord with common usage. Leibniz appears not to have any particular view of substance in mind here, since his comments follow a brief account of the Democritean view that space and body are distinct substances and the scholastic view that there are sensing and rational substances in addition to various other animated bodies (see GP II, 225). Rather his complaint is that substance pluralism is so prevalent that it should not be thrown aside. Leibniz’s second line of complaint draws a very direct response in the following letter: You add that my “notion of substance does not seem to apply to those things which are commonly given this name, but only to the most simple substance.”26 I believe that the first part is not opposed to my definition, since it is known that people commonly speak of these notions in a very confused way. (GP II, 229)

As we shall see, De Volder did not accept the charge of monism. But here he makes it clear that he has no problem with the kind of revisionary metaphysics which would follow if this were true. This is perhaps not so surprising from one who takes the criterion of clear and distinct perception seriously. Descartes’s method of doubt was predicated on the assumption that beliefs should not be trusted simply because they are deeply entrenched.27 For his part, Leibniz continues to defend common sense in the letter of December 27, 1701: I admit that you are within your rights to take the word ‘substance’ in such a way that God alone is a substance, and the rest are called something else. But I have it in mind to look for a notion which will apply to others as well, and which agrees with ordinary ways of speaking, according to which you, I, and anyone else is reckoned among the substances. And you will not deny that I am allowed to do this, and that it will be useful if it succeeds. (GP II, 232/W 173)

Although Leibniz continues to speak out in favor of substance pluralism, he no longer defends his position by a simple appeal to conceptual conservatism. Rather, he allows that De Volder may use the term substance however he will, but that he, Leibniz, has equal right to do this and that it may be useful to do so. Exactly how it might be useful, Leibniz left unclear. Unfortunately, this part of the discussion ends in a methodological impasse. Leibniz does not present any further argument by which De Volder might be persuaded to favor a more conservative approach.

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Indeed, Leibniz’s language in the last passage is sufficiently weak that it does not demand that De Volder give up on his concept. In fact, I think that Leibniz’s claims here are evidence of a more considered approach to the provision of philosophical principles. It is evidence of his belief that the main aim of philosophers in this regard is to uncover the innate concepts which we all employ in our thinking about the actual world. For this reason, the concept of substance is tied in an important sense to the traditional use of the term. The concept of substance is nothing other than the concept which is employed in our thinking about the things which get called substances. However, the correspondence itself does nothing more than gesture in the direction of this.28 As we have seen, Leibniz’s criticism of the revisionary nature of De Volder’s concept of substance was not his only complaint at this point. Leibniz charged that De Volder’s view was monistic and that De Volder himself had opposed such a position. This claim receives further elaboration in Leibniz’s December 31, 1700, letter. Here one might expect Leibniz to demonstrate the main premise of his argument, namely that only the first substance can be conceived independently of everything else. Instead, he tries to show that matter (considered as extended substance) and mind require other things in order to be conceived.29 Thus, the objection is transformed into the claim that there are things that De Volder, and indeed others, call substances which fail to satisfy the IC account. Leibniz continues: “I judge that minds are no more conceived through themselves since they have a cause – and generally creatures have a connection arising from a common cause” (GP II, 221). Minds and, indeed, other creatures such as matter cannot be conceived through themselves, and by De Volder’s IC, should not count as substances. But since, according to Leibniz at least, De Volder wishes to classify both minds and matter in this way, there is a prima facie problem. Assuming that he wishes to remain consistent, De Volder is faced with two options, either accept the implicit charge of Spinozism, or deny that his account of substance is monistic. De Volder was not particularly troubled by this and chose the latter. In his reply of February 13, 1701, he tells Leibniz: “Then you object that nothing except the first substance can be conceived through itself, since everything else obviously has a cause. I think that conceiving the existence of substance necessarily requires a cause, but not conceiving the essence, which is the issue here” (GP II, 223–4). De Volder insists that all that need be conceived independently to conceive a substance independently is its essence. This does nothing to appease Leibniz, who retorts: “my rejoinder is that the concept of a

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possible cause is required to conceive its essence, and the concept of an actual cause is required to conceive its existence” (GP II, 225/L 524) and then proceeds to predict the reply which De Volder will give: I can foresee an elegant rejoinder for you, based on a geometrical example: The essence of an ellipse, for example, does not depend on a cause, since different causes can produce the same ellipse, namely a conic section, a cylindrical section, or the motion of a thread. But the existence of an ellipse cannot be conceived unless some determinate cause is assumed. (ibid.)

De Volder’s supposed response, that the same thing may have many possible causes and, thus, does not require any particular cause for its proper conception, is met by two further responses from Leibniz. First, he notes that although “it is not necessary to conceive of some determinate mode of generation in order to conceive of the essence of an ellipse,” nevertheless every method by which an ellipse is generated must be demonstrable from the same “formal cause” (ibid.). Second, he suggests that this kind of example is, in fact, illegitimate. Although “incomplete things” may be similar to one another when they have different causes, “this cannot happen with complete things, and so one substance is not perfectly similar to another, nor can the same substance be generated in many ways” (ibid.). Leibniz’s position here is quite simple. He holds that any individual substance must have its own unique mode of generation and that to conceive of the essence of that substance one must conceive of the mode of generation, at least qua possible. Thus, there is no substance which can be conceived in absence of everything else, except the substance which is its own cause, or God. Despite Leibniz’s attempts to close off the avenues which might provide De Volder with opportunities to reply, the course of the argument does not end there. De Volder did not really understand Leibniz’s talk of complete and incomplete things, mistaking it for the distinction between things which have the power to act and those which are passively acted upon (GP II, 229). But this confusion is eclipsed by another remark: I would think that if the essence of substance cannot be conceived without its possible cause, then the essence of a substance is not conceived. Since it seems to me that I do indeed conceive the possible causes of modes, but not of substances, following the common way of speaking I say that they are created, that is, they have a cause by which they are produced, but I do not know how. (GP II, 228)

Here De Volder sidesteps most of what Leibniz has said and claims that we cannot have conceptions of substances which include their cause. Substances, unlike modes, come into being through the direct creation

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of God. Thus, although we know that substances all have the same cause, the way in which substances are caused is completely beyond our comprehension. So, if Leibniz insists that substances cannot be conceived without their causes, possible or actual, then he is precluding any conception of created substances at all. Leibniz did not respond to De Volder’s appeal to the inscrutability of divine activity. Whether this was implicit concession is hard to tell. I have not considered all of the objections which Leibniz raises to De Volder’s account of substance. However, I think it is fair to say that I have considered the most powerful ones. Furthermore, it should be clear from the foregoing discussion that Leibniz did not succeed in his efforts to disabuse De Volder of his conception of substance. Thus, I think that De Volder had every right to maintain his account in the face of Leibniz’s actual criticisms. However, this was only one of the components of De Volder’s argument for extended substance.

Extension Is Not a Substantial Nature The second premise of Ex. Sub. is the claim that extension is per se conceivable, or that extension satisfies the account of substantiality which De Volder advocates. Leibniz clearly rejects the claim that extension constitutes the nature of a substance. However, the way in which he engages with De Volder’s acceptance of this claim is far from elegant. One of the most significant obstacles to successful communication on this issue stems from the different notions of extension which the two men employ when considering crucial arguments. We know from Ex. Sub. that De Volder considers extension to be a substantial nature. In other words, it is something which can be conceived and exist independently of other things. Furthermore, it is clear that De Volder is articulating the conception of extended substance which Descartes had advocated. In the letter of February 18, 1699, he describes himself as having a commitment to the possible existence of “mathematical body” (GP II, 164). And, more generally, it seems that he conceives of the extension which is the nature of extended substance as something which may be identified with that which grounds truths of geometry. Leibniz uses the term extension in two quite distinct ways in the correspondence.30 At various points Leibniz speaks of “mathematical extension” (see GP II, 276/AG 182 and GP II, 249/L 529), and “mathematical body” (GP II, 268/L 535–6).31 As the terminology suggests, Leibniz, like

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De Volder, recognizes a kind of extension which is the ground for the truths of geometry. The clearest discussion which the notion receives is in the Reply to Bayle, which was sent to De Volder in lieu of a letter in 1702: I acknowledge that time, extension, and motion and the continuum in general, as we understand them in mathematics are only ideal things, that is things which express possibilities, just as numbers are [ . . . ] But to speak more accurately, Extension is the order of possible coexistence [ . . . ] This inclusion of the possible with the Existent makes a continuity which is uniform and indifferent to every division. (GP IV, 568/L 583)

This passage brings out two features of mathematical extension which are significant. First, Leibniz makes it clear that the thing which unites the notion of mathematical extension with other things that are understood mathematically is their “continuity,” which is supposed to involve indifference or indeterminacy, since they may be divided in any way. Second, he provides information concerning their ontological status. They are said to be “ideal,” a claim which expresses Leibniz’s belief that such entities exist only in minds. In the letter of June 20, 1703, he speaks of this variety of extension as one of a number of “mathematical concepts which thought supports but nature does not know in their bare form” (GP II, 249–50/L 529).32 Unlike De Volder, Leibniz explicitly denies that this kind of extension could be the nature of something actual (see GP IV, 568/L 583 and GP II, 277/AG 183).33 Although Leibniz denies that there are things in the actual world which are mathematically extended, he, nonetheless, speaks of extended things, extended matter,34 and of bodies being extended.35 I will refer to the notion of extension which is invoked in these contexts as actual extension.36 Leibniz characterizes it as follows in his letter of June 30, 1704: “extension is an abstraction from that which is extended, [ . . . ] and it expresses nothing other than a certain diffusion or repetition of the same nature (GP II, 269/L 536).37 De Volder remained confused by this second notion throughout the correspondence. One of the things which troubled De Volder should be considered here, namely the way in which Leibniz uses the term diffusion. In the letter of January 25, 1705(?), Leibniz responds to De Volder’s complaint that this notion still “appeared obscure” to him (GP II, 273): I intend the diffusion that I conceive of in extension and which seems to have put into you the suspicion of I know not what hidden paradox, to be nothing other than a continuation [continuatio] in which the part is similar to the whole, as we

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conceive of whiteness diffused in milk, and the same direction everywhere in a straight line, and equal curvedness in the circumference of a circle. (GP II, 277)

Here, Leibniz is explicit about the fact that diffusion requires a whole which has parts which are similar to it in some way. The example of whiteness in milk is invoked. Milk is white, and the whiteness is diffused throughout it since all the parts of the milk which we can conceive are white as well. The diffusion or continuity in an extended thing is no different from that; it is just a “spreading out” of some quality. We are now in a position to understand how Leibniz attacks De Volder’s commitment to extended substance. Two obvious routes are available, and Leibniz takes both of them. On the one hand, there are places in which he tries to show that premise (2) of Ex. Sub. is false, thus undermining De Volder’s case for extended substance. In addition, he attempts to show that there is something incoherent in the notion of extended substance itself. Unfortunately, the first of these two is executed rather badly. The most reasonable way for Leibniz to attack De Volder’s argument for extended substance would have been to do one of the following: show why De Volder’s conception of extension, namely mathematical extension, does not satisfy premise (2) of Ex. Sub., namely the claim that extension is conceived per se; or begin with a discussion of the concept of extension which he thinks applies to actual bodies, expose De Volder’s confusions, and then show that the “correct” conception of (i.e., actual extension) does not satisfy premise (2) of Ex. Sub. In fact, Leibniz took neither of these courses. Instead, he simply attacked premise (2) of Ex. Sub. using the concept of actual extension, which De Volder did not recognize.38 The discussions of why the concept of actual extension fails to satisfy the condition of per se conceivability are interesting. However, since they ultimately fail to engage with the position that De Volder adopts, I shall not discuss them here.39 Instead, I want to examine the reasons which Leibniz gives for thinking that there could not be a mathematically extended substance, without paying direct attention to Ex. Sub. Leibniz regards mathematical extension as the “order of possible coexistents” (GP II, 253/L 529). As such, he regards it as “a numerical determination [ . . . ] which remains the same under any change whatever” (GP II, 227/L 525–6), and holds that in virtue of this it has an ontological status which leaves it unsuitable to play the role accorded in Cartesian metaphysics. However, we have yet to see an argument which might persuade De Volder of this claim.

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Leibniz’s attack on De Volder’s conception of extended substance is perhaps best approached through a passage from the letter of June 30, 1704: from the fact that a mathematical body cannot be resolved into primary constituents, it may be inferred that it is certainly not real, but something mental, signifying nothing other than the possibility of parts, not something actual [ . . . ] [Here] the parts are only possible and absolutely indefinite [ . . . ] But in real things, namely, bodies, the parts are not indefinite (as they are in space, a mental thing) but are actually assigned in a certain way in accordance with the divisions and subdivisions that nature actually institutes which follow from the varieties of the motions; and although these divisions proceed to infinity, nonetheless, they all result from certain primary constituents, or from real unities, though an infinite number. (GP II, 268/L 535–6)40

Indeed, as Leibniz notes in the letter of January 25, 1705(?): in mathematical extension, by which possibles are understood, there is no actual division and no parts except those that we make by thinking. And there are no first elements, any more than a smallest number is found among the fractions, as it were, the element of the rest. [Hence number, hour, line motion, or degree of speed, and other ideal quantities of this kind, or mathematical entities, are not in fact aggregated from parts, since the way in which someone might intend to assign parts in them is completely undetermined. Actually it is necessary that they be understood in this way, for the reason that they signify nothing other than the mere possibility of assigning parts in any way whatever]. (GP II, 276/AG 182)41

Mathematical extension is that by which possible things may be understood and does not signify any determinate partition. It is contrasted with “real things” in the letter of October 11, 1705, where Leibniz observes: “there are no divisions in it, except those which the mind makes, and the part is posterior to the whole. In real things it is the opposite, unities are prior the multitude, and multitudes do not exist except through unities” (GP II, 278–9; translated in Russell 1937: 245). In this passage it becomes clear that a necessary condition for the reality of a thing is that it be grounded in “unities.” This idea is made more explicit in the letter of January 21, 1704, where Leibniz makes it clear that by “unities” he means “what cannot be divided into many,” and furthermore, that “those things which can be divided into parts have no reality unless there are things in them which cannot support being divided into parts” (GP II, 261). The claim that there must be unities, or indivisibles, in order that there be real things, is one which receives no direct support in the correspondence with De Volder and little in the rest of Leibniz’s works. Probably the most famous statement of the view in question is to be found in the

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letter to Arnauld of April 30, 1687, where Leibniz says the following: “I hold as axiomatic this basic proposition, which varies only in emphasis: that what is not truly one being is not truly one being either. It has always been thought that one and being are reciprocal things” (GP II, 97/ LA 121). We can see from this that Leibniz takes the unity of true beings, or real things to be axiomatic, and we should, perhaps, be unsurprised that he does little to justify his adherence to this claim when talking to Arnauld, or later in his career.42 And it may well be that our best option is to assume that Leibniz is expressing adherence to an idea from the Aristotelian tradition in which he was schooled as a young man, which seemed self-evident.43 With this axiom in place, Leibniz’s denial of the reality of mathematical extension can be understood. As we have seen, extension in this sense admits an infinite number of possible partitions, and it has no indivisible parts. Thus, for Leibniz there can be no mathematically extended constituents which are determinate. It follows for Leibniz that nothing which was merely mathematically extended could be real. I have suggested that Leibniz’s position here is easy to understand. However, it is less clear how adequate it is in the present context.44 De Volder responds to this line of argument in the letter of November 14, 1704: I admit, and I have admitted already in the previous letter, that indivisible unities are not to be found in mathematical body. But at the same time I would add, however, that I get stuck over whether or not this unity is found in infinite extended mass, since the parts which we conceive as distinct in this mass do not seem to be really divided, since no part can be either assumed or conceived unless all of them are assumed and conceived. (GP II, 272)45

Here, De Volder agrees that mathematical extension cannot be said to contain indivisible unities. But he does not see why this means that there could not be an infinite extended substance.46 For, on his view, the divisions which might occur in an extended substance would not be real divisions at all, since the parts which we conceive are necessarily connected to one another. De Volder explains the basis for his view here in greater detail earlier in the correspondence, when he originally presented Ex. Sub. In response to Leibniz’s suggestion that extended things always have parts, De Volder had noted: “It is the very opposite for me; it is more work to conceive really distinct parts in extension than unity” (GP II, 166). Given that De Volder denies that there are really distinct parts in extension, he must

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account for the actual division of the matter into bodies some other way. However, this aspect of De Volder’s view is not relevant to the challenge posed at this point. For Leibniz has claimed that there could not be an extended substance on the grounds that it would not be a unity. To argue that the actual world, with its divisions into bodies, is not such a substance would not speak to the conclusion of Ex. Sub., namely the claim the mathematical extension is a substantial nature. The argument which Leibniz presents is question begging at best. De Volder is quite willing to accept the convertibility of unity and being. But he is not worried by Leibniz’s argument because he does not accept that extended things are divisible into real parts. Leibniz never responded to this position head on. In the letter of January 25, 1705(?), he reiterated his conception of continuity and the unity of real things, but he said nothing to impugn the possible existence of an infinitely extended unity. Indeed, in this letter he moves quickly from stating his position on the unreality of mathematical extension to other arguments which trade on empirical claims about the need for real divisions in matter (see GP II, 277). We shall consider this argument. But it is important to note here that even if it is successful, it does not show that there is anything incoherent in the Cartesian conception of extended substance which De Volder defends. The most it can show is that the actual world does not contain such a substance.

Leibniz’s Critique of De Volder’s View of the Actual Material World We have seen how Leibniz attempts to defeat De Volder’s belief in extended substance using arguments which attack Ex. Sub. However, Leibniz also expends a large amount of effort providing arguments of a different kind. Each has the same basic form; Leibniz begins with his opponent’s assumption that the nature of the actual material world is to be found in extension alone, and then he attempts to show that various features of the material world cannot be explained by, or deduced from, this nature alone.47 Leibniz expresses the basis for these arguments in a letter to the editor of the Journal des savants: “If the essence of body consisted in extension, this extension ought to be sufficient on its own to account for all the affections of the body” (GP IV, 464/D 42).48 He does nothing to explain the justification for this principle in his correspondence with De Volder. But whatever the status of this claim, it is one which appears to be equally

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acceptable to both correspondents, and De Volder never complains about the strategy that Leibniz uses.49 The arguments which Leibniz offers include the complaint that extension cannot account for the activity of bodies (see GP II, 171/L 517 and GP II, 257/L 532), or what he calls their “inertia,” or resistance to being moved (see GP II, 162 and GP II, 170–1/L 516–17). However, it is unsurprising that they do not move De Volder. As we have seen, one of the main motivations for the correspondence from De Volder’s perspective was his desire to find an escape from his adherence to Cartesian principles which he regarded as explanatorily inadequate in just these ways.50 However, another of Leibniz’s objections speaks directly to De Volder’s position. To the extent that De Volder claims that the material world is extended substance, he embraces the view that individual bodies result from modifications of extension. This is view subjected to severe criticism by Leibniz in the letter of June 20, 1703, in which he tells De Volder the following: You judge that [ . . . ] those who place the distinction between bodies solely in what they think of as modes of extension (as almost everybody does today) do not disavow the view that bodies differ only modally [ . . . ] Furthermore, as they are commonly conceived, [bodies] will not even be found to be distinguished modally. For if you assume two bodies A and B, of equal size, with the same shape and motion, it will follow from such a notion of body, namely one drawn from the putative modes of extension alone, that intrinsically they have nothing at all by which they are distinguished. Does this mean that A and B are not different individuals? Or is it possible for there to be different things which in themselves cannot be distinguished in any way? (GP II, 249/L 528)

Here Leibniz claims, contra De Volder, that the modes of extended substance are not sufficient to ground a numerical distinction between individual bodies. He considers the possibility of two distinct bodies A and B, which have the same size, shape, and motion. He then offers the following dilemma: either A and B will not in fact be distinct individuals as originally assumed, or they will have to be distinct without having any differences which are intrinsic to them. It becomes clear that Leibniz does not think De Volder should embrace the second horn of this dilemma when he continues: “Things which are different must differ in something, or must have in them an attributable difference. It is strange that men have not applied this most obvious axiom, along with many others” (GP II, 249/L 529). Leibniz states that it is axiomatically true that there must be some difference between any two

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things which are distinct – a version of his famous principle of the identity of indiscernibles.51 And, although the first horn goes without further consideration, it seems that Leibniz takes it as evident from experience that there are distinct bodies such as A and B.52 The discussion here is complicated by the fact the neither man clarifies what is required for two bodies to have the same motion. However, since there is no disagreement over this, I suggest that they are appealing to the common sense idea that distinct bodies may be said to move in the same direction with the same speed, relative to some other set of bodies. Assuming this is what they have in mind, Leibniz’s question concerning the principle of their individuation seems a natural one. De Volder’s response to this challenge is as follows: Bodies A and B have the same size, figure and motion and no intrinsic differences. However, it is true that a reason can be given why body A occupies this place rather than that. But this is not derived from so much from the intrinsic nature of body A itself as from the system [systema] of the whole universe; at any given time, it follows from that structure that body A occupies this place and body B occupies that place. Indeed all the places that those bodies will each occupy in the future follow as well. (GP II, 255)

The bodies in question can be distinguished. Despite having identical modifications, they will occupy different places, which are determined by the “system of the whole universe.” It is far from obvious just what De Volder means when he uses this expression. However, it seems plausible to think that he is referring to the distribution of motion throughout the material world along with the developmental laws of that world.53 Assuming this, his position amounts to the claim that the law-governed behavior of the motion of bodies determines their place at any given moment. But although this may seem like a natural answer, and appears to obviate Leibniz’s demand for an intrinsic difference between the bodies, it presupposes a principle by which places may be individuated. There is nothing in the correspondence which helps us to understand De Volder’s views on the nature of place. In the Exercitationes academicae he defends a view which is essentially that of Descartes (see AT VIIIA 47/CSM I, 228).54 According to De Volder, space or place is a “way of conceiving” of body which “in general involves the size, shape and position of the body” (1695: II, 61–2). There is no account of the key notion of position. But I think one may assume that De Volder again follows Descartes in holding that the position of a body may be derived through an abstract

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consideration of a frame of reference determined by a choice of certain other bodies as those which are to be regarded as resting. If this were De Volder’s view, he could certainly allow the possibility of bodies such as A and B being individuated by their place. Even if this is the view of the Exercitationes, it is far from clear that it accords with what we find in the correspondence. For here it is the system of the universe which determines the place of individual bodies, not a frame of reference which has been imposed on that system. The most natural reading here is that De Volder assumes a notion of place or position which is a primitive feature of the material universe considered independently of its modifications. But it remains uncertain how this is supposed to work. Unfortunately, the correspondence itself is of little assistance at this point. Leibniz does not respond to De Volder’s suggestion directly. And the issue of the need for intrinsic differences among bodies receives no further elaboration. Instead, Leibniz reminds De Volder that he also had a “demonstration from the phenomena” (GP II, 257/L 532) which showed that the diversity among our sensory representations of the material world demands a “principle of distinction among the corporeal things themselves” (ibid.). This is a reference to a distinct argument which is never presented to De Volder in full but which Leibniz had published in his 1698 paper On Nature Itself (GP IV, 504–16/AG 155– 67). Although it shares some of the features of the current argument, it also relies on an appeal to the way in which the material world appears in our sensations.55 De Volder shows no signs of having appreciated the nature of this related argument, and it is never the subject of discussion. Although the discussion of the current argument remains unsatisfactory and inconclusive, Leibniz turns to a related issue in the letter of January 25, 1705(?). Here he challenges De Volder’s assumption that a mathematically extended mass could ever be broken up into bodies by motion. Leibniz claims that those who adopt a view like De Volder’s “have a mind that is possessed by [a] confused image [ . . . ] no foundation would arise for a distinction in corporeal things [ . . . ] since it is always the case that equivalent things are substituted for one another when anyone imagines such a mass as being in motion” (GP II, 277). The more interesting issue concerns De Volder’s claim that something whose nature was mathematical extension could be divided into moving parts. If, as Leibniz claims, the continuity of extension implies indeterminacy, then De Volder’s assumption that God could produce determinate

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structure through the introduction of motion may be open to question. However, Leibniz does not pursue this line of objection here. And again, it seems to me that the case against De Volder’s position which Leibniz actually offers is unpersuasive. For his part, De Volder offered nothing in response to this issue. He did not reply until after Leibniz had written again. In this letter of January 5, 1706, which was his last, De Volder was reluctant to engage with Leibniz directly, lamenting that he had “nothing new to reply” and that he was “worried [he] might make [Leibniz] nauseous by repeating the same things” (GP II, 279).

4. cartesian dualism and leibniz’s account of body I have suggested that Leibniz was unable to provide De Volder with the kind of arguments which would undermine his residual commitment to a conception of the material world as a single extended substance. However, there was yet another serious obstacle to fruitful agreement. This stems from the way in which De Volder’s Cartesian assumptions clouded his perception of Leibniz’s positive account of the nature of body. We do not have the space here to explore the complex account which Leibniz develops. However, it is important to note that it involves a commitment to the view that the reality of the material world is, at least in part, phenomenal, or mind-dependent, and grounded in complex representational relations between the perceptual and volitional states of an infinite number of immaterial, and unextended, monads. De Volder’s attempt to grasp this view is woefully unsuccessful and appears to have been the proximate cause of his abandoning the correspondence in 1706. However, we should not assume that he was entirely responsible for this lack of understanding. And, in the space which remains, I give a brief account of some of the main difficulties which he encountered. Part of the problem here, I think, can be attributed to two important expectations which De Volder brought to the correspondence. As we have already seen, he hoped that Leibniz would account for material reality by augmenting the Cartesian conception of corporeal substance in such a way that the activity of bodies could be deduced from it. But he also seems to have assumed that this would involve appeal to Leibniz’s account of the “pre-established harmony” between mind and body.

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De Volder had grasped the basic idea of the pre-established harmony – the states of the mind and the body evolve autonomously, but in such a way that the states of the mind are always adequate representations of the states of the body (see GP II, 167). Furthermore, he was enthusiastic about the view. Despite his Cartesian sympathies, he could not see how Descartes could account for mind-body interaction.56 But, for all its appeal, the preestablished harmony of mind and body still appeared to leave open the nature of the active principle, or entelechy, in bodies which enabled them to change autonomously. In the letter of May 13, 1699, De Volder suggests three “possibilities,” from within his broadly Cartesian perspective: (1) extension itself; (2) some modification of extension; or (3) some further substance independent of extension (GP II, 180). But, none are really serious suggestions. After all, the first two invoke entities which are entirely passive, and the third resurrects the problem of intersubstantial interaction. Two letters later De Volder discovered that Leibniz regarded entelechies as things “which do not differ in kind from the soul” (GP II, 198). And, despite earlier insistence that these active principles are “prior to extension and constitutive of the substance itself which is in an extended thing” (GP II, 187), De Volder understood Leibniz’s view as a version of the third option – after all, Leibniz was prepared to postulate a “primary matter [ . . . ] whose nature consists in inertia and antitypy” (GP II, 199), and entelechy “certainly differs” from this. To De Volder, it seemed that Leibniz must be dealing with two distinct substances, and given this assimilation of Leibniz’s suggestion to the Cartesian view, he remained baffled as to how entelechies could effect any change in an extended thing (see GP II, 189). By the letter of July 25, 1702, De Volder appears to have realized that Leibniz was attempting to move away from Cartesian dualism. He attributes to Leibniz the view that “corporeal substance is composed from matter to which [ . . . ] [he] ascribe[s] impenetrability and inertia, and activity from a force or entelechy” (GP II, 241). However, on closer examination, this apparent departure from a Cartesian reading of Leibniz turns out to be nothing more than that. Since De Volder cannot conceive force without matter but can conceive matter without force, he insists that the relation between the two must be that of substance and mode (see GP II, 243).57 Entelechy, as De Volder understands it here, is simply a modification of extended substance. It was at this point that De Volder received a copy of Leibniz’s Reply to Bayle rather than a direct response to his worries. After reading

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this piece he had a better grasp on Leibniz’s view of bodily reality. More precisely, De Volder realized that it involves a commitment to many corporeal substances, each of which has a separate entelechy and infinitely divisible mass, which in turn consists of further corporeal substances (see GP II, 245). But there were still problems, since De Volder appears to have understood Leibniz as a having a kind of dualistic version of the view which Daniel Garber attributed to Leibniz in his “middle years” (see Garber 1985)58 – with corporeal substances analogous to Descartes’s human beings – and this did nothing to appease. Even leaving aside issues of the unity of these corporeal substances, De Volder could not see past the, now innumerable, instances of the problem of Cartesian interaction which this view seemed to bring (see GP II, 247). At this point, things begin to get even more complex. De Volder latches on to Leibniz’s use of the term primitive force to refer to entelechy. But this simply adds to his frustration. The only notion of force which De Volder understands distinctly is what Leibniz calls “derivative force,” the physical quantity which is measured in terms of size and the square of speed. To speak of entelechy as a primitive force “from which derivative forces flow” (GP II, 266) seems to be nothing more than a smoke screen. Indeed, in a letter to Bernoulli written at the same time, De Volder complains: “Instead of being given a proof that substance is essentially active, I am being asked to accept his terminology of entelechies, and primitive force containing all changes within itself. I can understand nothing of this” (GM III, 753). Bernoulli passed this on to Leibniz, and, perhaps as a conciliatory move, Leibniz presented his most explicit account yet of the entelechies – as aspects of immaterial substances with natures analogous to our own. However, at the same time, he included the following wellknown claim: Indeed, considering the matter carefully, it must be said that there is nothing in the world except simple substances and in them, perception and appetite. Matter and motion, however, are not really substances or things as they are the phenomena of perceivers, whose reality is located in the harmony of the perceiver with itself [ . . . ] and other perceivers. (GP II, 270/L 537)

This was the final straw. Despite Leibniz’s subsequent insistence that “the same view has already been suggested in previous letters” (GP II, 275/AG 181), De Volder’s letter of November 14, 1704, indicates that he was genuinely surprised by the appearance of the claims in this statement and utterly confused by it. Could Leibniz really have intended all along that corporeal reality be reduced to appearances of mental acts and

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“bodies got rid of altogether” (GP II, 272)? Furthermore, with the real world apparently reduced to immaterial substances, an additional problem loomed for De Volder. How could “extension arise from their repetition” (GP II, 273)? De Volder’s tone in this letter is one of understandable exasperation. With hindsight we can perhaps read these theses into the earlier correspondence, but for the unwary correspondent there are very few clues. Leibniz tried to smooth things over in his reply, but with his phenomenalism in full view, the correspondence was essentially at an end. De Volder sent one more very brief letter on January 5, 1706, in which he reiterated his basic complaint about failing to understand Leibniz’s active principle and the difficulties over how extension might arise from unextended things (GP II, 279–81). And, although Leibniz replied quickly, trying once more to explain these issues, De Volder never responded, and the correspondence came to an end.

5. conclusion The aim of the foregoing has been to highlight the way in which much of Leibniz’s correspondence with De Volder is guided by Cartesianism assumptions which De Volder tentatively sanctions. Leibniz regarded his views as a superior alternative to those of Descartes and his followers. However, his attempts to convince De Volder of this was ultimately unsuccessful. Although I have not been able to present the entirety of Leibniz’s case against De Volder here, I have suggested that his main criticisms are unconvincing and that his own position was advanced in a an insufficiently explicit manner to be convincing. This is not to say that De Volder’s position is ultimately defensible. However, in the face of an opponent who was willing to stick doggedly to a considered position Leibniz appears to have been unable, or at least unwilling, to make his case in a non-question-begging way. One of the reasons for Leibniz’s failure with particular arguments may have been the simple fact that he had so many irons in the fire at the same time. A closer examination of the whole correspondence would reveal more clearly the extent to which Leibniz happily invokes new arguments when it becomes clear that De Volder is unreceptive to a particular line of attack, without always developing the initial objection to the full. Moreover, it should be noted that much of Leibniz’s case against De Volder consists of arguments which had been developed over many years, arguments which were often aimed at a generic Cartesianism rather

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than at the actual position of a given philosopher. When, in De Volder, Leibniz encountered an opponent with a carefully wrought version of the Cartesian doctrine as his default position, his off-the-shelf critiques often proved less than successful. As I suggested earlier, one might feel somewhat disappointed with such a conclusion. It might appear that we have nothing very much to learn from Leibniz’s close encounter with Cartesianism. But the fact that we have not found Leibniz presenting compelling arguments is interesting in its own right. Although his failure sometimes appears to be due to lack of application, the discussion has also unearthed a number of presuppositions which divide Leibniz and his Cartesian opponent. These presuppositions are clearly of great importance for understanding the positive views which Leibniz articulates in the correspondence and elsewhere. But in addition, we have learned something of the fundamental components of a brand of Cartesianism which was advanced in the last decade of the seventeenth century. It is only recently that the diversity of the views which fell under this title after Descartes’s death have begun to be understood. There is much to learn about later Cartesians such as De Volder, which will be valuable in its own right. But a better understanding of such figures is essential for a properly contextualized understanding of the views of Leibniz and others. Notes 1. For examples of book-length studies which involve numerous references to the correspondence, see Russell, B. 1937; Broad 1975; Adams, R. M. 1994; and Rutherford 1995. 2. Again, there are many examples, including Garber 1985; Wilson 1989; Hartz 1992 and 1998; Adams, R. M. 1994; and Rutherford 1990; 1994; and 1995. 3. Until recently there was just a single article (Russell, L. J. 1927) which dealt exclusively with the correspondence. 4. This introduction was by letter only. The two men never met, despite nearly eight years of correspondence throughout which Bernoulli remained their intermediary. Bernoulli’s initial report is found in his letter of July 5, 1698 (GM III, 505–6). Further information about De Volder’s attitude toward Leibniz emerges in the series of letters which follow (see GM III, 517–18; GM III, 528–9; and GM III, 539–40). 5. The primary source of information about De Volder’s life and works is Jean Le Clerc’s Elog´e de feu Mr. De Volder Professeur en Philosophie et aux Mathematiques, dans l’Academie de Leide, written on the occasion of De Volder’s death in 1709 (Le Clerc 1709). The sketch of De Volder’s career which I present here relies on this work, along with more recent accounts by De Pater 1975: 314–21 and Ruestow 1973: 74–148.

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6. The full title of this unauthorized collection, published in 1695, by Van Ravenstein in Amsterdam was Exercitationes academicae quibus Renatii Cartesii philosophia defenditur adversus Petri Danielis Huetii censuram philosophiae Cartesianae. 7. I do not find evidence, as some have (see Klever 1988 and Israel 2001), that De Volder was a “crypto-Spinozist.” For further discussion of my rejection of this characterization, see Lodge (forthcoming). 8. Although it is unclear when De Volder started to drift away from Cartesianism, Le Clerc suggests that it was caused by his encounters with the works of Newton, primarily the Principia, which he studied thoroughly after its publication in 1687, and other British philosophers such as Boyle (1709: 379–83). 9. In 1686 Leibniz had published a famous refutation of the Cartesian position the Brief Demonstration (A VI iv, 2027–30/L 296–8), which had generated a number of responses defending the Cartesian position, including two public disputes with Denis Papin and the Abb´e de Catelan (see Iltis 1971). De Volder came to the correspondence on the side of Papin but eventually came round to Leibniz’s view that force should be measured by the product of the size and the square of speed. 10. As Gerhardt suggests (GP II, 151n), De Volder had almost certainly read the paper On the Correction of First Philosophy and the Concept of Substance, which appeared in the Acta eruditorum of March 1694 (GP IV, 468–70/L 432–4). However, it is possible that De Volder was also familiar with the first part of the Specimen of Dynamics (GM VI, 234–54/L 435–52), which appeared in the issue of April 1696, and On Nature Itself, which appeared in September 1698 (GP IV, 504–16/AG 155–67). 11. One of De Volder’s background assumptions is that material reality is substantial. Indeed, he favors, what he takes to be, the Cartesian view that the material world is a single corporeal substance, whose nature is constituted by extension alone, and that bodies are modes of this substance (see GP II, 255). It is interesting to note that Leibniz disputes this reading, suggesting that “Descartes and others” believe that bodies have the same nature but are distinct substances (see GP II, 271). 12. Thus, it is hard to agree with Robert Adams’s assessment of De Volder as “one inclined to occasionalism” (1994: 312). 13. It should be noted that De Volder’s reliance on the criterion has a close affinity to Spinoza’s, since he nowhere suggests that clear and distinct perceptions are underwritten by divine benevolence. For discussion of Spinoza’s view, see Della Rocca 1994. 14. Essentially the same account is found in the Exercitationes academicae (De Volder 1695: I, 106–7 and II, 39–41). 15. De Volder’s account also bears a closer resemblance to the definition of substance which is familiar from Definition 3 of Part 1 of Spinoza’s Ethics (Gb II, 45/CWS I, 408). However, De Volder’s understanding of this concept is quite different, since it leads him to adopt a dualistic ontology (see De Volder 1698, 1). 16. Also see GP II, 178; 215; and 222.

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17. The argument here is similar to the argument which Descartes presents in Principles II, §§4 and 11 (AT VIIIA 42 and 46/CSM I, 224 and 227). 18. It is interesting to note that De Volder ascribes this view to Descartes himself (see GP II, 266), and that Leibniz responds by insisting that Descartes was committed to the existence of many extended substances (see GP II, 271). 19. Also see GP II, 243 and 273. 20. See Lodge 1998a for further discussion of Leibniz’s response to the request. 21. See GP II, 215. 22. As a referee for this volume pointed out, one might wonder whether the CS account is a plausible reading of what De Volder says. However, it is clear from the draft of his June 23, 1699 letter that this is how Leibniz understands the first of the two senses (GP II, 183/L 518–19). 23. Leibniz also argues that the concept of substance is not simple, thus violating CS (see GP II, 183/L 519), and that the IC account of substance would allow modes which inhered in more than one substance (see GP II, 221). 24. Although De Volder never explicitly sanctions this implication from CS to a single attribute view of substance, there are places in which he says things which strongly suggest that this is the view he holds (see GP II, 216 and 223). 25. See GP II, 233 for Leibniz’s original claim. 26. See GP II, 224. 27. While De Volder does not support his response to Leibniz by appeal to the method of doubt, the Exercitationes do contain a systematic defense of the rejection of common beliefs prior to the discovery of true knowledge (see De Volder 1695: II, 1–33). 28. I discuss this issue further in an unpublished manuscript “Leibniz and the Geometrical Method.” 29. With his provision of Ex. Sub., De Volder has made it quite clear that he sanctions extended substance, in addition to the divine substance. There is no direct support for his commitment to thinking substance in the correspondence. However, the commitment to extended substance suffices to establish substance pluralism. 30. This distinction appears to have been passed over in the accounts of extension offered by many commentators, for example, Nason 1946: 473; Adams, R. M. 1994: 232–4; Rutherford 1995: 248; and Garber 1995: 285. On one occasion, Leibniz uses the term extension in a third sense, to refer to matter (see GP II, 195/L 523). However, this is merely an attempt to accommodate De Volder’s vocabulary and plays no role in Leibniz’s own view. 31. Leibniz also uses the term space in this way in the correspondence (see GP II, 249/L 529; GP II, 268–9/L 535–6; and GP II, 278–9 – translated at Russell, B. 1937: 245), however, his use of the term space is not consistent throughout his career (see Hartz and Cover 1988). 32. Also see GP VII, 561 and 564. 33. Denials of the existence of geometrical shapes in nature occur at least as far back as 1680s – see GP II, 119/LA 152 and C 522/L 270. 34. See GP II, 169; 183–4; 186; 205; and 241.

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35. See GP II, 193 – also see GP VII, 394/AG 251. 36. Something like this notion appears in Leibniz’s writings until the end of his life. See GP VI, 584/L 621–2; GP VII, 398/LC 37; GP VII, 399/LC 68–9; and GP VII, 401/LC 71. 37. See GP II,195 and 233 – also see NE 149 from 1704. 38. In fact, the discussion becomes even more complicated since Leibniz engages with Ex. Sub. construed as involving the CS account and as involving the IC account. 39. For some discussion of these issues see Lodge 2001b: 158–60. 40. Also see GP II, 276/AG 182 and GP II, 278–9 – translated at Russell, B. 1937: 245. Leibniz explicitly equates the notions of unity and indivisibility in the letter of January 21, 1704 (GP II, 261). 41. The square brackets indicate material which was never sent to De Volder. 42. Also see GP II, 304; GP VI, 516; and NE 146 and 211. 43. The convertibility claim can be traced directly to Aristotle’s Metaphysics IV, 1003b 23–30. 44. Leibniz uses a similar argument in the correspondence with Arnauld. However, unlike De Volder, Arnauld admits a plurality of extended substances in the actual world. For this reason, his response is somewhat different to De Volder’s. See Sleigh 1990: ch.6; Lodge 2002; and the chapter by Martha Bolton in this volume. 45. Also see GP II, 166; 178; and 265. 46. De Volder also claims that this is possible in the Exercitationes academicae (1695: II, 72). 47. This strategy is by no means new to the De Volder correspondence. See Garber 1995: 270–88, for a useful summary of Leibniz’s earlier anti-Cartesian arguments. 48. As far back as 1669, in a letter to Thomasius, Leibniz was prepared to assert that “bodies must not be assumed to possess any properties the cause of which cannot be derived from their essence” (A II i, 23/L 101–2). 49. Descartes provides some basis for thinking that one sympathetic to his views ought to subscribe to such a claim. In §51 of part I of the Principles of Philosophy, Descartes introduces a notion of substance which includes a principle attribute, to which all the remainder of its accidents or modes are referred in both the metaphysical and the epistemological sense (see AT VIIIA, 25ff./CSM I, 210ff.). However, other passages, such as Principles II, §36 (AT VIIIA 61/CSM I, 240), support interpretations which are more occasionalist in flavor. 50. De Volder does not mention resistance to being moved in his initial list of things which he cannot explain given Cartesian principles – see GP II, 151–2. However, subsequent discussion of inertia reveals that he subsumes this under the more general heading of bodily activity and is no more surprised by the claim that extension is unable to explain this phenomenon – see GP II, 179. 51. Despite according this principle the status of an axiom here, Leibniz appears to have been willing to argue for its truth in other places – see Cover and O’Leary Hawthorne 1999: ch.5 and Rodriguez-Pereyra 1999).

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52. The argument could also have been presented as a reductio of De Volder’s position on the grounds that he wishes to admit the possibility of distinct bodies within his conceptual scheme. However, since neither man doubts the existence of individual bodies, the actual dispute turns on a posteriori concerns. 53. Another aspect of De Volder’s view is implicit in this account, namely a commitment to the causal closure of the material world – see GP II, 167 and 198. 54. For further discussion, see Garber 1992: 135–6. 55. In fact, the argument that Leibniz has in mind is mentioned in the previous letter (GP II, 250/L 529), and the one before that (GP II, 226–7/L 525). I discuss this argument at length in Lodge 1998b. 56. In his letter of November 12, 1699, De Volder responds to Leibniz’s veiled suggestion that he is a slavish follower of Descartes (GP II, 194/L 522) by citing his dissatisfaction with Cartesian accounts of mind-body interaction (GP II, 198). 57. As we saw in section 2 of this chapter, for De Volder, modes are the things which are not conceivable per se – see GP II, 215. 58. Also see Broad 1975: 67–86.

9 “All the time and everywhere everything’s the same as here” The Principle of Uniformity in the Correspondence Between Leibniz and Lady Masham Pauline Phemister

The privacy, real or illusory, afforded by the personal letter allows each participant the philosophical freedom to explore a range of possible opinions, to experiment with different ideas, to hesitate, and to change his or her mind in ways that published articles and books discourage. The private letter also allows the use of language and style of writing to be altered to suit the particular recipient. This is especially evident in Leibniz’s correspondence with Des Bosses. Sometimes, however, the intended recipient is not the addressee, as when Leibniz engaged with Locke through Thomas Burnett of Kemney. This situation was not an isolated occurrence in Leibniz’s dealings with Locke. In this chapter, we shall see how Leibniz attempted to engage with Locke through a second correspondence and how he adapted the style and presentation of his views, not for the main correspondent, Lady Masham, but for the other intended recipient. We shall also see that the views Leibniz presents confirm his loyalty during this period to an ontology of embodied, perceiving substances. The correspondence with Damaris Masham began shortly after Lady Masham sent Leibniz a copy of her father’s The True Intellectual System of the Universe (TIS) at the end of 1703. Learning that the book was on its way, Leibniz’s first letter was intended to thank her in advance. Leibniz’s interests set the agenda throughout the correspondence, despite the fact that Lady Masham would have been working on her second My thanks especially to Paul Lodge for questions that helped me clarify my thoughts and to Marc Bobro who gave careful commentary during the presentation of the material in this chapter at the Leibniz and His Correspondents conference.

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book, Occasional Thoughts in Reference to a Vertuous or Christian Life, published in 1705, which defends the education of women.1 But this work plays no part in her discussion with Leibniz.2 His attention at the time was focused on Cudworth’s doctrine of plastic natures and on Locke’s An Essay Concerning Human Understanding. Lady Masham was well placed in relation to both philosophers, being the daughter of the one and a close friend of the other. Here, we shall observe the parts these relationships play in relation to our interpretation of Leibniz’s views and their presentation in the correspondence. We shall begin by looking at Leibniz’s interests in Cudworth and Locke between 1703 and 1705 (sections 1 and 2). We shall then turn our attention to the Principle of Uniformity, a principle that Leibniz introduces early in the correspondence as a tool for making his opinions intelligible. Versions of this principle are found in Cudworth and Locke as well, and in section 3 we shall see that Leibniz’s use of the Principle appears not unlike Locke’s. However, in section 4, we notice that the Principle is granted wider scope by Leibniz than by Locke. This creates difficulties for a consistent deduction of Leibniz’s views from the Principle, unless, that is, Leibniz invokes the Principle on the basis of a different understanding of “experience,” one that underpins an ontology that is closer to Cudworth’s than to Locke’s (section 5). In section 6, I raise a problem arising from Leibniz’s use of the Principle of Uniformity. Throughout, it will become apparent that Leibniz was deliberately employing these tactics as part of a strategy to draw Locke into open debate.

1. leibniz and cudworth In the early years of the new millennium, Jean le Clerc, editor of the journal, Biblioth`eque choisie, having read of Leibniz’s doctrine of preestablished harmony in the entry Rorarius in Pierre Bayle’s Dictionnaire historique et critique, asked Leibniz to contrast his doctrine with Cudworth’s doctrine of plastic natures (see GP VI, 546–7). Leibniz’s paper, Considerations on Vital Principles and Plastic Natures (GP VI, 539–46/L 586–91), appeared in May 1705 as a letter to the editor of the Histoire des ouvrages des savants, Basnage de Beauval. We may safely assume that Leibniz was working on the paper in the early stages of his correspondence with Lady Masham. We might even expect that the correspondence would have been a good opportunity to raise issues about the best understanding of Cudworth’s thought. It is surprising, therefore, that only Leibniz’s first letter (late 1703 or early 1704) and the letters after October 1704 bear

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any direct reference to the debate over plastic natures and pre-established harmony. In his first letter, Leibniz describes how his system of pre-established harmony builds upon and improves her father’s metaphysics. He even directs Lady Masham to the Rorarius entry in Bayle’s Dictionnaire, albeit without actually mentioning the debate between Bayle and Le Clerc or his intention to make public his view of the relation of pre-established harmony to plastic natures (GP III, 336). In her reply, Lady Masham informs Leibniz that Locke is a long-term guest in the Masham household (GP III, 338). It is at this point that Leibniz’s presentation of his views changes. Leibniz only reopens explicit discussion about Cudworth in the letters that post-date Locke’s death on October 28, 1704. In the interim, he makes no direct references to Cudworth. We may suppose that Leibniz’s focus in the intervening years is Locke, not Cudworth. Once there is no longer any possibility of engaging in debate with Locke, Leibniz returns to his original discussion in his letter of July 10, 1705, which contains a summary of the main points from his Vital Principles paper that had been published the previous May and which now invites open discussion of Cudworth’s views (GP III, 368). Cudworth believed that “there is a Mixture of Life or Plastick Nature together with Mechanism, which runs through the whole Corporeal Universe” (TIS 1.3.37, art.3). The individual living being has two aspects: the immaterial active force and the matter or body upon which this active force “acts” and with which it forms a living being. Each plastic nature is an inner force that moves its own particular body. Leibniz recognised the intrinsically Aristotelian nature of this position insofar as there is in each thing an innate energy by which it thinks, perceives, and moves (Vital Principles: GP VI, 540/L 586–7). The position is also remarkably close to Leibniz’s own Aristotelian understanding of corporeal substance as a combination of soul or substantial form and organic body. Accordingly, Leibniz discerns much that is of value in Cudworth’s philosophy, and he suggests amendments and additions to what, for the most part, he thinks well supports his own views. In particular, he agrees with Cudworth that purely mechanistic explanations are insufficient to account for all phenomena, particularly their inability to explain the motion of bodies through extension alone. To correct the Cartesian model, Cudworth introduces plastic natures that, acting as God’s instruments, unconsciously bring about changes in extended matter, just as minds or souls do consciously (TIS 1.3.37, art.15). The unconscious powers within

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each individual living thing mean that each moves in accordance with God’s Will without being moved directly by God.3 All the same, Leibniz thinks that Cudworth’s doctrine fails to overcome the deficiencies of Cartesian mechanism. No intelligible explanation is offered as to how plastic natures change matter. Cudworth has not avoided the problems faced by Descartes over the interaction of the unextended soul and the extended body. He has only transferred the still unexplained interaction to a different level. We no more understand how an incorporeal plastic nature can act on the physical body than we can understand how an incorporeal soul can cause changes in its body. The mechanisms by which immaterial plastic natures act and that by which the Cartesian souls act remain equally unexplained. Nonetheless, Leibniz agrees that something akin to plastic natures has to be posited. In place of them, he advocates immortal souls and substantial forms, which, with the theory of pre-established harmony, obviate the need to account for the formation of living animals by regarding them as pre-formed as the universe was created (Vital Principles: GP VI, 544/ L 589). The result is a doctrine of organisms within organisms: I strengthen this opinion of Cudworth’s with the consideration that if matter is arranged by divine wisdom, it must be essentially organised throughout and that there must thus be machines in the parts of the natural machine to infinity, so many enveloping structures and so many organic bodies, enveloped, one within the other, that one can never produce any organic body entirely anew and without any preformation. (Vital Principles: GP VI, 544/L 589)4

In Leibniz’s opinion, pre-established harmony, pre-formation, and the embedding of organisms within organisms enhance Cudworth’s justified rejection of the bare extended matter of the Cartesians.

2. leibniz and locke Locke’s Essay Concerning Human Understanding had appeared in December 1689, with new editions appearing in 1694, 1695, and 1700. Pierre Coste translated it into French, and this edition appeared on the Continent in 1700. Ezekiel Burridge prepared a Latin translation, which was published in 1701.5 Leibniz had read parts, perhaps even all, of the Essay in its English edition, but Coste’s translation brought it back to his attention. In a letter of December 3, 1703, he remarked to Burnett that, “Locke’s book has been translated into French. That caused me to reread it, especially since I only had the English in the old edition; and

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to tell the truth, I see many things in it with which I do not agree” (GP III, 291/AG 284). Leibniz’s rereading of Locke obviously rekindled his initial interest, and he began work on his major response, the New Essays on Human Understanding (NE), in 1703. He was working on it while in correspondence with Lady Masham. Locke’s Essay is primarily a work of empiricist epistemology. Locke’s claim is that all our ideas come from “experience,” of which he finds two kinds, sensation and reflection: Let us then suppose the Mind to be, as we say, white Paper, void of all Characters, without any Ideas; How comes it to be furnished? Whence comes it by that vast store, which the busy and boundless Fancy of Man has painted on it, with an almost endless variety? Whence has it all the materials of Reason and Knowledge? To this I answer, in one word, From Experience: In that, all our Knowledge is founded; and from that it ultimately derives it self. Our Observation employ’d either about external, sensible Objects; or about the internal Operations of our Minds, perceived and reflected on by our selves, is that, which supplies our Understandings with all the materials of thinking. These two are the Fountains of Knowledge, from whence all the Ideas we have, or can naturally have, do spring. (Essay 2.1.2)

In sensation, it is supposed that external objects act on our senses to produce perceptions in the mind. Our sense organs convey to us ideas of the primary qualities of extension, shape, size, texture, number, motion, and rest as well as of the secondary qualities of colour, sound, odour, taste, and tactile qualities. Armed with at least some ideas of sensation, the mind is then able to adopt various mental attitudes in relation to them, such as perceiving, thinking, doubting, believing, and such like. Observing these in turn, the mind obtains the ideas of reflection, namely ideas of “Perception, Thinking, Doubting, Believing,” and so forth (Essay 2.1.4). Ideas of sensation are required prior to the ideas had from reflection. The mind needs some ideas of sensation as the material upon which it can perform various mental operations. Reflection is “the perception of the operations of our own mind within us, as it is employed about the ideas it has got” (ibid.), namely, the ideas of sensation. Among sensory ideas, those of primary qualities are regarded as more accurate representations of bodies’ qualities. These resemble the qualities as they exist in the objects themselves. Body, conceived as myriad particles each possessing primary qualities, is capable of existing independently of the mind and is capable of being perceived. Bodies’ secondary qualities are powers to produce certain sensations in us (Essay 2.8.15) and, as such, they depend on the possibility of being perceived. Their power is exercised

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through the primary qualities of the insensible particles in the object’s inner constitution, even though we are unable to conceive how: we can never be able to establish certain and undoubted Rules, of the Consequence or Co-existence of any secondary Qualities, though we could discover the size, figure, or motion of those invisible Parts, which immediately produce them. We are so far from knowing what figure, size, or motion of parts produce a yellow Colour, a sweet Taste, or a sharp Sound, that we can by no means conceive how any size, figure, or motion of any Particles, can possibly produce in us the Idea of any Colour, Taste, or Sound whatsoever; there is no conceivable connexion betwixt the one and the other. (Essay 4.3.13)

Locke thus postulates mind-independent external objects as aggregates of particles that possess primary qualities, which in turn produce ideas of primary and secondary qualities in us. These are the ideas of sensation whose presence in the mind creates the conditions for the acquisition of ideas of reflection. Locke’s aim in the Essay was to determine the “Original, Certainty, and Extent of humane Knowledge; together with the Grounds and Degrees of Belief, Opinion, and Assent” (Essay 1.1.2). This includes not only our knowledge of God, freedom, and morality but also our knowledge of the physical world. Locke’s conception of this world is essentially a modified Cartesian one. Although he stops short of denying active power in the material world (Essay 2.21.4), there is no suggestion that material particles possess the Leibnizian mental properties of perception and appetite or partake of Cudworth’s unconscious plastic natures. Locke admits that bodies cannot consist only in extension, adding solidity or impenetrability to the Cartesian account, but he does not add anything equivalent to active centres of force (Essay 2.4.1). Locke refines the Cartesian conception of matter; Cudworth and Leibniz contest it. In 1696, Leibniz had written a condensed set of reflections on Locke’s Essay,6 which, in an attempt to elicit a response, he passed to Locke via Burnett. The paper stayed in Burnett’s possession for a year, but even when Locke did receive it, he did not reply, although unbeknownst to Leibniz, he sent a transcript to Molyneux, together with a letter disparaging Leibniz’s intellectual abilities (To Molyneux, April 10, 1697: JLW 9, 407). Leibniz, awaiting a response, reworded his objections in a second paper.7 Still Locke did not reply in person, but an indirect correspondence followed in which Locke requested further elucidation from Leibniz through Burnett (see Jolley 1984: 38–9). The open philosophical discussion with Locke that Leibniz so much desired was never destined to be. Leibniz was finding that he was able

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to communicate with Locke only through third parties. Conscious of Locke’s presence in the Masham household, he seems to have written at least as much, if not more so, for Locke’s benefit as for Lady Masham’s, hoping that the latter would discuss his views with her houseguest and elicit his response. I consider my correspondence with My Lady Masham, almost as if it had been with Mr. Locke himself, because, as he was with her at Oates at the time this lady was writing to me and replying about my philosophical hypothesis and even noting that Mr. Locke saw our letters, it appears that he had some part in it, probably at least in the judgement that he made, and which he apparently did not conceal from this lady. (To Thomas Burnett, August 2, 1704: GP III, 297–8)

In fact, however, by this time, Locke’s health had deteriorated so much that it is unlikely he was taking much interest in the correspondence. In her letter of June 3, 1704, Lady Masham had explained that Locke’s ill health was preventing him from philosophising (GP III, 351–2). Nevertheless, in his reply on June 30, 1704, Leibniz made a number of direct references to Locke’s work, first to the exchange with Stillingfleet on the possibility of thinking matter, evidently trying to engage Locke with the contentious and provocative objection that thinking matter would involve God in continual miracles since there is nothing in the nature of matter per se, in its extension and impenetrability, that will produce it (GP III, 355/WF 213).8 Later, he makes a point of referring to Locke in connection with ideas of reflection (GP III, 356/WF 215). Replying on August 8, 1704, Lady Masham reiterates that Locke’s health is deteriorating (GP III, 361), and although she addresses the topic of thinking matter, she pointedly refers to her remarks as “these Thoughts of mine” (GP III, 360). Seemingly unwilling to admit the full seriousness of Locke’s illness, in his subsequent letter, Leibniz resorts to instructing Lady Masham to discuss matters with Locke, in particular, asking her to get Locke to explain the notion of an non-extended substance (To Masham, September 16, 1704: GP III, 362/WF 219). Towards the end of the same letter, he makes suitably flattering remarks about Locke’s chapter on freedom (GP III, 363/WF 219). Lady Masham did not receive this letter until October 31, the day of Locke’s funeral (see Masham to Leibniz, November 24, 1704: GP III, 365). Leibniz had written again on October 7, 1704, eager to discuss Locke’s remarks on the production of matter at Essay 4.10 (GP III, 364). This letter arrived on November 22. On November 24, Lady Masham informed Leibniz of Locke’s death. Leibniz had been interrupted by

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death on his side also, with the demise of the Queen of Prussia, Sophie Charlotte. When he did eventually reply on July 10, 1705, he directed the discussion back to the work of Cudworth. It is clear that, in his contact with Lady Masham, Leibniz had recognised a golden opportunity to try once again to explain his views to Locke. Having concentrated on Cudworth in his first letter, on learning of Locke’s presence in the Mashams’ home, he abandons explicit references to her father, instead raising questions he knows interest Locke and even openly inviting Locke’s contribution. Direct references to Cudworth only reappear after Locke’s death. Leibniz adopts other measures as well. He tailors the very presentation of his views in a way intended to make them more accessible to the English empiricist. His strategy is to appear as if he agrees with Locke’s empiricism, but to derive from it his own distinctive metaphysics. For this, he introduces a methodological principle that was accepted by both Cudworth and Locke, and which, superficially, Leibniz employs in a Lockean manner but which, in fact, is employed from a stance closer to Cudworth’s. It is possible that he calculated that Lady Masham would understand his argument given her familiarity with her father’s philosophy and hoped that she would facilitate its reception by Locke.

3. the principle of uniformity Leibniz introduces the “Principle of Uniformity” (hereafter PU) in his second letter to Lady Masham, written early May 1704. He describes it as the principle that “everywhere and all the time, everything’s the same as here,” a phrase he adapts from Fatouville’s Arlequin, empereur dans la lune (To Sophie Charlotte, May 8, 1704: GP III, 343/WF 220–1).9 The relatively few times that Leibniz uses PU in the form found in the Masham correspondence are almost invariably in relation to English philosophers.10 Leibniz ends his Vital Principles paper with the phrase in practically the same form as in the earlier letter to Cudworth’s daughter (GP VI, 546/ L 590). Other references to Arlequin occur in relation to Locke in the New Essays (NE 329; 472; and 490), and there is one reference in Leibniz’s last letter to Samuel Clarke (Leibniz’s fifth letter, §24: GP VII 394/ LC 62). Leibniz could reasonably assume that Lady Masham would accept the general reliability of PU, for it is implicit in her father’s work. The Principle underpins Cudworth’s assumption that the microscopic is not substantially different in kind from the macroscopic, as seen in his belief that powers similar to our own souls’ powers to move our bodies are

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probably in lower creatures as well. Cudworth attributes individual plastic natures to all living beings, and the higher self-conscious and rational minds are mirrored lower down the chain by the unconscious plastic natures in matter itself. Individual plastic natures in each and every living animal are like little worlds, microcosms harmonised through the general plastic nature: “Besides this Plastick Nature, which is in Animals, forming their several Bodies Artificially, as so many Microcosms or Little Worlds, there must be also a general Plastick Nature in the Macrocosm the whole Corporeal Universe, that which makes all things thus to conspire everywhere, and agree together into one Harmony” (TIS 1.3.37, art.23). Leibniz draws a number of conclusions using PU that concur with Cudworth’s views, principal among them being the claim that there are active beings throughout nature and an emphasis on beings as organic wholes. Despite this, however, the actual style of Leibniz’s application of PU bears greater outward resemblance to Locke’s empiricism. Locke assumes that our sensory experience provides the standard upon which our understanding of the invisible microscopic and the macroscopic aspects of the universe should be modelled. When he describes primary qualities as those that remain even when the body is not visible to us, he invites us to imagine a grain of wheat being repeatedly divided until its parts become too minute for us to discern. Still, he insists, each part possesses the primary qualities of solidity, extension, figure, and mobility (Essay 2.8.9). Much later, he takes pains to point out how little is our comprehension of the “whole nature of the Universe, and all the things contained in it,” but he also advises that “we can go no farther than particular Experience informs us of matter of fact, and by Analogy to guess what Effects the like Bodies are, upon other tryals, like to produce” (Essay 4.3.29). In other words, we can rely only upon our own experience, using PU to infer what is happening in the rest of the universe. With PU, Locke presumes that bodies too small or too large to be sensible to us are nonetheless similar to those we do sense. However, he is highly selective about which features of our experienced world he assigns to the insensible parts. He is comfortable applying PU in the case of the primary qualities. These are supposed to remain in objects whether we perceive them or not and our ideas of them are supposed to resemble the actual qualities themselves. We may safely presume that other creatures’ perceptions of primary qualities in bodies are equally veridical. Locke assumes that primary qualities are common to objects at all levels of being, from the macroscopic to the microscopic, uniformly present in

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the smallest physical object through to the largest. Thus, the mechanical operation of one body upon another by means of their extension, size, figure, and motion is, for him, as it was also for Cudworth and Leibniz, a constant feature throughout both the sensible and (to us) insensible regions of the universe. However, objects’ secondary qualities are assumed to differ depending upon the particular internal constitutions of creatures perceiving them. They are qualities arising out of the relations between the object’s real constitution, that is, the arrangement of its insensible particles, and the real constitutions of the perceivers.11 Our ideas of secondary qualities, therefore, cannot be assumed to resemble the secondary qualities in the bodies themselves, for these exist only as powers to affect creatures in diverse ways. Hence, other creatures presumably perceive different secondary qualities in bodies from the ones that we, as humans, do.12 These considerations prevent the application of PU in respect of the secondary qualities. Nor does Locke apply PU to all levels of being with respect to our ideas of reflection or to ourselves as conscious and self-conscious creatures. Although he is willing to postulate the existence of other rational minds, there is no evidence that he extended this to other creatures, nor any hint that, for instance, there may be microscopic creatures capable of having perceptions and appetites embedded throughout all matter. As already noted, while Leibniz and Cudworth argue for immaterial perceiving powers in even the smallest parts of matter, Locke is content to attribute only primary qualities to the particles of matter without requiring any immaterial powers in addition to these. At first, Leibniz’s description of PU suggests that his use of the Principle will adhere closely to Locke’s. He writes: “my whole theory comes down to recognizing in substances beyond our sight and observation something parallel to what we see [se remarque] in those which are within our range” (To Masham, early May 1704, GP III 339/WF 204). The emphasis, right from the beginning, is placed on sense experience, especially on the organs of sight. Leibniz highlights generalising from “sight and observation” those things that are “within our range.” We find similar appeals to the visual in other passages from the same letter as follows: “nature, as is her custom, gives us several visible examples to help us to work out what she keeps hidden” (GP III, 340/WF 205) and “one might say that the device used by the Epicureans against the argument based on the beauty of visible things” (GP III, 341/WF 207). We are invited, it seems, in typically Lockean style, not only to prioritise

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sensation but also to consider that what we sense around us is repeated in smaller versions in the microscopic, and that, similarly, the same patterns are repeated on far grander scales than we are capable of seeing. Frequent references to “experience” serve further to strengthen the appearance of an empiricist methodology, as for instance: “This same maxim of not unnecessarily supposing in created things anything not corresponding to our experience” (GP III, 340/WF 206). At other times, the experience is linked specifically to bodies and especially to bodies acting mechanistically: “But to extend the analogy with what we feel [experimentons] at present in our own bodies to the future and past, as well as to other bodies” (GP III, 340/WF 205) and “For we have experience of bodies acting on one another according to mechanical laws” (GP III, 340/WF 206). Applying PU to those bodies he encounters through sense experience, Leibniz infers that all bodies act on one another mechanically. We see that bodies’ actions are determined by strict mechanical laws, and we generalise these laws to govern the actions of all physical bodies (GP III, 340–1/WF 206). This affirmation of universal mechanism suggests that Leibniz applied PU as Locke did to our experience of objects’ primary qualities, and, like Locke, without also extending this either to our ideas of their secondary qualities or to the secondary qualities themselves, for it is by means of their primary qualities, particularly those of extension and motion, that purely mechanical operations take place. All the same, in the continuation of this second passage, Leibniz adds that we also have experience of “souls producing within themselves various internal actions” (GP III, 340/WF 206). This is most plausibly read as a reference to the soul’s operations, which for Locke served as the basis for our ideas of reflection. And even though Locke did not use PU in respect of mental states such as perceptions and desires, Leibniz’s introduction of reflection in a subsidiary position does enable him to underscore the similarities with Locke’s empiricism. Both Leibniz’s choice of language and the presentation of his argument are designed to appeal to those who endorse, or who are in general agreement with, a fundamentally empiricist approach. It is unlikely that these empiricist overtones were inserted for the benefit of Lady Masham, as they are absent in his first letter to her. It is more likely that having learned that Locke was the Mashams’ guest, he wrote in the hope that Locke might become a third participant. In framing the discussion in the way that he did, Leibniz was trying once again to engage philosophically with Locke, this time on as near to his own terms as he could manage.

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All the same, as we shall see in the next section, he does not apply PU in exactly the same way as Locke. This, as we shall observe, makes his argument appear weak and inconsistent until we revise our understanding of his starting point.

4. sensation or reflection Any meaningful discussion of the differences between Locke’s position and Leibniz’s requires that Locke first understands Leibniz’s view. To this end, Leibniz dons a makeshift empiricist cloak. Inevitably, it barely covers the differences between the two philosophical extremes. What similarities Leibniz does highlight mask deeper and more serious differences. Admittedly, he applies the same kind of reasoning as does Locke, but he bases it upon a fundamentally opposed understanding of “experience” that demands far wider application. He uses PU to draw conclusions not only about the nature of bodies’ primary qualities but also about souls’ perceptions and volitions. So he claims, In this I am doing no more than attributing to souls and bodies always and everywhere what we experience in them whenever the experience is distinct, that is to say, mechanical laws to bodies, and internal actions to souls. Everything therefore comes down to a present state combined with a tendency towards changes, changes which are brought about in the body by moving forces, and in the soul by perceptions of good and evil. (To Masham, early May 1704: GP III, 341/ WF 206)

Leibniz attends, as Locke did not, to the perceptive and appetitive states of the soul. He applies PU both on the basis of the soul’s experience of an external world, as well as its reflection on its inner experiences. He takes it as agreed on all sides that “there is in us a simple being endowed with action and perception” (GP III, 339/WF 204). The actions (appetitions) and perceptions of this being are known to him by reflection, although at this point in the letter, eager to emphasise the importance of “sight and observation,” he does not make much of this fact. He does use this knowledge based on inner experience, however, to conclude that “there are such active beings everywhere in matter, and that they differ only in the manner of their perception” (GP III, 339/WF 204). Leibniz goes on to argue that there are no separate souls, no (created) intelligences detached from matter. Since our souls are endowed with organic bodies, and we have no disembodied experiences, we infer that all the other perceiving beings also have organic bodies,13 and even,

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extending our present experience back into the past and onto the future, that they always have had and always will have organic bodies “appropriate to their perceptions” (GP III, 340/WF 205).14 All the same, Leibniz’s conclusions do not sit comfortably with the sensory evidence, which tends to belie the claim that there is life everywhere. There is much in the world that appears to be inanimate. We encounter objects that seem to be either at rest or moved only by others, that is to say, moved, not by themselves, but by us. While it is reasonable to infer, extrapolating from our own experience, that those bodies that move spontaneously are animated by perceiving souls, the sensory evidence, taken on its own, suggests that the majority of bodies do not move spontaneously and are presumably, therefore, bereft of inner perceiving souls or forms. On the basis of sense experience alone, PU does not justify the claim that there is life everywhere. PU states that “things are everywhere and always just as they are in us now” (To Masham, early May 1704: GP III, 340/WF 205). Having argued that there is life everywhere, Leibniz now wants to claim that this has been and always will be so. He says he is extending “the analogy with what we feel at present in our own bodies to the future and past” (GP III, 340/WF 205). What he feels in his own body is known by sensation, although the fact that he knows it is in his own body requires reflection. For further confirmation that all souls and entelechies will always have organic bodies and that no animal ever dies, and that instead, “generation and death can only be developments and envelopments,” he appeals to the “several visible examples” that nature provides so as “to help us to work out what she keeps hidden” (ibid.).15 A favourite example, absent from the Masham letters, is the transformation of the caterpillar into the butterfly (see NE 58). Again, however, the facts as they appear in everyday experience through sensation suggest that these transformations are unusual, and their extension to all creatures, past or future, near or distant, small or large, is fantastical. Experience suggests that the majority of creatures simply die, their bodies being broken up and reintegrated into the general mass of matter. Most creatures do not appear to be transformed anew. In this argument and in the previous, PU applied in the case of the evidence from inner experience (that we are embodied and living) is in conflict with what would be the case if PU were applied only in respect of outer experience (that there are inanimate objects). The reflective evidence suggests that there is life everywhere in space and through time, while the sensory evidence suggests otherwise.

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5. sensation and reflection We have seen that there is sometimes conflict between reflective and sensory data and that applying PU to the one instead of the other yields opposing results. Locke did not encounter any conflict because, even though he locates the empirical basis of knowledge in either sensation or reflection, he applies PU only in the case of the former. Leibniz, however, seems to allow the application of PU in respect of both sensation and reflection, and yet he offers no criteria for deciding, in cases of conflicting evidence, whether to prioritise sensation over reflection or vice versa. I propose that the reason why he does not offer such criteria is because none is required. Potential conflict arises only if PU is allowed to apply either to sensation or reflection. Although Leibniz generalises on the basis of reflective evidence and on the basis of sensory evidence, he does not generalise over them independently of each other. In sharp contrast to Locke, he locates the epistemological base in the combination of sensation and reflection and applies PU accordingly. For him, sensation and reflection are interdependent and are combined in one unified experience. He contends that even our most abstract thoughts “are in need of some sense perception” (Reply to the Thoughts Contained in the 2nd edition of the Critical Dictionary of M. Bayle: GP IV, 563/L 580). And because our conscious experience combines sensation and reflection, we are able to be conscious of ourselves as perceiving beings at the same time as we are aware of ourselves as embodied. Using sensation and reflection in conjunction, we experience ourselves as true unities (To Arnauld, 30 April 1687: GP II, 97/LA 122). We come to know ourselves as living, indivisible, corporeal substances, not as mere phenomenal aggregates. Of course, we and other corporeal substances are true unities whether we reflect upon the fact or not. What reflection adds to sense experience is the awareness of ourselves as living, indivisible, perceiving creatures. I confusedly sense-perceive my aggregate, organic body. Reflection is needed if I am to understand this organic body as mine and to understand that, together with it, I comprise a substantial unity. Reflection, he explains in the Preface to the New Essays, is nothing but attention to what is within us, and the senses do not give us what we carry with us already. In view of this, can it be denied that there is a great deal that is innate in our minds, since we are innate to ourselves, so to speak, and since we include Being, Unity, Substance, Duration, Change, Action, Perception, Pleasure, and hosts of other objects of our intellectual ideas? (NE 51)

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Reflection provides us with the understanding of “unity,” “substance,” “duration,” and “being” that we relate to the sense-perceptions we have of our organic bodies, and we come to recognise that these bodies are integral aspects of our being from which we are never separated, not even at death (e.g., see NE 58). Sensation and reflection are not naturally separable. Through this combined sensory-reflective experience, we know ourselves as thinking, corporeal substances.16 For Locke, too, reflection provides knowledge of the existence of the self (Essay 4.9.3), but Locke does not adopt the unified view found in Leibniz. Instead, Locke accepts a basically Cartesian-style dualism of mind and body according to which each can exist independently of the other. The differences between Leibniz and Locke on these points can be seen in their respective senses of the term experience. Locke had understood experience as a source of the materials for knowledge. We get our ideas from experience. When we check Locke’s use of the term experience in the Essay, we find that he generally, if not invariably, uses it as a noun. Experience is regarded simply as the thing that produces ideas in us. Once we have experienced something (and note the implicit assumption that experience is always an experience of something), we can almost, as it were, discard the experience and concentrate solely on the ideas it has provided. This approach is consistent with his overall strategy because he is concerned more with what is experienced than with the act of experiencing itself. Experience is what has provided him with ideas, and once he has these, he directs his attention to what the ideas are ideas of. Thus, as we saw earlier, Locke’s use of PU is directed towards the referents of his ideas. PU is applied in respect of the world to which ideas, provided by experience, refer. And since he regards this world as consisting entirely of mind-independent bodies with extension and motion and other primary qualities, Locke is content to generalise sensory evidence in isolation from ideas provided by reflection. In contrast, while not denying the informative nature of experience, Leibniz is primarily interested in experience as an activity. Accordingly, the letters to Masham employ the term usually as a verb in the active voice. Leibniz’s focus is not so much on the object towards which the experience is directed, as on the nature of the experience itself. And this experiential state is one in which sensation and reflection are combined so that, through self-awareness, he can understand himself as a thinking and perceiving being who is embodied and has sense-experiences of a world outside. This “insider’s” view of the relation of the mental and the physical in one unit is the basis from which Leibniz applies PU in

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the letters to Masham. The universe is presumed to be composed of living creatures whose souls experience the world17 from an embodied standpoint. Without the separation of sensation and reflection as isolated or isolatable features within experience, the problems that arose from treating them as separate are no longer troublesome. In cases such as those encountered at the end of the previous section, in which the sensory evidence taken in isolation conflicts with evidence based on both reflection and sensation, the latter carries the day. The conclusions – that there is life and perception throughout matter and that death is never anything other than a transformation of the animal or corporeal substance – are founded not on mere sense perception alone (which as we saw does not, for the most part, support them) but rather on the singular or individual experience that Leibniz has of himself as a unitary being that is both mental and physical. Reasoning from his own lived experience as an embodied being, Leibniz concludes that there is life and perception throughout matter, that all substances perceive, and that their perceptions, like ours, differ according to their degrees of confusion or distinctness. On the basis of PU, he is able to assert that all substances possess organic bodies and that souls are never separated from these. There are no separate souls, no (created) intelligences detached from matter.18 He is also able to maintain, contra the evidence that sensation alone may provide, that there is no matter that is not endowed with some animate principle, such as a mind, soul, or form.19 His knowledge of himself as alive, grounded in his reflective knowledge of his own mind or soul as the animating principle of his own physical body, is simply generalised to all other organic bodies everywhere. The position, as we noted at the beginning, is closer to that advanced by Cudworth than it is to Locke. As we saw at the end of section 4, Leibniz generalises over time as well as space. He writes to Sophie Charlotte that, “[p]erception, like matter, being universal with regard to place, is also universal in time; that is to say, each substance not only has perception and organs, but also it will have them always” (To Sophie Charlotte, May 8, 1704: GP III, 344/WF 221). Since there is presently life and perception everywhere in matter, PU suggests this has been and will always be the case. Hence, it is the very “essence of matter to be organic” (GP III, 345/WF 222), even in its smallest and most inaccessible parts and across time: “naturally, and speaking in metaphysical strictness, there is neither generation nor death, but only development and envelopment of the same animal. [ . . . ] Experience confirms these transformations in several animals, where nature

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herself gives us a small example of what is kept hidden elsewhere” (GP III, 345/WF 222). Substances, he concludes, are never naturally generated or destroyed.20 All have always had and will always have an organic body. What appears to sensation alone as completely new generation, on the evidence of the senses and reflection together, appears now as no more than a transformation – a transformation of a substance that has always existed and which has always had an organic body.21 Now we can understand the significance of the examples of animal transformations, as when the caterpillar becomes a butterfly. Transformations, however few, provide sensory evidence of what Leibniz already knows has to be the case because he has extended his own experience of himself as an embodied, living creature into the past and the future. Given that he is a corporeal substance endowed with a body and an animating principle, he infers that this has always been and will always be so, not only in his own case, but for all other creatures as well. The caterpillar that is transformed into a butterfly is simply a visible manifestation of what must be the case throughout the universe. Not all the conclusions that Leibniz draws using PU follow from the combination of sensation and reflection. In the case of his belief in universal mechanism, the generalisations are made on the basis of sensory evidence alone. In this instance, however, the dependence only on sensation causes no problems for here there is no conflict within the sensory evidence itself. In the case of the animal transformations, some animals appear to be transformed while others appear simply to die. In this case, we need to combine the sensory evidence with the reflective evidence in order to find the truth. But in the case of the mechanical operation of bodies, all bodies have so far been found to act in accordance with mechanical laws. We have never encountered any physical object to which these laws do not apply. It is acceptable in this instance to extend what we have found true of sensed bodies to those that we have not sensed. Besides, the fact that our experience combines both a free mind and a mechanically determined body, known by reflection and sensation, respectively, finds expression on a universal level in Leibniz’s doctrine of pre-established harmony. Leibniz generalises from his own experience of himself as a passively sense-perceiving, embodied being who is, nonetheless, endowed with a rational, self-conscious or reflective mind. He infers both the deterministic mechanism of bodies acting according to efficient causes and the inner spontaneity of minds, souls, and entelechies acting in accordance with final causes throughout the universe, just as both are found in us. Two explanatory systems apply in each and every

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situation: one of efficient causes and the other of final causes; the one based on the evidence of the senses and the other based on the evidence of internal reflection on our own perceptions and motivations (see Monadology §36: GP VI, 612–13/AG 217). Universal mechanism is thus found to be compatible with universal laws of grace.

6. a further difficulty Nonetheless, even with the help of an experiential state that combines sensation and reflection, not all of Leibniz’s conclusions follow straightforwardly. He admits that some of his perceptions are “accompanied by reflection” while others are not (To Masham, early 1704: GP III, 339/ WF 205). Leibniz then uses the fact of reflection as the basis for a distinction between ourselves as souls or minds who are capable of abstract thought and of knowing universal and necessary truths and other simple perceiving substantial forms, entelechies or souls that are “in animals and other created things in so far as they are organic wholes” (ibid.).22 This conclusion allows Leibniz to distinguish minds, as members of the City of God, from the common mass of substances who have no free will or moral accountability and that ground the extended world of body. Under this distinction, only some souls, the Elect (see Monadology §75: GP VI, 620/AG 222–3), reach the status of reason and moral freedom and qualify as citizens of the Kingdom of Grace.23 The view acceptable within the contemporary theological context was that which stated that there are some creatures whose perceptions have been, are, and will always remain, obscure and confused. Unfortunately for Leibniz’s argument in the Masham correspondence, PU, applied strictly, suggests a different result. Leibniz is starting from the observation that his different perceptual states vary in their degrees of clarity and distinctness. There are times when he has perceptions are obscure and confused and other times when his perceptions are clear and distinct. We might with reason then expect Leibniz to argue that there are beings who are similarly sometimes capable of reflection everywhere in matter. PU surely implies that what is the case in Leibniz’s experience will be the same for all other creatures, too, and that, therefore, they will all have a range of confused and distinct perceptions during the course of their lives. In the correspondence, Leibniz defends his separatist position on the grounds that we “see no vestige” (To Masham, early May 1704: GP III, 339/WF 205) in animals of the abstractions or universal necessary truths

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that arise from reflection. But absence of evidence does not entail the corresponding absence of the qualities themselves. Besides, even if we agree that our sensory experience of animals’ aggregate bodies does suggest that animals lack the ability to reflect upon their own mental operations, this does not entail that their mental abilities will always be so limited. Just as the external appearance of someone sleeping indicates with reasonable accuracy that his or her mental state is confused, so too, the external appearance of animals may be a reliable indicator of a similar confusion and lack of conscious awareness of themselves. But just as human beings awake from sleep, so other creatures may also one day awake to find themselves able to reflect upon the operations of their souls. Moreover, our own experience shows that the degrees of confusion in our mental states change over time, and there is no good reason not to extend this observation to the mental states of all creatures. In fact, PU may even be said to demand it.24 Thus, PU, by implying that all entelechies, souls, and minds will one day be rational, free citizens of a moral Kingdom, militates against the distinction of the two Kingdoms of Nature and of Grace in a way that prevents transfer of creatures between them. One reason why Leibniz did not acknowledge this tension in his thought may lie in his overall strategy and his hopes for a positive outcome in relation to Locke in the early stages of this correspondence. Outwardly, Leibniz was conveying his thoughts to Lady Masham, but his hidden agenda meant that the presentation of his thoughts in a format that Locke would find agreeable was at the forefront of his mind. Even if he did realise that the logic of his argument based on PU threatens his doctrine of the Elect and leads to a conclusion that neither Cudworth, Locke, nor Masham considered a possibility, Leibniz is unlikely to draw attention to this fact, given that his motivation in these letters is to engage with Locke as much on Locke’s own terms as he can manage, through a named correspondent who would realise the similarities between the ontology Leibniz derives using PU and that of her father, an ontology that populates the universe with living creatures that combine mental and physical characteristics in one indivisible unit, all of whom, even those that are not self-conscious, are modelled on our own experiences as human beings.

Notes 1. For an engaging discussion of Lady Masham’s philosophy as well as its relation to Locke’s, see Hutton 1993.

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2. Leibniz was probably unaware of Lady Masham’s own intellectual interests. He only discovered that she had already published her first book, A Discourse Concerning the Love of God (1696) when Coste told him shortly before February 1707 – see Leibniz’s letter to Burnett, February 22, 1707 (GP III, 313). 3. For more detail on Cudworth’s view of the natural world, see Jacob 1991: 110–114. I have also profited from Thiel 1991. 4. Leibniz also agrees with Cudworth that the laws of mechanism themselves depend on the Divine Will and the wise choice of the fittest and simplest laws (see TIS 1.3.37, art.2). 5. This was arranged through William Molyneux, Locke’s friend and confidante. 6. On the ‘Essay Concerning Human Understanding’ of Mr. Locke (GP V, 14–19). 7. A Selection of Reflections on the 1st and 2nd books of the ‘Essay Concerning Human Understanding of Mr. Locke (GP V, 20–4). 8. Leibniz here deliberately uses Locke’s definition of matter over Descartes’s. 9. Although this play has been attributed to Fatouville and dated from 1683 (see NE lxvi and WF 220 n.33), its actual publication history is more complex. The play seems to be a translation or adaptation from the Italian and is variously attribute to “D***,” “Monsieur D***,” where “D” is elucidated as Nolant de Fatouville or Anne Mauduit de Fatouville for some copies. The only editions that could have predated the correspondence with Masham are several that are undated and a Dutch translation published in Geneva in 1685. Leibniz does not divulge his source to Masham. 10. The exception is in a letter to Wagner, June 10, 1710 (GP VII, 530/W 506). 11. Similar remarks hold of the tertiary qualities, too. How the sun affects a rock or stone differs from how it affects wax. The interaction of the respective internal constitutions determines the overall effect – see Essay 2.8.24. 12. I base this interpretation on a combination of passages, including Essay 2.23.11–13 and 4.3.23. There is insufficient space to make the case in detail, but I do believe these are reasonable conclusions to draw from Locke’s statements. 13. Leibniz is generalising from his present experience. In this, he is aware of the existence of his own body. He then generalises over the existence of the body to its existence at other times. He does not claim (and it would not be reasonable to have done so) that he is always conscious of his own body’s existence, nor does he claim that all other creatures are aware of their bodies’ existences – see Monadology §14: GP VI, 608–9/AG 215 and §20: GP VI, 610/AG 216. 14. Leibniz further uses PU to argue that there is no natural generation or destruction; that all bodies operate by mechanical or efficient causes; that souls operate by final causes; and that since “we see no way of conceiving action of the soul on matter,” there is a pre-established harmony relating soul and body (GP III 340/WF 206). He does not think that our sensory perceptions suggest that other animate beings are like us in being reflective and capable of abstract thought. This point, we consider in section 6.

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15. See also the letter to Sophie Charlotte, May 8, 1704: GP III, 345/WF 222. He there also claims further that this implies that death consists in a violent decrease. 16. We also come to know ourselves as moral agents and as persons – see Discourse on Metaphysics §34: A VI iv, 1567–9/AG 65–6. 17. Some, but not all, of whom are conscious of themselves in this world. 18. “I believe that all created substance is accompanied by extension, and I do not recognize any which is entirely separate from matter” (To Masham, September 1704: GP III, 362/WF 219). 19. “[T]here are such active beings everywhere in matter” (To Masham, early May 1704: GP III, 339/WF 204). 20. He also justifies this by the principle of continuity. If there were either generation or death of an animal, “there would be too much of a jump, and through inexplicable changes of essence nature would lose too much of its character of uniformity” (GP III, 345/WF 222). 21. He does not claim that it always has the same organic body since our own bodies change even from day to day. The transformation of the caterpillar shows that the changes can be dramatic. 22. Also see Leibniz’s letter to Sophie Charlotte, May 8, 1704 (GP III, 344/WF 221). There he also allows that “there are even some which are wonderfully far ahead of us.” 23. The Kingdom of Grace is composed of a subset of those that make up the natural kingdom of souls acting in accordance with final causes, namely those self-conscious rational minds who choose in accordance with their own final causes – see Monadology §87 (GP VI, 622/AG 224). For discussion, see Phemister 2003. 24. Some years ago, Mark Kulstad showed the tension in Leibniz’s thought as a whole on the issue of animals’ capacity for reflection, arguing that the position arrived at in the New Essays allows a distinction between focused reflection, which allows humans to direct attention to the operations of their own minds, and simple or mere reflection, which allows animals to pay attention to external objects or internal sense images (1991: 24). The argument here is that a rigorous application of PU would extend focused reflection to the animals.

10 Idealism Declined Leibniz and Christian Wolff Donald Rutherford

Christian Wolff has often been seen as Leibniz’s direct philosophical descendant. Superficially, there is something to be said for this. On a personal level, Leibniz went out of his way to assist his younger compatriot in securing an academic position and looked favorably on Wolff ’s contributions to the advancement of learning in Germany. On a philosophical level, there is no doubt that Wolff drew heavily on the resources of Leibniz’s philosophy and laid out one path along which that philosophy might be developed. Still, it is easy to exaggerate the depth of the relationship between the two men. Despite the extensive correspondence they carried on for over decade (1704–16), Leibniz and Wolff each were not intimates. As Leibniz viewed the matter near the end of his life, Wolff was a bright and enterprising young academic, who had shown an interest in Leibniz’s views and was now principally engaged in teaching mathematics.1 Wolff was no more eager to claim a close kinship with Leibniz. As a bright and enterprising young academic, he above all wished to secure his reputation as the founder of a philosophical system that was indisputably his own. The last thing he wanted was to be known as a mere epigone of Leibniz.2 History, though, does not always respect the wishes of its agents, nor historiography the facts of history. Despite what Leibniz and Wolff each may have thought of their relationship, it has come to loom large in the subsequent telling of the history of philosophy. A common story about the development of philosophy in eighteenth-century Germany I wish to thank Martin Sch¨onfeld and Eric Watkins for their helpful comments on an earlier version of this chapter.

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traces a line of influence from Leibniz through Christian Wolff to Kant. In its crudest version the story begins with a position described as the “Leibnizian-Wolffian philosophy,” a system constructed by Wolff out of Leibniz’s fragmentary writings. This system, so the story goes, was one Kant embraced in his pre-Critical works and subsequently rejected because of its dogmatic metaphysical commitments. As history, this tale leaves much to be desired. In the first place it is implausible to regard Kant’s pre-Critical philosophy as a simple reflection of the views of Leibniz or Wolff. The series of works stretching from the 1746 Thoughts on the True Estimation of Living Forces to the 1770 Inaugural Dissertation record Kant’s evolving efforts to think through the consequences of ideas associated with his German predecessors, but at no time was Kant a card-carrying “Leibnizian-Wolffian.”3 Moreover, no one saw more perspicuously than the later Kant the divide between Leibniz’s metaphysics and that of the Wolffians. This is not to say that others were not eager to unite the two positions. Depending on the source, the label “LeibnizianWolffian” was coined either by Wolff’s student Georg Bernhard Bilfinger (see Wilson 1995: 445) or by Wolff’s early detractors at the University of Halle (see Beck 1969: 257). Bilfinger was among those supporters of Wolff who saw his teacher as extending the program of Leibnizian philosophy.4 Wolff himself, however, chafed under the identification of his views with those of Leibniz, and in this, I shall argue, his resistance was not without justice. Although strongly indebted to the framework of Leibniz’s philosophy, in terms of both method and doctrine, Wolff defends a significantly different set of views.5 The impetus to unite the philosophies of Leibniz and Wolff remained strong in Germany through the time of Kant. In the first Critique Kant himself refers disparagingly to the “Leibnizian-Wolffian philosophy” (CPR A44/B61). In other passages, however, Kant is careful to distinguish the views of Leibniz from those of his successors, who sought to synthesize his philosophy with that of Wolff (CPR A273/B329). Of particular interest in this connection is Kant’s interpretation of the monadology. While critical of any effort to attain theoretical knowledge beyond the limits of sensibility, Kant regards Leibniz’s monadology as at least a coherent attempt to reason about a supersensible reality of things in themselves. Kant isolates two features of Leibniz’s theory that he thinks distinguish it from the treatment of that theory in the hands of later (Wolffian) philosophers. The first is that, as Leibniz understands it, the monadology is not intended as an explanation of “natural,” or spatiotemporal, appearances. Rather, Kant argues, it is “a Platonic concept of the world,” “which is correct

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in itself insofar as the world is regarded not as an object of the senses but as a thing in itself, i.e., as merely an object of the understanding which nevertheless lies at the basis of the appearances of the senses” (Ak IV, 507/MFNS 55). The second point Kant emphasizes is that when the monadology is understood in this way Leibniz was right to think that its elements must be mind-like substances: As object of the pure understanding [ . . . ] every substance must have inner determinations and forces that pertain to its inner reality. Yet what can I think of as inner accidents except for those which my inner sense offers me? – namely that which is either itself a thinking or which is analogous to one. Thus because he represented them as noumena, taking away in thought everything that might signify outer relation, thus even composition, Leibniz made out of all substances even the constituents of matter, simple subjects gifted with powers of representation, in a word, monads. (CPR A265–6/B321–2)

As Kant sees it, then, it is a strength of Leibniz’s position that it is a type of metaphysical idealism, which proposes an account of reality as consisting solely of simple, mind-like substances, and which eschews the attempt to explicate the spatiotemporal characteristics of phenomena in terms of simple substances. The monads of Leibniz’s theory serve as a ground of appearances, but they do not explain why the phenomena appear as they do – a fact that can be explained only (though Leibniz did not fully recognize this) in terms of the constitutive forms of sensibility. It is on this point, Kant believes, that Leibniz’s monadology is successful in a way that subsequent Wolffian interpretations of it are not, for they fail to distinguish in a sufficiently sharp way the sensible from the intelligible, and they endeavor to explain natural appearances in terms of things in themselves. Kant’s reading of Leibniz’s monadology is, in my view, essentially correct, and I propose to employ it in exploring what I see as the central philosophical issue at stake in Leibniz’s correspondence with Christian Wolff. My thesis simply put is this: Leibniz is an idealist and Wolff is not. What I hope to show through an examination of their correspondence is that very early in his career Wolff was offered an entry into the inner recesses of Leibniz’s philosophy and politely declined the invitation. Thereafter, in his mature writings, Wolff justified this refusal with a philosophical system that makes clear his differences with Leibniz. This is a piece of philosophical history interesting in its own right, but I also want to use it to reinforce the thesis that Leibniz’s late philosophy is best understood as a version of metaphysical idealism, a reading on which I claim Kant as an ally.

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1. christian wolff Before turning to the correspondence, a few preliminary facts about Christian Wolff are in order.6 Wolff was born in Breslau in 1679 and received his university education at Jena, where he fell under the influence of the teachings of Erhard Weigel. Weigel’s program for applying the “mathematical method” to practical questions had a profound impact on Wolff’s conception of philosophy, as it did to a lesser extent on that of Leibniz.7 The difference is that whereas Leibniz merely talked about organizing his philosophy into a system of propositions demonstrated from definitions and self-evident axioms, Wolff put this vision into practice, producing a mammoth set of volumes, in German and Latin, dedicated to the enterprise. Through the support of Leibniz and Tschirnhaus, Wolff obtained his first academic position at Halle in 1706 as a professor of mathematics and natural science. He soon turned, though, to lecturing on philosophy, and in 1713 he published the first of a series of books of Vern¨unftige Gedanken (Rational Thoughts). These are the volumes standardly known as the German Logic, German Metaphysics, and so on, the last of which, a volume on natural theology, was published in 1724. In retrospect, the success of these books is nothing short of remarkable. Wolff arguably makes his philosophy accessible to the ordinary reader by presenting it in a series of bite-sized definitions and proofs. Yet it contains almost nothing that is likely to seize the imagination or stimulate an inquiring intelligence. Lewis White Beck’s description of Wolff’s style captures it to a tee: He illustrates what needs no illustration. He proves [ . . . ] what needs no proof and what admits of no proof. He defines what needs no definition. He cites, by elaborate cross-references, his other works, which all too often are found not to elucidate the passage in question but to be almost equivalent to it. He recommends his other books. He boasts of what he has accomplished. He moves with glacial celerity. He ruthlessly bores. (Beck 1969: 258)

Wolff’s teaching and publications earned him a wide following; but they also garnered him enemies among Halle’s Pietist theologians, who condemned his philosophy for its rationalism and implied determinism. Wolff himself exacerbated the situation through a public address, On the Practical Philosophy of the Chinese (1721), in which he sought, following the example of Leibniz, to disengage morality from revealed religion. The resulting intellectual battle grew into a political fight, which eventually reached the attention of the king of Prussia, Friedrich Wilhelm I, who was informed that Wolff drew from his determinism the conclusion that army

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deserters should not be punished because they could not help acting as they did.8 Angered by this, the king abruptly dismissed Wolff from his position at Halle on November 8, 1723, and ordered him to leave Prussia within forty-eight hours or be hanged. Wolff’s fame was such that he had no trouble finding another position. In the same year he accepted a chair at the Calvinist university at Marburg. Wolff now saw himself as addressing a wider European audience, including Catholics, and he worked at reformulating his philosophy in a series of large Latin volumes, extending from the Philosophia rationalis sive Logica of 1728 to the Philosophia practica universalis of 1738–40. By the late 1730s, Wolff’s reputation had been repaired in Prussia, and with the ascension of Frederick the Great to the throne in 1740, Wolff accepted an invitation to return to Halle. There he composed sixteen more volumes, mainly on natural law and ethics, before dying in 1754. This snapshot of Wolff ’s career will serve as a backdrop for examining his engagement with Leibniz’s philosophy. When their correspondence began in December 1704, Wolff was a month shy of his twenty-sixth birthday. Leibniz was fifty-eight. When Leibniz died in 1716, Wolff was thirtyseven and had published only the first of his German volumes, that on logic. The German Metaphysics was still three years away. The correspondence with Leibniz, thus, occurs before Wolff’s full flowering as an author. I shall suggest, however, that what we find in the correspondence is consistent with the contents of Wolff’s later published work.

2. the correspondence Catherine Wilson introduces the Leibniz – Wolff correspondence in these terms: “Wolff had come to the older man’s attention in 1704 when Leibniz had received a copy of his Inaugural Dissertation, De philosophica practica universalia methodo mathematica conscripta, and the two carried on a correspondence on mathematical, physical, and chemical subjects, which barely touched on metaphysical issues, until Leibniz’s death” (Wilson 1995: 445). This falls short of an adequate description of the scope of the correspondence, for in at least two areas it contains material of genuine philosophical importance. The first, which I shall touch on only briefly, concerns the relation between Leibniz’s metaphysics and his perfectionist ethical theory. It is evident from the beginning of the correspondence that Leibniz is in broad agreement with the conception of practical philosophy laid out in Wolff’s inaugural dissertation. Concluding the letter in which he acknowledges

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its receipt, he tells Wolff that he hopes his comments will not be received unfavorably, “for they are concerned with advancing your ideas rather than with correcting them” (LW 20). Like Wolff, Leibniz insists on disengaging morality from revealed religion and makes the progress toward greater perfection a fundamental principle of his ethical theory. “I do not think there can be in created beings a blessedness that is entirely the fruit of prayers,” he writes to Wolff, “but rather that the true blessedness of a created mind consists in the unimpeded progress to greater goods. It is not enough to enjoy a content and tranquil mind, for that belongs even to fools” (LW 18 – see LW 43). This resonates with remarks Leibniz makes in other writings, most notably the final section of the Principles of Nature and Grace, where he maintains that “our happiness will never consist, and must never consist, in complete joy, in which nothing is left to desire, and which would dull our mind, but must consist in a perpetual progress to new pleasures and new perfections” (GP VI, 606/AG 213). Late in the correspondence, Leibniz responds to Wolff’s request for guidance in defining the concept of perfection (LW 160/AG 230).9 The discussion centers on Leibniz’s definition of perfection as “the degree of positive reality, or what comes to the same thing, the degree of affirmative intelligibility” (LW 161/AG 230), yet Wolff stresses that he is interested in the concept because of its importance for moral philosophy, in which it is a “general rule or law of nature that our actions ought to be directed toward the highest perfection of ourselves and others” (LW 166/AG 232). This account, which echoes Leibniz’s position, remains integral to Wolff’s later presentations of his ethical theory.10 The second topic of importance, and the one on which I shall concentrate, develops a theme well known from the De Volder correspondence: the relationship between dynamical laws and properties and what Leibniz regards as their proper metaphysical ground. The background to this discussion is Leibniz’s broad-ranging critique of Descartes’s physics. Beginning in the late 1670s, Leibniz advances three increasingly strong claims against the Cartesian position. The first challenges the content of Descartes’s laws of motion. In place of Descartes’s principle of the conservation of quantity of motion, Leibniz defends as a fundamental law the conservation of force or power. On the basis of this point, he further argues that Cartesians have misconceived the essence of matter. Rather than being a mere res extensa, matter involves as part of its nature a res dynamica: an intrinsic force or power that explains the capacity of bodies to act and be acted on. Finally, Leibniz maintains that physical force cannot stand on its own as a complement to the spatial extension of matter.

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As a momentary, changeable property, force is an accident, which presupposes an enduring substance. Thus, in the terminology Leibniz adopts, the derivative forces of bodies can exist only as modifications of primitive force, which, he claims, is substance itself. Every substance by nature is an entelechy, or principle of force, which acts continuously insofar as it is able.11 Unsurprisingly, these three claims received different responses from Leibniz’s readers. The first very quickly was universally accepted. Leibniz showed conclusively that the Cartesian laws of motion were false, and a version of his own conservation principle remains accepted to this day. While perhaps not universally accepted, the second point also garnered widespread support. Descartes was wrong to think of matter as consisting of extension alone; in addition, matter involves real forces, by which change is effected. Leibniz’s third claim, however, was often met with skepticism or simple incomprehension: why is it necessary to posit a ground in substance for the physical forces of bodies? And if it is necessary to posit such a ground, why isn’t matter itself sufficient for this purpose? Furthermore, if forces are regarded as accidents of substance, other, more perplexing problems arise. Explanations of dynamical change typically appeal to the transfer of force from one body to another. When a moving body collides with a body at rest, the former gives the latter a force (or momentum) that it did not previously have. However, if forces are as Leibniz describes them, this account seems to imply that accidents can detach themselves from one substance and migrate to another – an example of the worst sort of scholastic excess. Finally, Leibniz’s readers were forced to confront the most bewildering claim of all: the substances grounding the physical forces of matter are not themselves material substances. Primitive active force, the reality underlying the derivative force of bodies, in fact, constitutes the nature of an unextended, soul-like substance, the monad.12 In the course of their correspondence, Leibniz leads Wolff through this tangle of metaphysical issues.13 By this time Wolff was a professor of mathematics and natural science at Halle. He was well acquainted with Newton’s works and with Leibniz’s published writings, particularly those appearing in the Acta eruditorum, to which Wolff was a frequent contributor. Although generally sympathetic to Leibniz’s views, Wolff used the occasion of their correspondence to raise doubts about the foundations of Leibniz’s dynamics. Beginning modestly in November 1708, Wolff writes: Nothing seems to me more certain than that there should be ascribed to matter some force from which its changes follow [ . . . ]. Moreover it is certain that with

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the mass of a body unchanged its force is increased. Thus, for example, the force of a stone is increased when it falls downward. From where, then, does this increase of force come? How should it be conceived? Is something superadded to matter which it did not have before? Or if it does have it, is it at least rendered more efficacious, or more powerful? Finally, the collisions of bodies show that the decrease of force in one body produces an increase of the same force in the other. What, then, should be said? Does something migrate from one body to another? Does God at the moment of contact annihilate something in one body and create the same thing in another? I have no doubt that these uncertainties arise from my not having sufficiently understood the theory of dynamics. (LW 101)

Leibniz’s initial response to Wolff is to argue that the problems he raises can be avoided, provided one is careful to distinguish derivative forces from primitive force and interprets the former as modifications of the latter: There is no need to conceive here any annihilation or creation, or passage of an accident from subject to subject, any more than when shapes are destroyed or produced, or transferred from one [piece of] matter to another; for derivative forces, as I have said, no less than shapes, consist in the modification of some persisting thing. But it is unsurprising if those who have not distinguished derivative forces from primitive forces, and conceive motion or endeavor [nisus] as though it were some substantial thing, fall into difficulties concerning the origin and transfer of endeavor, since it is no less a modification of form (or of primitive power) than shape is a modification of matter. (LW 103)

Leibniz rests his case here, as elsewhere, on an analogy with the relation of matter and shape. Just as matter can be modified to take on a new shape without our having to assume that it has received that shape from something acting on it, so a body can acquire new derivative force, as a modification of primitive force, without our having to assume that there has been a transfer of accidents from one subject to another. In both cases an accident (a particular shape or derivative force) is to be understood simply as the determination or limitation of a prior determinable property (extension or primitive force, respectively), and this Leibniz believes eliminates the need to posit a transfer of accidents. Following this exchange, the topic lies fallow for some time. Nearly two years later, however, Wolff raises the issue again, questioning whether the analogy Leibniz has offered succeeds in resolving the problem. “If derivative forces are to be considered modifications of primitive forces,” he writes, “an intelligible reason must still be given for this modification, just as a coherent reason can be given for the changes of shapes in extension: but I freely admit that I cannot yet comprehend it” (LW 128). To this point Wolff apparently had failed to appreciate an important feature

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of Leibniz’s dynamics, namely, that on his account all the forces that produce change in a body are internal to it. Strictly speaking, no body acts directly on another so as to alter its dynamical properties. Rather, the body that appears to be acted on acts on itself as a consequence of elastic forces internal to it. Thus, the analogy to shape is closer than Wolff may have realized. At the very least, Leibniz can claim that no body receives new derivative forces from another body; instead, those forces are modifications of primitive forces internal to that body. As he writes to Wolff, It is necessary that conatus and impetus, and the actions that follow from these, since they are accidents, be modifications of something substantial or permanent that must itself be active, lest there be more in the modification than in what is modified. Thus, I call it primitive entelechy, or even just entelechy. Derivative forces, therefore, are modifications of this substantial active thing, or primitive force, just as shapes are modifications of a substantial passive thing, namely, matter. It should be known, however, that forces do not pass from body to body, since any body whatever already has in itself the force that it exerts, even if it does not manifest it or convert it into motion of the whole prior to that new modification. For example, when a ball at rest is struck by another, it is moved by an innate force, namely, elastic force, without which there would be no collision. But the elastic force in the body arises from an internal motion invisible to us. And the primitive entelechy itself is modified corresponding to these mechanical or derivative [forces]. Therefore, it can be said that force is already present in every body, and it is determined only by modification. Furthermore, primitive force in fact is neither increased nor diminished, but is only determined in different ways. (LW 130–1)

This account, however, does not fully satisfy Wolff. Accepting that the issue is not one about the intelligibility of the transfer of accidents, he now focuses on what Leibniz means when he claims that “the primitive entelechy itself is modified corresponding to these mechanical or derivative [forces].” Wolff’s concern appears to be this. We know perfectly well what we mean when we talk about changes in the derivative force of a body; such changes can be observed and even measured, at least indirectly, through their effects. But what is involved in changes in the primitive force, or entelechy, and how do these changes ground the changes in derivative forces that depend upon them? In his letter to Leibniz of June 26, 1711, Wolff writes: Thus far I still have this difficulty, that I am not able to conceive distinctly enough how the primitive force is modified, when, e.g., motion is accelerated in a descending heavy object. Changes in extension through the decrease or increase in the number of parts and variation in their position are conceived clearly and

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distinctly: but I do not yet grasp what happens to primitive force, when, e.g., body A strikes body B, or when I throw body A. (LW 136)

In contrast to the case of a body’s change of shape, in which it is clear how that change comes about through the gain or loss of parts and changes in their positions, it is not at all clear, Wolff maintains, how primitive force is modified in a way that explains the changes in a body’s derivative force. Consequently, either Leibniz has left the issue of how change comes about in the entelechy wrapped in obscurity, or the move to the level of primitive force does no explanatory work, since all we can say about that force is that it is modified in whatever way is necessary to produce the observed derivative forces. Whatever Wolff might have been looking for by way of an explanation, he surely was not expecting what Leibniz delivered in his reply, dated July 9, 1711: You ask how primitive force is modified, for example, when the motion of heavy objects is accelerated in descent; I respond that the modification of primitive force, which is in the monad itself, cannot be better explained than by explaining how derivative force is changed in the phenomena. For what is exhibited extensively and mechanically in the phenomena is, concentratedly and vitally, in monads [ . . . ]. What is exhibited mechanically and extensively through the reaction of what resists and the restoration of what is compressed is concentrated dynamically and monadically (as I have already said) in the entelechy itself, in which there is the source of mechanism and a representation of mechanical [things]; for phenomena result from monads (which alone are true substances). And when mechanical [things] are determined by external circumstances, by that fact, in the source itself, the primitive entelechy is modified harmonically through itself, since it can be said that a body has all its derivative force from itself. (LW 138–9)

This remarkable passage introduces two theses that had not previously surfaced in the correspondence. The first, which I shall call the “monadic grounding thesis” (MG), maintains that not only are substances possessing primitive force necessary for grounding the physical forces of bodies, these substances are soul-like monads. The second, the “perceptual change thesis” (PC), expands on the first, drawing on the representative nature of the monad to provide an answer to Wolff’s question of how primitive force is modified corresponding to changes in the derivative force of bodies. According to PC, the modifications of primitive force that ground changes in derivative force are changes in perceptual states that represent those same physical phenomena: when changes occur in the physical forces of bodies, those changes are “concentrated dynamically

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and monadically [ . . . ] in the entelechy itself, in which there is the source of mechanism and a representation of mechanical [things].” Putting together the two theses, Leibniz presents Wolff with the following position: (1) When changes occur in the derivative force of bodies, those changes are grounded in changes in the modifications of the primitive force of monads (MG). (2) The modifications of primitive force are limited to perceptual states, which represent the physical states of bodies, and which are disposed to change in harmony with changes in the forces of the bodies they represent (PC). While this much I take to be uncontroversial based on the text, the details of Leibniz’s position are far from clear. This is especially so with respect to his treatment of derivative force. If we are to make sense of Leibniz’s reply in the context of his ongoing exchange with Wolff, the notion of derivative force must be understood realistically. The two men begin from a common conception of force as a real property of matter, and Leibniz presses the point that, as a changing, accidental property, derivative force cannot stand on its own but requires a ground in an enduring substance. Since derivative forces are the forces of matter, it is natural to assume that the primitive forces of which they are modifications also belong to matter, indeed are constitutive of matter – an assumption that is brought into question by Leibniz’s further assertion that these substantial principles are soul-like monads. This raises an obvious problem about the coherence of Leibniz’s position. Nevertheless, the point remains that MG presupposes a realism about force. As Leibniz defends his position to Wolff, properly conceived, the derivative forces of bodies are modifications of the primitive force of monads.14 A different understanding of derivative force is suggested by PC. PC is introduced by Leibniz in response to Wolff’s question of how primitive force is modified when changes occur in the dynamical states of bodies (the acceleration of falling bodies, collisions between bodies, etc.). Given MG, Leibniz is committed to the claim that changes in physical force are grounded in changes in the modifications of the primitive force of monads. Yet this leaves undefined the particular monadic changes that correspond to particular changes in physical force. In addressing this point, PC asserts that the relevant monadic states are ones that represent the physical forces in question. When a body acquires motion in freefall, for example, that change is grounded in the changing states of monads that represent the change in the body’s dynamical state. Taken on its own, then, PC makes it tempting to conclude that physical forces are grounded in monadic states by virtue of their being represented by those states; or,

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that such representations are constitutive of the grounding relation. If this were so, then Leibniz could be read as defending a version of phenomenalism. From the perspective of any monad, the derivative forces of bodies are nothing more than features of that monad’s representations of a changing physical world. From here it is a small step to conclude that all physical forces are merely phenomenal, and that their grounding in primitive force can be fully explained in terms of the agreement, or harmony, among the contents of monadic perceptions.15 Leibniz’s presentation of his position in the Wolff correspondence argues against such an interpretation. The view he defends is not, as the phenomenalist reading would have it, that the reality of bodies and their physical properties can be reduced to the contents of harmonious perceptions. Rather, from the outset, Leibniz maintains that the derivative forces of bodies must be identified with modifications of substantial primitive force. As he puts it to Wolff, primitive force is not of the essence of [merely passive] matter, though it is of the essence of body. It is necessary that conatus and impetus, and the actions that follow from these, since they are accidents, be modifications of something substantial or permanent that must itself be active, lest there be more in the modification than in what is modified [ . . . ]. Derivative forces, therefore, are modifications of this substantial active thing, or primitive force. (LW 130)

Here Leibniz asserts a completely general metaphysical thesis, which, if true, will hold even if the substances in which derivative forces are grounded, in fact, are soul-like monads. He makes this clear to Wolff later in the critical letter of July 9, 1711: “I have said at different times that a mode is a variation in the limits of that which constitutes an essence; and it is not necessary that the modifications in one thing always arise from something else, since they arise in the monad from itself. For monads, being in a state of flux, have force” (LW 140). This, I argue, is the thrust of MG. PC adds to this Leibniz’s method of identifying the monads that ground given instances of derivative force. Assuming that derivative forces are modifications of primitive force, PC answers the further question of which primitive forces those are.16 Admittedly, MG remains a puzzling thesis. How, one wonders, can Leibniz justify the claim that the changing physical forces of bodies, in fact, are modifications of the primitive force of soul-like monads? Leibniz’s idealism, I believe, is best understood in terms of what Kant calls a “Platonic concept” of the world. Such a position assumes a fundamental division between the world as an object of sensibility (the phenomena

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of bodies) and the world as it is in itself (the noumena of monads). According to Leibniz, monads are the only true substances, or per se real beings; however, he does not conclude from this that sensible things such as bodies are mere appearances, or objects of perception. Rather, he accepts the Platonic position that such phenomena are real insofar as they are grounded ontologically in a prior, absolute reality. The basis of this grounding relation, for Leibniz, is the possibility of understanding the being, or reality, of phenomena in terms of the per se reality of monads. Thus, we understand the derivative forces of bodies as modifications of the primitive force of monads, and, to that extent, such forces are real.17 One of the crucial points that emerges in Leibniz’s letter to Wolff of July 9, 1711 is that, while it is necessary for there be a substantial ground for the dynamical properties of matter, monads play only a limited role in explaining the appearances of bodies. Although the primitive force of monads grounds the derivative force of bodies, in the sense that the momentary states of the former are what we understand the latter to be, the existence of monads is not advanced as a complete explanation of the content of perceptual states. In particular, it does not explain why perception takes the form of a spatial manifold (what Leibniz calls “the representation of the external in the internal”18 ), or why matter as perceived is extended in space. On this score I take Kant’s judgment about the limited aims of Leibniz’s idealism to be correct. Leibniz does not attempt to explain the spatiality of appearances in terms of the reality of monads. On this point, indeed, the explanatory relation seems to run more clearly in the other direction. Leibniz’s account of how change occurs in the monad through the modification of primitive force makes explicit appeal to the content of a monad’s states, which is to say, to the dynamical interactions of spatially related bodies. As he tells Wolff, “while mechanical [things] are determined by external circumstances, by that fact [eo ipso], in the source itself, the primitive entelechy is modified harmonically through itself.” Thus, although the monad is the source of all change, change itself is explained through an account of how the monad’s perceptual states give way to new states, and this cannot be done without referring to the content of those states.19

3. a parting of the ways Having considered the position Leibniz introduces to Wolff, it is time to take stock of Wolff’s reaction to it. Here we are treated to another surprise. Given his relatively junior position, if he were not fully convinced

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by Leibniz’s argument, one might have expected Wolff to have persisted in his questioning, asking Leibniz to expand on one point or another. However, this is not what Wolff does. Instead, he leaves no doubt that for his part their exchange has reached an impasse. While responding with conventional flatteries, he makes it clear that Leibniz’s theorizing has moved in a direction in which he, Wolff, cannot follow him: because of the different requirements for philosophizing correctly contained in your most cherished letter, I had decided not to respond to it before defending these [requirements], especially since one or two points still remain doubtful to me, and in order to settle them it seems my entire method of philosophizing together with my hypotheses on this topic would have to be explained [ . . . ]. I add nothing now except to thank you profusely for such a wealth of exceedingly rare and fertile truths, with which it is fitting to enrich my knowledge. (LW 142)

Recall that this is 1711, nine years before the publication of Wolff’s German Metaphysics. Already, however, Wolff is prepared to assert that his philosophical views rely on a different method and different “hypotheses” than Leibniz’s. Since Wolff is not explicit about these differences, we are forced to speculate. The context strongly suggests that they are related to Leibniz’s presentation of his idealism. Previously, Leibniz had made no mention of monads as the bearers of primitive force, and Wolff had appeared eager to continue pressing him on the details of his dynamics. As soon as Leibniz makes the idealist underpinnings of his theory clear, Wolff withdraws, citing the difference in their “requirements for philosophizing correctly.”20 Wolff’s subsequent published works give a good sense of where his differences lie with Leibniz on issues of method and doctrine. Wolff’s method, explicated in the Discursus praeliminaris de philosophia in genere (1728), starts with a basic distinction between historical knowledge and philosophical knowledge. Historical knowledge is knowledge of fact: something that has been perceived, either directly or indirectly, to exist or occur. We move from historical to philosophical knowledge when we ask how, that is, in virtue of what reason, something that exists or occurs is possible. Wolff envisions this question being posed at ascending levels of abstraction, from particular facts of biology, geology, or climate to the most general truths of ontology, with answers at each stage providing a reason for the possibility of that fact or truth. What is crucial is that in acquiring knowledge one is always moving from the particular to the general, and even the most abstract truths of philosophy are only arrived at by reflecting on, and offering reasons for, particular facts of

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experience. As Wolff writes in §10 of the Discursus, “Historical knowledge provides the foundation for philosophical knowledge insofar as experience establishes those things from which the reason can be given for other things which are and occur, or can occur” (Wolff 1963: 6). What Wolff rules out with his method is any source of a priori intellectual truth: all philosophical knowledge is knowledge of reasoned fact, which has its foundation in experience. Wolff’s method has important consequences for his metaphysics, which on the surface closely resembles Leibniz’s. His definition of substance, for example, “that which contains in itself the principle of change” (Ont §872), agrees with Leibniz’s conception, as does his claim that all substances are simple substances, of which composite things are aggregates (Ont §793). However, Wolff refuses to accept Leibniz’s identification of simple substances with monads. For Wolff, the human soul is a simple substance endowed by nature with a “representative force [vis repraesentativa]” (Psy §§67–8). Yet Wolff denies that we are in a position to affirm this of simple substances in general. The basic constituents of matter, or “atoms of nature,” are unextended simple substances, but for Wolff they are not Leibnizian monads.21 With this distinction in hand we can better locate the source of Wolff’s resistance to Leibniz’s idealism. The following are three grounding theses, two of which Wolff accepts and the third of which he rejects: [UG] All composite things are grounded in true unities (unextended simple substances). [FG] All physical forces are grounded in substantial principles of force. [MG] All matter is grounded in monads (simple substances endowed with a power of representation). Wolff accepts UG and FG on the basis of arguments similar to those offered by Leibniz. In the Cosmologia Generalis, we encounter the following passages, which seem to be lifted straight from the Monadology: §176. Bodies are aggregates of simple substances. For they are composite beings (§119). And since composite beings are aggregates of simple substances (Ont §793), bodies also are aggregates of simple substances. §182. Simple substances are the elements of bodies. Bodies are aggregates of simple substances (Ont §176), and cannot exist without them (Ont §686). §186. That is called an atom of nature which is in itself indivisible, and thus is devoid of parts into which it could be resolved. But that is called a material atom which is

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in itself divisible, but for the division of which no existing causes in the nature of things suffice. §187. The elements of material things are atoms of nature, but not material atoms. §191. In the elements are contained the ultimate reasons for whatever is apprehended in material things.

And slightly later we find this defense of the grounding of physical forces in the primitive force of simple substances: §196. The individual elements of things are endowed with some force. For a body is endowed with active (§135) or motive (§137) force, which must be conceived through a mode of substance (§169) distinct from matter (§168) and as always belonging to the same thing, as we have already shown above (§180). But if there is force in composite substance, it must result from the forces of simple substances (Ont §795). Therefore, since a body is a composite being (§119) and the elements through which it is constituted are simple substances (§183), there must be some force in the elements of material things.

In both cases Wolff’s argument moves from a given thing or property to something that is a sufficient reason for the possibility of that thing. “Through simple substances,” he writes, “it is understood why bodies are possible, and thus the reason for the possibility of bodies is contained in them (Ont §56), consequently they are the ground of the being [principium essendi] of bodies” (Cosm §182).22 And Wolff further concludes that whatever is a ground of the being of bodies must be a ground of any essential property of body: “If there is force in composite substance, it must result from the forces of simple substances” (Ont §795). Yet Wolff insists there are limits to what can be inferred from these grounding arguments. For there to be composites, there must be simples, or “atoms of nature,” but this does not imply that those simples are Leibnizian monads endowed with the power of perception. Likewise, one can infer, following Leibniz, that the derivative force of bodies results from primitive force, whose reason in turn is found in the primary “elements” of bodies, that is, “atoms of nature” (Cosm §§362 and 358–60). However, one is not entitled to conclude from this that the modifications of primitive force can be explained by the perceptual change thesis. On the contrary, Wolff maintains that there is no deeper reason for the modifications of primitive force than the laws of motion themselves: Since moving force, in a collision of bodies through which derivative force results, is modified according to the rules of motion, through these it is understood why in a given case primitive force is modified in one way rather than another, and consequently the reason for the modification is given through these [rules], and

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so derivative forces are explained in an intelligible way through the rules of motion. (Cosm §365)

This is Wolff’s considered answer to the question posed in his letter to Leibniz of June 26, 1711, the letter that elicited Leibniz’s explicit statement of his idealism. We can now identify precisely where Leibniz and Wolff part ways. Leibniz is committed to all three of the grounding theses articulated earlier, and throughout his late writings UG and FG serve as arguments for MG. That is, as Leibniz sees it, in arguing for the grounding of composites in “true unities,” and of derivative force in primitive force, one is ipso facto arguing for the grounding of matter in monads.23 Obviously, though, a suppressed premise is at work, to the effect that whatever is a true unity and principle of force also possesses a representative nature, that is, is a soul-like monad. This is the premise Leibniz embraces and Wolff declines. Why they come down on opposite sides of this issue can be traced to what Wolff calls their “different requirements for philosophizing correctly.” Whereas Wolff limits philosophical knowledge to sufficient reasons for the possibility of objects of experience, Leibniz maintains that the source of philosophical knowledge lies in what cannot be known as an object of outer experience, namely, the soul itself. Responding to the objections of Bierling in the same year (1711), Leibniz writes: The source of mechanism [Mechanismi fons] is primitive force, but the laws of motion, according to which impetus and derivative forces arise from it, flow from the perception of good and evil, or that which is most fitting [convenientissimum]. And just as efficient causes depend on final causes and spiritual things are by nature prior to material things, so also are they prior for us in thought, since we perceive the soul (private to us) more intimately than the body, as Plato and Descartes also recognized. You say that this [primitive] force is known through effects, not such as it is in itself. I reply that this would be the case if we did not have a soul or did not know it. The soul has in itself perception and appetite, and these are included in its nature. (GP VII, 501)

The critical assumption Leibniz makes is that in having direct knowledge of the soul as it is in itself, we do not simply possess first-person knowledge of our soul, or knowledge of what it is to be a soul, endowed with sensation and reflective thought. In addition, we know what it is to be a substance: a true unity endowed with an intrinsic force or power. Thus, Leibniz regards himself as entitled to claim that substance, or primitive force, is both “the principle of perception or internal action, and of motion or external action” (GP VII, 329). “This principle of action is most intelligible,” he writes to De Volder, “since in it there is something

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analogous to what there is in us, namely perception and appetite.” And we are justified in inferring this, “because the nature of things is uniform, and our substance cannot differ altogether from the other simple substances of which the whole universe consists” (GP II, 270/AG 180–1).24 Thus, a priori knowledge of the soul supplies the basis for knowledge of the “inner nature” of the primary constituents of matter, and hence a path from the “phenomena of the senses” to the “intelligible world of substances” (NE 379).

4. idealism regained When a philosophical position that makes bold metaphysical claims is pitted against a position that makes more modest claims, there is a natural tendency to favor the latter, all things being equal. As Leibniz himself says, miracles are not to be multiplied beyond necessity. Accordingly, we might suppose that in their meeting Wolf’s caution ultimately prevails over Leibniz’s extravagance. Wolff was right to decline the invitation to enter the inner recesses of Leibniz’s philosophy, for that would have involved making metaphysical assumptions that he had no reason to make. Wolff believed he could complete the grounding project to which he and Leibniz were committed without supposing that the primary constituents of matter, the bearers of primitive force, were soul-like monads. So why assume this? Why accept the insult to common sense that Leibnizian idealism delivers? Leibniz has at least two answers at his disposal. One would appeal to further metaphysical principles, such as the principle of continuity and the principle of plenitude, that argue in favor of a world composed of an infinity of beings of the same ontological type, differing only in the degree to which they instantiate certain essential properties or perfections. Another answer, one stressed by Kant, would challenge a basic incoherence in Wolff’s own position. Recall that on Wolff’s view derivative forces are explained as modifications of the primitive force of “atoms of nature,” the basic elements of matter. Wolff is careful to deny that these elements are material atoms, which remain divisible in principle, or Zenonian points, which are distinguished by no intrinsic properties and hence can coincide (Cosm §§216–18). Atoms of nature differ from both of these in that they are, on the one hand, simple or without parts, and on the other, distinguished internally through their primitive forces. From this last point Wolff draws an extraordinary conclusion: although the elements of matter are genuine simples that do not occupy space, they

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nonetheless stand in relations to each other – relations of non-identity or difference – that determine the spatial extension of matter. As presented in the Cosmologia Generalis, his argument runs as follows: §219. The elements of material things exist externally with respect to each other. For the individual elements of material things are different from each other (§195), and so one can be distinguished from another (Ont §211). Therefore, individuals are external to each other, or all exist externally with respect to each other. §221. Aggregates of elements are extended. For when elements are aggregated, they exist externally to each other (§219) and united with each other (§220). Therefore, since individuals differ among themselves (§195), those things through which they must be distinguished from each other are different (Ont §211), and consequently they themselves are different (Ont §183). Thus, we have many different entities, or things existing external to each other, coexisting in one thing. Therefore, since that must be extended in which many different things, or existing things external to each other, are united (Ont §548), aggregates of elements are extended.25

Wolff is, thus, committed to explaining the spatial appearances of bodies in terms of the relations of simple, unextended substances via an argument that seems to rest on a simple conceptual error: the conflation of the idea of non-identity with that of externality. From early in his career, Leibniz constructs his metaphysics around avoiding just this sort of problem, that of the labyrinth of the continuum. The putative simples of space, indivisibilia or points, whose nature is exhausted by external relations, are not to be confused with “metaphysical points or points of substance (constituted by forms or souls),” which alone “are exact and real” (GP IV, 483/AG 142). The existence of matter presupposes the existence of “points of substance,” since “without true unities there would be no multitude,” yet these unities stand in no external relations out of which spatial extension can be constructed. Once again, Kant gets Leibniz exactly right on this point: Is it really believable that Leibniz, the great mathematician, held that bodies are composed of monads (and hence space composed of simple parts)? He did not mean the physical world, but its substrate, the intelligible world, which is unknown to us. This lies merely in the Idea of reason, and in it we must certainly represent to ourselves everything which we think as a composite substance as composed of simple substances. He also seems, with Plato, to attribute to the human mind, an original, although now only obscure, intellectual intuition of these supersensible beings. He infers nothing from this, however, concerning sensible beings. He wishes these to be considered as [ . . . ] mere appearances in the strictest sense, dependent upon (specific, particular) forms of intuition. (Ak VIII, 248)26

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What Leibniz recognized and Wolff missed, then, is that in conceiving of a truly simple thing that is, nonetheless, real, a thing whose determinations are entirely internal, one is limited to thinking of a substance that is not in space and that cannot be used to explain the spatiality of appearances. One can only think one’s way to the understanding of such beings as the necessary ground of matter; and if one has gone this far, there is no prima facie reason why one should not be open to the idea that these grounding substances are essentially mind-like.

Notes 1. Compare the following exchange with Nicolas Remond from 1714. On May 5, Remond wrote to Leibniz: “I have been told that Mr. Wolff has published a small essay on the soul [Vern¨unftige Gedanken von den Kr¨aften des menschlichen Verstandes (1713)], in German. I imagine that he will have relied on your principles. So long as you do not disapprove of it, I would be much obliged if you would have an exact translation made of it into Latin or French and send it to me” (GP III, 616). In July, Leibniz replied: “Mr. Wolff has had access to some of my views; but as he is very much occupied with teaching, chiefly in mathematics, and we have not had many exchanges together about philosophy, he could know for the most part only those of my views that I have published. I have seen something that some young men have written under him; I found much good in it, however, there are points with which I do not agree. Thus, if he has written something on the soul, in German or otherwise, I shall try to see it, so that I can speak of it” (GP III, 619). As we shall see, Leibniz fails to acknowledge here the full extent of his contact with Wolff. Nevertheless, in both personal and philosophical terms, the relationship was not as close as that formed during the same period with Bartholomew Des Bosses. 2. In addition to Wolff ’s desire to further his own reputation, his perceived association with Leibniz’s philosophy (especially the doctrine of preestablished harmony) fueled the attacks of his critics – see the following, and Watkins 1998. In the preface to one of his final works, Philosophia Moralis sive Ethica (1753), Wolff continued to stress his independence from Leibniz: “Although it is true that I corresponded regularly with Leibniz, and he often visited me when I was in Halle, he nonetheless communicated nothing to me about his philosophical opinions, with the result that he wrote to Remond just before his death that I could know nothing about his views, except what had appeared publicly” (Mor pref., viii). 3. On the development of Kant’s pre-Critical philosophy, see Sch¨onfeld 2000 and Watkins forthcoming. 4. Another was Alexander Baumgarten, on whose Metaphysica (1779) Kant lectured for many years. ´ 5. This point has been argued by others – see Corr 1975 and 1980 and Ecole 1990.

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6. For a fuller account, see Beck 1969: 256–61. 7. On the latter, see Rutherford 1996. 8. As Watkins 1998 argues, this charge hinged on Wolff ’s alleged defense of the doctrine of preestablished harmony. 9. Some of the key texts are translated in AG 230–4. For discussion of them, see Brown, G. 1988: 588–9 and Rutherford 1995, 34–5. 10. The extent of Leibniz’s influence on Wolff in this area can be measured by comparing the passage just quoted from LW 18 with Vern¨unftige Gedanken von der Menschen Tun und Lassen zu Bef¨orderung ihrer Gl¨uckseeligkeit (1720), §44: “Because the greatest perfection is really God and no creature can partake of it, it is also not possible that a man, even if he daily uses all his strength, should ever attain it. He can therefore achieve no more than to progress from one perfection to another and, increasingly, to avoid imperfection. And this is the highest good he can attain, so that the highest good of man or his blessedness is rightly explained as an unhindered progress to greater goods” (translated in Schneewind 1990: 337–8). 11. See Leibniz’s De primae philosophiae Emendatione, et de Notione Substantiae: GP IV, 468–70/L 432–4 and Specimen Dynamicum: GM VI, 234–54/AG 117–30, both originally published in the Acta eruditorum (in March 1694 and April 1695, respectively). 12. See De ipsa Natura, also published in the Acta eruditorum (in September 1698): “Secondary matter is, indeed, a complete substance, but it is not merely passive [ . . . ]. And so, we must add a soul or a form analogous to a soul, or a first entelechy, that is, a certain urge [nisus] or primitive force of acting, which itself is an inherent law, impressed by divine decree [ . . . ]. [S]omething constitutive, substantial, enduring, what I usually call a monad, in which there is something like perception and appetite” (GP IV, 512/AG 162–3). 13. In what I say about this part of the correspondence I am indebted to the discussion of Adams, R. M. 1994: 383–6. 14. Strictly speaking, we should say that macroscopic physical forces are aggregates of modifications of monadic primitive force. This qualification does not alter the point that, according to MG, the reality of physical force is explained in terms of the prior reality of primitive force. In what follows, I shall continue to refer to derivative forces generally as modifications of primitive force. 15. Central to the phenomenalist reading is the claim that whenever any monad (e.g., my dominant monad) perceives a certain dynamical change, there are other monads that “ground” that change by virtue of harmoniously perceiving it. By itself this does not suffice to identify the subclass of monads that are the grounds of that phenomena, since, in Leibniz’s view, the perceptions of all monads harmonize. What must be added to this, roughly, is that the grounding monads are those that represent themselves, via representations of their organic bodies, as the active and passive participants in such change. For a sophisticated version of such a reading, see Adams, R. M. 1994. 16. It is an open questions whether all the evidence of Leibniz’s late writings can be accommodated to this interpretation. The De Volder letters, in particular,

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contain passages that lend support to a phenomenalist reading (see, e.g., GP II, 270/AG 181; GP II, 275–6/AG 181–2; and GP II, 281–3/AG 184–6). I believe these texts can be reconciled with the interpretation defended here. Throughout his late writings, Leibniz stresses the distinction between the sensible (or imaginable) and the intelligible, and he identifies reality with the latter alone (see GP II, 170/AG 171–2; GP II, 269/AG 179–80; GP VI, 502–3/AG 189). A striking expression of this “Platonic concept” appears in the New Essays: “It is necessary to consider that matter [ . . . ] is only an aggregate of things, or what results from it, and that every real aggregate presupposes simple substances or real unities; and if one bears in mind what constitutes the nature of these real unities – that is, perception and its consequences – one is transported into another world, so to speak; from having existed entirely amongst the phenomena of the senses, one comes to occupy the intelligible world of substances. And this knowledge of the inner nature of matter shows well enough what it is naturally capable of” (NE 378–9). Although Leibniz does not mention here the relation of primitive and derivative force, the point is the same: an understanding of what is presupposed by the properties of matter – of what is necessary for those properties to exist – leads us from the “phenomena of the senses” to the “intelligible world of substances.” For further discussion, see Rutherford 1995: ch. 9. See his letter to Wagner of June 4, 1710: “Broadly speaking, the soul is the same as what is alive or a vital principle, namely, a principle of internal action existing in a simple thing or monad, to which external action corresponds. And that correspondence of internal and external, or representation of the external in the internal, the composite in the simple, a multitude in a unity, in fact constitutes perception. And in this sense a soul is ascribed not only to animals but also to all other perceiving things” (GP VII, 529). A similar conclusion is reached by Adams, who writes that, “In [Leibniz’s] philosophy of body, the objective reality or representational content of a perception is treated for all working purposes as a primitive feature of that perception [ . . . ]. [H]e provides no analysis of a corporeal universe’s appearing to us (as opposed to something else appearing to us)” (1994: 223–4). It is worth noting that at no point does Wolff criticize Leibniz for being an idealist. This is because, as Wolff understands the term, Leibniz is not an idealist. Although Wolff recognizes Leibniz’s commitment to the thesis that all simple substances are soul-like monads, he does not associate Leibniz with idealists such as Berkeley, who “concede only the ideal existence of bodies in our souls, and so deny the real existence of the world and bodies” (Psy §36 and not.). Consistent with the view defended in section 1 of this chapter, Wolff interprets Leibniz as explaining the existence of bodies and their properties in terms of the prior reality of monads and not simply in terms of the contents of their perceptions. “But when we consider a simple being, we are not concerned with the monad of More or the monad of Leibniz” (Ont §684, not.). “I leave to Leibniz his opinion about monads [ . . . ]. For me it is the same whether someone makes Leibnizian monads the most important things, or condemns and

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Donald Rutherford rejects them” (Cosm pref., xiv). “Although you may assume with Leibniz – an assumption we do not make – that the monads which are the elements of bodies are in a state of confused perception [ . . . ]” (Psy §712, not.). For ´ further citations, see Ecole 1990: 239 and 551. Sch¨onfeld has argued that on this issue Wolff ’s view develops over the course of his career: “Wolff first sympathized with the theory of monads, then distanced himself from it, and finally rejected it” (2002: 131). I find little evidence for such a development, as opposed to differences in emphasis in different texts. Sch¨onfeld points out that in GMet, Wolff does not reject outright the view that all simple substances are monads endowed with a vis repraesentativa. Wolff grants that this view is possible and consistent with the rest of his theory. Still, Wolff is explicit in saying that he has reservations [Bedencken] about accepting Leibniz’s view (§598). Likewise, in Wolff ’s late works, when according to Sch¨onfeld he has rejected the theory of monads, we find passages such as the following: “we defend only the simplicity of the elements of things, but we remain undecided [in dubio relinquamus] about what the innate force in them is” (Psy §644). “It is known that Leibniz attributed perceptions and tendencies to perceptions to his monads, nevertheless he never made public the system itself, such as he conceived it. I have left undecided [in medio reliqui] the concept of Leibnizian monads [ . . . ], and so I have also refrained from using the name, lest the things I propose about simple beings in general be taken for Leibniz’s theory of monads” (Mor pref., ix). Watkins’s description of Wolff as “agnostic” (1998: 140) on the question of representative force is consistent with such passages, though in my view it underplays Wolff ’s refusal to follow Leibniz down the path of idealism. See Ont §686: “Since, therefore, in the notion of a composite there is not contained a sufficient reason why something is composite (§56), and yet without a reason why something is composite rather than not composite, something cannot be composite (§70), the sufficient reason of the composite must be sought outside the composite, and hence in a simple being (§685). Therefore, if there exist composites, there must also exist simples, i.e., without simple beings, no composition can be conceived, nor consequently can it exist.” See the following passage from a 1705 letter to the Electress Sophie: “an analysis of the matter which is now found in space leads us demonstratively to substantial unities, to simple, indivisible, enduring substances, and consequently to souls, or principles of life, which can only be immortal and are spread throughout nature” (GP VII, 565). Compare also the following to De Volder: “everywhere and throughout everything, I posit [pono] nothing but what we all acknowledge in our souls on many occasions, namely, internal and spontaneous changes. And so, with one stroke of mind, I draw out the entirety of things” (GP II, 276/AG 182). The passage continues: “The same thing can also be shown in this way. Since an idea is a representation of a thing in the mind (Logica, §34), but every corporeal thing is an aggregate of simple substances (§176), and thus elements (§181), when we have the idea of a corporeal thing, aggregates of elements are represented in the mind. Thus, since those elements exist external to

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each other (§219) and are united with each other (§220), we represent to ourselves many existing things external to each other as though in one thing. In this way there arises in the mind the notion of extension (Ont §548) which we attribute to coexisting things.” For another version of the argument, see GMet §§602–4. 26. “On a Discovery According to Which Any New Critique of Pure Reason Has Been Made Superfluous by an Earlier One,” translated in Allison 1974: 158.

11 On Substance and Relations in Leibniz’s Correspondence with Des Bosses Brandon Look

Leibniz’s correspondence with the Jesuit theologian and philosopher Bartholomew Des Bosses is one of the richest sources of Leibniz’s mature philosophical thought.1 Occupying the last ten years of Leibniz’s life (1706–16), the period of composition of the Theodicy (1710), the Monadology (1714), and the Principles of Nature and Grace (1714), and comprising close to 140 letters, this correspondence shows Leibniz confronting some of the most difficult questions concerning his metaphysics: the nature of composite substance and the reality of relations. Moreover, because the correspondence was never meant to be published, it offers us a unique and salutary perspective on Leibniz’s philosophy, for it is here that Leibniz is at his most relaxed, working out ideas in his system.2 For many scholars, however, the Leibniz–Des Bosses correspondence is inextricably linked with that “enigma” (Blondel 1930) of modern philosophy, the vinculum substantiale, or substantial bond of monads – that which is apparently invoked by Leibniz to explain transubstantiation within his monadological metaphysics. It should not be surprising, then, that Bertrand Russell’s well-known, damning remark about the vinculum substantiale – that it was “rather the concession of a diplomatist than the creed of a philosopher” (1937: 152) – has cast a pall over much of the scholarship relating to the Leibniz–Des Bosses correspondence. Russell’s view, pushed to its extreme, seemed to be that the entire correspondence constitutes simply an attempt on Leibniz’s behalf to placate his benighted, My thanks to those who attended the conference Leibniz and His Correspondents at Tulane University in March 2001 for their questions and to Paul Lodge for helpful comments on an earlier draft.

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Catholic friend, and, as such, that we hardly need to concern ourselves with any of Leibniz’s arguments with Des Bosses. Yet, to reduce the correspondence to a set of texts about the vinculum substantiale is to lose sight of what is of real importance here. For Leibniz is not simply trying to pass off some fancifully contrived metaphysics on a silly theologian; rather he is trying, in general, to explain the nature of substance itself and, in particular, to test whether his monadology, on the one hand, can be made consistent with certain tenets of traditional philosophy that he himself endorses throughout his career, and, on the other hand, can account for certain doctrines of faith. In his letters with Des Bosses, Leibniz always strives to develop his monadological metaphysics within the context, and appealing to the conceptual apparatus, of traditional metaphysics, and it is the dialectic between the monadological metaphysics and Scholastic philosophy that ultimately reveals serious weaknesses in his own system. In this chapter I explore a set of issues related to Leibniz’s accounts of substance and relations in his correspondence with Des Bosses. In particular, I examine, first, the way in which Leibniz explains the unity and reality of composite substance and, second, the role of Leibniz’s general theory of relations vis-`a-vis his account of composite substance. By focusing on these subjects, I hope to introduce the reader to the central themes of the Leibniz–Des Bosses correspondence and to show what I take to be the most interesting result of the study of the correspondence, namely, that Leibniz’s mature monadological metaphysics faces troubles that are not obvious in his earlier and simpler view of substance.

1. the nature of substance: unity, reality, and composition If anything deserves to be called the fundamental tenet of Leibniz’s metaphysics, it is certainly the principle of the reciprocity of unity and being. As Leibniz puts it in a letter to Arnauld in 1687, “I hold this identical proposition, differentiated only by the emphasis to be an axiom, that what is not truly one being is not truly one being either” (GP II, 97/AG 86).3 That is, for something to be a real being, it must possess genuine unity. This axiom or tenet leads to the strong distinction within Leibniz’s system between, on the one hand, true unities, or unities per se, and, on the other hand, aggregates, or unities by aggregation, which can have only “phenomenal unity.” And throughout Leibniz’s career, bodies, the objects of study in natural philosophy, will be examples of such beings by aggregation, likened, in Leibniz’s favorite metaphor, to a rainbow, which,

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though constituted in some sense by innumerable simples (that is, drops of water), has its unity only in the mind of the perceiver.4 The reciprocity of unity and being is, of course, a standard Scholastic doctrine in metaphysics, and it is revived by Leibniz as part of his criticism of Cartesian metaphysics. Leibniz self-consciously describes himself as one who finds something worthwhile in the metaphysics of the schools and in the modern philosophy of the Cartesians. And it is well known that his chief criticism of the Cartesian account of body is that, if body were merely extension, there would be no principle of activity in substance; according to Leibniz, there must be something akin to a soul or a substantial form in a body (see Discourse on Metaphysics §12: A VI iv, 1545–6/ AG 44). In other words, Leibniz responds to the Cartesian account of body by appealing to the Scholastic notion of substances as composites of form and matter, the former providing what Leibniz will call a “primitive active force” of the substance, the latter a “primitive passive force” of the substance.5 Though Leibniz is not as clear as we might wish him to be, it seems that the primitive active force of a substance is the tendency to go from perception to perception according to a law in the nature of the substance (see Leibniz to De Volder, January 25, 1705(?): GP II, 275/AG 181); the primitive passive force, on the other hand, is roughly equated with the principle of resistance and antitypy (see the untitled piece from 1702: GP IV, 395/AG 252). More interesting is Leibniz’s claim early in his career that beings by aggregation will also have an aggregate of forces. According to the Specimen Dynamicum, for example, in an aggregate of bodies there will be a common, partial living force, by which “the aggregate itself can [ . . . ] act outside itself.” (GM VI, 239/AG 122) Consider an object lacking a “soul” or substantial form of the whole: it will consist of the substantial forms of all the substances that the aggregate comprises. Any body, however, insofar as it is truly only an aggregate, will possess only an aggregated sum of active and passive forces. Just as the unity of such a thing will be merely phenomenal, so the unity of the forces will be merely a mental fiction, useful when doing natural philosophy but not reflecting an underlying reality. With the development and elaboration of his monadological metaphysics, Leibniz continues his appeal to matter and form and to active and passive powers. Not surprisingly, however, the issues become slightly more complicated. For example, when appealing only to the language and ideas of Scholastic metaphysics, it is easy to see how I, as an individual substance, am completed by or composed of matter and form, body and

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soul. What happens, however, when I make the claim that I am constituted by an infinity of monads?6 That is, what will be the status of an animal, a being that is supposedly a genuine unity but that also is composed of an infinity of simple substances? In his letter to De Volder from June 1703, Leibniz begins to confront this issue, giving the following ontological scheme: I distinguish: (1) the primitive entelechy or soul; (2) the matter, namely, the primary matter or primitive passive power; (3) the monad made up of these two things; (4) the mass or secondary matter, or the organic machine in which innumerable subordinate monads concur [concurrunt]; and (5) the animal, that is, the corporeal substance, which the dominating monad makes into one machine. (GP II, 252/AG 177)

The monad, or simple substance, is again said to be made complete by the primitive entelechy, or primitive active power, and primary matter, or primitive passive power. Whereas earlier Leibniz had described secondary matter or mass as being derivative passive power, it is here the sum of subordinate monads (see GM VI, 236/AG 120). Insofar as I am an animal, or an individual corporeal substance, it is clear that I am unified by the action of my dominant monad, which, it seems, will be equivalent to my mind or soul. Nevertheless, a deep problem seems to remain concerning the relation between simple substances and composite substances. On the one hand, we have confident claims like the following from the opening sections of the Principles of Nature and Grace: A substance is a being capable of action. It is simple or composite. A simple substance is that which has no parts. A composite substance is a collection of simple substances, or monads [ . . . ]. Composites or bodies are multitudes; and simple substances – lives, souls, and minds – are unities [ . . . ] [E]ach distinct simple substance or monad, which makes up the center of a composite substance (an animal, for example) and is the principle of its unity, is surrounded by a mass composed of an infinity of other monads, which constitute the body belonging to this central monad (GP VI, 598–9/AG 207)

On the other hand, we have the claim in Leibniz’s earlier letter to Arnauld that that which is not one being is not a being. Therefore, given that Leibniz makes such a sharp distinction between genuine unities and unities by aggregation – the latter having only phenomenal unity – one is immediately confronted with the following question: In what sense, if any, can a composite substance be a genuine unity? If it cannot be shown that a composite being has some kind of real unity, then, it would seem,

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there is no difference between a composite, like an animal, and a mere aggregate, like an “inanimate” object. It is precisely this issue that is at the center of the correspondence with Des Bosses.

2. the problem of composite substance in the leibniz–des bosses correspondence It is fair to say that Des Bosses sets the tone for the entire correspondence in his second letter, where he asks Leibniz to give his opinion on several Scholastic or Aristotelian doctrines – the first of which is “ens et unum convertuntur,” or “being and one are convertible” (GP II, 296) – and goes on to ask about Leibniz’s dispute with Tournemine concerning mind-body unity (see GP VI, 595–7).7 In his response, Leibniz affirms the reciprocity of unity and being that we have seen before and goes on to make this claim about the relation of mind and body: “In general, the soul is an entelechy or primitive active power in a corporeal substance, through which the matter or primitive passive power of the same substance is completed; and by means of the modification of these primitive powers, actions and passions are produced in the corporeal substance itself” (GP II, 301). Here the claim is explicit that in a corporeal substance the soul is the entelechy or primitive active power, made complete by primitive passive power or matter; and where Leibniz speaks of the modifications of the primitive powers, he means the derivative powers of substances mentioned in the previous section. Whereas we have been content to let Leibniz label a substance made complete by form and matter a “simple substance,” Des Bosses is more persistent, pointing out that this is indeed a kind of composition, depending upon a flawed conception of matter: if being and one are convertible, then nothing may exist simply and actually in itself except that which is actually and simply one. But whatever is a fraction of unity or of what is actually and simply one is not itself actually and simply one, for otherwise one thing composed of matter and entelechy, whose fraction we are supposing, would be an aggregate of unities, and so not one; therefore, fractions of unity and of the simple will be only mathematical beings that result from a mental abstraction. (GP II, 302)

For his part, Leibniz moves from the “vulgar” talk of mind and body to his philosophically precise language of the monadology and points to the difference between primary matter, which completes a monad, and secondary matter, which is the “result” of many monads.

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It is otherwise if you mean primary matter or primary passive power, primary substratum, that is, primitive passive power or the principle of resistance, which consists not in extension but in the determination of extension, and completes the entelechy or primitive active power, with the result that it produces a complete substance or monad, in which modifications are contained virtually. We understand such matter, i.e., the principle of passion, to endure and to adhere to its entelechy; and in this way from many monads there results secondary matter, together with derivative forces, actions and passions, which are only beings through aggregation, and thus semi-mental things, like the rainbow and other well-founded phenomena. (GP II, 306)

We find here the same view that we saw in Leibniz’s letter to De Volder: A monad is completed by primitive active force and primary matter or primitive passive force; secondary matter is the result of the many monads. Nevertheless, where Leibniz had earlier spoken of the possibility of an animal unified by a dominating monad, he here seems to suggest that any and all manifestations of secondary matter (which is to say, the phenomenon of matter) are merely beings by aggregation. This passage makes clear, however, that there are now two issues that need to be separated: first, the way in which secondary matter arises from the innumerable monads, and, second, the relation between monads within an organism. Though the two issues are closely tied together, I wish to concentrate on the second issue and ask whether a composite substance can be a complete substance, or whether monads together constitute something real, over and above a mere aggregate of monads. It should also be clear at this point that there is a difference between explaining, on the one hand, the unity of mind and body in terms of preestablished harmony or the way in which a simple substance is “completed” by primitive active and passive powers and explaining, on the other hand, how a set of monads can constitute a composite substance. The latter requires an explanation of the way in which these distinct things, which are all of the same nature, can combine to form a per se unity. Leibniz goes to a great deal of effort indeed in his letters to Des Bosses to show that a composite substance is a complete substance, that is, a real and genuine unity. In his February 1712 letter, which is certainly the central text in the entire correspondence, Leibniz addresses the issue in the following way: If corporeal substance is something real over and above monads, as a line is taken to be something over and above points, we will have to say that corporeal substance consists in a certain union, or rather in a real unifier added to monads by God, and that from the union of the passive powers of monads there arises primary matter, which is to say, the demand for extension and antitypy, or diffusion and

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resistance. On the other hand, from the union of monadic entelechies, there arises substantial form, but one which could be generated and destroyed, and which would be destroyed with the cessation of that union, unless it should be preserved miraculously by God. But such a form then will not be a soul, which is a simple and indivisible substance. And this form, like matter, is in a perpetual flux, since, in fact, no point can be designated in matter which preserves the same place for more than an instant and which may not move away from any neighboring points. (GP II, 435/AG 198)8

Leibniz goes on to give Des Bosses two well-known options: either bodies are mere phenomena – and only monads are real – or “if faith drives us to corporeal substances, this substance consists in that unifying reality, which adds something absolute [ . . . ] to the things unified” (ibid.). And, in what is usually thought to be the first reference to the vinculum substantiale,9 Leibniz concludes his discussion thus: If that substantial bond of monads [vinculum substantiale monadum] were absent, then all bodies, together with all their qualities, would be nothing other than wellfounded phenomena, like a rainbow or an image in a mirror, continuous dreams perfectly in harmony with one another; and the reality of these phenomena would consist in this alone.” (GP II, 435–6/AG 198–9)

There is, of course, much in this letter that deserves comment. On the one hand, it is clear that Leibniz holds open the option that composite substances need not be anything real over and above monads; in this way, Leibniz can maintain the sparse ontology suggested in an earlier letter to De Volder, in which it is claimed that there are only monads and in them perceptions and appetitions (GP II, 270/AG 181).10 On the other hand, Leibniz gives a relatively clear account of what the nature of composite substance should be, granting that composite substances have more than merely phenomenal existence. Composite substances are somehow unified; that is, there is a unity of the active and passive powers within the composite substance. In this sense, just as the simple substance will be a being of primitive active power and primitive passive power, so a composite substance, which is to be somehow also a unity per se, will consist in the unification of primitive powers of the monads. Moreover, it should be noted that in Leibniz’s earlier years the substantial form was simply that which provided for the possibility or constituted the activity of the composite substance; here, however, it seems that the substantial form arises from the pre-existing primary active powers of the entelechies in a composite. The remainder of the Leibniz–Des Bosses correspondence is largely taken up with an evaluation, explication, and expansion of the claims

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in this letter. Unfortunately, it cannot be said that Leibniz develops a coherent and consistent view. Given what we have seen thus far, it is not surprising that Leibniz should attribute the unity and reality of composite substance to the presence of primitive active and passive powers; nor is it surprising that the unity of a composite substance should be couched in terms of the relation between dominant and subordinate monads. But Leibniz seems uncertain how best to tie these concepts together in his account of the nature of composite substance. For example, in his letter from April 1714, Leibniz says the following: It is worth considering what can be thought to be appropriate to produce in phenomena beyond the perceiving subject or what constitutes composite substance. As far as I can judge it will have to consist in primitive active and passive powers of the composite, and it will be what they call prime matter and substantial form. And it will be necessary that the accidents of the composite be modifications of it; which indeed are transitory, but the composite substance itself will endure and the dominant monad as well. Nevertheless, there is no composite substance, that is, a being constituting an unum per se, unless there is somewhere a dominant monad with a living organic body. (GP II, 485–6/L 609)

Later, in a table appended to a letter from the summer of 1715, which contains a more complete ontological categorization of the world,11 Leibniz says this: Composite [substances] like an animal or another organic being, [ . . . ] always remain and adhere to a dominant monad, but are affected by the influence of other composite substances. This [i.e., composite substance] consists in primitive active and passive powers, or it consists in prime matter, that is, a principle of resistance, and substantial form, that is, a principle of impetus. (GP II, 506/ L 617)

Yet, in his final letter to Des Bosses, Leibniz appears to discount the relation of domination and subordination: Composite substance does not consist formally in monads and their subordination, for then it would be a mere aggregate, i.e., an accidental being; rather, it consists in primitive active and passive force, from which arise the qualities, actions and passions of the composite, which are perceived by the senses, if they are supposed to be more than phenomena. (GP II, 517–18/AG 203–4)

Leibniz’s conclusion is, thus, that the relation of domination and subordination within a composite substance is of great importance in understanding the unity of the composite substance, but so, too, is the presence of, or recognition of, primitive active and passive powers within the composite substance. In fact, Leibniz seems to be saying that a composite

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substance that is a per se unity is really possible only insofar as we can attribute to it primitive active and passive powers. It is important to note that Leibniz indeed recognizes the possibility of single active and passive powers existing within, or at least being attributable to, a composite substance. Thus, despite the fact that a composite substance is constituted by an infinity of simple substances, each presumably being completed by matter and form, there are primitive forces of the composite that can be unique and unifiable. The particular questions that these passages raise for me, however, are the following: How do primary matter and substantial form “arise” from the union of monads or potentiae? That is, how are we to think of a unification of individual active and passive powers, especially if we consider active power as the tendency to go from perception to perception and passive power as resistance? Is this similar to Leibniz’s account earlier in his career or not? Is the union of monadic entelechies into a substantial form basically the same thing as the domination of a composite substance by one central monad? Is the unification of active powers analogous to the unification of passive powers? By concentrating on these questions, we shall see that something is amiss in Leibniz’s account of composite substance.

3. matter, form, and the unification of forces In the early stages of his philosophical career, Leibniz simply asserted that a substantial form and primary matter were both present and combined in the nature of a corporeal substance. But now that Leibniz has moved to his ontology of monads, which are to constitute the underlying reality in any phenomenon of body, he must, if he wishes to continue to employ the Scholastic concepts of substantial form and matter, talk about how form and matter “result” from the innumerable monads in a composite substance. Yet, Leibniz is far from clear on this matter. In his correspondence with De Volder, of course, Leibniz claims that each monad is itself a combination of primary matter and primitive entelechy; in the Monadology, on the other hand, it seems that a monad is a purely “spiritual substance” (whatever that might mean).12 It might be argued that the view of Leibniz’s 1703 letter to De Volder does not represent his considered view – Leibniz ought not to assert that monads themselves have a “material” or passive component. But it should be clear that Leibniz endorses the same view in his letters to Des Bosses. Let us grant, then, that monads have a component related to primitive entelechy or activity

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and primary matter or passivity. What does it mean to say that the forces are united? Are they tied together like a team of horses? Or does the composite substance have associated with it an irreducible force, like my lawn mower with its “five horsepower” engine? If the former is the case, then one would like to know what it takes to yoke abstract forces together. First, however, we need to address an ambiguity present in the majority of Leibniz’s pronouncements concerning primitive forces. Insofar as he typically speaks of them in the plural – the primitive active and passive forces – it is unclear whether, in the case of a composite he intends to speak of, say, a primitive active force and a primitive passive force or whether the active and passive components are themselves plural. I take it that in the case of a typical aggregate there are only plural forces, whereas in the case of a genuine composite substance – that is, in the case where a composite can constitute an unum per se – Leibniz must hold that there is in some sense really one primitive active force and one primitive passive force. Indeed, I should like to suggest that it is a condition for the real unity of a composite substance that there be only one primitive active force and one primitive passive force. The unity of the primitive active force in a composite ought to cause us few difficulties. Insofar as Leibniz equates the united primitive active forces with the substantial form of the composite, we seem justified in holding that the single primitive active force is, in fact, the dominant monad. And this view is something one sees in Leibniz’s well-known ontological scheme from his earlier letter to De Volder (GP II, 252/ AG 177 – quoted above in section 1). The dominant monad makes the animal into one machine by serving as the “nerve center,” so to speak, of all the primitive active forces of the subordinate monads. In Leibniz’s philosophy, of course, the primitive active force is associated with the substantial form and provides the source of activity of a substance. And, on the view I am suggesting here, the dominant monad will, insofar as it unifies the primitive active forces of its subordinates, become the source of the activity of a composite substance. The unity of the primitive passive force in a composite substance, on the other hand, poses more problems. As we have seen, this force is associated with matter and provides the principle of resistance of substance. When we move to Leibniz’s mature metaphysics with its idealistic trappings, the notion of matter becomes more complex, and conceiving of the way in which primitive passive forces can be unified becomes likewise difficult. One might think prima facie that there should be no distinction in the treatment of the matter of a composite substance as opposed to

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an aggregate; that is, the material aspect of an animal or composite substance is basically the same as the material aspect of a bowling ball or brick. But we know that Leibniz thought differently, for, in saying that in a composite substance the passive powers of the monads are united, Leibniz is attributing primary matter to a single thing, a composite substance, rather than to a multiplicity of things, the simple substances in an aggregate. Yet the important point here is that the claim of the unity of primitive passive forces need not reflect any kind of underlying reality; that is, it may be that the union of forces is something akin to a mental fiction. While we have already looked at several passages from Leibniz’s last letters to Des Bosses, there are several places where Leibniz appears to complicate matters even further. For example, in his letter from January 1716 he says, I do not see how it can be conceived that the thing realizing the phenomena is anything besides substance. For that realizing thing ought to bring it about that composite substance contains something substantial beyond monads, otherwise there will be no composite substance, that is, composites will be mere phenomena. And in this I think that I am absolutely of the same opinion as the Scholastics, whose primary matter and substantial form, active and passive powers, primitives of the composite, and whose complete thing resulting from these I judge is really that substantial bond [vinculum substantiale] that I urge. (GP II, 510–11)

This passage expresses a certain degree of conviction on the part of Leibniz to the doctrine of the substantial bond, but it also suggests that this bond will itself be the combined active and passive forces of the composite. In a similar vein, we see Leibniz in his last letter to Des Bosses asserting that there is a primitive entelechy for an entire composite substance, which is itself somehow responsible for the realization of the phenomena. You ask, finally, how my composite substance differs from an entelechy. I answer that it does not differ, except insofar as a whole differs from a part, i.e., the primary entelechy of the composite is a constitutive part of the composite substance, namely, primitive active power. But it differs from the monad, since it is realizing phenomena; but monads can exist, even if bodies were only phenomena. On the other hand, the entelechy of a composite substance always naturally accompanies its dominant monad; and so, if the monad is considered with the entelechy, it will contain the substantial form of the animal. (GP II, 519/AG 205)

What is perhaps most striking about this passage is the way in which Leibniz juxtaposes his quotidian metaphysical concepts – monad, substantial form, and entelechy. Here we learn that the entelechy of a

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composite substance naturally accompanies or perhaps is joined to [comitatur] its dominant monad, and that, if the (dominant) monad is considered with its entelechy, it will contain the substantial form of the composite. Two issues naturally arise at this point. First, to say that a composite substance is in any way connected with a dominant monad should lead us to conclude that by “composite substance” Leibniz simply means body. But, of course, this would seem to contradict the majority of his other writings (as well as other letters to Des Bosses), in which a composite substance is that entity composed of (i) the mind and body, (ii) a central monad and the body surrounding it, or (iii) a set of monads (where one monad is dominant over the others, and where the hierarchy extends down to infinity). Second, Leibniz claims that, if the dominant monad is considered with the entelechy, it will contain the substantial form of the animal. What could “contain” possibly mean here? One possible reading is that the dominant monad will contain the reasons for what happens in its subordinate monads, and this is essentially what domination and subordination consist in.13 To say that the substantial form is contained in the dominant monad is, then, just to say that the substantial form or the active force of the substance simply is the set of reasons for what happens within the substance and to, or within, its subordinates. When Leibniz claims that the primitive forces of a composite substance are united, there are three possibilities to consider: (i) the forces could be unified by virtue of some aspect of the constituent monads themselves; (ii) there could be some unifying thing over and above the monads doing the unification – the harnesses, as it were, for a team of horses; or (iii) these forces merely represent together, or can be understood as, one force of the composite – on the model of my five-horsepower lawn mower. In the case of the active forces, Leibniz gives us a seemingly satisfactory account of how something can unify the monads in a composite substance – namely, the dominant monad itself. It should be clear that this unification is internal to the monads of the composite substance in two senses: both within the composite substance and within the dominant monad itself, insofar as the dominant monad will unify its subordinates by virtue of containing reasons for what happens within them. In the case of the passive forces, on the other hand, Leibniz appears only able to suggest that we simply think of the composite as having a single power of resistance. For how could the powers of resistance of the innumerable monads in a composite be unified except by a process of abstraction? This unification of forces, however, is external to the composite substance itself. We now have an answer to one of the questions asked above, which in itself ought

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to cause us to pause: It seems that primitive active and passive powers can be unified in a composite substance but not in analogous ways. A tentative solution to the question of how the primitive active and passive forces are unified was presented earlier. But there is a problem here because Leibniz seems to talk about the substantial bond – the unifying thing – as necessary for having a substantial form for a composite substance; elsewhere, of course, Leibniz has no problems saying that a composite substance is unified (merely) by a dominant monad and its relations to its subordinates. In other words, the tentative solution offered earlier was simply that the primitive active forces were unified in and by the dominant monad of the composite substance. And yet Leibniz seems to add the condition in his letters to Des Bosses that a substantial bond is necessary for the presence of a substantial form. While we ought to reject the cynical reading of the Des Bosses correspondence, in which the substantial bond is simply advanced by Leibniz to placate his Catholic friend and ought, therefore, to be dismissed, there are good reasons to be unhappy with the doctrine of the substantial bond; and this is one of them: namely, Leibniz is guilty of multiplying entities beyond necessity.14 The more we look at Leibniz’s account of the unification of forces, the worse things appear for his monadology. For if the unification of passive forces is in some sense external to the composite substance, then there would appear to be no difference from the (phenomenal) unity that a mere aggregate has, in Leibniz’s view. And this, in turn, is to say that there really is no unification of passive forces in a composite substance at all. If this is so, then we have two possibilities before us: Either Leibniz cannot really give a coherent account of composite substances (where a composite substance is understood as a group of monads organized with a hierarchy of domination), or Leibniz can give us such an account but only by jettisoning the idea that monads themselves have active and passive powers that, in the composite, are to be “unified.” It should be clear, however, that this situation merely parallels the options that Leibniz himself proposes to Des Bosses in his February 1712 letter: Either only monads are real (and bodies are mere phenomena) or there is something over and above monads that unifies composite substance. I hope to offer a partial rescue of Leibniz in the next sections. Nevertheless, it needs to be stressed that part of the problem that Leibniz has created for himself has arisen not because he has attempted to explain transubstantiation to his Catholic friend but rather because he has attempted to combine his monadological metaphysics with Scholastic

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philosophy. When Leibniz says in his February 1712 letter that a substantial form arises from the union of monadic entelechies, warning lights ought to flash, and we ought to be very wary. On the one hand, the union of monadic entelechies takes place as the relation that exists between a dominant monad and its subordinates. Yet, we are also accustomed to making the following statements of equivalence within Leibniz’s various ways of speaking: A dominant monad is the soul of an organism, and a soul is the substantial form of a substance. And to say that a substantial form arises from the union of monadic entelechies seems to assert the equivalence of substantial form and the union of entelechies; or, again, to say that the dominant monad is the union of monadic entelechies. This view, while apparently contradictory, might be salvageable with a more detailed account of monadic domination or with a reconsideration of the notion of form.15 But, again, what of the unification of passive forces? To understand the sense in which these forces could be bound together we will need to examine another aspect of Leibniz’s correspondence with Des Bosses – his treatment of relations.

4. the ideality of relations Although the issue of the nature of composite substance is the most striking feature of the Leibniz–Des Bosses correspondence, Leibniz’s account of the nature of relations also plays a subtle role in the correspondence.16 First, a short reminder of important Leibnizian views on the subject is in order.17 Leibniz claims that there are no purely extrinsic denominations and holds that all relations between substances are reducible to non-relational properties or accidents of individual substances. For example, if there is some relation R between two substances a and b, the relation “aRb” ought, on Leibniz’s view, to be reducible to some intrinsic denomination of a and some intrinsic denomination of b. Thus, if we consider the relation between Paris and Helen, “Paris loves Helen” or “Helen is stolen away by Paris” will ultimately be reducible to certain definite properties of Paris and Helen: “Paris is X” and “Helen is Y.” For, according to Leibniz, “Paris is the lover of Helen” is identical with “Paris loves” and, eo ipso, “Helen is a loved one.” When two substances bear a particular relation to one another, we can say that each monad has a particular set of attributes such that this relation is determined by the concepts of the two individual substances; or more exactly, we can express the particular relation that exists between the two substances in terms of distinct subject-predicate statements somehow belonging to the distinct

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substances. Relations themselves may be said to be contained within the essences of the simple substances or monads. A further feature of Leibniz’s theory of relations that will be important for us in a moment is that it entails a special “reciprocity” or “inversion” that exists within the natures of simple substances or between the substances composing a complex individual. For example, when we say that a particular relation obtains between two substances, we are making a claim about the nature of the first substance and as a consequence a related claim about the nature of the second substance. Thus, in the passage about the relation between Paris and Helen alluded to earlier, Leibniz says the following, “And so it will best be explained that Paris is the lover of Helen, that is: Paris loves and by that very fact [et eo ipso] Helen is loved. There are therefore two propositions concisely collected in one. Or Paris is a lover, and by that very fact Helen is a loved one” (A VI iv, 114–15/ LP 14). I take it that Leibniz’s use of the phrase “et eo ipso” carries a special force; for it requires that, if two substances have a particular relation to one another, then any attribute to be found within the nature of one substance must be accompanied by a “mirroring” or corresponding attribute within the nature of the other substance. Our story of Leibniz’s view of relations does not end here, however, for he believes there to be an additional sense of relations between two things. Not only can a relation between a and b be reduced to properties of a and of b, but a relation can also consist in some kind of ideal thing between the two entities. This view should not be at all surprising given Leibniz’s nominalism; he will countenance relations as non-relational properties of individuals and as ideal things but never as real things existing in the world. Indeed, in two well-known passages in the literature on Leibniz’s doctrine of relations, the first coming from our correspondence, the second from his fifth letter to Clarke, Leibniz suggests precisely this. Writing to Des Bosses on April 21, 1714, Leibniz says, “Thus I think the following about relations: paternity in David is one thing, filiation in Solomon another, but the relation common to each is a merely mental thing, the foundation of which is the modifications of the individuals” (GP II, 486/L 609). And to Clarke: The ratio or proportion between two lines L and M may be conceived three ways: as a ratio of the greater L to the lesser M, as a ratio of the lesser M to the greater L, and lastly, as something abstracted from both, that is, the ratio between L and M without considering which is the antecedent or which the consequent, which the subject and which the object. And thus it is that proportions are considered in music. In the first way of considering them, L the greater,

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in the second, M the lesser, is the subject of that accident which philosophers call “relation.” But which of them will be the subject in the third way of considering them? It cannot be said that both of them, L and M together, are the subject of such an accident; for, if so, we should have an accident in two subjects, with one leg in one and the other in the other, which is contrary to the notion of accidents. Therefore, we must say that this relation, in this third way of considering it, is indeed out of the subjects; but being neither a substance nor an accident, it must be a mere ideal thing, the consideration of which is nevertheless useful. (GP VII, 401/AG 339)

Relations are thus, on Leibniz’s view, both accidents inherent in simple substances, intrinsic denominations, and entia rationis, purely ideal things, which do not, strictly speaking, exist in the natural world. In the case of David and Solomon, as Leibniz claims, we find a particular accident within the nature of David, another particular accident within the nature of Solomon, and, finally, we shall have the abstract relation within our minds – the relation of father and son. And this abstract relation will be the same in all cases in which we look at a father-son relation. In other words, the ideal relation we form by abstraction when looking at the relation between David and Solomon will be the same as that which we form when looking at the relation between Adam and Abel or Abraham and Isaac. The ideal relation is, therefore, simply the abstraction from the properties and attributes of the individuals, an abstraction that is possibly equivalent to the relation between other pairs or sets of individuals and that is present either to our minds to the mind of God.18 Thus, while relations are entia rationis, they still have a foundation in things insofar as they are reducible to qualities or attributes of individual substances.

5. the reality of relations Insofar as composite substances by definition depend upon the relations among the members of the composite, it should be clear that Leibniz’s account of relations will play an important role in any account of composite substance. And, insofar as Leibniz can guarantee the reality of relations, it would seem that he is taking steps toward guaranteeing the reality of composite substance. Indeed, what makes the Leibniz–Des Bosses correspondence so interesting and important is, to my mind, the way in which Leibniz can be seen wrestling with his accounts of (i) relations in general, (ii) the particular relation of dominant and subordinate monads, and (iii) the dependent notion of the unity and reality of composite substances. One should not simply be concerned with the way in which

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two simple substances can stand in a relation of domination and subordination within a composite substance, one should also consider the relations that exist between simple substances and composite substances. In other words, if composite substances are to be real, then Leibniz needs to give an analysis of such claims as “x belongs to C ” or “x is a member of C ” or, again, “C arises from x, y, z” (for simple substances x, y, z and composite C ).19 Just as the discussion of the nature and possibility of composite substances was tainted by Leibniz’s attempts to cast his metaphysics in the terms of Scholastic philosophy, there are also Aristotelian and Scholastic influences on the treatment of relations that can be seen throughout the correspondence.20 And just as Des Bosses, in his second letter, of February 12, 1706, set the tone for much of the correspondence concerning the nature of substance, he similarly sets the tone in this letter concerning the nature of relations. Referring to Leibniz’s dispute with Tournemine over the union of mind and body, he says the following: In any case, however obscure that union is, I am certain of this: it cannot consist in a relational mode; for relations, like other accidents, already presuppose a fixed substance. And it is for this reason that Aristotle denies that the parts of a substance are related, either to the whole or to each other, prior to the work of the mind. Indeed, since a relation is some order of one thing to another, what could this real order be when strictly speaking the thing is one? It must not be concluded, therefore, that there is a real relation between the soul and the body, but only a relation in a manner of speaking, as they say, which arises in the first place through a mental abstraction of the body and the mind from each other. Thus, it seems to me that it should be said that whatever constitutes the individual substance besides the soul and the body is the absolute existence itself of the whole concrete substance, which Aristotle and St. Thomas both hold is distinct from matter and form (which are, in fact, the essence of substance). (GP II, 299)

Several issues are here put on the table. What is the nature of the relation between mind and body? What is the relation between the constituents of a substance? What is the relation between any constituent and its whole? While Des Bosses speaks only of mind and body and matter and form, Leibniz will, of course, have to translate these issues into his monadological metaphysics. There is another issue here as well: In what sense can these relations be real? The issue of the nature of relations, nevertheless, remains under the surface of much of the correspondence, only to reemerge in Leibniz’s important February 1712 letter to Des Bosses. Here Leibniz makes an appeal to the notion of God’s knowledge by vision, or scientia visionis,

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but does so to make a point about, among other things, the status of relations.21 He says, “If bodies are phenomena, and are judged by our appearances, they will not be real, since they will appear differently to others. Thus, the reality of bodies, of space, motion and time seems to consist in this: that they are the phenomena of God, i.e., the object of scientia visionis” (GP II, 438/AG 199). Leibniz quite consciously lumps bodies (and, I believe, composite substances) in with such paradigmatic relations as motion, space, and time because he wishes to claim that the relations that obtain between monads are reified in much the same manner as the relations of space, time, and motion. On Leibniz’s view, relations can have reality insofar as they are objects of divine knowledge. And, thus, whereas before we had the case where relations were, first, reducible to features of the relata and, second, beings of reason (that is, beings of reason for our finite minds), we have here another sense in which relations will be in the mind of God. The reason that scientia visionis is important is that it seems to be a method by which Leibniz argues the relations between monads can be reified, and the reification of the relations between monads will serve to guarantee the reality of composite substances.22 But Leibniz also appeals to the vinculum substantiale as a guarantor of the relations within a composite.23 In the same letter he goes on to say the following: Moreover, God regards not only single monads and the modifications of every possible monad, but also their relations; and the reality of relations and truths consists in this. First among these relations are duration (or the order of successives), situation (or the order of coexistence), and intercourse (or reciprocal activity), namely, when the dependence of monads on each other is naturally conceived to be ideal; but immediate situation is presence. Besides presence and intercourse, a connection is added when monads are influenced with respect to one another. And through these, things seem to be made one for us and truths can in fact be expressed concerning the whole which are also valid according to God. However, besides these real relations, one more perfect can be conceived through which a single new substance can arise from many substances. And this will not be a simple result, i.e., it will not consist solely in true or real relations; some new substantiality or a substantial bond [vinculum substantiale] also will be added. And this will not only be an effect of the divine intellect, but also of the will. (GP II, 438/AG 199)

In other words, according to Leibniz, a substantial bond can be added to a collection of monads so that they can together constitute a single substance. Presumably, then, the relations of domination and subordination and, more importantly, the relations of membership within a distinct

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composite substance are somehow reified. Still, this passage raises a number of questions: What does it mean to appeal to a “more perfect” relation, made possible by the presence of the vinculum substantiale? Why does Leibniz seem to be concerned here with the status of intermonadic relations? And what does Leibniz mean when he speaks of “real relations,” given his apparent denial of the reality of relations? Here, we need to turn very briefly to the Aristotelian and Scholastic views that form the backdrop to this discussion. In his Metaphysics, Aristotle claims that there are three kinds of relations between things: numerical, causal, or psychological (see Metaphysics V 15, 1020b26–1021b11). An example of the first, for Aristotle, is the relation of the double to the half; of the second, the relation between the active and the passive; of the third, the relation of knower to known. Aquinas expands on this view by suggesting that the first two classes of relation are mutual, while the third is not. Moreover, in the Scholastic tradition, a relation is said to be “real” when its existence depends upon some extra-mental basis in the relata (see Henninger 1989: 7). Now, it might seem that, if this were the entire story, then all relations would be, for Leibniz, “real relations.” But Leibniz makes a strong distinction between garden variety relations like “paternity” and “real relations,” and he is able to do so because of a second aspect of the Thomistic characterization of real relations: A real relation consists in an order of one thing to another.24 And this view was part of Des Bosses’s argument concerning the relation between mind and body within a substance in his letter from February 1706 (GP II, 299 – quoted earlier in this section). Leibniz’s comments here again make manifest not only a certain tension between his monadology and traditional philosophy but also difficulties within his own system. On the one hand, given the brief account of Aristotelian and Thomistic conceptions of relations, it should not be surprising to see Leibniz, in the passage quoted in the previous paragraph, place space and time under the rubric of “real relation.” On the other hand, consider the relation of domination and subordination within a composite substance. Since Leibniz denies any real causal interaction between substances, this relation would seem to be much more like Aristotle’s example of the relation between knower and known. But, according to Aquinas at least, if we examine the relation of knower to known, we notice that there is a genuine basis of the relation in the knower, while there is no such basis in the thing known; and, as such, this cannot be an example of a real relation. It is odd, then, that Leibniz should claim that reciprocal activity is also a real relation, especially since

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such reciprocal activity within a composite substance is to be the ground for the unity of that substance. Leibniz speaks in his February 1712 letter of a “more perfect” relation, but I believe it is not until later that we can begin to see what Leibniz has in mind. In his last letter to Des Bosses, he writes the following: I think that unless there are corporeal substances, bodies collapse into phenomena. And aggregates themselves are nothing but phenomena, since besides the ingredient monads, the rest is added through perception alone, by the fact that they are perceived simultaneously. Moreover, if monads alone were substances, one of two things would be necessary: either bodies would be mere phenomena or a continuum would arise from points, which we agree is absurd. Real continuity can arise only from a substantial bond. If there existed nothing substantial in addition to monads, or if composites were mere phenomena, then extension itself would be nothing but a phenomenon resulting from coordinated simultaneous appearances; and as a result of this, all controversies concerning the composition of the continuum would cease. Now, what is added to monads in order that phenomena may be realized is not a modification of monads, since it changes nothing in their perceptions. For the orderings or relations which connect two monads are not in another monad, but in both equally and at the same time; i.e., really in neither, but in the mind alone; you will not understand this relation unless you add a real bond, or something substantial, which may be the subject of the union or connection of predicates and modifications. For I do not think you would settle for an accident that is simultaneously in two subjects, and has, so to speak, one foot in one and the other in the other. (GP II, 517/AG 203)

We can perhaps hear echoes in this passage of Leibniz’s earlier claim that relations will contain something in one relata, something in the other relata, and something mental or ideal existing in neither. But, of course, the striking feature of the discussion at this point is Leibniz’s claim that one cannot understand the relation that connects two monads unless one adds a substantial bond. In fact, the substantial bond apparently represents far more than a mental or ideal thing existing between the relata; according to Leibniz, it is that which reifies the relations that exist between monads in a composite substance. Presumably, insofar as intermonadic relations are reified in a composite substance by the vinculum substantiale, they constitute “more perfect” relations than the merely ideal relations we see in the rest of Leibniz’s writings. While Leibniz is nowhere clear about how this is to take place, I think we can construct the following outlines of a theory. On the one hand, the active forces of a composite seem to be able to be unified by the relation of domination and subordination, at least insofar as we can

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attribute all the tendencies to go from perception to perception within a composite substance to one dominant monad. On the other hand, as I suggested at the close of section 3, there seems to be only a very weak sense in which primitive passive forces can be said to be actually unified. Now, adopting a Leibnizian rhetorical strategy, I think we can say that if there are to be genuine composite substances, that is, per se unities each consisting of a set of monads, and if we are to conceive of them as having a single passive force, then we have to posit the existence of a single substratum for that passive force. In other words, Leibniz invokes the vinculum substantiale to serve as the seat of all passive forces of a composite substance. It acts as a real bond between the monads of a composite, by ensuring that the relations between them are more than merely ideal, that is, by providing a substratum for the forces and by ensuring that there is unity underlying the phenomenon of matter in a composite. Leibniz was, I think, genuinely worried about the possibility that a composite substance unified solely by the ideal relations of domination and subordination would lack the unity necessary for it to constitute a per se unity. The substantial bond exists to yoke these monads together, and by doing so harness the forces of the composite. If it is the case that the forces are harnessed and together constitute one force, this singular force is a real unity; it will be more than the ideal unity expressed by my attribution of the many passive forces to one thing, in the way I might do to any body, or being by aggregation.25

6. conclusion: the possibility of composite substance In this chapter I have focused on two of the more interesting features of Leibniz’s correspondence with Des Bosses: the unity and reality of composite substance and Leibniz’s theory of relations. The treatment of these issues not only shows Leibniz’s continuing attempt to reconcile traditional philosophy with his modern philosophy, but it also brings to light a deep problem, namely, the very possibility of composite substance within the Leibnizian monadology. It should be clear that if Leibniz believes that monads are the building blocks of the universe, consisting of active and passive forces on the model of substantial form and primary matter, and that genuine composite substances are possible, then he faces a real difficulty in explaining the unification of at least the passive forces into primary matter.

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This difficulty is addressed, and the two issues are tied together by Leibniz’s account of the nature of the vinculum substantiale. For, in his correspondence with Des Bosses, Leibniz appeals to the vinculum to show that a composite substance has unified active and passive forces. Nevertheless, this “solution” to the problem of the unity of composite substance is not without its own difficulties. If the vinculum substantiale is indeed some extra substance-like thing, then Leibniz has violated his principle that there is nothing in things but monads, and in them perception and appetition (see GP II 270/AG 181).26 Moreover, if the vinculum substantiale is posited as a substance-like thing that really acts to unify the monads in a composite, then we seem to have a substance that can exercise real causal powers on other substances – something that Leibniz is keen to reject in his writings. If, on the other hand, the vinculum substantiale is the relation that exists between the monads in a composite substance, then Leibniz has, in reifying this relation, violated his nominalism in general and his theory of relations in particular. In the end, study of the Leibniz–Des Bosses correspondence leads to the inescapable conclusion that Leibniz, despite the sanguine claims in his best-known works, cannot give us a consistent and convincing account of the unity and reality of composite substance.

Notes 1. Several scholars have, indeed, emphasized this correspondence in different works – see, for example, Mathieu 1960; Fr´emont 1981; and Robinet 1986. 2. This view is shared by Robert M. Adams – see 1994: 302–3. 3. For all works other than the Leibniz–Des Bosses correspondence, I have relied upon and cited standard translations. The translations from the Leibniz–Des Bosses correspondence are my own; nevertheless, whenever possible I have included a reference to a standard translation. 4. In the correspondences with Arnauld, De Volder, and Des Bosses alone, this metaphor appears some fifteen times – see, for example, GP II, 58; 71; 97; 262; 276; 306; 398; and 517. 5. This view leads to what Adams will call the “one-substance” conception of substance (1994: 267ff.). 6. While Leibniz often suggests that the self (or “I”) is a monad, it certainly must be permissible to say that I, qua organism, have many monads that belong to, or are part of, me. 7. Leibniz’s remarks are translated at AG 196–7. 8. The parts of this passage that fascinate me are, in Latin, “dicendum erit [ . . . ] ex unione quidem potentiae passivae monadum oriri materiam primam, [ . . . ] ex unione autem Entelechiarum monadicarum oriri formam substantialem.”

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9. In a draft of a letter from 1709, which was not sent to Des Bosses, however, Leibniz first gives expression to the idea of the vinculum substantiale, and he does so in such a way that it cannot be maintained that the vinculum substantiale was created to explain transubstantiation. Leibniz says, “The union that I find some difficulty explaining is that which joins the different simple substances or monads existing in our body with us, so that it makes one thing from them; nor is it sufficiently clear how, in addition to the existence of individual monads, there may arise a new existing thing, unless they are joined by a continuous bond [continui vinculo], which the phenomena display to us” (LBr 95, Bl. 11; quoted at Rutherford 1995: 277). 10. This is a passage that Adams, for example, stresses in ascribing a strong kind of idealism to Leibniz – see Adams, R. M. 1994: 5; 217–18; and 260–1. Of course, this statement by itself in no way precludes monads from being conceived as simple substances completed by primitive active and passive powers. 11. I reject Adams’s claim that this table should not be taken seriously because it is only proposed under the assumption of the vinculum substantiale. Adams is too quick to dismiss the possibility that composite substances are characterized by primitive active and passive powers – see Adams, R. M. 1994: 325 n. 47. 12. Compare Leibniz’s five-fold scheme (GP II, 252/AG 177 – quoted above in section 1), and Monadology §18: “One can call all simple substances or created monads entelechies, for they have in themselves a certain perfection; they have a sufficiency that makes them the sources of their internal actions, and, so to speak, incorporeal automata” (GP VI, 609–10/AG 215). 13. I treat this issue in more detail in Look 2002. 14. The cynical reading is typified by Bertrand Russell (1937: 152 – quoted in the introduction to this chapter). 15. Leibniz does see the contradiction, for in this passage he says not only that “from the union of monadic entelechies, there arises a substantial form” but also that “such a form then will not be a soul” (GP II, 435/AG 198). Nevertheless, this admission in itself reveals the instability in Leibniz’s metaphysics when appealing to two separate systems – the monadology and Scholastic philosophy – for theoretical grounding. 16. The importance of the Leibniz’s account of relations is suggested by the title of Christiane Fr´emont’s edition of the Leibniz–Des Bosses correspondence, L’ˆetre et la relation (1981). The issue of relations is there singled out, however, because Fr´emont holds the vinculum substantiale to be itself a relation between monads. I have argued against this view in Look 1999: 100–9. 17. The literature on this subject is extensive. What follows in my discussion is not entirely uncontroversial; however, a substantive defense of my view is beyond the scope of this chapter. I believe that my general characterization of Leibniz’s theory of relations is not so tendentious as to obviate the claims I will make in the next section. For more detailed analysis of this issue, see Earman 1977; Kulstad 1980; McGuire 1985; Ishiguro 1990; Sleigh 1990; Mugnai 1992; and Cover and O’Leary-Hawthorne 1999.

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18. This issue will become clearer when we get to the issue of God’s scientia visionis. 19. In his letters of February and June of 1712 Leibniz is careful to distinguish the relation between monads and material bodies, saying that monads are not ingredients of secondary matter, but rather secondary matter results from monads (see GP II, 435 and 451). It should be acceptable for our purposes, however, to claim that composite substance arises from a certain set of monads or that a particular monad belongs (as an ingredient) to a composite substance. 20. For more on Scholastic accounts of relations, see Krempel 1952; Weinberg 1965; and Henninger 1989. 21. For the traditional account of scientia visionis, see Thomas’s discussion in ST I, q. 14, art. 9. 22. This is argued in Rutherford 1994. 23. I offer this qualification of Rutherford 1994 in Look 1999: 109–16. 24. See Questio disputata de potentia q. 7, a. 10; quoted in Krempel 1952: 41. 25. This is, I believe, how Leibniz thought of the matter. Nevertheless, the language in this paragraph is perhaps so metaphorical that it still slips by one important issue: To say that the vinculum substantiale serves as the seat of a unified passive force of a composite substance is not at all to explain how the individual passive forces of the constituent monads are unified. In the end, I should like to suggest that Leibniz simply does not have the conceptual resources to explain what it would mean for primitive passive forces to be united. 26. I take it that a genuine composite substance, insofar as it is composed of the monads, would not violate this principle.

12 “[ . . . ] et je serai tousjours la mˆeme pour vous” Personal, Political, and Philosophical Dimensions of the Leibniz–Caroline Correspondence Gregory Brown

The papers that were exchanged between Leibniz and Samuel Clarke during the last year of Leibniz’s life constitute perhaps the most famous and influential of all philosophical correspondences. A neglected ancillary correspondence, from which that more noted correspondence was to emerge, had begun a year earlier between Leibniz and his erstwhile companion and student in Hanover – Caroline, the newly established Princess of Wales. As I will try to show, the correspondence with Caroline is important for understanding how and why the correspondence with Clarke arose and developed as it did, and it provides valuable insight into the personal, political, and philosophical issues that occupied Leibniz during the last two years of his life, especially the struggle against Newton and his followers that had been precipitated by the priority dispute concerning the discovery of the calculus. After briefly describing the events that set the stage for Leibniz’s correspondence with Caroline after her arrival in England, I discuss its evolution in three phases: (1) Caroline’s first year in England (December 1714–November 1715), (2) the beginning of the correspondence with Clarke (November 1715–January 1716), and (3) from Caroline’s apostasy to Leibniz’s death ( January 1716–November 1716).

1. setting the stage Leibniz in Vienna At the beginning of August 1714, Leibniz was residing in Vienna. He had been there for more than a year and a half, moonlighting at the court of 262

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Emperor Karl VI, where, with the reluctant permission of his employer, Elector Georg Ludwig of Hanover, he had recently obtained a position as imperial privy counselor. Six months prior to this, at the beginning of March, Georg Ludwig’s minister, Bernstorff, had written to Leibniz on behalf of the elector to enquire when Leibniz intended to return to Hanover (K XI, 6–7). Leibniz replied that he had been suffering from arthritis and wished to delay his departure until May, when the weather would be better and after he had had the chance to take the waters at Baden to treat his ailments (K XI, 7). His reasons for delay, however, went far beyond these concerns with his health. For Leibniz had been intent upon the establishment of a Society of Sciences in Vienna ever since the emperor had agreed to the project at the beginning of Leibniz’s stay in January 1713. Leibniz was especially keen on the project because the Society (later Academy) of Sciences that he had helped to found in Berlin in 1700 had been languishing.1 In replying to Bernstorff, however, Leibniz noted that “I have not employed the time badly, having had the luxury of being quite often at the library of the emperor and of perusing its historical manuscripts” (K XI, 7). Leibniz alludes here, of course, to his work on the history of the House of Brunswick, which he had begun many years ago while in the service of Georg Ludwig’s father, Ernst August. Georg Ludwig was becoming increasingly obsessed with the completion of this project, and Leibniz realized that his time away from Hanover had to be justified to some extent in the service of the elector. In July 1714, Bernstorff again sent word to Leibniz, enquiring about his return to Hanover. Leibniz again put him off by supplying a justification for his stay in Vienna and citing his long service to the court at Hanover (see Aiton 1985: 320).

The Death of Queen Anne and the Hanoverian Succession: Leibniz Caught Between Hanover (England) and Vienna But then there came news on August 1/12 of the death of Anne, queen in England. By the Act of Settlement of 1701 the English Parliament had made “the most excellent princess Sophia, Electress and duchess-dowager of Hanover” and “the heirs of her body being Protestant” successors to the throne in England.2 Since Sophie had preceded Anne in death by two months, her son, Georg Ludwig, was now the heir apparent. Given that, Leibniz knew he could no longer delay his departure from Vienna. He arrived back in Hanover on September 3/14, but by then the king had already departed for England with the electoral prince in tow; Leibniz

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had missed them by three days. He hurriedly sent letters of explanation and apology to a number of the king’s party, including Bernstorff and the electoral prince. The electoral princess, Caroline, however, was still in Hanover when Leibniz arrived – presumably to prepare herself and her children for the move to England. A week after his arrival in Hanover, Leibniz wrote a letter to count Bonneval (the adjutant to Prince Eug`ene of Savoy) in Vienna: I came here in order to work during this winter on some things which can free me from certain tasks3 that could delay my return to Vienna. But I am at present distracted from them here as I was at Vienna since the royal princess has wanted me to stay at Herrenhausen, where she will be until her departure for England. But I am very pleased to enjoy once more, as long as I can, the good graces of a princess so accomplished and so spiritual, who even wants to go over with me again (would you believe it?) the Theodicy, which she has read more than once. It seems to me that I intend you, sir, to accuse me of vanity, but I intend what I have just said to be praise of the princess and not of my work. For even if it be misguided, it is still a great thing that such a princess, surrounded by everything that can dissipate the spirit, gives so much attention to matters as elevated as those treated of in my work. If I were in a position to obey Her Royal Highness, I would accompany her to England. (K XI, 14–15)

Why does Leibniz suggest that he is unable to comply with Caroline’s wish that he accompany her to England?4 His letter intimates that he wanted to remain in Hanover to complete his history so that he might be free to return to Vienna. But why Vienna rather than England? On the positive side for Vienna was the unfinished business of the Society of Sciences. Clearly, Leibniz was deeply committed to the project, and although he had not sought the office, the emperor had already paid him the honor of issuing an official document, in August 1713, naming him president of the Society once it was established. Furthermore, as already noted, only five months before this, with the support of the grandfather of the empress, Anton Ulrich, the duke of Brunswick-Wolfenb¨uttel, Leibniz had been made imperial privy counselor, to which office the emperor had attached for Leibniz the special right of audience that was generally reserved only for the imperial ministers.5 Such a position was certainly more prestigious than any he had been accorded in his long years of service at Hanover and arguably more prestigious than any he might reasonably hope for in England. Leibniz obviously had many powerful friends in Vienna – not only the empress but also the Empress-dowager Amalie, the daughter of Leibniz’s first master in Hanover, Duke Johann Friedrich, as well as her lady-in-waiting, the redoubtable Fr¨aulein Klenck.6

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There was as much, and more, on the negative side against England. Georg Ludwig seemed to have little interest in anything Leibniz was doing that did not touch on the history of the House of Brunswick; and now he was especially roused against Leibniz because of the latter’s long absence in Vienna.7 Then, too, even if Georg Ludwig should have wanted to appoint Leibniz to a position in England, Leibniz knew that the Act of Settlement had expressly forbidden the heir to the throne following William III from granting offices to the foreign born or offering them English rewards (see Hatton 1978: 77). Leibniz could only hope to retain his office as privy counselor to Georg Ludwig in his role as elector of Hanover. But it might be thought that England held out the promise of at least one thing that Leibniz could not resist, namely, the chance to act on a big stage with the great figures of science and philosophy and to participate directly in the activities of the Royal Society of London, of which he had been a member since 1673. By any standard, Hanover was in comparison with London an intellectual backwater.8 But then again, Hanover was not Vienna, nor was Vienna Hanover; and now that Leibniz had established himself in Vienna and had the prospect of creating and governing an imperial Society of Sciences that could draw upon talent from across the German empire and Europe at large, the threat of intellectual isolation was no longer so pressing. What is more important is that any hopes he might have had to find intellectual camaraderie in England had long since fallen victim to the priority dispute that had arisen between himself and Newton concerning the discovery of the calculus – and therein, perhaps, lies the primary source of such antipathy as Leibniz may have felt toward England.

The Dispute with the Newtonians On February 27/March 10, 1714, John Chamberlayne – one of only a very few Englishmen and members of the Royal Society still friendly toward Leibniz – stepped into the increasingly bitter war of words between the Newtonians and Leibnizians over the discovery of the calculus and sought peace. In a letter to Leibniz of that date, he wrote: I have been inform’d of the Differences Fatal to Learning between two of the greatest Philosophers & Mathematicians of Europe, I need not say I mean Sr. Isaac Newton and Mr. Leibnitz, one the Glory of Germany the other of Great Britain [ . . . ]. [I]t would be very Glorious to me, as well as Advantageous to the common Wealth of Learning, if I could bring such an Affair to a happy end, I humbly offer my Poor Mediation. (TSHT VI, 71)

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Leibniz responded to Chamberlayne on April 17/28 (see TSHT VI, 103–4) and protested the findings of the Commercium epistolicum. This was the notorious report of the Royal Society – written by the Society’s then president Isaac Newton himself and rubber-stamped by a select committee of his supporters – that upheld John Keill’s charge that Leibniz had stolen the calculus from Newton.9 Chamberlayne showed Leibniz’s letter to Newton in the hopes of initiating a private reconciliation, but Newton had other plans and intended to place Leibniz’s letter before the Royal Society.10 And so on May 20/31 Chamberlayne wrote to Newton and reminded him of some impending political realities: I am very sorry I can’t wait on you this Afternoon when you are to consider of the Letter from Mr Leibnitz to me, concerning you, which Letter I did not intend to have expos’d to anybody’s view, but your own, because I am not sure it wil be agreable to the writer, but since you have desired it, & to shew my Respect to you [ . . . ] I am content you should make what use you please thereof, only submitting it as a matter of Prudence how far you, in your private Capacity, may think it is adviseable to keep some Measures with a Gentleman that is in the Highest Esteem at the Court of Hanover. (TSHT VI, 140)

Chamberlayne’s admirable attempt to reconcile Leibniz and Newton – including the political warning he sounded here scarcely two and a half months before the death of Queen Anne and the succession of the House of Hanover – would prove to be of no avail. When he finally responded to Leibniz on June 30/July 11, Chamberlayne reported that “our Society has been prevail’d upon to vote that what you writ was insufficient & that it was not fit for them to concern themselves any further in that Affair &c, as will more fully appear by the Resolution enter’d into their Books of which I shal shortly send you a copy” (TSHT VI, 152–3). Leibniz replied on August 14/25, already nearly two weeks after the death of Queen Anne, threatening to retaliate by publishing his own Commercium epistolicum concerning the calculus affair (see TSHT VI, 173). So even as the wheels of the succession began to turn, Leibniz recognized that it was a foul wind indeed that was blowing his way from England. But it is worth remarking that at the time the Court of Hanover apparently knew little or nothing of the dark and dreary affair that had engulfed Leibniz, Newton, and their respective allies. The court, including Caroline, was still none the wiser when Caroline left Leibniz behind in Hanover and departed for England on October 1/12. All of that, of course, would soon change. But Chamberlayne seemed certain about where the future political advantage would lie when the facts became known, as they inevitably would; and Leibniz also seems to have thought that such advantage as there might

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be could eventually be turned to his account. In retrospect, it can be seen that thus far each man mistook much; but given the circumstances at the time, even Leibniz must have realized that setting sail under Caroline’s banner to storm Newton’s bulwarks on the shores of England would have been a hazardous and unpleasant maneuver, as much for Caroline as for himself. And so, I think, he thought better of it and chose to stay behind in Hanover, where he could discreetly cultivate his garden in Vienna.

2. the correspondence. phase one: the princess goes to london Leibniz Requests an Appointment as Historiographer of Great Britain It will be useful for expository purposes to divide the correspondence that transpired between Leibniz and Caroline after her departure for England into three distinct phases. In the first of these I place the letters roughly covering Caroline’s first year in England – up to her letter to Leibniz of November 3/14, 1715 – which takes us to the beginning of the controversy with Clarke. Leibniz initiated the exchange with an undated letter to Caroline that was probably composed at the beginning of December 1714. He began by telling her that “the departure of Your Royal Highness has certainly caused me much grief and has made Hanover unbearable for me at first sight, and in order to recover myself, I have been obliged to travel to Saxony” (K XI, 19). He then informed her that Count Bonneval had written from Vienna to say “that prince Eug`ene [of Savoy] asks why, not having gone to England I do not return to Vienna, where it is maintained that I ought not be badly off” (K XI, 19–20). His intention, however, as he told Caroline, was to spend the winter working on his history of the House of Brunswick, and this led him to propose that the king make him an historiographer of Great Britain, concerning which, he said, he had written to Minister Bernstorff (K XI, 20). When he wrote to Minister Bernstorff on November 27/December 8 he had already received the latter’s letter advising him to stay in Hanover and work on his history (see K XI, 22). In response Leibniz explained that he intended to complete one volume of his history that winter, and he gave a sketch of the material that it would cover. When he then stated his proposal for the position of historiographer, he argued specifically, even if somewhat speciously, that “the act of Parliament [i.e., the Act of Settlement], which

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appears to deny offices to foreigners, concerns only offices that require naturalization” (K XI, 21). Onno Klopp has cited these two letters to Caroline and Bernstorff, requesting the position of historiographer of Great Britain, in support of his claim that Leibniz was vacillating between Hanover (that is to say, England) and Vienna (K XI, xxiii). However, there is no indication in these letters, nor in any of the other letters that Leibniz wrote to Caroline, that Leibniz actually wanted to go England. Indeed, even when Caroline expressly stated her wish that Leibniz should come to England, as she would do on more than one occasion in her later letters, Leibniz simply ignored the suggestion or put it off. This is not to say, of course, that he did not want the position of historiographer. For I think it is likely that Leibniz thought he could moonlight as an historiographer of Great Britain even while operating out of Vienna as an imperial privy counselor and president of the proposed imperial Society of Sciences. After all, he had already been working both sides of the Hanover–Vienna street for some time, and there was no reason why he should not have wanted to exploit any third lane that might open up and permit him access to an additional pension from Great Britain. But as we shall see, beyond the promise of another pension there was an even more important goal that Leibniz seems to have had in mind when he made his proposal – one having quite specifically to do with his quarrel with Newton.

Leibniz’s Suspicions and the Increasingly Bitter Dispute with the Newtonians Caroline responded to Leibniz on January 5/16, 1715, explaining that “I am sending the letter Mr. Bernstorff has given me to respond to you, and this is the reason that I have not responded sooner to your two letters”; she added that “I believe, sir, that if you will take the trouble to apply yourself to the history of the family, all that you wish can be yours” (K XI, 32). To judge from Leibniz’s reply two weeks later, his foray into political commentary in his previous letters (see K XI, 20–1 and 25) seems to have been the subject of the letter from Bernstorff that Caroline included with her own, and his reply to this very first letter received from Caroline in England was darkly suspicious. “It appears,” he wrote, that Your Royal Highness has chosen to take pleasure in honoring me with a letter in which everything was mysterious and somewhat strange, and it seems that She has chosen to present me with an enigma for exercising the mind [ . . . ]. The

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response of others placed inside instead of that of Your Royal Highness prevents me from distinguishing her sentiments, which are laws for me, from those of others. I do not understand to what purpose the inserted response speaks to me about Whigs and Tories in a manner of reproach; for I do not believe that I have given reason to think that I have criticized what is done [ . . . ]. They will also have me remain in perfect uncertainly about what I had desired. It depends on Your Royal Highness to leave me in these doubts or to extract me from them in part. (K XI, 32–3)

The very same day, and more pointedly still, he wrote to the Countess B¨uckeburg, one of Caroline’s Hanoverian attendants: I hope that Her Royal Highness will not have abandoned us entirely in favor of the English, nor will have chosen to diminish her kindnesses to us through division, as the sun does not shine less on each in order to shine on several. Your Excellency who belongs to us will take care of us in this regard, and I hope that you, Madame, will choose to protect me in particular against the harmful effects of the absence that I have only too much reason to fear. (K XI, 33)

Caroline was nonplussed at Leibniz’s suspicions, and in her next letter she sought to reassure him: I do not know of what enigma you mean to speak, sir, in the letter that you have written to me. I have sent you the letter that Mr. Bernstorff gave me to send to you. I added to it with my own hand, as you apparently did not notice, that I was nearly certain that if you applied yourself this winter to the history of the family that the king holds dear, I would expect that what you hope for can then be obtained from the king. It seems to me that this is sufficient by itself. I would hope to be able to contribute to it, believing that I do my duty when I am able to do something for the establishment of a man of your merit. (K XI, 34–5)

Bernstorff wrote to Leibniz a month later with the same message: no chance for the position of historiographer until the king sees progress on the history of the House of Hanover. Then, sometime at the beginning of May, Leibniz received a letter from Henrietta Charlotte von P¨ollnitz11 with news from Caroline: I just received a letter from Her Royal Highness, the Princess of Wales. She writes me these words: “I am reading the books of Locke. Those on the understanding appear good to me, but completely ignorant as I am, I should think that there would be some response to them, and I believe that Mr. Leibniz will be of my view. I bid you to tell him that I will not respond to him until the king grants me the office he desires. (K XI, 37)

When Leibniz wrote to Caroline on April 29/May 10, he had some reason to be upset and concerned. For his dispute with the Newtonians had been growing ever more bitter. In the Journal Literaire of The Hague in

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the summer of 1714, John Keill had published a nasty reply to Leibniz, accusing him of, among other things, incompetence in the handling of second-order derivatives in one of his published treatises.12 Keill’s “answer” had been communicated to Leibniz by Christian Wolff in a letter of September 22/October 3, and Wolff had urged Leibniz to make some reply (LW 160/TSHT VI, 179–80). Wolff wrote to Leibniz again in February 1715, urging him once more to reply to Keill. When Leibniz finally replied in a letter of March 22/April 2, 1715, he declared that “I cannot bring myself to make a reply to that crude man Keill” (LW 162/TSHT VI, 211). A month later Wolff was still pressing Leibniz for a reply to Keill (see LW 164–5/TSHT VI, 216–17), and on May 7/18 Leibniz responded with a harshness of language that only Keill seems ever to have been able to provoke in him: “Since Keill writes like a bumpkin, I wish to have no dealings with a man of that sort. [ . . . ] I think of knocking the man down, some time, with things rather than words” (LW 168/TSHT VI, 222–3). Just eight days before this Leibniz had written to Caroline to acknowledge the message she had sent him through Fr¨aulein von P¨ollnitz; but perhaps as a result of the latest provocation from Keill, he had then steered directly to the business of informing Caroline, apparently for the first time, of his dispute with Newton. With Caroline now behind enemy lines in England, Leibniz apparently felt it was not prudent to keep his peace any longer: What Your Royal Highness communicated to me through Mademoiselle P¨ollnitz can be considered a very remarkable favor or a very great threat. It is only on the condition that she obtain from the king the office that I request that she gives me hope of being able to see again one day her precious hand-writing addressed to me. [ . . . ] It is true that what makes me aspire to it is in good part a point of honor. I would not want to concede any of it to a certain antagonist that the English have placed in front of me. Your Royal Highness will perhaps know that the Chevalier Newton has a pension from the king, because he has superintendence of the mint, which the king has entrusted to him. (K XI, 37–8)13

Leibniz went on to point out that a French journalist had written that the dispute had taken on the flavor of an international confrontation between England and Germany, and Leibniz suggested that the attack on him was primarily due to “certain rigid gentleman, not very favorable to the party of Hanover, many from Cambridge (whence Mr. Newton arrived in London) and Oxford, where his supporters are found” (K XI, 38). This was obviously an attempt, certainly unfair, to associate Newton with anti-Hanoverian factions within England and to place the dispute

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in terms that might appeal to Caroline’s sense of national pride. “I dare say,” Leibniz wrote, “that if the king were at least to make me the equal of Mr. Newton in all things and in all respects, then in these circumstances it would give honor to Hanover and to Germany in my name. And the title of historian with which I aspire to be distinguished furnishes a fine occasion for it” (K XI, 38). He told Caroline that he had not had time to respond to the Newtonians, saying that he “prefer[s] to satisfy the king by publishing my annals” and adding that “His Majesty will better be able to refute them than I by treating me as the equal of Chevalier Newton, which will assuredly sting these gentlemen who have little love for Hanover.” Newton “is my rival,” he declared, “and that is all there is to say” (K XI, 39). But Leibniz could not have adopted a more unpromising strategy. The last thing the Hanoverians could afford to do at the beginning of their reign was to present the appearance of split loyalties between England and Hanover. Caroline herself could scarcely have been expected to sympathize with Leibniz’s motivations. She had gone to England – never to return to Germany – determined one day to become England’s queen. There is no doubt she wanted Leibniz to obtain the office he desired, and it is clear that she worked hard to obtain it for him. But she could not have desired it for him on his own terms – as a reproach to Newton, the greatest light of the realm that was now her own. For such terms were politically impossible. Thus, even as she worked for Leibniz’s promotion, she strove with increasing fervor to reconcile him with Newton.

Cultivating the Garden in Vienna Caroline did hold her peace for more than four months, but when she finally broke silence in a letter of September 2/13, 1715 she had bad news concerning the position Leibniz sought. “The king,” she wrote, “gave me this response: ‘He must first show me that he can write history; I hear that he is diligent’” (K XI, 46). But as the king was planning to return to Hanover the following summer, Caroline expressed her belief that the matter would then be resolved in Leibniz’s favor. In the meantime, Leibniz had not neglected Vienna. On June 17/28 he had written a long letter to the Empress-dowager Amalie describing in detail his plans for the imperial Society of Sciences and suggesting a scheme for its funding. But he also described his historical work and its importance for establishing the rights of the empire. Significantly, he now referred to the work not simply as a history of the House of Brunswick but as “the annals of the empire and of Brunswick” (K XI, 41), and he told the empress-dowager

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that “as I hope with the aid of God to see to it that this work is put in a publishable state this year, I am ready to return to Vienna the following year” (K XI, 42). Of interest in connection with this is an undated draft of a letter, intended for Caroline, that Leibniz appears to have written sometime in the second half of September or the first half of October 1715. It is marked by Leibniz as unsent, but in it he wrote that “the king was advised that I would go to Vienna soon, and thereupon the council ordered me in a forbidding way [to do] what I should have done quite well without its order.” He was dismayed that the king might believe he would behave in such a dishonorable way. “It is true,” he conceded, that I would not be badly received in Vienna, and perhaps someone who understood that has conjectured that I would hasten there as soon as possible. But I prefer my duty even to my interests, and I desire that the king and the public be satisfied above all. If this false report should serve as a pretext for delaying longer the payment of my arrearages,14 I would not know what to say. Is it supposed that I would run away after receiving them? Is it possible to suspect me of such base actions? I believe that the king is incapable of attributing these things to me. (K XI, 47–8)

While there is, thus, little reason to doubt that Leibniz intended to do his “duty” and complete what he had promised to write on the history during the winter, there is also little reason to doubt that he intended thereupon to return to Vienna, where, he suggested, his “interests” lay.

3. the correspondence. phase two: the beginning of the dispute with clarke Plans for an English Translation of the Theodicy and Leibniz’s Indictment of English Philosophy Although Leibniz did not send the letter protesting the suspicions about his designs on Vienna, he apparently did send one, now lost, in which he worried openly that Caroline had forgotten him. For in her letter of November 3/14, 1715, Caroline began by asking, “How do you come to believe, sir, that I am able to forget a man such as you?” “The whole world,” she said, “would remind me of you” (K XI, 49). Later she mentioned that she had talked with the Bishop of Lincoln (William Wake) about translating the Theodicy into English. The possibility of such a translation had already been broached in a letter Leibniz had written to Caroline some six months before. Just how the matter first came up is unclear, but Leibniz had written that “it does not appear that my book is considered obscure in France, or more obscure than the books of Father Malebranche and

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others, which are well enough in fashion” (K XI, 35). In a postscript he recommended Mr. de la Roche as a suitable translator,15 although, he said, “I would rather have an Anglican theologian undertake its translation” (K XI, 36). Caroline now reported, however, that the Bishop of Lincoln “assures me that there is no one capable of it except Dr. Clarke, whose books I have sent you” (K XI, 50), adding ominously that “this man is an intimate of Chevalier Newton, and I do not believe the matter is in very good hands” (K XI, 50). This suggests that in the lost letter to which Caroline was responding here, Leibniz had somehow linked the translation of the Theodicy to his dispute with the Newtonians. Indeed, in his previous letter of April 29/May 10, in which he first broached the issue of the calculus dispute, Leibniz had quickly turned the discussion to philosophy, saying that the “new philosophy of M. Newton is a bit extraordinary”: He claims that a body attracts another, at whatever distance it may be, and that a grain of sand on earth exercises an attractive force as far as the sun, without any medium or means. After that how will these gentlemen attempt to deny that, by the omnipotence of God, we can share in the body and blood of Jesus Christ without any hindrance of distance? – This is good way to embarrass them, who, by a disposition contrary to the House of Hanover, now give themselves license more than ever to speak badly of our religion, as if our Eucharistic reality was absurd. (K XI, 38–9)

Leibniz never did raise the issue of the Eucharist in his discussions with Clarke,16 but the passage in Leibniz’s letter of April 29/May 10 comparing the Lutheran doctrine of the Eucharist and the Newtonian doctrine of gravitation clearly alluded to – and was undoubtedly intended to remind Caroline of – the similar discussion in §19 of the Preliminary Dissertation of the Theodicy (GP VI, 61–2/Th 85–6). At any rate, Leibniz seems to have decided early on that the best way to make his case to Caroline against the Newtonians was to turn the issue to philosophy – to natural religion, in particular – and away from mathematics – something that he had already done to some extent in his published writings and to an even larger extent in his private papers and correspondence.17 And, thus, either in the lost letter to which Caroline responded on November 3/14, or, more likely, in another letter, also lost, that he sent shortly thereafter, Leibniz laid the philosophical lumber to England’s backside: “Natural Religion itself,” he observed, “seems to decay (in England) very much” (K XI, 54). Leibniz’s well-known indictment of the English philosophers involved three particulars: First, many suppose the soul to be material; second, Newton in particular holds that space is God’s sense organ; third, and most importantly for Caroline, the Newtonians suppose that God made

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an imperfect world that requires miraculous fixing from time to time and, thus, implies that God himself is imperfect.

Caroline’s Allegiance to Leibniz and Her Dispute with Clarke Caroline’s response in her letter of November 15/26 was everything that Leibniz could have hoped for. After pronouncing herself absolutely satisfied with Leibniz’s case for the payment of his arrearages and telling him that the king also seemed satisfied, she announced that “we are thinking seriously about having your Theodicy translated, but we are searching for a good translator” (K XI, 52). But now, after having spoken with Clarke and having shown him Leibniz’s indictment against English philosophy, she firmly declared that “he is too much of the opinion of Sir Isaac Newton, and I am myself engaged in a dispute with him” (ibid.). Clarke, she said, gilds the pill and does not want entirely to admit that M. Newton has the views that you attribute to him. But in fact you will see from his papers enclosed with this that it comes to the same thing. I can only ever believe what is proper to the perfection of God. I find this much more perfect in your views than in those of Mr. Newton. For in effect, [on his view] God must always be present in order to repair the machine, because he could not do it at the beginning. Neither Dr. Clarke nor Newton are willing to say that they are followers of Mr. Locke, but I cannot be, nor want to be, one of theirs. (K XI, 53)

There seems little room for doubt that when he formulated his indictment against English philosophy in his lost letter to Caroline, Leibniz had consciously invoked the authority of his Theodicy, a book that he well knew was close to Caroline’s heart. When he later informed Johann Bernoulli of his ongoing dispute with Clarke on May 27/June 7, 1716, he somewhat disingenuously suggested that “I had casually [forte] written to Her Royal Highness the Princess of Wales who on account of her fine intellect is not uninterested in these matters, that philosophy, or rather natural theology, declines somewhat in England” (GM III, 963/TSHT VI, 354, my emphasis). But the attack on the English philosophers seems to have been anything but “casual.” Earlier, on December 12/23, 1715, and thus not long after he had sent his reply to Clarke’s first paper, Leibniz had written to Christian Wolff, saying that the Newtonians have also attacked my philosophical principles the better to persuade me to answer them. But here too they bite off more than they can chew. Her Highness the Princess of Wales, who read my Theodicy with an attentive mind and was delighted with it, not long ago disputed in its favor with a certain Englishman in Holy Orders [i.e., Clarke], having access to the Court, as she herself informed

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me. She rejects what Newton and his [followers] maintain, that God repeatedly has need to correct and revivify his machine. (LW 180–1/TSHT VI, 258)

Of course it was Leibniz himself who had disputed with the English philosophers in favor of the Theodicy in his lost letter to Caroline, and Caroline had merely followed his lead. But one would scarcely know this from what Leibniz told Wolff. And at the end of his letter to Wolff, Leibniz slyly declared that “it is welcome that my opponent has touched upon matters which are not to be resolved by mathematical considerations, but about which the Princess herself can easily form a judgment” (LW 181/TSHT VI, 258–9) – even though, of course, it was Leibniz himself who had steered the debate in the direction of natural theology and away from mathematics. His reasons for wanting to do so are not far to seek. It was no depreciation of Caroline that Leibniz implied that she could not fathom the details of the mathematical debate. In one of his letters to Leibniz, Minister Bothmer decried Leibniz’s calculus dispute with Newton on the grounds that “it vexes you and diverts you from occupations that you are given for his [i.e., the king’s] service, for the public welfare, and for your own glory, which certainly will be much greater and more eternal through your history than through a dispute about a matter concerning which scarcely a single person out of a thousand understands anything” (K XI, 92). Shortsighted it certainly was, but there was more than a little truth in Bothmer’s observation. If Leibniz wanted to elicit Caroline’s sympathy in his dispute with Newton, he had to frame the debate in terms she could appreciate and in terms that would appear favorable to his own position. Given Caroline’s interest in philosophy and natural religion and her devotion to the Theodicy, Leibniz’s decision was a “no-brainer.”

Leibniz’s Response to Clarke, the Abb´e Conti, and Caroline’s Continuing Loyalty In his reply to Caroline’s letter, in which he enclosed his second paper, Leibniz dismissed Clarke’s response as a writing “done as well as it can be for supporting a weak position” (K XI, 60) and then proceeded, to his later regret, to introduce the queen to a man of his acquaintance then in England: There is now a noble Venetian in England, named Abb´e Conti, who applies himself assiduously to the study of fine things. When he was in France, he declared himself to be strongly of my party, and he wrote me a nice letter in which he

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reveals, among other things, that he has marked well the beauty of the system that I established, above all concerning souls. I do not know if my antagonists from London would not have won him over a little since then. He probably has good reason to be accommodating in order to profit more from their conversation. However, I hope that Mr. Abb´e Conti will preserve some place for me. My wish would be that he might have the honor of the acquaintance of Your Royal Highness, and I have advised him to endeavor to obtain it, if he has not already done so. (K XI, 62–3)

In his absence, Leibniz knew he needed allies in England to prosecute his case, but the fact that he nominated Abb´e Conti for the position – someone he already suspected of being somewhat irregular in his affections – is an indication of the paucity of candidates. In her letter of December 30/January 10, 1715/1716, with which she enclosed Clarke’s second paper, Caroline volunteered that “I do not know if the bias I have for your merit makes me partial, but I find all his [i.e., Clarke’s] replies just words, without being able to call them replies” (K XI, 71). So far, so good for Leibniz. Caroline was still on his team and was willing to share intelligence about the enemy: “[You] are not mistaken about the author of the responses,” she confided, “they are not written without the advice of Chevalier Newton” (K XI, 71). By then the Abb´e Conti had introduced himself to Caroline, who thanked Leibniz for his acquaintance and notified him that she and the Abb´e had set themselves up as mediators between himself and Newton. But on the philosophical issue that mattered most to her, Caroline made it clear that she was not going to be a neutral observer: I was not able to prevent myself from saying to Dr. Clarke that your opinion appeared to me to be the most fitting to the perfection of God and that all philosophy which sought to alienate me from it appeared to me to be imperfect, since in my view it was done, or ought to be studied, in order to soothe us and to strengthen ourselves against ourselves, and against everything that assails us from outside. He spoke with me for a very long time in order to convert me to his opinion, and he wasted his Latin. I beseech you to respond to him. (K XI, 72)

If this were not enough to convince Leibniz that his Theodicy strategy was working, Caroline ended by noting that her friend the Bishop of Lincoln had just been elevated to the Archbishopric of Canterbury and that he had talked with her that day about “your wonderful Theodicy.” “After his installation is done,” she wrote, “we are thinking about having it translated,” and then ended on this splendid note: I am completely blessed to have the same views as this great man who finds that the more this book is read, the more it is found incomparable. The fondness that

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I have for this book reminds me of another bishop who was said to love being admired by the greatest ignoramuses. I expect that you have the same view. Thus you ought to be very pleased to be admired by as great an ignoramus as I, but the truth moves the ignorant as well as the most wise, and this is what I took the liberty of saying to the late electress [Sophie], who pretended not to be able to understand it [i.e., the Theodicy]. (K XI, 72)

4. the correspondence. phase three: caroline’s apostasy and the end of the affair Leibniz’s Suspicions and the Newtonian Blitz to Convert Caroline Leibniz drafted a response to Caroline’s letter on February 14/25 and sent it along with his third paper for Clarke. He thanked Caroline for her wish to reconcile him with Newton and suggested that there was a real possibility for this since all the noise had been made not by Newton (although he had “connived” in it) but by “a certain man who does not appear to be among the better regulated” – by which, of course, he meant Keill (see K XI, 78). Later, between the beginning of March and the middle of April, Leibniz wrote two further letters to Caroline. One of these, undated, is a long letter in which he attempted to enlist Caroline’s help in his scheme to unite the Reformed (i.e., Calvinist) churches of Brandenburg with the Evangelical (i.e., Lutheran) churches of Hanover through the mediation of the Anglican church in England (see K XI, 85–90). The other is lost, but it is clearly referred to in Caroline’s letter of April 13/24. In it Leibniz apparently again worried that Caroline had changed her feelings toward him and complained that Clarke had published something of their exchanges without his permission. In Caroline’s reply there was unfortunate news of the Abb´e Conti: He “has taken the trouble to lose some of the papers which you wanted me to entrust to him” (K XI, 90–1). But there were also some reassurances: “Whence does it come that you suspect me of not being the same for you? I believe that to be loyal to our friends is one of the points of our duty, and I appeal to the king on account of it. Dr. Clarke has not printed anything of what has passed between you and him” (K XI, 90). Despite this, the rest of Caroline’s letter could scarcely have encouraged Leibniz. She had previously told him that Clarke “wasted his Latin” in attempting to convert her; but now all that had changed: “Last Saturday I had the Abb´e Conti and Mr. Clarke from 6 till 10 o’clock. I should have liked very much for you to be here to support me. Mr. Clarke’s knowledge and manner of clear reasoning has nearly converted me in favor of the vacuum” (ibid.). She noted that

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she had “seen the letter that Chevalier Newton sent you through Conti”18 and reported that Newton claims that everything he said in it is a matter of fact. I eagerly await your response. I am in despair to see that people of such great knowledge as you and Newton are not reconciled. The public would profit immensely if it could be brought about, but in this great men resemble women who never give up their lovers except with the utmost regret and extreme anger. And that, gentlemen, is where your opinions have left you. (K XI, 91)

Caroline ended her letter with another plea for reconciliation, but added a most portentous postscript: “P.S. [ . . . ] The day after tomorrow we will have the experiments of Chevalier Newton. The king has a made a room available for this. I wish you were here for that, and also for Saturday, when Chevalier Newton, Abb´e Conti and Mr. Clarke will be with me” (K XI, 92). Caroline wrote again three weeks later to send Clarke’s third paper, “which by good fortune,” she explained, “has been recovered” (K XI, 93). In a spirit of liberality, she advised Leibniz to “let go of your serious disputes and prove to us the plenum, as the Chevalier and Clarke, on their side, prove the vacuum”; but she ended on a note that seemed to suggest that the Newtonians had already won her over, or nearly so: “Tomorrow we will see the experiments on colors, and one that I have seen to prove the vacuum has nearly converted me. It is your business sir, to bring me back to the right path, and I await the response that you will make to Clarke” (K XI, 93).

Caroline Begins to Turn These last two letters from Caroline mark a watershed in her correspondence with Leibniz. It is ironic that in the second of them she signed off by writing: “You will find me, despite your suspicions, always the same” (ibid.). In one sense, I suppose, she was the same: She still regarded herself Leibniz’s friend and still continued to promote him to the king. But in another sense, of course, nearly everything had changed. No longer in these letters, nor in any of the others she would later write to Leibniz, do we find her defending Leibniz’s position as more consonant with divine perfection than that of Clarke and Newton; and now she was on the verge of accepting the doctrine of atoms and the void, which she knew that Leibniz opposed. At best, she was now neutral: “[Prove] to us the plenum,” she told Leibniz, “as the Chevalier and Clarke, on their

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side, prove the vacuum.” We know from these letters that the Newtonians were in the process of applying a “full-court press” to win Caroline over to their side. She was the only one in the Hanoverian court who cared much about philosophy or who knew enough about it to have been able to express favor for Leibniz’s views, and last, but not least, of course, she was the future queen of England. The Newtonians realized that for political reasons they had to win her to their side. Leibniz must have realized it, too, which may account for his increasing paranoia. As time wore on, the sheer weight of words, of personalities, and of experimental dramatics could not have failed to have had something of their intended effects on Caroline. And Clarke was not without persuasive arguments. In his second paper, he had responded to Leibniz’s charge that on the Newtonian view the world is imperfect and requires occasional, miraculous repairs. “The wisdom of God consists,” he argued, in framing originally the perfect and complete idea of a work, which begun and continues, according to that original perfect idea, by the continual uninterrupted exercise of his power and government. The word correction, or amendment, is to be understood, not with regard to God, but to us only. The present frame of the solar system (for instance,) according to the present laws of motion, will in time fall into confusion; and perhaps, after that, will be amended or put into a new form. But this amendment is only relative, with regard to our conceptions. In reality, and with regard to God; the present frame, and the consequent disorder, and the following renovation, are all equally parts of the design framed in God’s original perfect idea. (GP VII, 361/LC 22–3)

Clarke’s argument was fair enough, and it is one I think he may have prosecuted to good effect in his long discussions with Caroline. According to the Newtonians, the world will want a reformation “according to the present laws of motion” – and that will represent no violation of the laws by which God rules the world but only of our still imperfect understanding of them.19 This was enough to deflect Leibniz’s criticism that the Newtonian view implies an imperfect creation and, hence, an imperfect creator. The account of miracles implicit in this passage, and later made explicit in Clarke’s third paper (GP VII, 371/LC 35), was, of course, one that Newton himself had embraced.20 But Leibniz argued that “divines will not grant the author’s position against me; viz. that there is no difference, with respect to God, between natural and supernatural: and it will be still less approved by most philosophers” (GP VII, 366/LC 29). Leibniz had always sought to accommodate his philosophical views, as much as possible, to the demands of theology, and he often cited the authority of divines against Clarke in their correspondence (see Bertoloni Meli 1999: 484–5).

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But Clarke and Newton were theological radicals, often hostile to conventional theological views.21 And Clarke’s response to Leibniz does seem to get it exactly right: “The question,” he wrote, “is not what it is that divines or philosophers usually allow or not allow; but what reasons men allege for their opinions” (GP VII, 371/LC 35). This response, I think, likely appealed to Caroline, who was certainly an independent thinker with an unconventional streak of her own when it came to theological matters.

Leibniz’s Attack on Atomism and the Void and Caroline’s Collusion with Newton On May 1/12, 1716, Leibniz wrote to “beg the pardon of Your Royal Highness if I feared some coolness,” which he blamed on the behavior of the Abb´e Conti: He is a little irregular in regard to me, and I have made him aware of it with a response as cold as his letter,22 but that scarcely matters. He does not appear to have fixed principles and is similar to a chameleon who takes (it is said) the color of the things which it touches. When he goes over again to France, they will make him return to the plenum from the vacuum. (K XI, 100)

And speaking of the vacuum, Leibniz declared that “since [it] has been preached to Your Royal Highness, I express my view about it in a separate paper,” which he attached as a postscript (K XI, 101–2). He was still suspicious of Caroline and wrote that he was “astonished that she has found any time for me,” given that “the duchess of Orl´eans [tells] me that Your Royal Highness writes her two very considerable letters every week.” “That consoles me,” he added, “about the fact that Your Royal Highness has seemed a little wavering, not in her good will towards me, but perhaps in her good opinion of me and my opinions, above all since it seems the translation of the Theodicy remains in arrears” (K XI, 102). From here on in the correspondence, Caroline’s handling of the Theodicy translation would be treated by Leibniz as a measure of her loyalty to him. Caroline responded to Leibniz’s apology by declaring that “you have reason to beg my pardon, sir, for having suspected me of not being the same for you, as your merit would bind me to you always” (K XI, 112). After defending Conti’s efforts at mediation and urging Leibniz “to employ your time more usefully than in disputing together,” Caroline gave an enthusiastic report of the experiments with which the Newtonians had regaled her; there was no indication that Leibniz’s postscript against the vacuum had had any appreciable effect on her views. “I am in on the

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experiments,” she gushed, “and I am more and more charmed by colors. I can’t help being a little biased in favor of the vacuum” (ibid.). Caroline did eventually mention the paper against the void that Leibniz had sent in his last letter, but only to say that “I have given it to the king, that he may never quit thinking about you” (K XI, 113).23 But the king was not the only one to whom Caroline gave Leibniz’s postscript on the void. For, as Richard Westfall has noted, Among Newton’s papers is a copy in his own hand of the insulting passage on atoms and voids printed as a postscript to Leibniz’s fourth letter. At the bottom Newton wrote, “Received of ye Princess May 7th 1716, & copied May 8.” Though attached to Leibniz’s letter of 2 June in the published correspondence, this passage was a postscript to Leibniz’s letter of 12 May (that is, 1 May in the Julian calendar); the princess must have dispatched it as soon as it arrived. (1980: 778)

Westfall observes that “at the least, Newton’s copy of it indicates his active interest in the correspondence” between Clarke and Leibniz. To be sure. But what is even more significant for our purposes is that it indicates Caroline’s now active engagement with Newton on the matters discussed in the correspondence – at least those in which she took a particular interest. Given her evident delight with the experiments she had witnessed Newton perform to demonstrate the existence of the void, and given her consequent attraction to the Newtonian doctrine, it may well be that, in a fine reversal of loyalties, she was now seeking Newton’s help in answering Leibniz as she had initially sought Leibniz’s help in answering Clarke. Thus, Leibniz may not have been far wrong when he worried that Caroline might be “a little wavering [ . . . ] in her good opinion of [him] and [his] opinions.” Still, Caroline ended her letter by addressing Leibniz’s worry about her finding time for him: “There now,” she wrote, “a great letter which will show you that I always have time to remember my friends” (K XI, 113).

Leibniz’s Continuing Suspicions and the Theodicy Project When Leibniz responded on May 22/June 2, 1716, to send his fourth paper for Clarke, he was clearly unhappy. He complained that Clarke had failed to understand his principle of sufficient reason, a failure that led him to suppose in his second paper that “this sufficient reason is ofttimes no other, than the mere will of God” (GP VII, 359/LC 20). He reminded Caroline that he had refuted this “error of vague indifference” in the Theodicy, an error, he noted, that “is also the source of the vacuum

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and atoms.” The experiments with which Caroline was so enthralled were dismissed as demonstrating nothing, since they “only exclude a gross matter.” The Theodicy strategy, by which Leibniz first brought Caroline around to his side in the battle against Newton, was now redeployed against the void: I would not have touched on this question of the vacuum if I had not found that the hypothesis of the vacuum derogates from the perfections of God, as do nearly all the other philosophical views which are contrary to mine. For those of mine are nearly all tied to the great principle of the supreme reason and perfection of God. Thus I do not fear that Your Royal Highness will easily abandon what she will have had the leisure to understand adequately about my views: her penetration and her zeal for the glory of God are my sureties. (GP VIII, 379)

He angrily rejected Caroline’s suggestions that he had mistreated Conti: “I could not fail,” he wrote, “to respond coldly to a letter as cold as his;24 but there is nothing which ought to offend him. It is for the master to esteem and favor who seems good to him” (GP VII, 380). Seizing this moment to raise further doubts about Caroline’s loyalty to him, he wrote that If your Royal Highness herself had less esteem for my view than before, I would be displeased by it, but I would not have any reason to complain about it. It suffices that she retains her kindness for me, and she has given great and real proofs of it. The continuation of her esteem can be recognized through what relates to the translation of the Theodicy. (GP VII, 380)

In the letter she wrote to dispatch Clarke’s fourth paper, Caroline reacted sharply to the comments in Leibniz’s previous letter: “ You will permit me to say, in spite of what I found rather harsh against me in your letter, that I am upset to see men of your merit trouble themselves for vanity, which you ought to destroy by the soundness of your reasonings” (K XI, 114). Her anger drove so far as to ask, “What difference does it make whether you or Chevalier Newton discovered the calculus?” (K XI, 115). Her response to Leibniz’s attempt to leverage the translation of the Theodicy was not encouraging: “You understand,” she wrote, “that the translation of the Theodicy is extremely difficult at this time. The archbishop [of Canterbury, William Wake] admires it, but he is not in total agreement with you. I will re-read it in the presence of Mr. Conti and Dr. Clarke, with your permission” (ibid.). At the end of her letter, Caroline mentioned the impending trip of the king back to Hanover, and surprisingly, perhaps, informed Leibniz that the king “has much kindness for you and [ . . . ] is angry when one is not entirely of your view.” She

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wrote that she expected “that there [would] perhaps soon be something here to bring you to this island,” and closed once more with a variation on her now standard line of reassurance: “I will eagerly seek occasions to show you that I am always the same” (K XI, 116). Leibniz responded on Friday, July 20/31, explaining that he has been forced to defer his response to Clarke’s fourth paper and reporting that the king had arrived in Hanover the previous Sunday. His preoccupation with the quarrel between himself and Newton and Clarke showed not only in his attempt at the beginning of the letter to vindicate his reply to Newton’s letter to Conti, but also in his remarks at the end of the letter, where he reported that “I had the honor of dining with His Majesty the day after he arrived, and he seemed cheerful to me, to the point that he reproached me because I appeared somewhat less so than I formerly did” (K XI, 130).25 Again pressuring Caroline concerning the Theodicy, he told her that “it will be applauded by the English to the degree that Your Royal Highness is satisfied with it” (K XI, 129). Given the Royal Society’s refusal to satisfy his demand for redress against the Newtonians, Leibniz had clearly come to regard Caroline’s public approval of the Theodicy as perhaps his only means of vindication in his fight against Newton. Realizing both his need for defenders in England and their near extinction after the defection of Conti, Leibniz responded to Caroline’s request for permission to re-read the Theodicy in the presence of Conti and Clarke by attempting to recruit at least some neutral observers: You are a competent judge, Madame, and as the Abb´e Conti and Dr. Clarke read it before you, that is to say, prosecute it before your tribunal, it would be desirable for me also to have an advocate at that time, who was disposed to defend my cause. I do not know anyone in London to nominate, unless it might be Mr. Des Maizeaux or Mr. Coste, although they are, perhaps, at most only neutral. (K XI, 129)

To retreat for a moment to May 27/June 7, 1716 – five days after he had sent his fourth paper to Caroline – Leibniz wrote to Johann Bernoulli to inform him of the nature of his ongoing exchange with Clarke. This letter ended with one of those enigmatic statements that could nag a suspicious mind into doubts about Leibniz’s sincerity: “Perhaps,” he wrote, “our encounter [ . . . ] will be further protracted; I shall see how it turns out. For encounters of this sort, because they are in philosophy, are a game and amusement to me” (GM III, 964/TSHT VI, 355–6). Writing to Caroline roughly two months later in order to dispatch the first installment of his fifth and final paper for Clarke, Leibniz now made

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it clear that he was growing weary of the game: “This response is very extensive because I wanted to explain things thoroughly and to see from that whether there is hope of making Mr. Clarke see reason. For if he falls into repeating himself, there will be nothing to do with him, and it will be necessary to try to end politely” (K XI, 132).26 He informed Caroline that he had been in touch with Des Maizeaux about a translator for the Theodicy and reported that both a good translator and a bookseller willing to print it had been found. But “they desire,” he wrote, “that it may be permitted to dedicate the book to Your Royal Highness and to indicate on the title-page that the translation was made by her order,” which latter request he suggested “would be to honor the book too much when it could be a hundred times better than it is” (ibid.). Still, as Clarke later observed in his own dedication to Caroline of his 1717 edition of the correspondence with Leibniz: “[The] late learned Mr. Leibnitz well understood, how great an honor and reputation it would be to him, to have his arguments approved by a person of Your Royal Hignesses [sic] character” (LC 5); and so, indeed, Leibniz continued: But I believe that Your Royal Highness will indeed allow it to be dedicated to her and allow it to be indicated in the dedication that Your Royal Highness wanted this book to be translated, since by saying that the truth is told, and that will be of great importance in publicizing a defense of religion and firm piety. (K XI, 132–3)

Caroline wrote very briefly to Leibniz on August 17/28 to remind him that Conti had lost many of his papers and to renew her request for replacements. Writing again three days later to acknowledge the receipt of the fifth paper for Clarke, she had news concerning the translation of the Theodicy: “I have seen a man who told me he that he would translate your incomparable Theodicy, and that he would dedicate it to me, which I have accepted with much pleasure. I believe that Mr. Clarke will respond to it. So much the better, since the truth cannot be examined minutely enough” (K XI, 181). Concerning his last comments for Clarke, Caroline explained that she had read them with pleasure: “I do not know what he will be able to say in response to them,” she wrote, but then confessed that “in my opinion he is a man of the greatest vivacity and of incomparable eloquence.” There is a studied neutrality in all of this: Caroline expressed her hope “that the king will bring you to this country,” but it was so that she might have “the pleasure of hearing you [i.e., Leibniz and Clarke] speaking together” (K XI, 182).

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The End of the Affair During the first half of September, two months before his death, Leibniz wrote two final letters to Caroline. In one of these, dated August 31/ September 11, Leibniz thanked her “for the permission she has given to dedicate the translation of the Theodicy to her and to speak in the dedication of the approval she has given to this plan” (K XI, 185). From both letters it is clear that Leibniz now saw the major part of his debate with Clarke – concerning atomism, space, and time – as hinging on the principle of sufficient reason as against Clarke’s avowal of voluntarism. Three weeks earlier he had told Des Maizeaux that “the followers of Newton are found to deny the great principle of the need for a sufficient reason, by which I beat them into ruin” (K XI, 179). In the undated letter he now told Caroline that if Clarke “does not grant me entirely this great received axiom [ . . . ] I could not help doubting his sincerity, and if he grants it, goodbye to the philosophy of Mr. Newton” (K XI, 189–90). “Still,” he said in the other letter, “I hope for the best, above all because everything is being done under the eyes of Your Royal Highness, whom it is not easy to fool” (K XI, 186). But if Caroline accepted Leibniz’s version of the principle of sufficient reason as against Clarke’s voluntarism, there is no indication of it in her final four letters, all of which are extremely brief and assiduously avoid mention of the matters at issue between Leibniz and Clarke. In the undated letter Leibniz also reported that he was working very hard on his history; and so, in response to Caroline’s wish that the king might bring him back to England, he wistfully explained his situation: I do not hope to go to England so soon. Nothing could give me a greater desire to go there than the kindnesses of Your Royal Highness; but as I do not hope to go soon, I do not know if I can hope to go later; for there is not a lot of later to hope for in me. (K XI, 189)

On September 4/15 Caroline responded with her regrets: I am sorry to see you put off for so long your trip here to England. You could work on the history in London as well as in Hanover, and your friends could have the pleasure of delighting in your conversation. I would gladly play the part of the college of the Sorbonne, provided that I had the pleasure of talking with you here and of being, although very ignorant, witness to your disputes with Mr. Clarke. You will find me always the same person who esteems you so much [ . . . ] Caroline. (K XI, 190)

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Four days later she wrote to Leibniz again at the behest of Clarke, who wished to have Leibniz’s assurance that if he should decide to print their papers he would do so in the language in which they were written. She reported the pleasure she had taken in her conversation with Clarke that day and ended with another expression of hope that Leibniz might join the two of them in England: “I wish so much to see you together, and I hope that you will choose me when you decide to see each other to speak one on one. I will always be forever among your friends” (K XI, 191). Leibniz never responded to these two letters from Caroline, but the day after Caroline had written the second of them, on September 9/20, Leibniz was busy writing to Vienna – to the Empress-dowager Amalie and to her lady-in-waiting Fr¨aulein Klenck. He was seeking assurance from both of them that his salary as imperial privy counselor was not being suspended, as rumor had reached him that it was, and he offered both of them his own assurance that he was planning to return to Vienna the following year – “when the king of Great Britain will have gone back across the sea,” as he put it to the empress-dowager (K XI, 193). This is not to say, of course, that Leibniz had abandoned his desire for the office of historiographer of Great Britain, although it does suggest, as I argued earlier, that Leibniz did not desire that office as a passport to England but primarily as a means to establish his position vis-`a-vis Newton. A month later, Georg Ludwig’s Hanoverian minister, Bothmer, sent Leibniz an optimistic note from London: I observe with much pleasure by the honor of your letter of the ninth of this month the assiduousness with which you continue to labor on your illustrious work. I do not doubt that Bernstorff and [secretary of state James] Stanhope are employing themselves effectively in return to procure for you, on the return of the king from Gh¨orde, the position that you hope for here of historiographer of His Majesty. Everyone readily agrees that no one merits it more deservedly than you, not only for your knowledge, but more particularly still for the work of which I have spoken. (K XI, 198 – also see K XI, 130–1)

Onno Klopp has argued that “the repeated indications of the princess of Wales, as well as this letter of minister Bothmer, show that the appointment of Leibniz to the position of historiographer of the king was a matter already resolved, whose realization was only delayed because the king himself was in Gh¨orde” (K XI, xxxv). There is no doubt, as Klopp has also noted, that “the letters of the princess of Wales to Leibniz, as well as his own concerning his re-encounter with [the king], have verified that in the case of the latter every ill feeling about the long absence of Leibniz in Vienna had been extinguished and that the princess passionately desired

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him to be in England” (K XI, xxxvii). Still, and even so, it seems hard not to think that Klopp’s optimistic assessment of Leibniz’s prospects for appointment underestimates, or perhaps even ignores, the political realities under which Georg Ludwig had to labor at this very early stage in his reign. Not only was there the matter of the Act of Settlement, which forbad grant of British offices to foreigners – a prohibition that the king had assiduously respected (see Hatton 1978: 156) – but there was also, and perhaps more importantly, the matter of Newton. We have seen that Leibniz hoped that his appointment would “sting,” as he expressed it, Newton and his supporters, as surely it would have; but then this very fact would just as surely have led Georg Ludwig’s English ministers to advise strongly against the appointment, given that Newton was the ornament of England and that Leibniz had been portrayed as his mortal enemy. Georg Ludwig could scarcely afford to alienate such an important constituency when the legitimacy of his own nascent reign was still so much in doubt.27 Nearly four years after Leibniz’s death, still obsessed, Newton wrote to de Moivre early in 1720 and exalted in the power he had exerted to frustrate the designs of Leibniz’s friends, including, presumably, Caroline and Conti: “When the Court of Hanover came to London,” he wrote, “[Leibniz’s] friends endeavoured to reconcile us in order to bring him over to London, but they could not get me to yield” (TSHT VII, 83). Caroline wrote to Leibniz again at the end of September to inform him that “I have given Dr. Clarke your papers, and he is making me a collection of everything” (K XI, 197). As for the Theodicy, she wrote that “I have not yet seen the translation of your incomparable book. I accepted it as a great honor that it is to be dedicated to me” (ibid.). In what must have been a final disappointment for Leibniz, she added that “the response [of Clarke] will also be dedicated to me” (ibid.). Clarke was no fool, and when he learned that Leibniz had arranged to have a translation of the Theodicy dedicated to Caroline, he apparently committed himself forthwith to writing a reply and then, determined to match Leibniz dedication for dedication, secured Caroline’s imprimatur for his anticipated rebuttal. Tit for tat – and that was that for Leibniz’s plan to secure his vindication against the Newtonians through Caroline’s endorsement of the translation of the Theodicy. When Leibniz died, the project of translating the Theodicy died with him, and it is ironic that what translation there came to be of it was at the hands of Clarke himself, who provided translations of leading passages from the Theodicy in an appendix to his polemical 1717 edition of the correspondence with Leibniz – dedicated, of

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course, to Caroline. But it is really no surprise that Caroline had accepted Clarke’s earlier proposal to dedicate his planned rebuttal of the Theodicy to her. For over the previous five months – ever since the Newtonians had charmed her with their experiments on colors and the void and had launched their propaganda blitz to win her over to their side – Caroline had increasingly assumed in her letters to Leibniz the stance of a disinterested observer, no longer the advocate for his cause, as surely she had been at the beginning of her acquaintance with Clarke. Some particulars are worth recalling. She had told Leibniz to “prove to us the plenum as the Chevalier [Newton] and Clarke on their side, prove the vacuum”; she and her ladies, she said, would play the part of witnesses to the dispute, like so many characters in a play by Moli`ere (K XI, 93). Later, and less facetiously, she had said that she “would gladly play the part of the college of the Sorbonne, provided that [she] had the pleasure of talking with you [ . . . ] and of being, although very ignorant, witness to your disputes with Mr. Clarke” (ibid.) She had confessed her ignorance more than once and had become Socratic. The dispute between Clarke and Leibniz had, I think, taught her that philosophical debate rarely issues in a clear-cut victor, and that it has to remain, by its nature, forever deeply ambiguous. When she discovered herself a patroness of philosophy and the arts, she seems to have realized that her role was not to declare a winner but to secure and protect a civil forum, and then let the chips fall where they may. Her retreat into neutrality undoubtedly stung Leibniz, but it was, I think, all to her credit. It must have been a final and bitter irony to Leibniz that Caroline ended her penultimate letter to him by saying that “I should be pleased if you could make the acquaintance of Mr. Clarke” and suggesting that “you would assuredly approve of him.” She told him that “I expect to see you here with the king,” and ended with her usual assurance that “you will find me always the same” (K XI, 197). Her last letter, written just two weeks before Leibniz’s death for the purpose of transmitting Clarke’s fifth paper, was a thin, four-sentence affair, flatly non-committal on the dispute that had occupied them for so long: I add these few lines to the response of Dr. Clarke. I hope that you find it at least pleasant even if you do not find it favorable. I have made the acquaintance of a man who admires you a lot, the archbishop of Dublin. I will respond to your letters in the following post, and I will always be the same for you. (K XI, 198)

But really too much had transpired in Caroline’s life since Hanover for it to be true in any unequivocal sense that she was still the same for

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Leibniz. From the beginning, proximity and politics had given Clarke and the Newtonians a decided edge in their competition for Caroline’s favor; and Clarke himself, as Caroline often intimated, was not without his charms. Indeed, he soon became, and would so remain until his death, Caroline’s closest advisor on matters philosophical and theological. At the time of her last writing to Leibniz, her erstwhile comrade in mediation, the chameleon Abb´e Conti, was making his way to Germany, on a mission to meet with Leibniz. But he arrived too late, and he wrote to Newton on November 18/29 to report that “M. Leibniz is dead, and the dispute is finished” (TSHT VI, 376). I have found no record of how Caroline reacted to this news, but there appear to have been no memorials. When Newton died some eleven years later – three months before Caroline became queen – he was, of course, buried as a national hero in Westminster Abbey, and the court, that is to say, Caroline, offered Clarke Newton’s old position as master of the mint, although he promptly refused it. When Clarke himself died two years later, Caroline hung his portrait in Kensington Palace with a commemorative inscription beneath (see Arkell 1939: 230). She had then been nearly two years on the throne in England. She had never returned to Germany, nor would she ever. By then, both Hanover and Leibniz were, perhaps, fond but certainly distant memories.

Notes 1. The Berlin Society of Sciences grew out of a proposal made by Georg Ludwig’s sister, Sophie Charlotte, electress of Brandenburg (from 1688) and later first queen in Prussia (1701). This proposal was for the construction of an observatory in Berlin, and when Leibniz heard of it, he wrote to the then electress to suggest that an academy of sciences, like those in Paris and London, be established in conjunction with the proposed observatory (see K VIII, 48– 50). Undoubtedly with encouragement from Sophie Charlotte, the elector of Brandenburg, Friedrich III, issued a Stiftungsbrief for both the observatory and the Society of Sciences on March 8/19, 1700 (see K X, 325–8). Leibniz was officially proclaimed president of the Society on July 1/12 (see K X, 328– 30). However, in an act of singular ingratitude at the end of the year 1715, the Society first reduced, and then cancelled altogether, the small sum that had been allotted to Leibniz to cover his expenses for travel and correspondence (see the letters exchanged between Leibniz and the director of the society, Baron von Printzen, K X, 458–64). This effectively ended Leibniz’s work on behalf of the Berlin Society of Sciences. 2. Leibniz himself had worked hard to establish this succession for the House of Hanover. Sophie qualified in light of her Protestant credentials and her descent from James I through his daughter, Elizabeth Stuart, who was the wife of the elector Palatine, Friedrich V, the ill-starred “Winter King” of Bohemia.

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3. The allusion, again, is to Leibniz’s history of the House of Brunswick. 4. Leibniz wrote to Nicolas Remond early the next year, on February 1/11, 1715, saying that “misgivings I have about my health prevented me from accompanying the princess of Wales [i.e., Caroline]; in fact the gout has seized me since then” (GP III, 634). It is true that Leibniz had frequently been bedeviled by attacks of arthritis and the gout, and at his age at the time, sixty-eight, he had reason to be concerned for his health. But having had a month to recover from his trip to Hanover from Vienna before Caroline departed for England, it is hard to believe that health concerns alone would have prevented Leibniz from going with Caroline had he really wanted to. 5. See the postscript to Leibniz’s letter to the electress Sophie, November 18/ 29, 1713 (K IX, 414). 6. For evidence of the close relationship between Leibniz and Fr¨aulein Klenck, as well as her very considerable efforts on his behalf, see letters XII, XXIX, LXV.1, LXV.3, and LXX in K XI. 7. Upon his return to Hanover from Vienna, Caroline informed Leibniz that Georg Ludwig had said of him that “he comes only when I have become king,” and in his letter to the electoral prince Leibniz expressed the hope that the king was speaking merely in jest (K XI, 10). 8. Indeed, in March of 1696 Leibniz had complained of his plight in Hanover to his English correspondent, Thomas Burnett. “All that bothers me,” he wrote, is that I am not in a great city like Paris or London, which are full of learned men from whom one can benefit and even be helped. For there are many things that one cannot do by oneself. But here one finds scarcely anyone with whom to talk; or rather, in this region a courtier is not supposed to speak of learned matters, and without the electress [Sophie] they would be spoken of even less. (GP III, 175)

9. In a paper he wrote in 1708, which appeared in the Philosophical Transactions in 1710, Keill accused Leibniz not only of stealing Newton’s method of fluxions but also of deliberately trying to cover up his thievery by changing “the name and symbolism” – see Hall 1980: 145. 10. Newton translated Leibniz’s letter from the original French (see TSHT VI, 105–6) and, as the following letter from Chamberlayne suggests, intended to present it at the meeting of the Royal Society on May 20/31, 1714. In fact, he apparently presented it at the preceding meeting – see TSHT VI, 140. 11. Mademoiselle von P¨ollnitz had been a lady-in-waiting for Sophie Charlotte, late queen of Prussia and patroness of Leibniz, who had assumed guardianship of Caroline when she was thirteen, following the death of her mother. 12. This was the Tentamen de motuum coelestium causis (Essay on the causes of the heavenly motions), which had been published in the Acta eruditorum in 1689. For a discussion of Keill’s charge, see Hall 1980: 207–11. 13. Newton had been appointed a warden of the mint in the spring of 1696; he was appointed master of the mint at the beginning of the year 1700. 14. The king did not want to pay Leibniz for any more than three of the months that he had spent in Vienna. On the matter of Leibniz’s arrearages, see Leibniz’s letters to Bernstorff of September 9/20 (K XI, 12–14) and December 17/28, 1714 (K XI, 26–7).

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15. Ironically, it was de la Roche who later translated Clarke’s letters into French for Clarke’s 1717 edition of the correspondence between himself and Leibniz. 16. This is perhaps because he later decided to enlist Caroline’s aid in a scheme to unite the Protestant churches – in which the disagreement among the churches on the issue of the Eucharist would eventually have to be addressed – and he wanted his own participation in it to be kept a secret (see K XI, 85–90). 17. In addition to what he had said about gravity in §19 of the Preliminary Dissertation of the Theodicy, Leibniz disparaged the Newtonian concept of gravity in a letter of January 26/February 6, 1711 to the Dutch philosopher Nicolaus Hartsoeker. In the letter, which was published in the Memoires de Tr´evoux in March 1712 and reprinted in the Memoirs of Literature of London in May 1712 and the Amsterdam edition of the Journal des Sc¸avans in December 1712, Leibniz wrote: The ancients and moderns, who avow gravity is an occult quality, are right if they understand by that that there is a certain mechanism unknown to them, by which bodies are impelled toward the center of the earth. But if their view is that this is done without any mechanism, by a simple primitive property, or by a law of God which brings about this effect without using any intelligible means, then it is a unintelligible occult quality, which is so very occult that it can never become intelligible, even if an angel, not to say God himself, should try to explain it. (GP III, 519)

18. This was Newton’s response (see TSHT VI, 285–90) to a letter of November 25/December 6, 1715 (see THST VI, 250–5) that Leibniz had sent to Conti and that Conti had then sent to Newton in an attempt to open a dialog between the two. Leibniz responded to Newton’s letter on March 29/April 9, 1716 – see TSHT VI, 304–18. 19. For an enlightening discussion of the Newtonian view of miracles, see Dobbs 1991: 230–43 and Harrison 1995. 20. In a draft – perhaps written while preparing his letter of February 26/ March 8, 1716, to Conti (see TSHT VI, 285–90) in response to Leibniz’s letter charging that on Newton’s view “gravity will be a scholastic occult quality or else the effect of a miracle” (TSHT VI, 251) – Newton wrote: For Miracles are so called not because they are the works of God but because they happen seldom & for that reason create wonder. If they should happen constantly according to certain laws imprest upon the nature of things, they would be no longer wonders or miracles but might be considered in Philosophy as a part of the Phenomena of Nature notwithstanding that the cause of their causes might be unknown to us (as quoted in Dobbs 1991: 230).

21. While the degree of Newton’s theological heterodoxy has been debated, most modern scholars would not dispute that his views were extremely unconventional. Richard Westfall is typical of many who view Newton as having been adherent of the heretical doctrine of Arianism from an early age until his death: “Pious he undoubtedly was,” Westfall argues, “but his piety had been stained indelibly by the touch of cold philosophy. It is impossible to wash the Arianism out of his religious views” (Westfall 1980: 826). A somewhat less radical interpretation of Newton’s heterodoxy has recently been suggested

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by Pfizenmaier 1997. Unlike Newton, who kept his theological views from the public eye, Clarke was widely accused in his own day of being an adherent of Arianism. He was removed from his position as a chaplain to queen Anne as the result of the controversy aroused by his book, The Scripture Doctrine of the Trinity. 22. Leibniz refers to his response of March 29/April 9 (see TSHT VI, 304–18) to Conti’s letter to him of March 1716 (TSHT VI, 295–6), with which letter Conti had transmitted to Leibniz Newton’s letter of February 26/March 8 (TSHT VI, 285–90) – see note 17. 23. Thus, the king was kept well informed about Leibniz’s dispute with Newton. Early in May Leibniz apparently sent Minister Bothmer a letter in which he addressed the issue of his dispute with Newton in a postscript. For in a letter to Leibniz of May 18/29, 1716, Bothmer thanked Leibniz “for the information that you have given me through your P.S. about the state of your differences with Chevalier Newton.” He went on to note that “I have informed the king of the content of you P.S., in order to show him that you have not offended Mr. Newton and that what you propose is reasonable” (K XI, 114). Later, in a letter of June 29/ July 10, Bothmer told Leibniz: Sir. I have shown your P.S. to some friends of Mr. Newton who seemed very happy with it, but I do not know yet what he himself says about it. At the same time, I have made it known that this does not serve the king well, to divert you with such cavils from important work for the glory of his family which occupies you. (K XI, 128)

24. 25.

26.

27.

Further evidence of the king’s knowledge of Leibniz’s dispute with Newton is found in Conti’s letter to Leibniz of March 1716: “His Majesty has wanted me to inform him of all that has happened between M. Newton and you. I have done my best, and I would that it were successfully done for both” (TSHT VI, 295). See note 22. The king may have guessed at the source of Leibniz’s despondency, since Leibniz reports in his next letter, two and half weeks later, that “the king has joked more than once about my dispute with Mr. Newton” (K XI, 133). When Leibniz wrote to Des Maizeaux three days later, he confirmed his intention to end the affair sooner rather than later: “I hope you have received what has passed between Mr. Clarke and me, down to his fourth paper inclusively, to which I am responding more fully than to the others in order to clarify the matter thoroughly and in order to advance to the end of the dispute” (K XI, 178–9). The previous year had seen the Jacobite Rebellion of 1715 – an attempt to place James Edward Stuart on the throne in England – and there always remained the threat that Stuart sympathizers would attempt to undo the Hanoverian succession, which they regarded as illegitimate.

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Index

Adams, Robert his conception of Leibniz as an idealist, 134–138 aggregates reality of, 104–107, 115, 116 unity of, 115, 116 Amalie, Empress-dowager, 264, 271, 286 Anaxagoras, 22 Anne of England, Queen, 263, 266 Anton Ulrich of Brunswick-Wolfenb¨uttel, 264 Apollonius, 82 Aquinas, St. Thomas on relations, 256–257 Aristotelianism, 15–16, 17, 19, 21–22 Aristotle, 12–13, 15–16, 17–18, 19, 20, 22, 23, 24–25, 29, 30, 32–36, 38, 111, 114–118, 159 on relations, 256–257 Arnauld, Antoine, 11, 80, 97–118, 123, 124, 125, 135, 162, 179, 239, 241 Ars characteristica, 63–67 atomism, 21–22, 102 Leibniz’s attack on, 280–282 Augustine, St., 81–82, 124, 126–127 Bacon, Francis, 18, 49 Basnage de Beauval, Henri, 194

Bayle, Pierre, 74, 79, 127, 194–195 Beck, Cave, 67 Berkeley, George, 127–128 Bernard, Edward, 69 Bernoulli, Johann, 163, 164, 283 von Bernstorff, Andreas Gottlieb, 263–264, 267–269, 286 Bierling, Friedrich Wilhelm, 230 Bilfinger, Georg Bernhard, 215 bodies as aggregates of substances, 129–133, 137 body, 23, 24–25, 27–31 as a momentary mind, 61 as merely extended substance, 99–109 Leibniz’s Aristotelianism concerning, 100 Leibniz’s Platonism concerning, 100 substantiality of, 98–118 also see extended substance Bonneval, Count, 264, 267 Borel, Pierre, 58 Borelli, Giovanni, 124 Bossuet, Jacques B´enigne, 88 von Bothmer, Hans Caspar, 275, 286 Bourget, Louis, 145 Bouvet, Joachim, 149, 151–152, 153–154, 156

305

306

Index

Boyle, Robert, 49, 59, 68 Brahe, Tycho, 40 Bu¨ ckeburg, Countess, 269 bullae, 58 Burgersdijk, Franco, 163 Burgh, Albert, 142 Burnett of Kemney, Thomas, 193, 196, 198 Burridge, Ezekiel, 196 Calculus Leibniz’s dispute with the Newtonians concerning the, 265–267, 269–271, 282 Caroline of Wales, Princess, 262–289 Cavalieri, Bonaventura, 61 Caze, Caesar, 145 Chamberlayne, John, 265–267 China, 141–151, 160 Chinese language, 156–157 medicine, 156 morality, 157–158 Clarke, Samuel, 200, 252–253, 262, 267, 272–289 Clauberg, Johann, 24 cohesion, 60 Colbert, Jean Baptiste, 155 Collins, John, 63 Comenius, John Amos, 11, 49–50, 64, 67–68 conatus see endeavor conciliatory eclecticism, 14–15 Leibniz’s adherence to, 31 concomitant causes, hypothesis of see preestablished harmony, the doctrine of Confucius, 143 Conring, Herman, 51 Conti, Abb´e, 275–276, 277–278, 280, 282–283, 284, 287, 289 Copernicus, Nicolas, 40 Cordemoy, Geraud de, 102 corporeal substance, 22, 35–36, 97–118, 123–138, 195, 206–208 and true unity, 111, 114–118

cosmological argument, the, 23, 25, 30 Coste, Pierre, 196, 283 Couplet, Phillipe, 149 Cudworth, Ralph, 194–196, 198, 200 cultural exchange foundations in Leibniz’s philosophy for, 145–148 Dalgarno, George, 64, 65, 67 de Carcavy, Pierre, 11 de Fatouville, Nolant, 200 de la Mare, Philibert, 75 de Moivre, Abraham, 287 de Raey, Johannes, 17–18, 24 de Roberval, Gilles, 82 de Volder, Burchard, 162–188, 230, 238–241, 246, 247, 259 the Cartesianism of, 163–168 on the material world, 164–168, 181–183 also see substance – De Volder’s concept of Democritus, 20 Des Bosses, Bartholomew, 143, 193, 230, 238–259 des Maizeaux, Pierre, 283–284, 285 Descartes, Ren´e, 17–18, 20, 24, 32, 60, 76–78, 79, 81, 86–87, 90, 92, 93, 127–128, 137, 146, 162, 163, 164, 165, 166, 172, 185, 188, 196 Leibniz’s critique of his physics, 219–220 Desgabets, Robert, 75, 76, 80, 81 Digby, Kenelm, 21, 22, 61 Duhamel, Jean-Baptiste, 87 Dury, John, 49 dynamics metaphysical grounds for, 219–233 elasticity, 56 elements, the four, 58 Elizabeth of Bohemia, Princess, 79 endeavor, 60–61 Epicurus, 24

Index Ernst August of Hanover, Elector, 263 ethical perfectionism, 218–219 Euclid, 82 Eug`ene of Savoy, Prince, 267 extended substance aggregate argument against, 104–105 modal argument against, 105–108 also see body extension actual 176–177 mathematical, 175–176 Fardella, Michelangelo, 123–138 the augustiniazed Cartesianism of, 126–128 Ficino, Marsilio, 80 figura, 22–23, 25, 29–30, 34 figure, 25 final causes, 39–40 Fogel, Martin, 55 force of aggregates, 240 primitive active and primitive passive, 240, 242–251 primitive and derivative, 219–226 foreknowledge divine, 128–129 form secondary, 36 also see substantial forms Foucher, Simon, 74–94 his objections to Descartes’s philosophy, 76–77 Friedrich Wilhelm I of Prussia, King, 217–218 Galilei, Galileo, 17–18 Gassendi, Pierre, 17–18, 20, 21, 22, 60 Georg Ludwig of Hanover, Elector, 263–265 George I of England, King, 271–272, 281, 282–283, 284, 286–287, 288 also see Georg Ludwig of Hanover, Elector

307

Giorgi, Matteo, 126, 137 gravity, 56 Grimaldi, Claudio Filippo, 141–144, 149–150, 151, 154–155, 160 Hartlib, Samuel, 49–50, 67–68 Heidanus, Abraham, 164 Hesenthaler, Marcus, 64 Hevelius, Johannes, 49–50 Hiob, Ludolf, 145 Hobbes, Thomas, 18, 20–21, 22, 51, 60–62 Hooke, Robert, 16–17, 58, 59 Huet, Pierre-Daniel, 74, 164 Humanism, 14–15 Huygens, Christian, 53, 55, 59–60, 63, 68 hypotheses criteria for their truth, 57–58 idealism, 123–138 vs. realism, 134–138 Jesuits, the, 141–160 Johann Friedrich, Duke, 54, 264 Kant, Immanuel, 163 his reading of Leibniz as an idealist, 215–216, 225–226, 231–233 Karl VI, Emperor, 263 Keill, John, 266, 269–270, 277 Kirch, Gottfried, 145 Kircher, Athanasius, 63 Klenck, Fra¨ulein, 264, 286 Kochanski, Adam, 149 Lamy, Bernard, 124 Lantin, Jean-Baptiste, 75, 80, 81 Laureati, Giovanni, 150 le Clerc, Jean, 194–195 Leibniz An Example of Philosophical Questions Concerning Law, 11 Brief Demonstration (Brevis demonstratio), 81 Catholic Demonstrations, 27

308

Index

Leibniz (cont.) Confession of Nature against the Atheists, 11, 27–28 Considerations on Vital Principles and Plastic Natures, 194–196 Critical remarks on Descartes’s Principles of Philosophy, 93 De Principio Individui, 11 De quadratura arithmetica circuli, 68 Discourse on Metaphysics, 98, 107 Discourse on the Natural Theology of the Chinese, 143 Dissertation on the Combinatorial Art (Dissertatio de arte combinatoria), 11, 22–28, 64, 65, 143 Dynamics, 87 Examination of the Christian Religion, 83 Meditations on Knowledge, Truth, and Ideas, 80 Monadology, 128, 238, 246 New Essays on Human Understanding, 91, 92–93, 147, 157, 206–207 New Physical Hypothesis (Hypothesis physica nova), 38, 48, 51–59, 68–69 New System of the Nature and Communication of Substances . . . , 76, 88, 89–91 Notationes generales, 116 Novissima Sinica, 141, 143, 144, 151, 157 On the True Method of Philosophy and Theology, 84 On Transubstantiation, 28–29, 30–31 Preface to an Edition of Nizolius, 11 Principles of Nature and Grace, 219, 238, 241 Reply to Bayle, 176, 185 Specimen Dynamicum, 240 Theodicy, 238, 272–277, 280, 281–285, 287–288 Theory of Abstract Motion (Theoria motus abstracti), 11, 38, 48, 54, 58–63, 64, 68

Whether the Essence of Body Consists in Extension, 85 Leichner, Eccard, 50 Locke, John, 142, 193–194, 195, 196–208, 273–274, 289 on the origin of ideas, 197–198 Louis XIV, King, 85 Luther, Martin, 17 Machiavelli, Niccolo, 20 magnetism, 56 Malebranche, Nicolas, 75, 77, 79–80, 87, 90, 124, 127, 272 Mariotte, Abb´e Edme, 80 Martyn, John, 62 Masham, Lady Damaris, 193–211 Matter, 25 and figura, 29–30 endless divisibility of, 101–102 prime (primary), 22–23, 36, 135 secondary, 242–243 Mauritius, Erich, 54–55 mechanical philosophy, the 20–22 Leibniz’s critique of, 27–28 Mersenne, Marin, 63, 79 miracles the Newtonian conception of, 279–280 monads, 131, 134–136, 184, 216, 223–226 and composite substance, 240–251 as perspectives on the universe and God, 146 domination and subordination of, 245–246, 247–251, 257–258 Montaigne, Michel Eyquem, 142, 146 moral certainty, 92–94 Moray, Robert, 69 Newton, Sir Isaac, 220, 265–267, 268, 270–271, 273–274, 289 Nizolio, Mario, 14, 38 Oldenburg, Henry, 11, 47–69 ontological argument, the, 92 Ozanam, Jacques, 87

Index Paperbroch, Daniel, 149–150 Parmenides, 111–113 Patrizzi, Francesco, 80 Pell, John, 59 Pellisson-Fontanier, Paul, 84 Peter the Great, 145 Petty, William, 49 Plato, 16, 23, 38–39, 75, 77–78, 79, 80, 81, 111, 113, 159 Platonism, 16–17, 19, 80 point, 60–61 Poisson, Nicolas-Joseph, 124 Porphyry, 16 preestablished harmony the doctrine of, 38–39, 40, 85–86, 128–129, 184–185, 196, 209–210 Proclus, 82 Ranelagh, Lady, 49 R´egis, Pierre-Sylvain, 87, 124 realism weak vs. strong, 134 also see idealism Recent Thinkers (Recentiores) 32, 35 Reformers (Reformatores), 32 Reformed Philosophy, 17–18 Leibniz’s version of, 32–36 relations as ideal, 251–253 as real, 253–258 Remond, Nicolas, 12 Rites Controversy, the, 143, 150 Rohault, Jacques, 74, 124 Royal Society, the, 47–69, 265–267 scepticism academic, 74–94 Schro¨eck, Lucas, 145 scientia, 83–85 scientia visionis, 254–255 Scotus, John Duns, 101 Sophie Charlotte of Brandenburg, 144, 200 Sophie of Hanover, Electress, 263, 277

309

soul immortality of, 86 unity of, 86–87 Spinoza, Baruch, 11, 92–93, 142, 146 Spitzel, Gottlieb, 156 Stanhope, James, 286 Stillingfleet, Edward, 199 substance, 25, 26–27, 35–36 activity of, 28–31 Arnauld’s definition of, 104 as true unities, 98 complete concept theory of, 103, 107 composite, 238–259 De Volder’s concept of, 165–166, 169–175 self-sufficiency of, 28–31, 35–36 unity of, 103, 114–118, 239–242 also see corporeal substance substantial bond, 238–239, 243–246, 248–251, 255–259 substantial form, 23, 24–25, 26–27, 33, 36, 39, 97, 99–103, 105, 109–113 as conferring reality on extended things, 109–113 as figura, 34 Sylvius, Francis de le Bo¨e, 163 Tachen, Otto, 58 Tentzel, Wilhelm, 145 Thevenot, Melchisedec, 87 Thomasius, Jakob, 10–42 Toland, John, 144–145 Tournemine, Ren´e Joseph, 242 uniformity the principle of, 194, 200–211 universal character (characteristic), 48, 157 universal language, 63–67 universal science, 66 vacuum, the, 277–282 Leibniz’s attack on, 280–282, 288 Verjus, Antoine, 141, 143, 149, 150 vinculum substantiale see substantial bond

310

Index

void, the see vacuum, the von Boineburg, Johann Christian, 21, 26, 47, 48, 51, 61, 68 von Guericke, Otto, 11 von Loewenheim, Philipp Jakob Sachs, 51 von P¨ollnitz, Henrietta Charlotte, 268, 270 von Schoenborn, Johann Philipp, 47 von Tschirnhaus, Ehrenfried Walther, 67

Wake, Archbishop William, 272, 282 Wallis, John, 55, 59, 61–62, 63, 68, 69 Weigel, Erhard, 11, 20–21, 47, 217 White, Thomas, 61 Wilkins, John, 49, 63–64, 65 Witsen, Nicholas, 145 Wittichius, Christoph, 163 Wolff, Christian, 214–233, 270, 274–275 his response to Leibniz’s idealism, 226–231 Wren, Sir Christopher, 53, 55, 59–60, 63