Ignorance and Imagination: The Epistemic Origin of the Problem of Consciousness (Philosophy of Mind Series.)

Ignorance and Imagination: The Epistemic Origin of the Problem of Consciousness

Daniel Stoljar

OXFORD UNIVERSITY PRESS

IGNORANCE AND IMAGINATION

PHILOSOPHY OF MIND SERIES Series Editor David J. Chalmers, Australian National University Self Expressions: Minds, Morals, and the Meaning of Life Owen Flanagan The Conscious Mind: In Search of a Fundamental Theory David J. Chalmers Deconstructing the Mind Stephen P. Stich The Human Animal: Personal Identity without Psychology Eric Olson Minds and Bodies: Philosophers and Their Ideas Colin McGinn What’s Within? Nativism Reconsidered Fiona Cowie Purple Haze: The Puzzle of Consciousness Joseph Levine Consciousness and Cognition: A Unified Account Michael Thau Thinking without Words Jose´ Luis Bermu´dez Identifying the Mind: Selected Papers of U. T. Place Edited by George Graham and Elizabeth R. Valentine A Place for Consciousness: Probing the Deep Structure of the Natural World Gregg Rosenberg Three Faces of Desire Timothy Schroder Gut Reactions: Perceptual Theory of Emotion Jesse J. Prinz Ignorance and Imagination: The Epistemic Origin of the Problem of Consciousness Daniel Stoljar

IGNORANCE AND IMAGINATION The Epistemic Origin of the Problem of Consciousness

Daniel Stoljar

1 2006

1 Oxford University Press, Inc., publishes works that further Oxford University’s objective of excellence in research, scholarship, and education. Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With offices in Argentina Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam

Copyright Ó 2006 by Oxford University Press Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York 10016 www.oup.com Oxford is a registered trademark of Oxford University Press All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of Oxford University Press. Library of Congress Cataloging-in-Publication Data Stoljar, Daniel. Ignorance and imagination: The epistemic origin of the problem of consciousness / Daniel Stoljar. p. cm.—(Philosophy of mind) Includes bibliographical references (p. ) and index. ISBN-13 978-0-19-530658-3 ISBN 0-19-530658-9 1. Consciousness. 2. Epistemics. I. Title. II. Philosophy of mind series. B808.9.S725 2006 126—dc22 2005054714

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Preface

Apart from its phenomenological obviousness, the two central facts about conscious experience are these: it is philosophically puzzling, and we are scientifically ignorant with respect to it. The aim of this book is to turn the second of these facts against the first. Philosophical puzzlement concerning conscious experience arises because various arguments and thought experiments apparently suggest that, if it exists at all, conscious experience is irreducible—that is, wholly distinct from everything else. The reasoning involved in these arguments has considerable initial appeal; moreover, it is of a kind widely accepted in other cases. On the other hand, the idea that conscious experience is irreducible is at odds with some very natural beliefs that we have about the place of human beings and other sentient creatures in the universe. The challenge is to reconcile the philosophical arguments with these natural beliefs, or else to make sense of the impossibility of this sort of reconciliation. In addition to philosophical puzzlement, conscious experience provokes an empirical or scientific impulse of a more straightforward sort. Here is a phenomenon that characterizes large parts of our psychological lives and that of other creatures. We would like an explanation of this phenomenon, but, alas, none is currently available. Of course, we know very general facts about consciousness: we know it arises somehow in the brain, for example, as do other psychological phenomena such as vision, memory, and the capacity for language. But beyond this we are quite ignorant. We have no general framework within which the explanation of consciousness and its various manifestations may proceed, and we have no inkling about how to integrate any potential framework into existing frameworks that explain other aspects of the natural world. It is the absence of these general

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frameworks or schemes of research that I have in mind when I speak of the fact—for it is a fact—of our ignorance with respect to consciousness. What is the relation between these two facts, between scientific ignorance and philosophical puzzlement? The leading idea of this book is that progress on the philosophical issues will be achieved only if we keep ignorance in mind. On the one hand, the reasoning that is central to the philosophical questions starts from imagination or conceivability. We imagine possibilities and draw apparently objectionable conclusions from what we imagine. On the other hand, ignorance has an impact on imagination. What in our ignorance we believe ourselves to imagine and what we in fact imagine are distinct. In particular, the possibilities we believe ourselves to imagine do or would have objectionable consequences, but we do not imagine them in the relevant sense, and those possibilities we do genuinely imagine don’t imply anything objectionable. And this, I argue, solves the philosophical problem of conscious experience. Imagination leads us into the problem; ignorance leads us out of it. The view that ignorance has an impact on the philosophical problem of consciousness—the epistemic view, as I will call it—seems to me, as I hope it seems to you, remarkably simple and straightforward. Hence it ought to be surprising that in philosophy of mind it is anything but standard. No doubt part of the reason for this is a natural tendency to ignore our own ignorance. But for me the more interesting and important reason is a cluster of ideas about what philosophical problems are like and what a contribution to them would be—a cluster of ideas that blocks us, I think, from accepting the epistemic view. In particular, most philosophers think that the philosophical issue about consciousness is conceptual in origin; that is, it arises because of some mistaken picture or theory that we implicitly have about consciousness, or perhaps about our thought and talk about consciousness. If the problem were conceptual, a contribution to it would essentially involve the identification of a mistake in how we are thinking about consciousness and a corrective to that mistake. From this perspective, the epistemic view is almost invisible as a theoretical option. After all, if the problem were conceptual, it presumably would persist even if ignorance of the kind I am interested in were taken away. But I will argue in what follows that to understand the problem this way is to misunderstand it. Indeed, in my view the problem is not how we think about consciousness: the problem is how we think about the philosophical problem of consciousness; namely, we think of it as conceptual when in fact it is epistemic. The epistemic view is not a widely held position in contemporary philosophy, but versions of it, or at least closely related views, have been put forward in markedly different ways by a number of prominent writers; I have in mind Block (e.g., 2002), Chomsky (e.g., 2000), Churchland (1985, 1996), Gunderson (1964, 1971), Jackson (1982), Nagel (1974, 1986, 2002), Sellars (1962), Strawson (1994), and especially McGinn (1991, 2004). I owe a considerable debt to these philosophers. My position has been formulated

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in large measure as a consequence of thinking about theirs. But, as important as these contributions are, in the end they leave a gap that the present work is designed to fill. For they are either not developed in any detail or else developed in a way that associates the basic position with doctrines that are (as it seems to me) implausible or unnecessary—with skepticism about philosophical problems, for example, or with the speculation that the scientific explanation of consciousness is beyond the cognitive powers of human beings. Indeed, a striking fact about the epistemic view is that, while its leading idea is extremely straightforward—the sense that we are missing something occurs to almost anyone who thinks seriously about the subject—the development of the idea in contemporary thought typically assumes a self-consciously avant-garde and radical mood. The ‘‘trouble with the usual theories of the mind-body relation,’’ Colin McGinn recently said (quoting Peter Unger quoting Michael Lockwood), ‘‘is that they aren’t crazy enough’’ (2004, p. 138). I am not opposed to the avant-garde or even craziness, on principle, but the fact is that, once we place the epistemic view in its correct dialectical setting, there is nothing much avant-garde or crazy here. Some will find this a disappointment, but for me its very ordinariness is a main reason to think the view true. In previous work (see Stoljar 2001a, 2001b), I, too, advanced a version of the epistemic view, though not under that label. I now think these papers should similarly be criticized on the ground that they associate the basic position with extraneous and unnecessary doctrines. In that work, the position is developed via a metaphysical distinction between dispositional and categorical truths and an associated epistemological thesis about our ignorance of the categorical truths. Suitably qualified, these latter claims are, I think, plausible, and they were certainly important in my coming to the view that I now hold. Indeed, the present work is largely the result of asking what the position of those papers would look like if it was separated from the theoretical background presupposed there—a question briefly discussed in Stoljar 2001b. But, as we will see in chapter 6, there is no internal connection between these metaphysical and epistemological claims and the epistemic view—an important fact, for the controversy surrounding those doctrines makes the epistemic view seem more controversial than it is. The phrase ‘‘epistemic view’’ is used by Sturgeon 1994 (see also Sturgeon 2000) for a different view from the one at issue here. Sturgeon uses it to denote a version of the a posteriori entailment view I discuss in chapter 9. The phrase is well suited for that use, but it is, I think, even more natural for us, and it is for this reason I have adopted it. Ignorance is, of course, a theme in philosophy generally. The epistemic view of vagueness (see Williamson 1994) provides one example, as does the hidden variable view in philosophy of physics (see Price 1996), as does Bromberger’s (1992) rational ignoramus; other examples might also be cited. The project of comparing other discussions of ignorance to our own might be fruitful, but it is not one I will attempt.

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In addition to presenting bits and pieces of this material to many venues over the last few years, I was very fortunate to give talks in 2003–2004 in which the main argument of the book was summarized at Princeton University, Harvard University, University of Michigan, University of California— Davis, Australian National University, and Monash University. I would like to thank the audiences at these universities for providing me with such stimulating discussion. Questions from at least the following people prompted significant changes in my thinking: Gilbert Harman, Jeff King, Jim Pryor, Graham Oppy, John Bigelow, Gideon Rosen, Scott Soames, Rich Thomason, and George Wilson. Some of the ideas in chapters 2 and 3 date from a period when I was a graduate student at Massachusetts Institute of Technology. I would like to thank the (then) members of the department, in particular: Ned Block, Andrew Botterell, Sylvain Bromberger, Alex Byrne, Noam Chomsky, Robert Stainton, Robert Stalnaker, Jason Stanley, Zolta´n Sza´bo, and Judith Jarvis Thomson. I hope it is obvious how much the relevant writings of Block and Chomsky have influenced what follows. Some of the ideas in chapter 6 date from when I was an assistant professor at the University of Colorado at Boulder. I would like to thank the (then) members of that department, too; in particular, George Bealer, Michael Griffin, Stephen Leeds, Graham Oddie, Robert Pasnau, Michael Tooley, and Adam Vinueza. I presented a draft of the book to my graduate seminar at the University of Michigan during a period I spent there in 2004 as the Marshall Weinberg Distinguished Visiting Professor of Philosophy. I would like to thank Peter Railton and the rest of the department for inviting me and for making my stay there such an enjoyable one and to thank Marshall Weinberg for making it possible. I am very grateful to those people who took the time to come to the seminar and discuss a version of the manuscript: Mike Allers, Aaron Bronfman, Josh Brown, Janice Dowell, Alexa Forrester, Allan Gibbard, John Ku, Bruce Lacey, Pat Lewtas, Martin Lin, Eric Lormand, Ivan Meyerhofer, Gerhard Nuffer, and Steve Petersen. Particular thanks go to Jason Stanley for discussing many of the ideas in this book and for being such a great host while I was in Ann Arbor. During the writing of this book, I have been in the Philosophy Program of the Research School of Social Sciences, Australian National University. The students, faculty, administrators, and visitors at ANU make it one of the best places in the world to work. I thank in particular the following for their help: Karen Bennett, Ben Blumson, Jacek Brzozowski, Philippe Chuard, Aisling Crean, Di Crosse, Martin Davies, Tyler Doggett, Liam Dwyer, Andy Egan, Daniel Friedrich, Peter Godfrey-Smith, Alan Ha´jek, Frank Jackson, Yujin Nagasawa, John O’Dea, L. A. Paul, Adam Pautz, Derk Pereboom, Philip Pettit, Laura Schroeter, Stewart Saunders, Michael Smith, and David Wall. (I am sure I have left people out; to them I apologize.) Susanna Siegel, one of our more regular visitors in recent years, read an early version of the

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manuscript and gave fantastic feedback. A much later version was the subject matter of the inaugural reading group of the Centre for Consciousness at ANU set up by David Chalmers. I am extremely grateful to the members of that group—I have already named them—for stimulating discussion and comments. I am particularly indebted to David Chalmers and Frank Jackson: I hope it is obvious how much their works have influenced this one. Thanks also to Nic Damnjanovic for help with the bibliography and index and with preparing the manuscript for publication. Robert Miller, Peter Ohlin, Lara Zoble, Stephanie Attia, and Emily Voigt at Oxford University Press, New York, have been extremely straightforward and helpful—model editors. Alex Byrne and Brie Gertler were my readers for the press and provided excellent comments on the entire manuscript; Brie even sent me her entire annotated copy of the manuscript. Marion Obar was very kind to permit the use of her slug mosaic for the cover. While searching for something suitable for the jacket, I came across a picture of her mosaic on the web. I was amazed by how close it comes to capturing the story of the slugs and tiles, which is the starting point of the book. And thanks go again to David Chalmers, this time in his capacity as editor of the relevant OUP series. He gave extremely good advice, not only on philosophy but also how to frame the ideas in this book in the best possible way; if Dave didn’t exist, we would have to invent him. I have included in the text some passages that have been excerpted and adapted from the following previously published works of mine: ‘‘Two Conceptions of the Physical,’’ published in Philosophy and Phenomenological Research; ‘‘The Conceivability Argument and Two Conceptions of the Physical,’’ published in Metaphysics; and ‘‘Physicalism and Phenomenal Concepts,’’ published in Mind and Language. I am grateful to the publishers for permission to use this material. Finally, this book was written during a period in my life when Helen Keane and I got married and had two sons. I dedicate it, with much love and gratitude, to her.

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Contents

Introduction: The Slugs and the Tiles

3

Part I The Problem 1. The Phenomenal Conception

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2. Three Problems of Experience 25 3. The Skeptical Challenge

Part II

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The Proposal 4. Error from Ignorance 67 5. General Plausibility 87 6. Russellian Speculations 7. Historical Precedent

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8. Objections and Replies

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Part III The Alternatives 9. A Posteriori Entailment 10. A Priori Entailment

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11. Genuine Rivals, Revelation, and Concluding Remarks References Index

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IGNORANCE AND IMAGINATION

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Introduction The Slugs and the Tiles

Imagine a mosaic completely constructed from two sorts of tiles, triangles and pieces of pie. The mosaic may have many different shapes in it, so long as those shapes are constructed from the basic ones: circles, figure eights, half-moons, rectangles, rhombuses, and so on. Now imagine a population of intelligent slugs who live on the mosaic and are cognitively sophisticated but whose perceptual access to it is limited (never mind why) to two shapedetecting systems: the first scans the mosaic and detects triangles; the second scans it and detects circles. Given their access to the mosaic, it would be natural for these slugs to think that, at least so far as the tiles of the mosaic are concerned, it was constituted only of triangles and circles. Of course, this is a mistake, but it would be a natural one in the situation. Now imagine further that among these slugs there is a group of philosophers called slugists who begin to wonder about the nature of the mosaic and to formulate a synoptic vision of what it is and what it is like. For reasons that again need not concern us, many of the slugists take it that the circle-detecting system cannot tell them about the mosaic in its most fundamental nature and, in consequence, that circles must not be fundamental or primitive; the circular, they say, supervenes on the noncircular. In particular, the slugists think, the basic element of the mosaic is the triangle. What the mosaic consists of, one of them says, is a vast array of triangular tiles set out in a medium, with every other shape being a construction from these. The slugists now face what they call the problem of the circle: the circle-detecting system tells them that there are circles, and yet there is apparently no place for circles in a mosaic completely constructed by triangles. Why is there apparently no place for circles in a mosaic completely constructed by triangles? Some slugists insist that this is simply obvious, 3

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but even they admit that this insistence is, as they put it, weak from a polemical point of view. So two distinct lines of argument are presented to establish, as far as is possible, that the circular does not supervene on the noncircular. The first argument proceeds from the premises, first, that it is conceivable that there is a mosaic identical to the actual mosaic in all noncircular respects but for which circles are completely absent and, second, that what is conceivable is possible. The second argument proceeds from a thought experiment wherein a superslug is presumed to know everything noncircular about the mosaic but is not permitted to exercise her circle-detecting system. The superslug would never know whether the mosaic contained any circles or not. Both arguments conclude that circles are something over and above the rest of the mosaic. As one of the slugists puts it, circles are a special creation: when God was creating the mosaic, he created first the noncircular aspects, and then he had to create the circles in a quite independent act of creation. Different slugists respond to these arguments in different ways. Some respond that the circle-detecting system is not to be trusted and that in fact there are no circles—or at least no circles-as-we-traditionally-conceivethem. Others agree that circles are indeed primitive items and postulate laws linking them and triangles. A third group says that there must be some sort of elusive and extremely nonobvious analysis of circles into triangles. And a fourth says that circles and triangles are necessarily connected in a manner that is irreducibly a posteriori or synthetic in nature. For us who are neither slugs nor slugists, it is clear that all these responses are mistaken and that the arguments that give rise to them are fallacious. It is not possible that there is a duplicate mosaic in the sense we have defined. A mosaic exactly like the actual mosaic in noncircular respects would be exactly like it in terms of both triangles and pieces of pie—but such a mosaic would also be exactly like the actual mosaic in terms of circles. In other words, circles are not a special creation of God, and we stand in need of a plausible diagnosis of what has gone wrong in arguments leading to the nonsupervenience of the circular on the noncircular. What has gone wrong? The obvious and correct answer is that, in view of their perceptual limitation, the slugs have only a selective access to the mosaic. They think that the noncircular truths of the mosaic are completely a matter of triangles. In that situation it is understandable that they find a mosaic without circles possible, and within the confines of this deficit their reasoning is impeccable—understandable and impeccable, but wrong.

The Epistemic View The story of the slugs and the tiles (the slugs and slugists, though not the tiles, are due to Jackson 1982; see also chapter 5 in this book) allows me to introduce the main idea to be debated and defended in what follows: the

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epistemic solution to the problem of consciousness, or experience, in philosophy of mind—more briefly, the epistemic view. The core of this view is the hypothesis that our epistemic position with respect to the empirical world is analogous to that of the slugs to the mosaic. If our epistemic position is analogous, the correct response to the problem of conscious experience in philosophy of mind is likewise analogous to the correct response to the problem of the circle. Like the slugists, contemporary philosophers have formulated a synoptic view of what the empirical world is and what it is like. For reasons we will come to, many philosophers take it that introspection cannot tell us about the world in its most fundamental nature and, in consequence, that experiences must not be fundamental or primitive; the experiential, they say, supervenes on the nonexperiential. In particular, many philosophers think, a complete account of the nature of the world could in principle be given in nonexperiential terms. Contemporary philosophy now faces a problem of consciousness, or conscious experience, or—as I will usually call it—the problem of experience: introspection tells us that there are conscious experiences, and yet there is apparently no place for experiences in a world that is fundamentally nonexperiential. Why is there apparently no place for experiences in a world that is fundamentally nonexperiential? Some insist that this is obvious, but even they agree that this is weak from a polemical point of view. And so two distinct lines of argument are presented to establish that the experiential does not supervene on the nonexperiential. The first proceeds from the premises, first, that it is conceivable that there is a world identical to the actual world in all nonexperiential respects but different from it in some experiential respects and, second, that what is conceivable is possible. The second proceeds from a thought experiment wherein a superscientist is presumed to know everything about the nonexperiential but has had no relevant experiences herself. The superscientist would not know the whole truth about these experiences. Both arguments conclude that the experiential is something over and above the nonexperiential, a conclusion inconsistent with the dominant worldview. The problem of experience is the problem of resolving, or learning to live with, this inconsistency. The problem is simple but remarkably persistent and difficult, and it survives a great many variations in terminology, formulation, and emphasis. How are we to solve it? Well, here is an idea: Our position really is analogous to that of the slugs. Then the mistake in our thinking when confronted with the problem of experience would be analogous to the mistake in theirs when confronted with the problem of the circle. In particular, ignorance would explain two things: why we find so persuasive the two arguments that lead us to suppose that the experiential fails to supervene and why it is nevertheless mistaken to follow them through to their conclusion. In short, if our position is analogous to that of the slugs, the arguments that generate the problem of experience would be mistaken, and the problem itself would be solved.

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The Ignorance Hypothesis Of course, to suggest that our epistemic position is analogous to that of the slugs is not to suggest that the two positions are identical in every potential respect. Here are some ways in which the example might be misleading: (i) The slugs are ignorant of what is intuitively an element of the mosaic, and so of the world in which they live. Theirs is a basiclevel ignorance, as I will put it later on (see chapters 4 and 7). By contrast, our own ignorance might well take a nonbasic form; that is, we may be ignorant of truths that supervene on the basic truths rather than being themselves basic truths. (ii) The truths of which the slugs are ignorant are by themselves sufficient to account for all the truths about circles. By contrast (see chapter 4), the truths of which we are ignorant might account for experience only in combination with other truths and, in particular, with truths we already know. (iii) The pie pieces are similar in one way to circles and in another to triangles, and this might suggest a certain form of (what philosophers often call) a dual aspect theory, a kind of anti-physicalism that says that the world is fundamentally neither mental nor physical. By contrast, the position I advance is perfectly consistent with a version of physicalism. (iv) Finally, the perceptual limitation of the slugs will be interpreted by some as resulting in a cognitive limitation and hence as resulting in the slugs being cognitively closed—in McGinn’s (1989) phrase—with respect to the truths in question, that is, in its being a biological impossibility that the slugs come to know these truths. By contrast (see chapter 5), the truths of which we are ignorant may well turn out to be knowable from our point of view. Instead of these aspects of the slugs’ position, the salient thing for our purposes is this: the slugs are ignorant of a type of truth that is not itself about circles—pie pieces are not circles, after all—but that is nevertheless relevant to the nature of circles. So, too, if the epistemic view is correct, we are ignorant of a type of truth that is not itself a truth about experience but that is relevant to the nature of experiences—in brief, a type of experiencerelevant nonexperiential truth. Suppose we call the hypothesis that we are ignorant of a type of experience-relevant nonexperiential truth the ignorance hypothesis. Then we may formulate the epistemic view as the conjunction of two theses. The first is a conditional thesis linking the ignorance hypothesis and the problem of experience: E1.

If the ignorance hypothesis is true, the problem of experience is solved.

The second is the categorical thesis about the antecedent of this conditional: E2.

The ignorance hypothesis is true.

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The epistemic view may therefore be assessed for plausibility at both points. We may ask whether the connection between ignorance and the problem of experience is as E1 says. And we may ask whether it is the case, as E2 says, that we are ignorant in this way. In my view, both questions can be plausibly answered in the affirmative, but it is important to see first that they are different questions.

The Plausibility of the First Part The reasons for answering both questions in the affirmative will be our concern throughout this book. However, to present the main ideas briefly, the crucial considerations in the case of E1 are, first, that the arguments that give rise to the problem of experience are in one form or another modal arguments and, second, that ignorance has an impact on modal arguments. By a modal argument, I mean an argument whose starting points are various imaginable or conceivable cases, whose interim conclusions are various claims about what is and is not possible, and whose final conclusions are claims about the nature of the actual world. That there is some connection between ignorance and modal arguments is clear from examples. The slugs advance modal arguments that are frustrated by ignorance. To the extent that our epistemic position is analogous to theirs, our modal arguments would be likewise frustrated. However, not only is the connection between ignorance and modal arguments intuitively clear, it also may be embedded and explained within an attractive framework of ideas for thinking about modal arguments, a framework articulated by a number of philosophers, including in particular Kripke, and this fact has an important bearing on the plausibility of the epistemic view. In Naming and Necessity (1980), Kripke suggested that if we are faced with a modal argument whose conclusion we know or believe to be false, the argument might be disarmed by showing that the proponent of the argument has confused the proposition whose modal status is under discussion for a contrasting proposition that is, in the context, unobjectionable. Kripke himself thought that this method of disarming modal arguments could not be brought to bear in the special case of arguments about experience, a conclusion that to a large degree sets up the contemporary debate: on the one hand, many philosophers believe that the arguments about experience must be disarmed, but on the other hand, the standard ways of disarming the arguments apparently fail. As I will argue, an attractive feature of the epistemic view is that it avoids this dilemma entirely. For Kripke’s conclusion presupposes the falsity of the ignorance hypothesis: without the hypothesis, the situation seems, as Kripke implied, completely impenetrable; with the hypothesis, the arguments are susceptible to a version of the standard analysis he outlined, and everything falls into place.

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The Plausibility of the Second Part So much for E1, the thesis about the connection between the ignorance hypothesis and the problem of experience. What about E2, that the hypothesis itself is true? Because the ignorance hypothesis is contingent, it is unreasonable here to expect considerations of a logical sort. Nor should one expect a proponent of the epistemic view to produce the truths of which we are supposed to be ignorant; obviously, this is ruled out by the nature of the case. However, what can be done, and what I attempt in what follows, is to present grounds that render the ignorance hypothesis plausible, even if we cannot argue directly that it is true. As we will see in chapters 5 through 7, there are a number of different grounds here. Some have their source in very general observations about humans and their place in the world and about the sort of philosophical problem that the problem of experience is. Another has its source in some metaphysical speculation that is due in large measure to Russell’s discussion in The Analysis of Matter (1927) and elsewhere. However, the most persuasive consideration from my point of view emerges from the idea that the intellectual situation that confronts us when we reflect on experience is not unprecedented, and the precedents strongly suggest the epistemic view. One precedent is the discussion of linguistic understanding characteristic of the seventeenth century; another is the discussion about chemistry central to the nineteenth and early twentieth centuries. In these cases, philosophers advanced modal arguments similar to those advanced today concerning experience. In these cases, the modal arguments were a symptom of ignorance; a natural inference is that our own situation is a symptom of ignorance, too.

Dialectical Considerations In addition to these plausibility considerations in favor of the ignorance hypothesis, a number of dialectical considerations will figure prominently in our discussion. The first arises from the fact that, while most philosophers would presumably not deny that we are ignorant of the nature of consciousness in some sense or other, they would also hold that this ignorance is not relevant to the distinctively philosophical aspects of the issue. They hold, or can be brought to hold, that philosophical problems are such that they ‘‘are solved, not by giving new information, but by arranging what we have always known’’—the phrase is from Wittgenstein’s Philosophical Investigations (1953, 47). This idea, or something like it, is remarkably influential in philosophy of mind, much more influential than the Wittgensteinian apparatus within which it first found expression. For example, in The View from Nowhere (1986), Thomas Nagel holds that the origin of the problem is the contrast between the objective and the subjective

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standpoints. Similarly, in The Conscious Mind (1996), David Chalmers holds that the origin of the problem is the contrast between truths that concern (what he calls) structure and function and those that do not. If either of these positions is correct, the epistemic view is not simply wrong: It is quite disastrously misguided. For if these views are correct, the problem is conceptual, and as such would persist through the acquisition of the type of knowledge I think is absent. But I will argue in chapter 8 that these views are not correct and that the problem of experience is not conceptual in origin but epistemic. Indeed, in my view it is the misclassification of the problem as conceptual that constitutes the greatest blockage to progress on the topic. A different dialectical consideration is that positions alternative to the epistemic view are implausible. What are these alternatives? The contemporary literature is dominated by four positions, parallel to those adopted by the slugs in response to the problem of the circle. I call them eliminativism, primitivism, the a priori entailment view, and the a posteriori entailment view. Eliminativism says that there are no experiences, or at least no experiences-as-we-standardly-conceive-them. Primitivism says that experiences are metaphysically distinct from other things and postulates laws linking the experiential and the nonexperiential. The a priori entailment view says that there must be some sort of elusive and extremely nonobvious analysis of the experiential into the nonexperiential. And the a posteriori entailment view says that the experiential and nonexperiential are related by a relation of necessity that is irreducibly a posteriori or synthetic in nature. These views are very different from one another and raise all sorts of important and interesting questions. But I will argue in chapters 9 through 11 that, to the extent that they present genuine alternatives to the epistemic view—an issue that, as we will see, is controversial—they do not provide plausible solutions to the problem of experience.

Different Versions of the Same View Although the epistemic view is not in the standard catalogue, versions of it have certainly been suggested before, and in that sense I claim no great originality in advancing it. What, then, is distinctive about the present discussion? Some new elements, or at least elements not set out elsewhere the way I do here, have already been mentioned: the spelling out of the connection between ignorance and modal epistemology, the claim that our present situation has important historical precedent, and the critique of positions that deny the ignorance hypothesis, either as an account of the problem itself or as an account of a solution to the problem. But there are three further features that differentiate my own contribution from others. The first is an emphasis on the distinctive nature of the philosophical problem of experience. Philosophers who appeal to ignorance are sometimes viewed as, and sometimes are, skeptical of their subject. The position

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Introduction

adopted here is not skeptical in this sense; on the contrary, the first part of the book is a defense of a philosophical problem. In fact, the difference between empirical and philosophical questions is important for my position. For suppose the only interesting problem or problems in the area were empirical. Then our position would hardly merit formulation; obviously we are empirically ignorant with respect to experience. On the other hand, if there are distinctively philosophical problems in the area, our position is not only interesting but also widely held to be false. For many contemporary philosophers, the solution to the philosophical questions of experience lies not in ignorance of some relevant facts but rather in correcting a mistaken conception or picture of experience, or else a mistaken conception or picture of our thought and talk about experience. I think these suggestions are unpersuasive, but it is important to see at the outset that they are different from my own. Indeed, from my point of view, the problem is not a mistaken conception of experience so much as a mistaken conception of the problem of experience; in particular, it is a mistake to think of it as at root conceptual. The second distinctive feature is an emphasis on the particularity of the problem of experience. Many contemporary philosophers emphasize the similarity among the problems they discuss. Problems about conscious experience, the self, morality, modality, semantics, and probability are all presented as having a similar structure and even as reflecting a single underlying problem that has a ‘‘value case,’’ a ‘‘probability case,’’ and so on. Of course, in one sense this is unobjectionable; we may certainly learn something about a problem by comparing it with others, and we ourselves will do a certain amount of comparing and contrasting in what follows. But the approach also tends to suppress the differences among problems and, in consequence, suppresses the possibility of the epistemic view. For when we look sideways at many other philosophical problems, a counterpart of the epistemic view is often implausible. If these other problems are a guide to the experience problem, the inevitable conclusion is that the epistemic view is implausible in this case, too. But in my view this conclusion is quite mistaken: the implausibility of the appeal to ignorance in other cases is evidence not of the falsity of the epistemic view but of the difference between the problem of experience and other philosophical problems. The third distinctive feature of our discussion has to do with the fact that, in the past, appeals to ignorance have been made within the context of relatively radical views about the nature and content of the ignorance in question. For example, some view the ignorance hypothesis as essentially involving an appeal to new physics or to quantum theory or at least as involving speculation about the future course of science. Some view our ignorance as a consequence of the scientific or intellectual paradigm that we are currently in, and that in consequence we cannot remedy it without revising the notion of the material world, the notion of experience, or both. Some view our ignorance as a consequence of the cognitive structures that

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are part of our genetic endowment, and that as such we are cognitively closed with respect to the solution to the problem. And some view our ignorance as a consequence not of historical or psychological facts but of the a priori structure of empirical inquiry, as following from the fact (if it is a fact) that empirical inquiry does not acquaint us with the intrinsic nature of matter. Whatever the plausibility of these views considered alone, they will play no essential role in the version of the epistemic view defended here. My view is that a hypothesis about our current epistemic situation is the best explanation for the distinctively philosophical predicament we are confronted with when we think about experience. No quantum mechanical theory of consciousness follows from this, no speculations about the future course of science, and nothing at all about the limits of thought, regardless of whether those limits are of a historical, psychological, or a priori nature. The effects of my emphasis on the uniqueness of the problem of experience, and of divorcing the epistemic view from its radical context, will, I hope, be felt throughout our discussion. But one effect should be stated immediately. The fact that this view has implausible counterparts in other cases and has often been associated with radical views encourages the impression that a view of this kind is itself radical and implausible, and this encourages the further impression that it might legitimately be set aside; if you already think a view is implausible, it does not take much persuasion to ignore it. I think this greatly underestimates the epistemic view. Not only is the view not radical, it is the obvious and commonsense position to adopt in the circumstances—at any rate, so I hope to have convinced you by the end of the book.

Outline of the Argument So that is the epistemic view, or at least an initial sketch of the view. How is our defense of it to proceed? Part I (chapters 1 through 3) is concerned with the identification of the problem for which the epistemic view is a solution. In chapter 1, I identify the subject matter of the problem: experience as presented by the phenomenal conception. According to this conception, experiences are psychological events whose defining characteristic is that there is something it is like to undergo them—whose defining characteristic is their phenomenal character, as it sometimes put. I argue that the phenomenal conception is a minimal conception in that it is neutral on many aspects of experience that are thought to be philosophically puzzling. In chapter 2, I identify the problem to be discussed about this subject matter: the logical problem. The logical problem is best presented as the conjunction of three theses that are individually plausible but jointly inconsistent: the thesis that there are experiential truths; the thesis that if

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there are experiential truths, such truths are entailed by nonexperiential truths; and the thesis that if there are experiential truths, such truths are not entailed by nonexperiential truths. I distinguish the logical problem from two other problems with which it is apt to be confused, the empirical problem and the traditional mind-body problem. In chapter 3, I discuss the skeptical challenge that it is mistaken to suppose that there is a genuinely philosophical problem of experience at all. According to one version of the challenge, the problem should be rejected on methodological grounds: it is mistaken to reason from conceivability to possibility at all. My response is that this reasoning is ubiquitous in philosophy, and thus to the extent that there is a problem here, it is everyone’s rather than mine. According to another version of the challenge, the problem should be rejected on conceptual grounds: the thesis of physicalism certainly made sense at a particular moment in the history of science, but that moment is long gone and contemporary interpretations of it do not permit the questions typical of philosophy of mind to be legitimately raised. My response is that physicalism and related concepts play an illustrative or inessential role, rather than an essential role, in the logical problem, and that, once this is appreciated, the basis for skepticism evaporates. Part II (chapters 4 through 8) sets out and defends our solution to the problem. In chapter 4, I take up E1, the thesis that if the ignorance hypothesis is true, the logical problem is solved. My defense of this thesis begins from the idea that there are a number of distinctive ways that a modal argument can go wrong—a number of standard mistakes, as I call them. The philosophical challenge presented by the modal arguments that are constitutive of the logical problem is that it is hard to see in these cases that we are making any of these standard mistakes. On the other hand, if the ignorance hypothesis is true, it becomes immediately plausible to suppose that we are making one (or a combination) of these mistakes. This suggests in turn that E1 is true: if the ignorance hypothesis is true, the logical problem is solved. In chapters 5 through 7, I turn from E1 to E2 and discuss the case for believing the ignorance hypothesis in the first place. Chapter 5 starts by emphasizing our ignorance in general, our ignorance of experience in particular, the way in which the assumption of ignorance explains a philosophical predicament that otherwise remains elusive, and the way in which the ignorance hypothesis is suggested by the basic structure of the logical problem. Chapter 6 takes up Russell’s idea that reflection on the nature of scientific inquiry prompts a version of the ignorance hypothesis, an idea much discussed in contemporary philosophy. Chapter 7 proceeds by pointing out that the epistemic view is known to be correct for older philosophical problems that are structurally analogous to the logical problem, problems that concern not the phenomenal character of experience but the intellectual character of thought and the chemical features of physical objects.

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In chapter 8, I respond to objections, concentrating on two in particular. According to the first, the epistemic view is mistaken because if the problem at issue is understood correctly, we are in possession of the relevant truths; according to the second, the epistemic view is mistaken because it has a range of alarming side effects, some of which have been suggested by proponents of the view themselves. These objections raise important questions, but I will suggest that reflection on them strengthens, rather than weakens, our position. Part III (chapters 9 through 11) is concerned with alternatives to our position and with securing the suggestion that a comparative analysis favors the epistemic view. In chapter 9, I discuss a posteriori entailment, the view that the supervenience of the experiential on the nonexperiential is irreducibly a posteriori. The main problem for this view emerges when we notice that the philosopher who did the most to make it prominent, Kripke, also considered and rejected it. In my view, the lesson of Kripke’s discussion on this point is that the mere idea of a posteriori entailment does not solve the problem of experience and therefore that a proponent of the a posteriori entailment view is obliged to add further material. On the other hand, an examination of what this further material might be yields the result that the a posteriori entailment view either has no answer to the arguments or else collapses into the epistemic view. In chapter 10, I advance an analogous argument in the case of the a priori entailment view. On the one hand, the mere idea of a priori entailment will not answer the argument; you need to add further material. On the other hand, an examination of what this further material might be yields the result that the a priori entailment view either has no answer to the arguments or else collapses into the epistemic view. In chapter 11, I conclude the overall discussion by doing three things: I review the reasons for rejecting eliminativism and primitivism; I criticize an independent argument for these views that would, if successful, also undermine our own position (an argument founded on the idea, known as ‘‘revelation,’’ that understanding experience means knowing its essence); finally, I summarize and make explicit some general morals.

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PART I THE PROBLEM

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1 The Phenomenal Conception

1.1. Introduction Recent years have seen considerable discussion about conscious experience and related notions both in the cognitive and neural sciences and in philosophy of mind. In philosophy, the problem is often seen as a continuation of (what is usually called) the traditional mind-body problem, famously posed by Descartes in the seventeenth century and discussed nowadays in every introductory philosophy class. In the sciences, the problem is usually thought of as an empirical problem perhaps beyond present-day technique but nevertheless importantly shaped by its close association with the traditional mind-body problem. Indeed, it is not unreasonable in response to these discussions to assume that here we have a roughly unified question, or set of questions, approached differently: the problem in the sciences is just the same as the problem in contemporary philosophy that was discussed by Descartes; it is just that the problem is being addressed in different ways. On reflection, however, this assumption—same problem, different approaches—is neither mandatory nor obvious. Different fields and traditions of study modify the questions they pursue to a considerable extent. So it is not always clear that a problem that goes under a given name in one domain is the same as a problem that goes under the same or a similar name in another. Hence my goal in part I of the book: to identify the problem with which we are concerned—the problem of conscious experience in philosophy of mind—and to chart its relations to other problems with which it is apt to get confused. What I will suggest is that the problem mainly at issue in contemporary philosophy is distinct both from the mind-body problem as that problem is traditionally understood and from the problem as it is, or might be, pursued in the sciences. 17

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In parts II and III, I will go on to argue that recognizing this fact has consequences for the way we think about the issues and, in particular, that it opens the path to a solution to our problem. But discussion of the solution will be postponed until we have identified the problem.

1.2. A Framework for Discussion The question ‘‘What is the problem of experience?’’ may be divided into two subquestions:



What is the topic, or subject matter, of the problem? What sort of problem, or problems, are we raising about this topic?

In distinguishing these questions, I don’t mean to imply that there can be no interaction between them. One’s position on what experience is might well be conditioned by what problem one thinks is raised by experience. Nevertheless, the distinction is a reasonable one to adopt initially, and, in the light of it, our discussion in part I will be organized as follows: In this chapter I will consider the first question, and in chapter 2 I will discuss the second. Then, in chapter 3, I will discuss a challenge to our inquiry emanating from the skeptical idea that it is a mistake to think that there is a problem of experience of a distinctively philosophical kind at all. I will argue that the skeptical challenge is mistaken, but to simplify matters, I will largely ignore it until discussion of it becomes inevitable. How can we approach the question of what our subject matter is? One possibility is to undertake an analysis of the concept of consciousness or experience in the traditional sense. On this approach, we would try to complete, in terms that do not themselves involve the notion, a claim of the form ‘‘S has or undergoes experience E if and only if. . . .’’ This is not the approach I will adopt here. Many extremely clever people have despaired of analyzing the notion of experience (e.g., Block 1995). There is no reason to believe that I will be more successful than they have been. It is also in general both unrealistic and unnecessary to analyze or define a notion before one can usefully talk about it. The goal ought to be to understand it to a sufficient extent that relevant questions can be fruitfully posed and discussed. So in what follows, I will introduce the conception of experience that is the starting point of this discussion and indeed many others—I call it the phenomenal conception— and then go on to explain the sense in which the phenomenal conception is, as I will put it, a minimal conception of experience.

1.3. The Phenomenal Conception Suppose I am looking at the gray filing cabinet in the corner of my office. In one natural use of the term, we may say that this event—my seeing the gray

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filing cabinet—is an experience that I have. Of course this experience has many properties. It occurs in time. It has a place in an overall causal structure of events. It stands in interesting relations to other psychological events and states, to neurological and other factors, to my social and physical environment, to my behavior and history, and so on and so forth. All these facts are interesting and raise interesting questions, some of which our discussion to follow will bear on. However, according to the phenomenal conception, there is one fact about the experience more important than the others: that there is something it is like to have it. According to the phenomenal conception, this fact about my seeing the filing cabinet is what makes it an experience. Without this, my seeing the gray filing cabinet might be many things. But it would not be an experience. So far as I know, it was Wittgenstein who first drew attention to the connection between experience and the expression ‘‘what it is like.’’ In Remarks on the Philosophy of Psychology, Vol. 1 (1980), x91, which dates from 1946–1947, Wittgenstein writes: ‘‘The ‘content’ of experience, of experiencing: I know what tooth-aches are like, I am acquainted with them, *I know what it’s like to see red, green, blue, yellow, I know what it’s like to feel sorrow, hope, fear, joy, affection. . . .’’ (It is interesting to note that Wittgenstein wrote the material following the asterisk in English rather than his usual German.) The connection was then discussed by Farrell 1950 and Sprigge 1971 and, finally, with much more penetration, by Nagel 1974. Here is a passage from Nagel’s seminal paper: Conscious experience is a widespread phenomenon. It occurs at many levels of animal life, though we cannot be sure of its presence in the simpler organisms, and it is very difficult to say in general what provides evidence of it. (Some extremists have been prepared to deny it even of mammals other than man.) No doubt it occurs in countless forms totally unimaginable to us, on other planets in other solar systems throughout the universe. But no matter how the form may vary, the fact that an organism has conscious experience at all means, basically, that there is something it is like to be that organism. (1974, 519) Nagel talks here (as in fact I have already done) of conscious experience rather than of experience tout court. This raises the issue of the relation of experience to consciousness; the issue is important but may ignored for the moment. And he also concentrates on what it is like to be an organism rather than what it like for an organism to be in some psychological state or undergo a psychological episode. But, as a number of commentators (e.g., Jackson 1982) have noticed, the crucial issue seems to emerge when we focus on certain psychological events—such as seeing a gray filing cabinet— and notice that there is such a thing as what it is like to undergo those events. However, setting aside these differences, Nagel is clearly voicing the phenomenal conception: a psychological event counts as an experience just in case there is something it is like for the subject to undergo that event.

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The Problem

Nagel speaks not only of what it is like to have or undergo an experience but also of the subjective character of experience; that is, he uses ‘‘subjective character’’ as a name for the property psychological events have when they are experiences. And other philosophers have used ‘‘phenomenal character’’ for the same purpose. This permits an alternative formulation of the phenomenal conception as follows: a psychological event is an experience if and only if it has some phenomenal character. It is perhaps in this formulation that the naturalness of the conception is closest to the surface. For notice that the expression ‘‘the experience of seeing a filing cabinet’’ may be interpreted, not as denoting the event of seeing a filing cabinet—as I have been assuming so far—but rather the phenomenal character of seeing a filing cabinet. We in fact do say that the experience of this event is identical to the experience of that event and mean by this only that the phenomenal character of this is identical to the phenomenal character of that. This suggests, more generally, that when we speak of what it is like to undergo an experience, or the phenomenal character of that experience, we are really speaking of the experience of undergoing that experience. This simple idea—that there is such a thing as the experience of (i.e., the phenomenal character of) undergoing an (event of) experience—lies at the heart of the phenomenal conception. This then is our starting point: experience as construed by the phenomenal conception. It is not an absolutely uncontroversial starting point. One of the consolations of philosophy is that there is always someone who finds what you say controversial. But it is true also that for many philosophers the phenomenal conception operates as a minimal or baseline conception: although many notions of experience inflate it, developing it in various ways, no notion, or almost no notion, deflates it. At any rate, that it is a minimal conception will be my assumption in what follows.

1.4. The Phenomenal Conception as a Minimal Conception In saying that the phenomenal conception is a minimal conception, I mean, as I have said, that it is a baseline conception in our thinking. But I also mean that it is neutral on many of the issues that one might raise in the course of thinking about experience. To develop this point and to set the stage for what follows, it will be useful to briefly mention what some of these issues are and therefore to indicate what the phenomenal conception is and is not committed to.

1.4.1. Metaphysics of Mind To begin with, the phenomenal conception does not raise or prejudice any of the traditional questions associated with the mind-body problem— questions we may lump together under the heading ‘‘metaphysics of mind.’’

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We have not identified experiences with any event in the brain of the person having that experience. We have said nothing about the truth of physicalism or dualism, or about the related question of whether and to what extent it is possible to construct a recognizably scientific theory of experience or particular experiences. Nor have we raised any concerns about subjectivity and objectivity. Later, we will of course address these questions. But the phenomenal conception by itself does not.

1.4.2. Ontology The idea that experiences are events and that phenomenal character is the defining property of such events raises questions of a very general nature about what exactly events are and what exactly it is to be a property of an event (or of anything else for that matter). These questions are interesting, but I will not pursue them. My policy is to be easygoing about ontology. In general, some ontological framework is required to pose and discuss questions about experience. But the precise interpretation of that framework should not concern us; certainly, nothing is forced on us by the phenomenal conception. In fact, even the reference to events in our discussion should be interpreted in the light of this easygoing policy. Suppose compelling reasons are produced to the effect that an item of some other ontological category has phenomenal character and so should be called an experience—a process or state or fact, say. In my view that would be neither surprising nor antipathetic to the basic thrust of the phenomenal conception.

1.4.3. Epistemic Principles Contemporary philosophy has formulated a number of epistemic principles about the relationship between experience, on the one hand, and knowledge of, or justified belief about, experience on the other. One is self-presentation: if Jones is in pain, he thereby is in a position to know or justifiably believe that he is. (Compare: if Jones is in debt, he is not thereby in a position to know that he is; he would have to talk to an accountant or examine his bank statements.) Another is revelation: if Jones is in pain, he thereby knows, or is in a position to know, the essence of his pain. (Compare: if Jones is in debt, he is not thereby in a position to know the essence of his debt; he can be in debt and have no real idea of what debts are.) There is much to say about the nature and plausibility (or implausibility) of these principles, and we ourselves will take up some of these issues in what follows (see chapters 9 and 11). But—again—the phenomenal conception does not do so.

1.4.4. Intentionality When I see the filing cabinet, there is a sense in which the world seems or appears to me to be a certain way, and we may go on to ask whether the

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world is in fact the way it appears. If the experience in question is an outright hallucination or is illusory in some respect, the world is not as it appears. (Perhaps in that case it would be incorrect to describe it as a seeing of a filing cabinet.) In short, just like speech acts, beliefs, sentences, gestures, road signs, and maps, experiences represent the world as being a certain way and, as such, can be evaluated for correctness or incorrectness. Philosophers mark this feature by calling it the intentionality of experience: experiences have intentionality because in having an experience, it appears to you that the world is a certain way, and it is a legitimate question whether the world is the way that it appears. The idea that experiences exhibit intentionality constitutes a major juncture of our topic with others. Here the topic of experience connects with some of the central questions of philosophy of language and metaphysics and with questions about the relation between experience and other aspects of psychology broader than we have so far considered—questions about the distinct functional role of experience compared with other psychological states and events, and questions about the connection between experience and belief. Later in our discussion (see chapter 10), we will address some (not all) of these topics, but the phenomenal conception by itself does not. The phenomenal conception does not entail that experiences have intentionality or that they do not, nor does it take a stand on what philosophical significance, if any, the intentionality of mental states has.

1.4.5. Consciousness When I see the gray filing cabinet and thereby have an experience, the experience in question was conscious, or so we may suppose. But what is it to say that a psychological event or episode is conscious? On one view, a psychological event is conscious just in case it has some phenomenal character. So, on this view, an event is an experience just in case it is conscious, and conscious just in case it is an experience. More generally, instead of saying that our topic is the phenomenal conception of experience, we could equally have said that our topic is consciousness. The two topics are one and the same: talk of consciousness recapitulates talk of experience. It is this understanding of consciousness that I employ when I move back and forth—as I have so far done and will continue to do—between talk of consciousness, experience, and conscious experience. Block (1995) calls the notion of consciousness just introduced ‘‘phenomenal consciousness’’ and contrasts it with another notion, ‘‘access consciousness.’’ So, adopting this phraseology, a psychological event is phenomenally conscious just in case it has some phenomenal character, and a psychological event is access-conscious just in case it is the object of the right sort of awareness or attention. And our topic could then be described as phenomenal consciousness. However, as Block also makes clear, what

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the relation is between these two notions is controversial; is phenomenal consciousness—consciousness in the phenomenal sense—reducible to access consciousness and, if so, what significance attaches to this fact? I will go into these issues to some extent later (chapter 10). But again, the point for us is that the phenomenal conception does not prejudge them.

1.4.6. Qualia For some philosophers, to explain the phenomenal character of experience, one must postulate or assume particular qualities of the experience, qualia (singular: quale). The obvious difficulty in evaluating the idea of qualia derives from the large variation in how this notion is understood. In one usage, the quale of an experience is simply its phenomenal character. In this sense, we have been talking of qualia all along, and qualia add nothing except an annoying Latinism to the discussion. In another, commitment to qualia is a way of registering one’s belief that the phenomenal conception cannot be accounted for in intentional or perhaps physical terms. As I have noted, these questions go beyond commitment to the phenomenal conception itself. In still a third sense, the notion of qualia is tied constitutively to the traditional philosophical idea of sense data: qualia are the properties of the mental particulars (i.e., sense data) that are the objects of perception. But mere commitment to the phenomenal conception does not involve commitment to sense data, and so here, too, qualia go beyond what we have introduced. In view of the many different ideas that might be at issue when what is at issue is qualia, it is prudent to avoid the notion, and that will be my policy in what follows.

1.4.7. Diaphanousness When I try to attend or reflect on the experience of seeing the filing cabinet, my attention normally seems to be directed at the filing cabinet itself. The experience itself seems—as it is often put—diaphanous or transparent to introspective attention. This idea has been used in a number of ways in the history of philosophy of mind. G. E. Moore (1903a) offered it as a psychological explanation as to why idealists make a mistake (in his view) characteristic of idealism. Farrell (1950) drew attention to it while arguing that the traditional questions of philosophy of mind were pseudoquestions, a position he summarized, somewhat remarkably, by saying that experience ‘‘is not the sort of thing of which one can fruitfully say ‘it is a sort of thing’ ’’ (180). Harman (1990) appeals to diaphanousness in the course of an attack on the notion of qualia. Once again, these questions are interesting, but the phenomenal conception takes no stand on them. For our purposes, the thesis that experience is diaphanous is distinct from, but compatible with, the phenomenal conception: what it is like to have an experience is one thing, and what is like to reflect on experience is quite another.

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1.4.8. Distribution Some events of perception, imagination, and sensation have phenomenal character. But do all such events? In the case of perception, the phenomena of blind sight and more generally unconscious perception make it problematic to assume so—or so at least it is sometimes argued. And what about psychological states or events different from these? Do moods have phenomenal character? What about thoughts? And what about the psychological states and events enjoyed by nonhuman animals—do these have phenomenal character? (See Nagel’s extremist in the passage quoted earlier.) How simple does an organism have to get before it is appropriate to deny it experience? These issues of distribution are interesting, but the phenomenal conception does not take a stand on them, nor will it be important for our purposes to examine them in detail. It is clear that certain paradigm instances of mental events have phenomenal character. These examples suffice to motivate our discussion. Our topic is experience (or consciousness) as presented by the phenomenal conception; now, what sort of problem, or problems, does this topic present?

2 Three Problems of Experience

2.1. Introduction In one sense, it is easy to say what problem is raised by our topic. The problem is to provide something we don’t have—that is, an explanation or understanding of experience and its phenomenal character. This answer is fine so far as it goes, but it doesn’t go very far. For it is not clear that when cognitive or neural scientists ask for an explanation of conscious experience, they have in mind the same sort of concern that is voiced in philosophy. And discussions in philosophy are notoriously frustrated by a failure to state precisely what problem it is that is supposed to be solved and what would count as a solution to that problem. Vague injunctions to ‘‘explain conscious experience’’ or to provide a ‘‘theory of consciousness’’ are unlikely to be of help in this regard. So, although it is certainly true that we are interested in explanation and understanding, it is also reasonable to demand further details. It is these further details that will be my concern in this chapter. I start by explaining the main problem I want to discuss. I call it the logical problem of experience. Then I compare and contrast the logical problem with two others, which I call the empirical problem and the traditional mind-body problem. The crucial point will be that the three problems are different from each other and thus that our response to the logical problem may be developed in relative isolation from any response to the others. As will emerge in later chapters, the logical problem is to be set apart not only from these problems but also from others. But these further comparisons will not be our topic in this chapter.

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The Problem

2.2. The Logical Problem The logical problem can be presented compactly by considering three theses that, on reflection, we have reason to endorse but are jointly contradictory. T1. T2. T3.

There are experiential truths. If there are experiential truths, every experiential truth is entailed by some nonexperiential truth. If there are experiential truths, not every experiential truth is entailed by some nonexperiential truth.

Logically speaking, these three are jointly contradictory: if any two of them are true, the third must be false. So one thing we know is that, barring some subtle ambiguity, at least one of T1–T3 is false. On the other hand, each of the theses has powerful considerations, or what seem initially to be powerful considerations, in its favor. In consequence, we find ourselves in the following position: either we are wrong to assume that T1–T3 are incompatible—that is, there must be some subtle ambiguity here—or else the considerations that seem so powerful are not powerful after all. To decide which course of action to adopt when placed in this position, and how precisely to adopt it, is the intellectual project presented by the logical problem. It is this project that will concern us in parts II and III of this book. But, first, what are the initially powerful considerations in favor of each of T1–T3?

2.3. The Case for T1 Well, given our discussion in the previous chapter, when we speak of experiential truths, what we mainly have in mind are truths with a certain distinctive subject matter—namely, events of sensory, perceptual, and imaginative experience, events whose defining property is that there is something it is like to undergo them. Likewise, when we speak of nonexperiential truths, what we have in mind are truths with a certain, different, distinctive subject matter—namely, events that are not experiences. From that point of view, the first of our three theses says that there are (will be, have been) such experiences. So understood, T1 is contingent and empirical, something that might have been otherwise. One can easily imagine a world at which there are no experiences whatsoever. But T1 is also an empirical claim of quite astounding obviousness. It is something we know or believe in our own case on the basis of introspection and in the case of others (both human and animal) on the basis of observation: I am having experiences right now; that is at least one experiential truth; so T1 is true.

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2.3.1. Compounds I have said that experiential truths are those with a certain distinctive subject matter. But this leaves a notorious set of questions unanswered, questions raised famously in a related context by Prior 1949 (see also Restall and Russell 2005). Suppose that E is some experiential truth and I is some nonexperiential truth. How are we to classify compound claims—that is, claims formed from E and I by standard logical operations? For example, how are we to classify claims of the form ‘‘it is not the case that E’’ or ‘‘it is not the case that I ’’? On the one hand, it is natural to say that negations of experiential truths are themselves experiential. On the other hand, to say this is to confront a problem. For if ‘‘it is not the case that E’’ is an experiential claim just as E is, then T1 is not an empirical truth as I just claimed. For it is a logical truth that either E or its negation is true, and if either is an experiential truth, it is a logical matter that there are experiential truths. This problem is in fact a remarkably difficult one, but I propose here to deal with it by stipulation—that is, by somewhat arbitrarily restricting attention in what follows to positive noncompound experiential truths. Of course, this immediately raises the question of how to justify the restriction. However, justifying the restriction will not matter to the main issues we will discuss, and therefore I will not try to do so here. It is true that there is something it is like to look at the gray filing cabinet in the corner of your office or (to vary the example) to stick a needle into the joint of your big toe. These truths are enough to motivate our problem. How exactly to classify compound truths formed from these need not concern us.

2.4. Entailment So much for the reasons for believing T1; what about T2 and T3? Well, both T2 and T3 introduce a new notion into the discussion, entailment. Entailment can sometimes mean something that holds between truths in virtue of their logical form. That is not what is meant here. What is meant, rather, is the modal notion of entailment, according to which, where E is an experiential truth and N is a nonexperiential truth, N entails E just in case, if N is true, E must be true; equivalently, N entails E just in case if N is true, it is impossible that E is false. This notion of entailment is closely related to what philosophers point to under the label ‘‘supervenience.’’ Indeed, for our purposes though not for all, supervenience is the converse of entailment: to say that every experiential truth is such that it is entailed by some nonexperiential truth is to say that every experiential truth is such that it supervenes on some nonexperiential truth. More particularly, it is useful in what follows to

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introduce the doctrine of experiential supervenience. One way to formulate this doctrine is: (1) Experiential supervenience is true at a world w if and only if every experiential truth at w is entailed by some nonexperiential truth at w. In the light of this, we may say that what T2 says is that if there are experiential truths, then experiential supervenience is true, and what T3 says is that if there are experiential truths, then experiential supervenience is false. There has been considerable discussion of the notion of supervenience in recent literature, particularly in the work of Jaegwon Kim (e.g., 1993) and Terry Horgan (e.g., 1993). Many different notions have been distinguished— for example, strong and weak supervenience, local and global supervenience—and the relative merits of these notions, and how they relate to one another, have been greatly discussed. For our purposes, however, it is not necessary to discuss these matters in any detail, and so I will set them aside.

2.5. The Case for T2 Experiential supervenience says that the experiential truths supervene on the nonexperiential truths. And T2 says that if there are experiential truths, experiential supervenience is true. However, why believe T2 so understood? It is possible to distinguish two considerations in favor of T2: the argument from physicalism and the argument from manifest supervenience. Later we will consider the cogency of these arguments; for the moment, our goal is to formulate them.

2.5.1. The Argument from Physicalism Physicalism is a thesis about the contingent nature of the world, according to which everything is physical. Of course, physicalists don’t deny that there are many things that don’t appear at first glance to be physical, but they nonetheless think that at the end of the day, everything is physical. Physicalism is widely held to be plausible in contemporary philosophy on the grounds, first, that it summarizes the basic picture of the world offered to us by modern science and, second, that it is reasonable to believe the picture of the world, whatever it is, that modern science offers us.

2.5.1.1. Physicalism and Supervenience What do physicalists mean when they say that everything is physical? The answer is that they mean a supervenience thesis akin to the one we have already introduced. One way to formulate the doctrine is as follows:

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(2) Physicalism is true at a possible world w if and only if every contingent truth at w is entailed by some physical truth at w. So understood, physicalism is not the thesis that there are no nonphysical truths. Perhaps psychological or social or biological truths are properly thought of as nonphysical. What physicalism says, rather, is that these truths, if there are any, are entailed by physical truths. Just as there has been considerable discussion of supervenience in the recent literature, there has been considerable discussion of the use of supervenience in formulating physicalism. Other formulations of physicalism have been proposed—for example, formulations founded on identity or realization—and the relative merits of these formulations have been greatly discussed (see, e.g., the papers in Gillett and Loewer 2002). Once again, however, the question of whether to formulate physicalism as a supervenience doctrine or in some other way will not greatly affect what I want to say, and so I will set it aside.

2.5.1.2. Understanding ‘‘Physical’’ Supervenience provides some clarification of the thesis of physicalism, but it leaves unanswered an important question. What exactly are the physical truths that, according to the physicalist, provide the supervenience basis for every other truth? This question does not require a definition of what it is to be physical; as noted earlier, it is in general both unrealistic and unnecessary to analyze or define a notion before one can usefully talk about it. The question calls for understanding, not analysis. How then is ‘‘physical’’ to be understood? In the next chapter, I will discuss further aspects of this issue; for the moment, it is enough to note that we will here operate with what might be called the paradigm physical object view of the physical. To introduce the paradigm physical object view, it is useful to begin with a different thesis, mechanism. Mechanism is a version of physicalism and might therefore be stated, if we wished, as a supervenience thesis in what is by now for us the normal way. According to this way of stating it, mechanism is the doctrine that any truth at all is entailed by the mechanical truths of the world. If we state mechanism this way, we arrive at the same point in the discussion— namely, the point at which we ask what a mechanical truth is. In this case, however, there is a procedure for explaining what a mechanical truth is. The first stage draws attention to the fact we have an ordinary conception (without being able to analyze it) of what a paradigmatic machine is; that is, we know that toasters, computers, and telephones are paradigmatic machines, and likewise we know that yaks, comets, and rosebushes are not paradigmatic machines. (I am not saying that it might not turn out that yaks are machines in some sense. The point is they are not paradigmatic machines, just as they are not paradigmatic pieces of garden furniture.) The

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second stage defines a mechanical truth as any truth that is required in the explanation of the intrinsic or essential nature of paradigmatic machines. Putting this together with supervenience, we arrive at the idea that mechanism is the view that truths of this sort are such that they entail all the truths. More colloquially, mechanism might be formulated from the perspective of an imaginary mechanist as follows: ‘‘Take objects like this toaster, and now take whatever principles and theories are required to explain their nature and operation. My view is that these are the principles and theories that explain the whole world—or, to be more cautious about it, provide the supervenience base for whatever it is that explains the whole world.’’ The paradigm physical object view may now be introduced by a variation of the procedure just rehearsed in the case of mechanism. First, we point out that we have an ordinary conception of what a paradigmatic physical object is; that is, stones and trees are paradigmatic physical objects, and numbers and propositions are not. Second, we explain the idea of a physical truth as any truth required in the explanation of the intrinsic nature of physical objects. That gives us an account of what a physical truth is, and supervenience does the rest. Once again, we may formulate physicalism in the mouth of an imaginary physicalist as follows: ‘‘Take objects like stones and trees, and now take whatever principles and theories are required to explain their nature and operation. My view is that these are the principles and theories that explain the whole world—or to be more cautious about it, provide the supervenience base for whatever it is that explains the whole world.’’ It is sometimes objected that this method of explaining what it is for something to be physical has a fatal flaw. What if physical objects turn out to be completely different from what we think? For example, what if idealism is true and physical objects really have a spiritual nature? Given the account of ‘‘physical’’ that I have offered, physicalism might still be true. But surely no account of the physical should entail that physicalism and idealism would turn out to be compatible! I think this objection shows something, but I don’t think what it shows is sufficient to reject the paradigm physical object view. What the objection shows is that the paradigm physical object view has an empirical presupposition—namely, that physical objects are more or less as we think they are. Now, it may be true that there is no way to explain the notion of the physical except by making some empirical assumptions. But it is not clear that this is a problem. Suppose I tell you that everything in the next room is painted red, and you ask me to explain what ‘‘red’’ means. I might say: by ‘‘red’’ I mean the color of the inside of a watermelon, so my thesis is that everything in the next room is the color of the inside of a watermelon. What I have said is perfectly legitimate and explains my thesis for all practical purposes; I have met your reasonable demand for clarification. On the other hand, it is also true that if the inside of a watermelon miraculously changed to blue, my attempted explanation would fail.

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2.5.1.3. Physicalism and T2 If this is physicalism, the argument from it to experiential supervenience is very straightforward. It starts from the claim—assumed to be plausible in the light of modern science—that: P1.

Physicalism is true.

Because physicalism is a supervenience thesis, it immediately follows from P1 that: P2.

If there are experiential truths, then those truths supervene on physical truths.

In addition, if we assume that physical truths are nonexperiential truths, it follows that: P3.

If there are experiential truths, those truths supervene on nonexperiential truths.

But of course, given our understanding of the relation between supervenience and entailment, P3 is equivalent to T2. In sum, if we agree that physicalism is true, and if we agree that physical truths are nonexperiential, we cannot but agree that T2 is true, too.

2.5.2. The Argument from Manifest Supervenience The second argument for T2 takes as its premise a thesis that I will call manifest supervenience. This thesis is less familiar than physicalism, and so I will start by introducing the distinction on which it is based.

2.5.2.1. The Manifest Image and the Scientific Image Wilfred Sellars (1962) famously contrasted what he called the manifest image of the world with the scientific image. The world presented in the manifest image is the world of sophisticated common sense—that is, the world of persons, ordinary physical objects, colors, experiences, and so on. The world presented in the scientific image, on the other hand, is the world of developing science. In introducing this distinction, Sellars was, as I read him, supposing—and I will follow him in this—that truths characteristic of the scientific world, whatever those truths happen to be, are distinct from the truths distinctive of the manifest world—more briefly, that scientific truths are distinct from manifest truths. Now, if scientific truths are distinct from manifest truths, it is natural to go on and ask what the relationship is between the manifest world and the scientific world. For some, the very task of philosophy is to formulate a synoptic vision—a stereoscopic vision, in Sellars’s phrase—of this relationship. But even if we don’t adopt this ambitious account of what philosophy is, the

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question is surely a good one. The thesis of manifest supervenience provides one answer to this question. This thesis would take the now familiar form: (3) Manifest supervenience is true at w if and only if every manifest truth at w is entailed by some scientific truth at w. Again, manifest supervenience does not tell us that there are no manifest truths—that is, that the manifest world is an illusion. What it tells us is only that, if there are manifest truths, they supervene on scientific truths. Why is the thesis of manifest supervenience plausible? I take it that the reason it is plausible is the very same reason that physicalism is plausible. Manifest supervenience is held to be implicit in the worldview of modern science, and it is rational to believe that worldview, whatever it happens to be, that is implicit in science. The general thought—admittedly rather vague—is that reflection on modern forms of knowledge makes plausible a kind of Platonism, according to which the truth about the world is quite different from how it appears on the surface: the truth of the world is anything but manifest to us in ordinary experience.

2.5.2.2. Manifest Supervenience and T2 If this is the thesis of manifest supervenience, the argument from it to experiential supervenience is very straightforward. It starts from the claim— again, assumed to be implicit in modern science—that: MS1.

Manifest supervenience is true.

Because manifest supervenience is (of course) a supervenience thesis, it immediately follows from MS1 that: MS2.

If there are manifest truths, then manifest truths supervene on scientific (i.e., nonmanifest) truths.

In addition, if we assume that experiential truths are manifest truths and, mutatis mutandis, that nonmanifest or scientific truths are nonexperiential, it in turn follows that: MS3.

If there are experiential truths, then experiential truths supervene on nonexperiential truths.

But of course, given our understanding of the relation between supervenience and entailment, MS3 is equivalent to T2. In sum, if we agree that manifest supervenience is true, and if we agree that scientific truths are nonexperiential, we cannot but agree that T2 is true, too.

2.5.2.3. Physicalism versus Manifest Supervenience We have seen that the reasons for believing physicalism and manifest supervenience are largely the same—namely, science. But it will be

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important later to see also that they are nevertheless distinct doctrines in this sense: physicalism is neither necessary nor sufficient for manifest supervenience. So what we have here are two distinct (though compatible) routes to T2. Physicalism is not sufficient for manifest supervenience, for it is easy to imagine versions of physicalism for which the relevant physical truths are manifest and not scientific in the sense we are discussing. Descartes, for example, famously held that matter, and so the physical, is just extension. On the other hand, extension is most naturally classified as part of the manifest image: extension is as much a part of common sense as, say, shape or color. But imagine now a Cartesian version of physicalism—Cartesian physicalism, for short—according to which every truth is entailed by some truth about extension, but truths about extension are themselves not entailed by anything more basic. (Obviously, Descartes himself would have rejected such a view.) It is possible that Cartesian physicalism is true, even while manifest supervenience is not true. Hence physicalism is not sufficient for manifest supervenience. Physicalism is not necessary for manifest supervenience, for it is easy to imagine a world in which the scientific truths are not physical in the sense we have introduced. Suppose, for example, that somewhere in that world there is some object or process or event whose explanation requires principles that go beyond what is required for physical objects. That would count as a violation of physicalism, but it would not count as violation of manifest supervenience. Hence, in such a world, manifest supervenience is or might be true, but physicalism is false. Hence physicalism is not necessary for manifest supervenience.

2.6. The Case for T3 If both T1 and T2 are true, we can conclude both that there are experiential truths and that the experiential supervenes on the nonexperiential. But T3 denies just this: T3 says that if experiences exist at all, the experiential supervenience thesis is false; that is, the experiential does not supervene on the nonexperiential. Now, this is a surprising claim. As we have just seen, it is on the face of it implausible that the experiential truths are nonsupervenient. However, what T3 has in its favor are a number of philosophical arguments and thought experiments, all of which point toward the conclusion that experiential truths do not supervene on nonexperiential truths. The literature on these issues is populated with a variety of such arguments. However, in the main body of our inquiry, it is reasonable to concentrate on two: the conceivability argument (CA) and the knowledge argument (KA). Once again, we will consider the cogency of these arguments later; for the moment, our goal is to formulate them.

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2.6.1. The Experiential Conditional We may start with the observation that both arguments are modal arguments. As we saw in the introduction, a modal argument is an argument whose starting point is various imaginable or conceivable cases, whose intermediate conclusions are theses about what is and is not possible, and whose final conclusions are claims about the nature of the actual world. Now, an initial problem about any argument of this sort is with its third step. Experiential supervenience is, if true, a contingent truth. The thesis it rules out, primitivism, is not impossible; it is simply unlikely or, rather, has been held by many to be unlikely. On the other hand, a modal argument establishes, if it is successful, the existence of a possibility. But how can the fact that something is possible by itself have a bearing on some contingent claim about the actual world? After all, suppose a certain thing is possible— say, that there are blue swans. By itself, this tells us nothing at all about the color of actual swans. How, then, could a modal argument have any bearing on experiential supervenience, which is, as we have seen, a contingent thesis? The problem is made more acute if we bear in mind that what is at issue in the logical problem, and indeed throughout our discussion, is the completely unrestricted sense of possibility that philosophers sometimes call ‘‘logical’’ or ‘‘metaphysical’’ possibility. Sometimes when we talk about possibility or impossibility, we have in mind a restricted notion; it is physically impossible that something travels faster than light, and financially impossible that I buy a Ferrari. Now, a crucial factor about restricted possibility is that if something is not possible in this restricted sense, there is always another sense in which it is possible. This is not so with the unrestricted sense; in this sense, if something is not possible, then there is no further sense in which it is possible. And this makes the puzzle just stated about modal arguments all the more acute. Suppose a modal argument succeeds in establishing that something is possible in the completely unrestricted sense. How could that possibility, whatever it is, put any pressure on experiential supervenience? The answer to this question is that although experiential supervenience is contingent, it nevertheless entails something necessary—and necessary in the unrestricted sense—or at least does so when combined with further premises. To illustrate this, consider the following example: Suppose I claim that my aunt’s favorite statement entails my uncle’s favorite. This claim—which we might call C—is contingent if true, for it is a contingent matter which statement is my aunt’s favorite and which is my uncle’s. If my aunt’s favorite is ‘‘snow is white’’ and my uncle’s favorite is ‘‘something is white,’’ what I said is true. Alternatively, if my aunt’s favorite is ‘‘snow is white’’ and my uncle’s favorite is ‘‘look upon my works ye mighty and despair,’’ what I said is false. On the other hand, suppose we agree (never

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mind why) that C is in fact true. It now follows that there is some statement, P, which is my aunt’s favorite, and some statement, Q, which is my uncle’s. In addition, it follows that the truth-functional conditional formed from P and Q (‘‘If P, then Q’’) is necessary. The reason is that P entails Q and it is not contingent which statements P and Q are. In sum, from a contingent entailment claim, plus two further contingent assumptions, we may derive a necessary entailment claim. The situation is the same when we turn to experiential supervenience. Experiential supervenience is the thesis (or is equivalent to the thesis) that the nonexperiential truths entail the experiential truths. This thesis is contingent because it is contingent which truths are the nonexperiential truths and which are the experiential truths. On the other hand, suppose it is true, and suppose in addition that all the nonexperiential truths that in fact obtain are conjoined into one large truth (call it N ), and all the experiential truths are conjoined into another large truth (call it E ). (It may be that these truths could not be expressed in a language we could speak or understand, but let us set that aside.) Now consider the truth-functional conditional formed by N and E (‘‘If N, then E’’), and call this ‘‘the experiential conditional.’’ Then, if experiential supervenience is true, the experiential conditional is necessarily true. The reason is that N entails E and yet it is not contingent which statements N and E are. In short, if experiential supervenience is true, the experiential conditional is necessary. The problem we are considering is how a modal argument, which establishes the existence of a logical or metaphysical possibility, can put pressure on experiential supervenience, which is a thesis about the contingent world. The solution involves making two points: first, if experiential supervenience is true, the experiential conditional is necessary; second, a modal argument, if successful, might well tell us that the experiential conditional is contingent. Putting these two points together, if the right sort of modal argument is sound, experiential supervenience is false.

2.6.2. Two Points about Rigid Designation The idea that our discussion may proceed by focusing on the experiential conditional is connected to two controversial topics in philosophy of mind, both of which concern the notion of rigid designation. The first arises from Kripke’s suggestion, in Naming and Necessity (1980), that, because ‘‘pain’’ is a rigid designator—that is, an expression that denotes the same thing in all worlds in which the thing exists—statements such as ‘‘pain ¼ c-fiber stimulation’’ are, if true, necessary. He then produced a modal argument to the effect that they are not necessary and pointed out, as we saw in the introduction, that none of the standard ways of defeating a modal argument would defeat this argument. Lewis (1980; see also Lycan 1974) responded that, in his view, ‘‘pain’’ is not a rigid

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designator and thus that Kripke’s argument concerning this example is unmotivated. Now, the problem with this debate is that it is hard to see how to resolve it: Kripke says that ‘‘pain’’ is rigid; Lewis says it isn’t—who is right? (One possibility is that both are right and that Kripke-English is not Lewis-English.) On the other hand, by focusing on the experiential conditional, we avoid the issue completely. Regardless of whether you think that ‘‘pain’’ is a rigid designator, you will certainly think that the experiential conditional is necessarily true if you believe experiential supervenience at all. And this is enough to raise the issue. The second issue arises from a standard way of introducing the question of how experiential supervenience, and supervenience theses in general, can be contingent. I have been assuming that supervenience theses are entailment theses and that some entailment theses are contingent while some are necessary. The reason for this is that the constituent expressions of contingent entailment claims are nonrigid. For example, the expression ‘‘the experiential truths’’ is a nonrigid designator of a set of truths; at some worlds it denotes one set of truths, and at another it denotes a different set. From this point of view, the issue about contingent supervenience is just the same as the issue about contingent identity that was the focus of so much discussion in the 1970s and, in particular, in Naming and Necessity. The background relation is of course distinct—entailment is not identity—but the principles are the same. However, while this is one natural way of raising the issue about contingent supervenience, in the recent literature the point is usually raised in a different way. In particular, it is usually made via reference to a possible world W* that is exactly like our world in respect of the distribution of physical and mental properties except for one major difference: it contains some pure experience that does not interact causally with anything else in the world—epiphenomenal ectoplasm, to give it its usual name. I have not discussed the problem in this form for three reasons: First, there are a number of existing solutions to the epiphenomenal ectoplasm problem (e.g., Lewis 1983, Horgan 1982, and Jackson 1994, 1998), and I have nothing to add to what others have said. Second, the epiphenomenal ectoplasm problem and the solutions to it are usually discussed in a framework for thinking about supervenience slightly different from the one adopted here, and comparison of these different frameworks would take us too far afield and, in any case, will not affect anything substantial that I have to say. Third, putting the issue in terms of epiphenomenal ectoplasm does not seem to me to capture the main thing that people have in mind when they express puzzlement over contingent supervenience theses. When people say they don’t understand how supervenience theses can be contingent, I take it they mean that they don’t understand how supervenience theses can be contingent, given that such theses are necessary or apparently so. But from that point of view, the puzzle about contingent supervenience is directly analogous to the puzzle about contingent identity.

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2.6.3. The Conceivability Argument We have seen that a modal argument is of interest to us only if it provides a reason for supposing that the experiential conditional is contingent. By that standard, CA certainly is of interest, for it does precisely this. (The conceivability argument has a long history, but its presentation in contemporary philosophy is largely due to the last lecture of Kripke 1980, as well as to Chalmers 1996.) There are a number of ways to formulate the argument, but for our purposes it is sufficient to view it as proceeding from two premises: C1.

C2.

It is conceivable that there is a situation identical to the actual situation in respect of all nonexperiential truths and yet different from it in respect of some experiential truth. If this is conceivable, then it is possible.

If C1 and C2 are both true, it is possible that there is a situation that duplicates the actual situation in respect of nonexperiential truths but is different from it in respect of experiential truths. But that is just to assert the possibility of a situation that is identical to the actual situation in respect of N but distinct from it in respect of E—and, in turn, to imagine the falsity of the experiential conditional. On the other hand, if it is possible that the experiential conditional is false, it is at best contingently true. As we have already seen, however, if supervenience is correct, the experiential conditional is necessarily true. Hence, C1 and C2 jointly entail the falsity of experiential supervenience. More generally, if the conceivability argument is sound, T3 is true. Now, because CA in this form is clearly valid when construed as an argument against experiential supervenience, its plausibility turns on the plausibility of its premises. Are they plausible? This is an issue that will occupy a large part of the discussion to follow. For the moment, it suffices to note that at least the first premise of the argument has considerable intuitive force. This may be brought out in a number of different ways, depending on which sort of experiential difference is at issue: (i) One might imagine that one’s duplicate in the relevant situation lacks a particular experience that you have but is otherwise identical to you—the possibility discussed by Kripke 1980. (ii) One might imagine that one’s duplicate lacks all experiences but is otherwise identical to you (the possibility sometimes called ‘‘the zombie hypothesis,’’ discussed by Campbell 1984 and Chalmers 1996, among others). (iii) One might imagine that one’s duplicate inhabits a world completely devoid of experiences (sometimes called ‘‘the zombie world hypothesis,’’ discussed by Chalmers 1996). (iv) One might imagine one’s duplicate to have experiences that are inverted with respect to yours—for example, one’s duplicate gets the experience you have when you see ripe tomatoes when he

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The Problem sees grass. (This is the inverted spectrum hypothesis discussed most famously in recent times by Shoemaker 1982, see also Byrne 2004). (v) One might imagine that one’s duplicate has a body of experiences that are completely alien to the ones you have but that exhibit the identical structure (the alien experience hypothesis). (vi) One might imagine that one’s duplicate has experiences that are the same as yours but increased on some phenomenal dimension or other—for example, the same except everything is more vivid or less vivid, or brighter or less bright.

There may also be other possibilities. The important point is that enumerating these different reasons for C1 reveals that the conceivability argument represents a family of arguments rather than a single argument.

2.6.4. The Knowledge Argument Regarding the knowledge argument, Frank Jackson is responsible for the classic contemporary discussion. He writes: Mary is confined to a black-and-white room, is educated through blackand-white books and through lectures relayed on black-and-white television. In this way she learns everything there is to know about the physical nature of the world. She knows all the physical facts about us and our environment, in a wide sense of ‘physical’ which includes everything in completed physics, chemistry, and neurophysiology, and all there is to know about the causal and relational facts consequent upon all this, including of course functional roles. If physicalism is true, she knows all there is to know. For to suppose otherwise is to suppose that there is more to know than every physical fact, and that is just what physicalism denies. . . . It seems, however, that Mary does not know all there is to know. For when she is let out of the black-and-white room or given a color television, she will learn what it is like to see something red, say. This is rightly described as learning—she will not say ‘‘ho, hum.’’ Hence, physicalism is false. (Jackson 1986, 291) Until the very last sentence of this passage, Jackson is describing a certain possibility. In the last sentence, he draws a conclusion about the actual world from this possibility. In short, like the conceivability argument, the knowledge argument moves from a premise about what is possible to a conclusion about the actual world. Later on in our discussion (see chapter 10), we will see that there is some controversy about exactly how to formulate the modal premise of the knowledge argument. For the moment, however, it is reasonable to work with the following formulation: K1.

It is possible for a logically omniscient and conceptually sophisticated person to know all the nonexperiential truths and yet learn some experiential truth on the basis of experience.

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If K1 is true, it is possible for a person to know the antecedent of the experiential conditional and yet not know the conditional itself because they do not know its consequent. (It is part of the logic of learning that if you learn something at a certain time, you did not know it just prior to that time.) Further, K1 asserts that this is not simply because they have not put everything together in the right way (they are logically omniscient) or because they do not have the required concepts to understand the conditional (they are conceptually sophisticated). The proponent of the argument then infers from K1 to the conclusion that the experiential conditional is, if true, contingent. As we have seen, however, if the experiential conditional is contingent, then experiential supervenience is false, for experiential supervenience entails the necessary truth of that conditional. Now, for KA in this form to be persuasive, it must be both that the premise is true and that it supports the conclusion that the experiential conditional is contingent. The premise of the argument receives, as we have just seen, considerable support from the example of Mary. Prior to her release, Mary seems to be a logically omniscient and conceptually sophisticated person who knows all the nonexperiential truths and yet does not know all the experiential truths. But this is precisely the possibility asserted by K1. What, then, of the inference? Here we face a challenge that does not arise in the case of CA and shows that KA is different from its more straightforward sibling. In the case of CA, there is no question but that its premises entails its conclusion. In the case of KA, however, the situation is more controversial. K1 says that it is possible for someone to know the antecedent of the conditional without knowing the consequent. But it does not follow from this alone that the conditional is contingent. How, then, are we supposed to go from K1 to anything that puts pressure on experiential supervenience? The problem is not simply that the premise does not entail the conclusion. By itself, that would not be a problem. Presumably, it is as reasonable here as elsewhere to suppose that a premise can make a conclusion plausible without entailing it outright. The problem, rather, is that that it is hard to see how the premise by itself lends any weight to the conclusion at all.

2.6.4.1. The Knowledge Argument and the Open Question Argument This last point may be developed by contrasting the knowledge argument with another famous argument, the open question argument due to Moore 1903b. Moore’s argument is intended to show that it is always a mistake to define the moral in terms of the nonmoral—that ‘‘definitional naturalism’’ is false, as it is often put. Suppose D is a summation of the descriptive or nonmoral truths and M is any moral truth at all. Then Moore’s premise is that, even if you know for a fact that D is true, it would still be rationally

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open to you to ask whether M is true—that is, knowledge of D leaves the question of M open. A simple permutation of this premise renders it very similar to K1: O1.

It is possible for a logically omniscient and conceptually sophisticated person to know all the nonmoral or descriptive truths about the world and yet not know the moral truths, because the question of which moral truths are true would remain rationally open.

There are many questions that might be raised about the open question argument. But for us the important point is that, if O1 is true, it does not begin to follow that the relation between the moral and the nonmoral is a contingent one. Indeed, both Moore and the philosophers who followed him supposed that quite the opposite is true and insisted that the relation here was one of necessity rather than contingency. So, turning back to the knowledge argument, it is hard to see how K1 alone is going to provide any basis from which a conclusion about contingency might be drawn.

2.6.4.2. Adding Premises As so far presented, therefore, the knowledge argument is surprisingly weak. K1 is plausible, but the distance from it to anything that threatens experiential supervenience is considerable. There is no choice but to add further premises to the argument. What might these further premises be? I think there are two possibilities here. The first is to advance considerations from which it follows that the experiential conditional is (not only necessary but also) a priori. In fact, this is Jackson’s procedure, both in the original 1982 paper and in subsequent writings. We will see later (chapter 9) that Jackson defends a neodescription theory from which it is plausible to suppose that any (knowable) necessary a posteriori truth follows a priori from a contingent truth. From this, it follows that the experiential conditional is, if true, both necessary and a priori. With this further premise in place, it is obvious that K1 puts pressure on the experiential conditional and thereby on experiential supervenience itself: KI tells us that the experiential conditional is not a priori; Jackson’s view is that if experiential supervenience is true, the experiential conditional is a priori; so, experiential supervenience is false. However, although this is one way to develop the knowledge argument, it is not the option I want to take here. The problem, as we will see later, is that Jackson’s argument for the a priori nature of the experiential conditional is extremely controversial. For that reason, therefore, it is unwise to build his neodescription theory into our account of what the knowledge argument is and so into our account of the logical problem. The second strategy for developing the argument starts with the observation that if a truth is a posteriori, then it very often exhibits—to adopt Kripke’s (1980) phrase—an appearance of contingency. The reason for this is roughly, first, that if a truth is a posteriori, one will learn it on the basis of

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learning some contingent fact of the world and, second, that in most cases the contingency of the fact on the basis of which one learns the truth will attach also to the truth itself. Now, on the assumption that an a posteriori truth does very often exhibit an appearance of contingency, we may state the reasoning from K1 to the falsity of experiential supervenience in the following way: If K1 is true, the experiential conditional is a posteriori. If the experiential conditional is a posteriori, it exhibits an appearance of contingency. If this appearance of contingency cannot be explained away, then it should be taken at face value, and the experiential conditional should be treated as contingent. Putting these points together, if K1 is true, the experiential conditional is contingent. Of course, this statement of the knowledge argument invites the response that the appearance of contingency can be explained away. Indeed, I will argue later that it can. But our project at the moment is not to defend the argument but to formulate it, and what I have suggested is that it is possible to formulate the knowledge argument in such a way that it does not rely on the idea that the experiential conditional is, if true, a priori.

2.6.5. Two Points of Comparison We may complete our introduction of CA and KA—and of the logical problem itself—by entering two points about their comparison. First, when we imagine a situation identical in all nonexperiential respects but different in experiential respects, and when we imagine someone who knows all the nonexperiential truths but not the experiential truths, the notion of experience at issue is the conception of experience I set out in the previous chapter, the phenomenal conception. This suggests that the problem of experience that I want to discuss has a certain sort of robustness. Suppose for a moment that CA or KA arose only if one held, say, the sense datum theory of experience. Then one might easily reject the arguments by rejecting the sense datum theory—which there is ample reason to do anyway. However, neither of the arguments just considered rests on a conception of experience committed to the sense datum theory. The second point emerges from the fact that the example of Mary is widely accepted among philosophers of mind as representing a genuine possibility. This is in contrast to examples that are at the heart of the conceivability argument, for there is no common agreement that these represent genuine possibilities. Hence discussion of KA has tended to avoid the epistemological questions that are central to CA. On the other hand, the fact that the possibility represented by the Mary example is widely accepted obscures the point that even here we rely on conceivability. Suppose someone challenges the Mary example. So far as I can see, the only option at this point is to fall back on the claim that it is conceivable and that what is conceivable is possible. In short, the knowledge argument is itself a form of conceivability argument.

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2.7. The Empirical Problem The logical problem of experience has a structure that is familiar and well understood: we have three jointly contradictory theses that, when taken independently, have a considerable amount of support: T1 is supported by introspection, T2 by physicalism and manifest supervenience, and T3 by the modal arguments, CA and KA. But the very familiarity of its structure in a certain sense makes the nature of the problem somewhat hard to see. To bring out the problem in more detail, therefore, in the remainder of the chapter I take up a comparison of the logical problem with two others, the empirical problem and the traditional mind-body problem.

2.7.1. The Problem Outlined The empirical problem is the problem of what the scientific explanation, description, and analysis of experience is. This problem takes for granted that in focusing on experience we are focusing on some phenomenon to be explained, and it simply asks: ‘‘What is the explanation of this phenomenon?’’ Of course, because it is an obvious empirical fact that conscious experience arises somehow from cellular structures (or perhaps other structures) in the brain, this problem often takes the form of asking how consciousness arises in the brain. Indeed, because particular experiential events or states presumably arise from particular cellular structures, the issue also involves answering the question of why those particular states are involved rather than some others. Nevertheless, the problem is still in essence a straightforward scientific one that is to be pursued, as far as is possible, by straightforward scientific means. Put differently, the empirical question treats the ‘‘problem of experience’’ as something that is on a par with the problem of the formation of the moon or the problem of whether human beings evolved in Africa first and then dispersed to the rest of the globe. In both cases, we have a phenomenon to be explained, and we simply ask what the explanation is. Notice that it is not a presupposition of the empirical question that the explanation will take any particular form. Nor is it a presupposition that we will be able to provide the explanation. Nor indeed is it being assumed that we have here a single problem in any serious sense: ‘‘the empirical problem’’ is just a name for a whole cluster of related issues that one faces when attempting to approach the problem of experience from an unabashedly empirical point of view.

2.7.2. The Two Problems Distinguished What is the relation between the empirical problem and the logical problem? On the face of it, they seem different, calling for different sorts of solutions. First, the logical problem begins with the observation that three very abstract and general beliefs about experience cannot all be true. If you like,

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the logical problem begins by pointing out a paradox in our thought about experience and seeks to resolve that paradox. But the empirical problem begins by drawing attention to an interesting phenomenon that we want to explain, and there is no guarantee that the project of finding out about the nature of some phenomenon will coincide with the project of resolving a tension in our thought about it. Nor is it obvious that phenomena about which we might raise empirical questions are going to provoke logical questions of the sort I have outlined. There is no logical problem associated with the formation of the moon, for example. This is simply an interesting phenomenon we would like to explain. Second, the sorts of considerations that one would bring to bear to solve the empirical problem seem to be quite different from those one would use to solve the logical problem. To solve the empirical problem, one would presumably need to develop a framework of ideas within which detailed empirical investigation of conscious experience would proceed. And we would need to integrate that framework with existing frameworks within which we solve and explain outstanding problems in the empirical world. To solve the logical problem, on the other hand, we need to scrutinize the general beliefs about experience I have outlined and evaluate the reasons for holding them.

2.7.2.1. The Duhem-Quine Thesis The distinction between the logical and empirical problems may seem to violate a widely held view that has come to be called the Duhem-Quine thesis (see Quine 1953, 1960; the reference is to the nineteenth-century philosopher of science Pierre Duhem). As I understand it, the Duhem-Quine thesis concerns the relation between beliefs and evidence. Rather than supposing that each belief has a proprietary body of evidence that can in principle provide a secure epistemic foundation for it, the thesis asks us instead to suppose that one’s beliefs meet the evidence as a system rather than individually. The result is that one cannot quarantine the assessment of philosophical beliefs from any other sort of beliefs. A natural corollary of this is that there cannot be a method of inquiry or assessment that is special to philosophy and one that is special to science. On the other hand, the idea that we can distinguish between the logical and empirical problems of experience appears to violate that very principle. However, a distinction between methodologies is one thing, and a distinction between problems is quite another. The Duhem-Quine thesis does not forbid us from distinguishing various sorts of problems and concentrating on some of these as opposed to others. Admittedly, the labels I have used—‘‘logical’’ and ‘‘empirical’’—do suggest a pre-Quinean division into a logical and an empirical methodology. But the proper response to this is: don’t be misled by labels. In particular, one can draw the distinction at issue without using these labels. One class of questions arises when we notice

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that there are various well-entrenched beliefs that we have about experience and that these cannot be true together. A different class of questions arises when we turn to the elaborate scientific analysis of experience. But different sorts of questions require different sorts of answers—there is nothing in the Duhem-Quine thesis to deny this.

2.7.3. A Research Decision If the empirical problem can be distinguished from the logical problem in the ways indicated, and if our topic is the logical problem, we have in effect made a research decision—namely, to set aside the empirical problem. This decision about what to work on is, of course, simply that, so in one sense it cannot be evaluated for truth. However, it is also a decision based on at least three important facts. First, part of what makes the empirical problem of experience so hard is that it is associated with the logical problem (and indeed with the traditional mind-body problems that I will discuss in a moment). If we can clearly separate out the empirical problem from these other problems, we might hope to make it somewhat easier to solve. So we can make progress on the empirical problem simply by decoupling it from these other problems. Second, we are in fact much closer to solving the logical problem than the empirical problem. Following Chomsky (1965; see also Cummins 1983), it is natural to divide the task of providing theoretical understanding of conscious experience into two: there is the descriptive task, in which we try to achieve a theoretical description of the facts to be explained, and then there is the explanatory task, in which we try to explain the facts so described. I think it is fair to say that in the case of experience we are not even close to completing the first sort of task. Apart from a number of informal comments, a theoretical description of the thing to be explained has, in the case of experience, not been achieved. That is a sobering fact, if true, because it tells us that we are really a considerable distance from solving the empirical problem. This provides an incentive for studying the logical problem. Third, as we noted in the introduction, unless we clearly distinguish the logical problem from the empirical problem, the epistemic view disappears as a reasonable perspective on the issues. In particular, if we are mainly interested in the question ‘‘what is the explanation of the phenomenon of consciousness?’’ the remark ‘‘we are ignorant of its nature’’ is, while perhaps true, completely irrelevant. Indeed, it is so irrelevant that it is not even clear that it makes sense as an answer: ‘‘Of course, we are ignorant,’’ we might say in exasperated response; ‘‘that is why we want an explanation.’’ On the other hand, if we are mainly interested in the question ‘‘What leads us to three very general but inconsistent beliefs about experience?’’ the remark ‘‘we are ignorant of its nature’’ makes perfect sense. That we are ignorant of its nature may indeed lead us to have these inconsistent beliefs; in fact, that it does so is the main idea of the epistemic view.

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2.8. The Traditional Mind-Body Problem The logical problem of experience needs to be distinguished not only from the empirical problem but also from the traditional mind-body problem. Indeed, both the empirical and the logical problems need to be distinguished from the mind-body problem.

2.8.1. The Problem Outlined The traditional mind-body problem, as I understand it, starts from a basic distinction between mental or psychological phenomena, on the one hand, and physical or material phenomena on the other. It then develops this distinction by distinguishing on this basis two accounts of the nature of human beings (and perhaps sentient creatures generally) and their place in the world. One view, dualism, is the view that humans are a complex of a material body and an immaterial mind—or in most modern versions, that humans have both irreducibly physical and irreducibly mental properties. The other view, physicalism, is, as we have seen, that physical truths entail the psychological truths and thus that human beings are really just complex physical objects. The problem asks which of these positions is true and, more generally, what the relation is between the mental and the physical. The traditional mind-body problem is familiar from the history of philosophy, in particular from Descartes’ classic discussion of the problem in the Meditations. However, even though it is a problem that is much discussed in academic philosophy, it is presumably mistaken to view the problem as arising only in that context. On the contrary, both the problem and the language we use to express it seem to have considerable psychological force. Students know instinctively what the distinction is between dualism and physicalism, without it being spelled out to them. And the distinction, or something like it, obviously forms a part of many religious and folk attempts at explaining the world. Perhaps the reasons for this are cultural, or perhaps they lie in the cognitive architecture of the mind, in a more basic psychological distinction between folk psychology and folk physics. But in any case, the psychological naturalness of the mind-body problem is remarkable and cries out for explanation. (For an interesting recent discussion, see Bloom 2004.)

2.8.2. The Three Problems Distinguished What is the relation between the mind-body problem and the two other problems we have distinguished? In the case of the relation between the empirical problem and the mindbody problem, the issues are largely the same as that between the empirical and the logical problems. The only further feature is that the empirical question does not start off from the position that we really have two options

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here—or perhaps four, if one includes neutral monism and idealism. Of course, it is quite consistent with the empirical problem that, in the course of a scientific engagement with conscious experience, we might eventually arrive at a position that looks a bit like traditional dualism or physicalism. It is not a priori that dualism is true or false, after all. But this does not in itself diminish the difference between the problems. Turning to the distinction between the logical problem and the traditional mind-body problem, there are two main differences here. First, the logical problem is focused on experience—one psychological phenomenon among many—whereas the traditional mind-body problem is focused on psychological phenomena in general. But is unclear that there is a single philosophical problem about psychological phenomena in general. For some psychological phenomena—such as those postulated by empirical psychology and neuroscience—it is unclear that there is any philosophical problem at all, at least none of the sort we are considering. Questions about other psychological phenomena, such as intentionality, do seem to me to pose genuine philosophical problems. But as we will see in chapters 5 and 10, these problems are quite different from the problems posed by experience. So the mind-body problem seems to include in its sweep a number of quite distinct problems that are, or might be, completely different in character. The second feature is that the focus of the traditional mind-body problem is on the contrast between the mental and the physical, whereas the focus of the logical problem is the contrast between experience and everything else. The idea that we might contrast the mental and the physical carries with it a number of presuppositions that are typical of reductionist projects in philosophy: the physical is presumed to be epistemologically and metaphysically in good order, and the mental is questionable. The structure is familiar from logicism, the attempt the reduce mathematics to logic, or behaviorism, the attempt to reduce psychological reports to behavior. On the other hand, these reductionist ideas are not really at issue in the logical problem. Here the problem is with experience itself and with the fact that it appears to be metaphysically distinct from everything else.

2.8.2.1. The Moorean Flavor of Our Problem The conclusion to which we are heading is this: our problem has (what might be called) a Moorean flavor. Moore (1903b) held that many philosophically interesting properties, such as good, true, and yellow, were unanalyzable, simple, qualities distinct from everything else. As we have been developing it, the logical problem raises a similar problem about experience. It might be objected that the distinction I am trying to draw—that is, between the logical problem and the traditional mind-body problem—is illusory. Isn’t it necessary to provide a positive account of what nonexperiential

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truths are? Moreover, when you provide that account, won’t the distinction between the logical problem and the mind-body problem evaporate? In response, it is certainly true that, for the body of nonexperiential truths that happen to be true in the actual world, there is a positive characterization to be given; at any rate, nothing that I have said denies that there is such an account. Nevertheless, it is not required for our discussion that we provide such an account. What is important for us is not so much what the scientific truths of the world are as what they are not: what they are not is experiential. More particularly, the contrast we are working with is between experience and everything else, not between experience and another category that is presumed to be epistemologically and metaphysically in good order.

2.8.3. Another Research Decision If the logical problem is indeed distinct from the mind-body problem and the empirical problem, and if our topic is the logical problem, we have in effect made another research decision—namely, to set aside the traditional mind-body problem. Once again, this is in one sense a decision, and so there can be little discussion about it. But it is also a decision founded on two important facts. First, part of what makes the mind-body problem controversial is that it makes essential use of the notion of the body, or of the physical, and this notion has been the focus of critical attack in recent times—a point I will discuss in the next chapter. If we can separate out the mind-body problem from the problem of experience, we ought to be able to avoid those controversies and so set our discussion on a more secure foundation. Second, one of the themes I want to develop in parts II and III of this book is that the problem of experience is really rather different from other philosophical problems—a fact that makes the epistemic view more plausible than it would otherwise be. On the other hand, identifying our topic as the mind-body problem threatens to blur the distinction between the problem of experience and these other problems.

2.9. Conclusion Our discussion so far has identified both a topic and a problem, as well as a distinction between that problem and others. It would be agreeable if we could proceed straightaway to the business of how to solve that problem. However, in the present intellectual climate, this is impossible. The reason is that many philosophers think that what we have said so far is premised on a mistake and, in fact, two mistakes. It is to this challenge that I now turn.

3 The Skeptical Challenge

3.1. Introduction Of the many currents in contemporary philosophy of mind, one of the most challenging is a deeply skeptical one about the nature of the problems themselves, including in particular the problem of experience we have been discussing. There are different forms this challenge can take, but it is possible to discern a straightforward argument lying behind it. The argument takes the form of a dilemma and runs as follows. In discussing the questions of experience, you might be concerned with one of two problems. First, you might be concerned with the traditional mind-body problem or perhaps with one or another strand of that problem. Second, you might be concerned with any of a range of scientific questions about what the explanation of conscious experience is or might be. But—the argument proceeds—neither option is very appealing. On the one hand, the traditional mind-body problem is a problem whose presuppositions have been the subject of sustained and detailed attack. It seems reasonable, in the face of this attack, to reject the problem rather than take it up and discuss it seriously. On the other hand, while the scientific questions of experience are extremely interesting and perplexing, there seems about as much point to discussing them in philosophy of mind as there is to discussing enzyme secretion (see Searle 1992) or the formation of the moon. The conclusion of the argument is that, properly understood, there is no such problem as ‘‘the problem of experience in philosophy of mind.’’ There is the problem of experience in the history of philosophy (this is the traditional mind-body problem), and there is the problem of experience in the cognitive and neural sciences. But there is no further problem. 48

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Why is the traditional mind-body problem a problem whose presuppositions have been the subject of sustained and detailed attack? At this point the argument can be, and has been, developed in a number of different ways. In the middle part of the twentieth century, it was common to reject the problem on the ground that neither physicalism nor dualism is verifiable (e.g., Ayer 1936) or that experiential reports were not genuinely in the fact-stating business (e.g., Ryle 1949, Farrell 1950). But in contemporary philosophy, two different lines of thought have dominated, and it is these I will concentrate on. According to the first, which I will call the methodological version of the skeptical challenge (in brief: the methodological challenge), the mind-body problem should be rejected on the ground that it involves questionable assumptions in modal epistemology. We have noted that modal arguments typically have three stages. At the first stage, one imagines or conceives of various scenarios; at the second, one draws various conclusions about what is possible; at the final stage, one draws conclusions about the nature of the actual world from claims about what is possible. In the previous chapter, we considered the suggestion that the final stage of this style of argument is unwarranted. The methodological challenge focuses rather on the first and second stages and questions whether imagined or conceived cases can be taken to be evidence for claims about what is possible or necessary. If skepticism concerning this methodology is correct, and if the mind-body problem essentially involves this methodology, the only problem about experience in good standing is the empirical one. According to the second line of thought—the conceptual version of the skeptical challenge (in brief: the conceptual challenge)—the mind-body problem should be rejected on the ground that it involves an illegitimate concept of the physical. We have already introduced the doctrine of physicalism, according to which every truth is entailed by the physical truths, where the physical truths are those required for the explanation of typical physical objects. For proponents of the skeptical challenge, however, such ideas may have made sense at a certain historical moment, but that moment is long gone, and subsequent developments make it quite unclear that the concept of the physical has a continued role to play in either philosophy or the sciences. If this conceptual skepticism concerning the physical is correct, and if the mind-body problem makes essential reference to the physical, the only problem about experience in good standing is the empirical one. Now, it might appear that the answer to both challenges is easy from our point of view. As we saw in the previous chapter, our topic is not the mindbody problem as such but the problem of experience. Why, then, be concerned with an argument whose target is the mind-body problem? The answer is that the skeptical challenge concerns both problems, or anyway so it is reasonable to think initially. This is obviously true in the case of the methodological version, for both problems rely on modal reasoning. But it is also true in the case of the conceptual version. Perhaps physicalism plays

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a different role in the logical problem than it does in the mind-body problem, but it still plays some role, and so the conceptual challenge looks to be as damaging here as elsewhere. There is also a further reason why an examination of these forms of skepticism is important for our discussion: Both have been associated with the epistemic view. Paul Churchland, for example, advances a version of the epistemic view, but his presentation associates it with methodological skepticism. After constructing a revealing parody of some of the central pieces of reasoning in philosophy of mind, including CA and KA, Churchland concludes that in almost all of these cases, ‘‘the audience’s presumed ignorance is . . . the lubricant that smooths the path of a worthless argument’’ (1996; 366). It is hard to read this as endorsing anything less than methodological skepticism and, moreover, methodological skepticism generated by ignorance of the relevant facts. In short, for Churchland, methodological skepticism is part and parcel of the epistemic view. Similarly, Noam Chomsky in many places defends or suggests an epistemic view, but his presentation associates it with conceptual skepticism. Chomsky often emphasizes that contemporary questions about consciousness are parallel to questions raised in earlier periods about other phenomena. But—as we will see in this chapter—he is also a conceptual skeptic. In consequence, it is easy to form the impression that conceptual skepticism is somehow constitutive of the epistemic view. However, as will emerge as we proceed, my own view is that there is no reason why a proponent of the epistemic view must be either a methodological or a conceptual skeptic. I will also suggest more generally that the challenge presented by both forms of skepticism can be met.

3.2. The Methodological Version Skepticism about inferences from conceivability to possibility—or, more briefly, about modal reasoning—may have a variety of sources: (i) It may be argued that sometimes this reasoning goes wrong; how do we know that it does not always go wrong? (ii) It may be argued that we have no account of the reliability of the reasoning, that is, about why inferences from conceivability to possibility should be reliable. (iii) It may be argued that conceivability could be only a guide to possibility on some particular sense of ‘‘conceivability’’ or ‘‘possibility’’ or both, and that it is unclear what these senses are. (iv) It may be argued that the reasoning is question-begging because the claim that something is conceivable is at the end of the day in need of as much defense as the claim that it is possible. (v) Finally, it may be argued that the Kripkean idea that necessity is one thing and a priority another is proof that conceivability is no guide to possibility.

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One way to deal with the methodological challenge is to go through these reasons one by one. This is not the approach I will adopt. For one thing, others have done it, and in more detail that I am able to do here (see, e.g., Yablo 1993; see also the papers in Gendler and Hawthorne 2002). For another, to the extent that I will require answers to some of these questions, these will come out in the course of our discussion. In chapter 4, for example, I discuss various proposals about how modal reasoning can go wrong, proposals that make it plain that it does not always go wrong in these ways, and I will also discuss various ways in which conceivability is to be understood. And in chapter 9, I will discuss the impact of the necessary a posteriori on the connection between conceivability and possibility. In this chapter, therefore, I will mount what is sometimes called a Berkeley’s defense response to the methodological challenge. The story—I heard it from David Armstrong—is that Berkeley was criticized by his contemporaries on the ground that his metaphysical system did not solve the problem of evil. His response was that nobody had solved the problem of evil and that everyone’s problem was nobody’s problem. Similarly, to the extent that there is reason to be skeptical about inferences going from conceivability to possibility, this is a problem for philosophy generally and has nothing much to do with our discussion in particular. To reject such reasoning outright sounds hardheaded at first, and a quick way to avoid our problem. But it forgets that such reasoning is ubiquitous.

3.2.1. Two Examples What justifies the claim that modal reasoning is ubiquitous in philosophy? The only procedure I know of here is the consideration of examples.

Example 1. The Experience Machine In discussions of the nature of value, one well-known position is hedonism, which equates (at least in its very simple versions) what is valuable with what is pleasurable: value is pleasure, to put it in slogan form. But Robert Nozick 1974 produced a counterexample to hedonism. Imagine a machine, Nozick said, that could artificially create in you a course of experience that is vastly more pleasurable than the one you have in your actual life. The state of affairs in which you are placed in such a machine is, according to hedonism, more valuable than the actual state of affairs, assuming other things remain the same. But this seems false: there is something important about actually living a life, quite apart from the pleasure you may derive from it. So, if what Nozick describes is a genuine possibility, hedonism is false. It is useful for our purposes to represent the experience machine argument as a conceivability argument in the contemporary style:

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N1.

N2.

It is conceivable that there might be a situation more pleasurable than the actual situation but less valuable (i.e., one in which you are placed in Nozick’s experience machine). If this is conceivable, then it is possible.

These two premises entail that hedonism, at least in the simple version we are considering, is false. Hedonism entails that a world more pleasurable than the actual world is ipso facto more valuable. But if it is possible that there is a situation more pleasurable but less valuable than the actual situation, this is false.

Example 2. Perfect Actors A large period of the history of philosophy and psychology in the twentieth century is dominated by behaviorism. In its philosophical guise, behaviorism was the view that psychological claims, including experiential claims, were analytically equivalent to behavioral claims—that is, claims reporting actual behavior and dispositions to behave. But Hilary Putnam 1975 produced a counterexample to behaviorism. Imagine, Putnam said, a population of perfect actors who behave actually and potentially just as ordinary people do but who have quite different phenomenal states. For example, perfect actors behave just as we do when tickled by a feather, but instead of feeling tickles, they feel pain. If behaviorism is true, perfect actors have exactly the same psychological states as we do. But that is not so: the mere fact that you behave as I do does not mean that we feel the same. So, if what Putnam describes is a genuine possibility, behaviorism is false. Once again it will be useful for our purposes to represent the argument as a conceivability argument in the contemporary style: P1.

P2.

It is conceivable that I have a perfect actor duplicate—that is, that there is a perfect actor who is behaviorally identical to me and yet experientially different. If it is conceivable that I have a perfect actor duplicate, then it is possible that I do.

These two premises entail that behaviorism is false. Behaviorism entails that anyone behaviorally identical to me must be psychologically identical. But if it is possible for someone to be identical to me in behavioral respects but have different experiences, behaviorism is false. In the light of these examples, we may explain our position on the methodological challenge as follows: The proponent of the challenge is suggesting that CA and KA should be rejected simply because they are modal arguments. But this idea has the consequence that arguments drawn from many other areas of philosophy should likewise be rejected. In turn, this consequence is disastrous for the proponent of the challenge, and for two reasons. First, the consequence makes it plain that modal skepticism is

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a general problem and so can legitimately be set aside. Such skepticism might, of course, raise serious concerns, but it is mistaken to suppose that in discussing the problem of experience we are under any special obligation to allay them. After all, skepticism about induction likewise raises serious concerns, but we are under no obligation to allay them; why should modal skepticism be different? Second, the consequence suggests that there must be something wrong with modal skepticism even if we cannot put our finger on what it is. The fact is that Nozick’s and Putnam’s arguments are not rejected on skeptical grounds: to the contrary, they are routinely accepted in philosophical discussions of their respective subject matters. Hence, contrary to modal skepticism, they are not rejected because they are modal arguments.

3.2.2. Replies and Rejoinders How might a proponent of the methodological challenge reply to this Berkeleyan response? First, it might be replied that, although it is true that such that arguments are routinely accepted, this is a merely sociological fact—perhaps skepticism is in fact the correct approach here. However, this reply forgets how compelling these arguments are. In a standard philosophy of mind class, for example, you begin by discussing dualism and why it is implausible, then you turn to behaviorism and why it is implausible, and then you move on to other things. But how did you explain to the students that behaviorism is implausible? The answer is that you presented them with arguments such as the perfect actor argument. Students find these arguments completely persuasive; the simplest explanation of this is that they are completely persuasive. Second, it might be suggested that these points do not answer the concerns that are raised by the methodological challenge. Doesn’t it remain true that this form of reasoning is ill understood? However, this is no objection to our position. I am not denying that there are plenty of good questions to ask about modal reasoning. The point, rather, is that, given what our topic is, there is no reason why we should seek to answer them in any detail. Framing matters a bit differently, CA and KA represent a certain kind of reasoning, and of course there are questions about the precise characterization of this kind of reasoning. Because this reasoning is accepted in other cases, however, a discussion of CA and KA may legitimately proceed in the absence of such a characterization, and this will be my policy in what follows. Third, it might be objected that, although there is nothing wrong with modal arguments in general, there might nevertheless be something wrong with CA and KA in particular. However, once again this is no objection to anything we have said. I am not denying that there might be something wrong with CA and KA; on the contrary, I will argue in part II that both fail

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because they mistakenly presuppose full disclosure of the relevant facts. What I am denying is that these arguments go wrong merely because of their form. If they go wrong, as I think they do, it is for another reason entirely. Fourth, it might be objected that, although modal skepticism may or may not be right, the proponent of the epistemic view is in no position to reject it, for—it might be thought—the epistemic view involves a rejection of modal arguments. I will take up this issue in more detail in chapter 8. For the moment, let me simply say that the mere assertion that CA and KA fail because they mistakenly presuppose complete knowledge of the relevant facts does not entail that all modal arguments fail in this way. In particular, as I will argue in chapter 8, there are certainly arguments that do not fail in this way.

3.2.3. A Condition of Adequacy That the modal arguments that are at issue in the debates about experience are in structure identical to arguments that are used throughout philosophy suggests a condition of adequacy on any response to these arguments. The condition of adequacy is this: if you think you have isolated a factor that constitutes the mistake in CA or KA, check to see if that factor is present in parallel arguments you accept; if the factor is present in modal arguments you accept, consign your proposal to the flames. As will emerge as we proceed through later chapters, this condition of adequacy will play an important role in the discussion to come. In particular, I will argue that a contrast between the perfect actor argument, on the one hand, and CA and KA, on the other, will establish not only that my own view meets this condition of adequacy (chapter 8) but also that many rival views do not (chapter 9).

3.3. The Conceptual Version Having answered, or at least indefinitely postponed, the methodological version of the skeptical challenge, I turn now to the conceptual version. A prominent proponent of the conceptual version is, as we noted earlier, Noam Chomsky. Chomsky’s ideas on these topics are scattered throughout his writings, but a particularly famous statement is as follows: The mind-body problem can be posed sensibly only insofar as we have a definite conception of body. If we have no such definite or fixed conception, we cannot ask whether some phenomena fall beyond its range. The Cartesians offered a fairly definite conception of body in terms of their contact mechanics, which in many respects reflects commonsense understanding. Therefore they could sensibly formulate the mind-body problem. (1988, 142)

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For Chomsky, the mind-body problem—and by implication the logical problem, too—should be rejected on the grounds that it presupposes a mistaken view of the development of the notion of the physical from the seventeenth century on. Cartesian science provides a fairly definite understanding of the notion of the physical, an understanding that permits a distinction between the mental and the physical and, correlatively, the formulation of physicalism and of the mind-body problem. But subsequent scientific theorizing rejected this notion. To the extent that it is in use at all, Chomsky thinks, the concept is redundant or emphatic: ‘‘physical’’ in ‘‘physical world’’ should be understood more on the analogy of ‘‘true’’ in ‘‘true fact’’ than ‘‘red’’ in ‘‘red ball.’’ The consequence of this is obvious enough: it makes no sense to ask whether, for example, experience is ultimately physical; this would be like asking whether a fact is ultimately true. Suggestions akin to Chomsky’s have been made in different ways by different writers, not all of whom emphasize the historical issues in the way that he does or share his presuppositions: (i) Strawson 1994 suggests that ‘‘physical’’ is the ultimate natural kind term and that a competent user of a natural kind term can use it without any, or at least much, knowledge of the nature of the referent of the term. As a result, there is no way to exclude irreducible experiences from lying within its extension. (ii) Searle 1992 suggests that contemporary discussion presupposes a conception of the physical according to which, whatever the physical is, it is objective. But this, he argues, is to adopt an overly restrictive conception. (iii) Hempel 1969 suggests (as do Crane and Mellor 1990) that if ‘‘physical’’ is understood in the light of contemporary physics, physicalism is false, but if ‘‘physical’’ is understood in the light of complete or ultimate or ideal physics, physicalism is trivial. In the discussion to follow, I will for the most part have Chomsky’s development of the challenge in mind, but what I have to say has a straightforward application to these other views. What is common to all of them is the premise that, despite what it is tempting to think, the notion of the physical as it is used in contemporary philosophy of mind cannot be clarified in such a way that the contrast between ‘‘the physical’’ and ‘‘the mental’’ (‘‘the experiential,’’ etc.) is preserved. The conclusion drawn from this premise—again, by all of the views in question—is that the mind-body problem and, by implication, the logical problem—should be rejected rather than taken up and discussed seriously. How, then, do we react to the conceptual challenge? One possibility is to concentrate on the premise of the argument and then defend or explore different accounts of the physical. This is not the approach I will adopt. For one thing, it is not obvious what it would take to clarify the concept of the physical to a greater extent than we have already done. In the previous chapter, we examined one way to introduce the notion, the paradigm

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physical object view. I doubt very much that further examination of this notion will quiet a proponent of the conceptual challenge. Moreover, what Chomsky says about the history of the notion of the physical seems to me at least to have considerable prima facie force. If his view on this point is mistaken, this could be established only by a fairly elaborate examination of the development of the relevant parts of science and philosophy. I am certainly not in a position to say how such an examination would go or what it would reveal when completed. Instead of concentrating on the premise of the conceptual challenge, therefore, I will argue instead that the premise does not entail the conclusion. More particularly, even if it were true—and true on the grounds Chomsky suggests—that the notion of the physical fails to meet minimal standards of clarity, it does not follow that the problem ought to be rejected. On the contrary, this would follow only if the notion of the physical played an essential role in that problem. If, on the other hand, it does not play any essential role in the problem, it would be quite mistaken to reject the problem because the notion of the physical cannot be reasonably clarified. So the question we need to consider is this: what is the role of the notion of the physical and related notions in the philosophical debates about experience? My answer will be that, although these notions may play an essential role in some aspects of the mind-body problem, they play only an illustrative or inessential role in the logical problem. Then Chomsky’s criticism has no effect on us, regardless of its impact elsewhere.

3.3.1. Two Examples What is it for a notion or thesis to play an inessential role in a philosophical problem? Once again, the only procedure I know of here is the consideration of examples.

Example 1. Identity in the Debate about Personal Identity The usual way of presenting this debate is to see it as concerning how certain statements of identity can be true, even though the expressions involved in these statements apparently denote distinct objects. Thus, consider (1): (1) That contented little boy of yesteryear is this alienated intellectual now before you. The problem presented by (1) is that while it is true, or at least could perfectly well be, it apparently is in violation of a logical truth—namely, Leibniz’s law. Leibniz’s law articulates a necessary condition on identity: for any x and y, if x and y are identical, then every property of x is a property of y. Hence, if the little boy is identical with the alienated intellectual, then, by Leibniz’s law, ‘‘they’’ must share every property. On the other hand, the

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little boy in question presumably is not alienated. How, then, can he be, strictly speaking, identical with someone who is? On the surface, this debate is squarely about identity. But to assume this is to confront a puzzle, for the notion of identity is completely transparent. Roughly, identity is that relation R that is reflexive, transitive, and symmetrical and—if this is different—that satisfies Leibiz’s law. So in a sense there are no problems about identity. On the other hand, personal identity seems to raise a genuine question whose answer is far from transparent. Roughly, the question seems to concern what sort of change a person can undergo while remaining that person, and this is a question that proves extremely difficult to answer. What is going on? How can the notion of identity be transparent when the notion of personal identity is not? As a number of philosophers have suggested (e.g., Parfit 1971, Lewis 1986), the answer is that questions about personal identity are formulated in terms of identity but they are nevertheless not about identity. Identity plays an inessential role in the problem.

Example 2. Truth in the Question of Realism The usual way of presenting this debate is to see it as concerning whether certain statements can be true, even if there is no possible way to verify or establish by empirical means that they are true. Thus, consider (2): (2) There is at least one object in the universe that has no effect on anything else. According to the realist, (2) is either true or false, depending on whether there is at least one object meeting this condition, and the fact—assuming for the moment it to be a fact—that we cannot verify its truth is quite irrelevant. According to the antirealist, by contrast, if it is genuinely impossible to verify whether (2) is true, then—despite the fact that it is syntactically well formed and each word in it has a relatively determinate meaning—it is mistaken to say that it is true or false. For the antirealist, the very idea of a statement’s being true or false logically presupposes that we can verify it, at least in principle. On the surface, this debate is squarely about truth and its connection to verification. But as many philosophers (e.g., Leeds 1978, Devitt 1997, Horwich 1998, Soames 1999) have emphasized, this appearance is misleading. One way to make this point is to notice that the issue can be formulated—at least if we focus on this example—without recourse to the notion of truth by asking, ‘‘Could there be at least one object that has no effect on anything else, even though we could not in principle find out that there is?’’ In response, the antirealist says no, and the realist says yes. Moreover, antirealists might go on to say that for a whole series of related questions, the correct answer is similar. This allows them to formulate their view with an infinite conjunction that has something like the following form:

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The Problem (3) It is not possible that there is at least one object that has no effect on anything else and we could not find out that there is at least one object that has no effect on anything else, and it is not possible that snow is white and we could not find out that snow is white, and it is not possible that snow is blue and we could not find out that snow is blue, and it is not possible that torture is wrong and we could not find out that torture is wrong . . . etc.

Now, to formulate this generalization succinctly, we need the notion of truth. So we need to be able to say: (4) For all p, it is not possible that p is true and we could not find out that p is true. This last claim is a formulation of the idea that there is no truth beyond verification. And we can certainly formulate the difference between the realist and the antirealist by noting that, according to the former, (4) is true. Nevertheless, it is mistaken to say that the dispute is about truth. Instead, the dispute is simply formulated in terms of truth. In the light of these examples, we may explain our position on the conceptual challenge as follows: the concept of the physical plays a role in the debate about experience that is akin to that of identity in the debates about personal identity and that of truth in the debates about realism. Of course, I do not want to overplay the analogy. Physicalism is not a logical or quasi-logical notion in the way that truth and identity are, and the concept of truth plays a role in formulating generalizations that the thesis of physicalism certainly does not. Nevertheless, it is a fact that one is often in the position of raising a philosophical question in the name of something not actually essential to the question. I think a fact of this type obtains here. If so, the logical problem is not in this sense about physicalism, even if physicalism plays an important role in the discussion. It follows that the conceptual challenge collapses. Imagine a philosopher who (never mind why) rejected as unclear the notions of identity and truth. It would not follow that problems stated in terms of identity and truth should be dismissed; mutatis mutandis, for the notion of the physical and the problem of experience.

3.4. The Role of Physicalism in the Logical Problem Chomsky’s suggestion is that the problem of experience can be posed sensibly only insofar as we have a reasonably definite conception of the physical. My reply is that, if the concept of the physical plays only an inessential role in the problem, it may be posed even in the absence of such a concept. But at this point it might be objected that what I have said so far is disappointingly conditional. True, if physicalism plays an inessential role, the conceptual challenge can be met. But why suppose it plays that role?

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We will not answer this question by staring at T1–T3 and asking what role physicalism plays in them. Rather, we need to recall the reasons for believing T1–T3 set out in the previous chapter and ask what role physicalism plays in those reasons. In the case of the arguments for T1, physicalism plays no role at all, and so we can set it aside. But physicalism does play a role in the arguments for T2 and T3. I will consider these in turn.

3.4.1. Its Role in the Case for T2 In the previous chapter, I distinguished two arguments for T2, the argument from physicalism and the argument from manifest supervenience. If the conceptual challenge is correct, and physicalism as currently formulated has little or no content, it is clear that the argument from physicalism is not going to carry much weight in support of T2. To see this, we need only notice that the argument from physicalism that I presented in the previous chapter presupposed that a physical truth is a nonexperiential truth. If the notion of the physical is as empty as proponents of the skeptical challenge make out, this will not be a reasonable assumption, and the argument from physicalism to T2 will fail. However, even if it were so, it does not constitute a reason for rejecting the logical problem. Whatever is true of the argument from physicalism, the argument from manifest supervenience is untouched. Hence, in response to the conceptual challenge, a friend of the logical problem may point out that, even if that challenge were successful, it would at most remove one reason for believing T2. But, as there are two reasons for believing T2, the conceptual challenge could not remove all reason for believing T2 as a matter of principle. It might be replied that dropping physicalism in favor of manifest supervenience does not alter the basic thrust of the conceptual challenge, for the version of the challenge applies here, too. However, a version of the challenge does not apply. Perhaps it is true that the concept of the physical is so elastic that even an experiential truth would count as a physical truth. But the concept of a scientific truth is not like that, if only because it is introduced by Sellars—and we have followed him in this—in such a way that scientific truths are not manifest truths. And, because experiential truths are manifest truths par excellence, scientific truths must be nonexperiential. Alternatively, it might be replied that switching from physicalism to manifest supervenience does not alter matters for a different reason— namely, that manifest supervenience is to be rejected, or anyway would be rejected, by a proponent of the skeptical challenge. However, although some proponents of the skeptical challenge certainly do reject manifest supervenience, this has nothing to do with skepticism per se and must be argued for on independent grounds. Searle, for example, seems to me to deny manifest supervenience when he writes: ‘‘No description of the third-person,

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objective, physiological facts would convey the subjective, first-person character of pain, simply because the first-person features are different from the third-person features’’ (1992, 117). However, his reasons for doing so are precisely CA and KA, versions of which Searle regards as ‘‘ludicrously simple and quite decisive’’ (p. 118). So at this point Searle is not rejecting the logical problem at all. What he is doing is adopting a primitivist solution to the problem. The only difference between Searle’s primitivism and other versions is that Searle insists that the concept of the physical can be understood in such a way that primitivism and physicalism are cotenable. Moreover, not all proponents of the skeptical challenge do deny manifest supervenience. Chomsky, for example, seems to me to assert manifest supervenience when he writes: ‘‘Methodological naturalists do not expect to find counterparts to . . . informal statements . . . within the explanatory theories they self-consciously devise’’ (2000, 88). What Chomsky seems to be suggesting is that there is a manifest image and a scientific image, and that the concepts and claims distinctive of the first are quite distinct from the concepts and claims distinctive of the second. In turn, this is remarkably close not only to manifest supervenience but also to T2 itself. In short, skepticism about physicalism need not issue in skepticism about manifest supervenience. We have seen that, even if the conceptual challenge were right, it would not remove all reason for believing T2. But one might nevertheless wonder how this is relevant to our earlier discussion. Perhaps what I have said shows that the skeptical challenge has no impact on T2, but it nowhere shows that physicalism plays a role in the logical problem rather like the role played by identity in the personal identity problem. With this I agree; the idea that physicalism plays an accidental rather than essential role in this sense emerges, not when we consider the reasons for T2, but when we consider the reasons for T3. So it is to these that I now turn.

3.4.2. Its Role in the Case for T3 Just as we distinguished two arguments for T2, we also distinguished two arguments for T3, CA and KA. Now, an important fact about both arguments that I have so far been ignoring is that they are usually understood as arguments that appeal to physicalism as an essential component. How, in the face of that fact, can I possibly maintain that physicalism plays in these arguments only an accidental role? The reason emerges from a consideration of one of the earliest responses to the knowledge argument, voiced with considerable force in this passage from David Lewis (see also Churchland 1985): Some of you may have welcomed the Knowledge Argument because you thought all along that physical information was inadequate to explain the phenomena of mind. You may have been convinced all along that the mind could do things that no physical system could do:

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bend spoons, invent new jokes, demonstrate the inconsistency of arithmetic, reduce the wave-packet, or what have you. You may have been convinced that the full causal story of how the deeds of mind are accomplished involves the causal interactions not only of material bodies but also of astral bodies; not only the vibrations of the electromagnetic field but also the good or bad vibrations of the psionic field; not only protoplasm but ectoplasm. I doubt it, but never mind. It’s irrelevant to our topic. The Knowledge Argument is targeted against you no less than it is against Materialism itself. Let parapsychology be the science of all the non-physical things, properties, causal processes, laws of nature and so forth that may be required to explain the things we do. Let us suppose that we learn ever so much parapsychology. It will make no difference. Black-andwhite Mary may study all the parapsychology as well as all the psychophysics of color vision, but she still won’t know what it is like. Lessons on the aura of Vegemite will do no more for us than lessons on its chemical composition. And so it goes. Our intuitive starting point wasn’t just that physics lessons couldn’t help the inexperienced know what it’s like, it was that lessons couldn’t help. If there is such a thing as phenomenal information, it isn’t just independent of physical information. It’s independent of every sort of information that could be served up in lessons for the inexperienced. (1988, pp. 588–589) Lewis’s point in this passage is that, while the knowledge argument is on the surface directed at physicalism, it is not directed only at physicalism: if it were successful against physicalism, Lewis argues, it would be successful against dualism, too, or at least dualism of a certain form. Of course, the point does not entail that KA is unsuccessful; for all that’s been said, the argument might refute both physicalism and dualism. But Lewis’s point does raise the question of whether it is possible to formulate a thesis that KA is primarily aimed against. In other words, what, short of their inclusive disjunction, is shared by physicalism and dualism such that the knowledge argument, if successful, would refute both? Now, in general, the mere fact that an argument is targeted against two theses a and b does not mean that there is an interesting third thesis c such that, if successful, the argument would refute c. But in this case it is surprisingly easy to produce such a thesis and, in fact, two such theses. The first is suggested in the final sentence of the passage quoted. Lewis suggests that experiential truths (‘‘phenomenal information’’) are ‘‘independent of every sort of information that could be served up in lessons for the inexperienced.’’ I take him to mean here something that is sometimes expressed, in particular by Nagel (e.g., 1986), in terms of objectivity. As we will see in more detail in chapter 8, objective truths are those that can be understood from more than one point of view and so may be served up in lessons to the inexperienced. So, on this interpretation, what Lewis is suggesting is that the argument would, if successful, refute the thesis that experiential truths

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supervene on objective truths. Both physicalism and the sort of dualism he describes emerge simply as special cases of this more general thesis, for the reason that physical and—to adopt Lewis’s phrase—parapsychological truths are objective. Another candidate for the more general thesis is the one I have been operating with all along: experiential supervenience, the thesis that experiential truths supervene on nonexperiential truths. (Indeed, it seems to me to be possible to read a suggestion along these lines into the passage from Lewis.) On this interpretation, both physicalism and the sort of dualism Lewis has in mind emerge as special cases of the more general thesis that the experiential supervenes on the nonexperiential. At least given reasonable assumptions, both physical truths and parapsychological truths are nonexperiential; hence, both physicalism and dualism are special cases of experiential supervenience. Which of these two theses is at issue in the argument? I am going to assume in what follows that it is the second thesis that is at issue. The reason for this is largely because objectivity involves some further issues that I want to put aside for the moment; we will return to them in chapter 8. But, however this issue is resolved, the crucial point for present purposes is that there is certainly a general thesis that is not physicalism but at which KA aims. My assumption is that this general thesis is experiential supervenience, but if a reason is produced that it must instead be a thesis that involves objectivity, the points that I will make apply in that case, too. Suppose then that KA really is directed against a more general thesis. And suppose in addition that the general thesis in question is experiential supervenience. What does that tell us about the role of physicalism in the argument? What it tells us is that physicalism plays an inessential role. Of course, in standard presentations, the target of the knowledge argument is presented as an argument against physicalism. But physicalism here is simply a stand-in for any thesis at all that entails that experiential truths supervene on nonexperiential truths. Moreover, it seems reasonable that similar points will apply, mutatis mutandis, in the case of CA. But then we arrive at the conclusion that what is really at issue in the arguments for T3 is not physicalism per se but something more general; physicalism, a doctrine that is highly controversial, plays at most an inessential role.

3.5. Have We Robbed the Arguments of Their Appeal? Our response to the conceptual challenge is that it misconstrues the role of physicalism in the logical problem: in principle, the reference to physicalism (the physical, etc.) could be dropped and the challenge avoided. But it might be objected that this succeeds only at the cost of robbing KA and CA of their great initial appeal. This appeal seems to depend completely on

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the contrast between the mental and the physical, a contrast that, as I noted in the previous chapter, has considerable psychological force. On the other hand, suppose we say that these arguments are properly understood to be about the relation between the experiential and the nonexperiential, and not about the physical. What then explains their appeal? (I am indebted to David Chalmers for this objection.) I have three replies. First, the same thing might be said about the question of personal identity with the notion of identity removed, or the question of realism with the notion of truth removed. Much of what gives these issues their grip on our imagination is precisely the notions of identity and truth. Nevertheless, it is true (or, rather, plausible) that in these cases the issues are not about, respectively, identity or truth. To put this point in a slightly different way, in suggesting that physicalism plays an illustrative role in our problem, I am not suggesting that we may not use the vocabulary of physicalism in formulating and discussing the problem. Second, it is not clear in any case that the intuitive basis of the problem has been removed, once we shift focus from the contrast between the mental and physical to the contrast between the experiential and the nonexperiential. As noted in the previous chapter, our problem has a Moorean flavor, but problems of this kind have an incredible grip on our imagination. In supposing that moral goodness, for example, is apparently quite distinct from anything else, Moore was putting his finger on something about it that we seem to perceive dimly. What I am suggesting is that something similar is going on here. Our discussions of experience in philosophy seem to have perceived dimly that what is really at issue is the thought that experience is metaphysically distinct from everything else. Of course, we have clothed this thought in the traditional vocabulary. But this doesn’t mean that the thought itself has no appeal. Third, the objection pushes us toward the epistemic view. Why does it seem implausible that KA could tell us that the experiential is quite distinct from the nonexperiential? The answer, I think, is that stating KA in terms of the contrast between the experiential and the nonexperiential makes it more vivid than it would otherwise be that there are many types of nonexperiential truth of which we are ignorant. So once we shift our attention to the nonexperiential, the idea that we are ignorant of some relevant truths seems to come more sharply into focus.

3.6. Conclusion We are now in a position to summarize the main points of part I. In chapters 1 and 2, I undertook to identify our topic and to explain the sort of question we are posing about that topic. This I have now done. The topic is the notion of experience as it is understood by the phenomenal conception, and the

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problem we are raising about this topic is that we tend to have inconsistent beliefs about it, as illustrated by the logical problem. We have also seen, in this chapter, that the logical problem does not succumb to a form of argument that would otherwise threaten to undermine our discussion. In the next parts of our discussion, I turn from the identification of the problem to the question of how to solve it.

PART II THE PROPOSAL

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4 Error from Ignorance

4.1. Introduction So far, we have seen that our problem presents us with three inconsistent theses, T1–T3, each of which we have reason to believe: T1. T2. T3.

There are experiential truths. If there are experiential truths, every experiential truth is entailed by some nonexperiential truth. If there are experiential truths, not every experiential truth is entailed by some nonexperiential truth.

We have seen also that the solution I favor to this problem is the epistemic view, which says that we are in roughly the same epistemic position as that of the slugs in our introductory example. (If you don’t remember the example, now is a good time to go back and reread it.) Reflection on this example prompted us to formulate the ignorance hypothesis, according to which we are ignorant of a type of experience-relevant nonexperiential truth. In the light of this hypothesis, the epistemic view may be formulated as a doctrine with two parts. The first is the conditional thesis linking the hypothesis and the problem: E1.

If the ignorance hypothesis is true, the problem of experience is solved.

The second is a categorical thesis about the antecedent of the conditional: E2.

The ignorance hypothesis is true.

The aim of part II is to explain and defend these two theses.

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4.2. A Framework for Discussion When initially confronted with the epistemic view, a common reaction is something like this: ‘‘Although the view you are imagining might be true, there is no way we could demonstrate that it is true, and so in practice there is no point considering it. Don’t we have to work with the concepts we have rather than speculate about concepts we don’t have?’’ This line of thought has some prima facie appeal, but we should not be put off by it. If you live in a part of the country where wood is plentiful, it is good practical advice to build your house with wood rather than dreaming about stone or, worse, of some as-yet-undiscovered building material as light as wood and strong as stone. But our issue is not in this sense practical; we are interested not in what to build but in what to believe. For us, the central question might be put roughly as follows: is the probability of our ignorance greater or less than the probability that (e.g.) primitivism is true? The injunction to work with what one has is irrelevant to this comparison. In any case, there are at least three ways to defend the epistemic view, short of actually producing the missing truths. First, E1 may be defended without supposing that we are ignorant in any sense. All E1 says is that if the ignorance hypothesis is true, the logical problem is solved; one may defend this conditional without defending its antecedent. Second, it is possible to provide reasons for supposing that we are ignorant in the way that E2 says, without saying exactly what we are ignorant of. This would be to provide plausibility considerations (as I will put it) in favor of the hypothesis. Third, it is possible to defend the epistemic view dialectically—that is, to show that it is free from objection and that its alternatives are not free from objection. In the light of this, the discussion in part II will be organized as follows: In this chapter, I consider the reasons for supposing that the conditional E1 is true. In chapters 5, 6, and 7, I turn to the plausibility considerations in favor of E2. Finally, in chapter 8, I discuss objections to the epistemic view. The considerations of alternatives will be postponed until Part III. How should the defense of E1 proceed? It should be clear that if the ignorance hypothesis has an impact on the logical problem at all, it does so by having an impact on the reasons for T3—namely, the conceivability argument (CA) and the knowledge argument (KA). It is clear also that these are arguments of a general style—namely, modal arguments. This suggests that E1 will be plausible to the extent that it is plausible in general to suppose that ignorance has an impact on modal arguments. It is this general claim that I want to explore and defend.

4.3. The Ignorance Hypothesis Examined We may start by looking more closely at what the ignorance hypothesis says. In one sense, it is clear enough: we are unaware of a type of

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experience-relevant nonexperiential truth. But three phrases here need further explanation: ‘‘unaware,’’ ‘‘experience-relevant,’’ and ‘‘type of nonexperiential truth.’’ As usual, it is not necessary or desirable to define these phrases; the point is to indicate how they are to be understood.

4.3.1. ‘‘Unaware’’ The hypothesis does not say merely that there are experience-relevant nonexperiential propositions and that we do not know the truth of those propositions. To say that is consistent with saying that we are aware of or understand the propositions in question but we just don’t happen to know that they are true. What, then, do we mean when we say that we are unaware of some nonexperiential truths? The sense of ignorance or unawareness here is hard to characterize but easy to grasp. The slugs, for example, are unaware in this sense of a type of circle-relevant noncircular truth, the truths about the pieces of pie. It is reasonable to characterize the ignorance here as one of a failure of concept possession or understanding or, equivalently, as a failure of knowing what the pie pieces are. The sort of unawareness or ignorance I have in mind is this sort of unawareness. Later (in chapter 6), we will examine an argument defended by Russell that we are unaware of, or ignorant of, the categorical features of matter. The idea of unawareness or ignorance that we have invoked in formulating the ignorance hypothesis is the same. Russell himself explained this sort of ignorance by drawing an analogy with a blind person’s lack of knowledge of light or color. According to Russell, a blind person—that is, a person who by definition has not had the relevant experiences—is ignorant in a certain dramatic way about color (1967, p. 34). The blind person may know certain truths about color, but it remains true that there is a type of truth concerning color of which the blind person is ignorant. So we might put Russell’s example of the blind person alongside the example of the slugs. Both illustrate the kind of lack of knowledge that I have in mind.

4.3.2. ‘‘Experience-Relevant’’ The hypothesis does not say that we are ignorant of any old nonexperiential truths. If that was all it said, it would be an uninteresting thesis that very few people would deny. On any reasonable view of our epistemic position, there are many nonexperiential truths that we are unaware of. The point is, rather, that we are ignorant of some nonexperiential truths that are relevant to the nature of experience. Again, the slugs are ignorant of a type of noncircular truth about the mosaic that is relevant to the circular truths, and this is what generated for them the problem of the circle. But to say this is not to deny that they might be ignorant of other types of noncircular truths, truths that are not relevant in this sense. For example, suppose the slugs could not detect right-angle triangles. The truths about right-angle triangles

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might then constitute a noncircular truth of which they are ignorant, but this is not a type of truth that is relevant to the truths about circles. What does it mean to say that one truth is relevant to another? On this matter, the example of the slugs is apt to be misleading. As we noted in the introduction, the truths of which the slugs are ignorant by themselves entail the truths about circles. Does ‘‘relevance’’ then mean ‘‘entailment’’? No— entailment is sufficient for relevance but not necessary. In the sense at issue here, one truth T is relevant to a truth T* just in case T is an essential part of a set of truths that together entail T*. To illustrate, consider the argument ‘‘All men are mortal; Socrates is a man; therefore, Socrates is mortal.’’ The premise ‘‘All men are mortal’’ is relevant to the conclusion but does not entail it; rather, it is an essential part of a set of truths that does entail the conclusion—namely, the set that contains ‘‘All men are mortal’’ and ‘‘Socrates is a man.’’ When I say that we are ignorant of an experience-relevant truth, I mean that we are ignorant of a truth that stands to experiential truths in much the same way. (The notion of relevance at issue here is similar to the notion of an INUS condition, discussed by Mackie 1974, p. 62.) It might be thought that, by building the notion of relevance into the ignorance hypothesis, our position is trivialized. ‘‘Of course, if they are relevant, you can solve the problem,’’ you might think, ‘‘but you can’t just assume that!’’ I have two replies to this: First, if correct, this objection would at most show the triviality of the first part of the epistemic view, it would not show that the second part is trivial, and so it would not show that the epistemic view is itself trivial. Second, even if it is trivial in one sense, the question remains as to why it is true; that is, why should it be that ignorance has an impact on modal reasoning? That is the question that we are concerned with.

4.3.3. ‘‘Type of Nonexperiential Truth’’ The hypothesis does not say simply that there are particular nonexperiential truths of which we are unaware. There are many particular truths that the slugs might be ignorant of—say, about the particular location of a triangular tile. The claim is rather that there is a type of nonexperiential truth of which we are ignorant, not simply that we are ignorant of particular nonexperiential truths. Once again, this idea is easy to grasp but difficult to explicate. There are many ways of grouping a body of truths into types. (We don’t want to claim that we are ignorant of the type of truth normally thought of on a Tuesday.) But once again, we may use the slugs to bring out the relevant sense of type. The slugs are ignorant of a type of noncircular truth. That is the sense of ‘‘type of truth’’ I intend. It needs to be admitted that in saying that truths fall into types, I am appealing to an idea that is mentioned often in the course of doing philosophy but is not at all clear. This is the idea that the body of truths that describe the world is not an undifferentiated blob but rather a structure that

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contains genuine difference and similarity—as it is sometimes put, that the various sort of things in the world fall into objective resemblance classes (Lewis 1983). I don’t at all claim to have clarified this idea, nor do I have any good suggestions about how to do so; still less do I know how one might explain it to the uninitiated. My excuse is that I don’t believe that any reader is uninitiated. My hope is to use examples such as that of the slugs Menostyle to activate a concept that I think is already dormant within us. In view of the difficulty of the notion of a type of experiential truth, one might wonder why I insist on it. The easiest way to answer this is to consider again Putnam’s perfect actor objection to behaviorism, discussed in chapter 3. How do most people react to this argument? As I mentioned then, it is common to view the argument as successful—certainly, I view it as successful. But this is not to say that most people draw the conclusion that some sort of primitivism or eliminativism is true. What most people think, at least implicitly, is that there must be a type of truth that is relevant to the nature of experience but which is quite distinct from behavioral truths. Of course, there is some controversy about what sort of truths these might be; some say they are truths concerning neurophysiology, for example, and others that they are truths that are partially defined in terms of other psychological states. But whatever the truths are, they are of a type altogether different from behavioral truths: they do not concern behavior but instead concern a quite distinct subject matter. In other words, the common reaction to the perfect actor objection involves precisely the notion that I have invoked in discussing the epistemic view, the notion of a distinct type of truth. This shows at least that the notion of a type of truth is accepted in philosophy of mind, and so our adoption of the notion here is relatively normal. But why does it explain or justify my insistence on the notion? Well, suppose, in response to the perfect actor objection, we did not insist on the notion of a type of truth distinct from any behavioral truth. Suppose, in other words, that it was suggested that all the argument showed is that there must be a particular truth distinct from any that was in play, but the truth in question might be of a familiar kind. The problem with this suggestion is that, if it was right, the perfect actor objection would fail as an argument against behaviorism. A behaviorist is perfectly entitled to say that there are particular behavioral truths that the objection fails to consider; what the behaviorist is not entitled to say is that there are nonbehavioral truths that the objection fails to consider. On the other hand, I am assuming here that the perfect actor objection is a good objection to behaviorism. In view of this, we may draw the moral that what is required for the ignorance hypothesis is not merely that we are ignorant of a distinct particular truth of a type already known to us but that we are ignorant of a distinct type of truth. The basic point may be put differently by recalling the condition of adequacy set out in chapter 3 for any potential response to CA and KA.

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According to this condition, if you think you have isolated a factor that constitutes the mistake in CA or KA, check to see if that factor is present in modal arguments you accept; if the factor is present in modal argument you accept, consign your proposal to the flames. In effect, what I have been suggesting is that to operate with the notion of a particular truth would be to fail this condition of adequacy, for to do so would be to hand the behaviorist the materials to respond to Putnam. Turning this point around, if we require our account to meet this condition, we must assume that we are ignorant of a type of truth.

4.4. Varieties of Ignorance I have been talking so far about what the ignorance hypothesis says. From the point of view of the plausibility of our position, however, it is just as important to have a clear understanding of what it does not say. In particular, it is important to have a clear understanding that the ignorance hypothesis is consistent with a wide variety of different kinds of ignorance. We may approach the issue by considering first the intuitive idea that the world is organized into a series of levels. Presumably, the bottom level is the level described by physics, with various other sciences describing other levels, each of which is metaphysically or logically sufficient for the next. Presumably, too, any realistic implementation idea will involve the postulation of a lot of levels. This admittedly rather vague idea suggests in turn a contrast between basic-level ignorance (as I will put it) and intermediatelevel ignorance. Basic-level ignorance is ignorance of a truth concerning a particular element of nature or a basic fact of the world. Intermediate-level ignorance is ignorance of a truth that is not itself basic but is determined by basic facts. Now, in the light of this distinction, it should be clear that the sort of ignorance exemplified in the example of the slugs is basic-level ignorance. The world of the slugs is constructed out of a number of elements combined together in a certain way. The slugs are ignorant of one of those elements and of the truths pertaining to that element. Because this has been our main example to date, one might form the impression that, according to the epistemic view, our ignorance is of a type of basic-level nonexperiential truth. This is an impression I am keen to dispel. The epistemic view as I shall develop it is neutral on the issue of whether the type of nonexperiential truth of which we are ignorant is a basic-level truth, an intermediate-level truth, or indeed both. More generally, it is important for my purposes to emphasize the variety of situations that may obtain compatibly with the ignorance hypothesis. The less the hypothesis rules out, the more plausible it is. In particular, the hypothesis leaves it open whether our ignorance is of a basic-level truth or

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fact or of an intermediate-level truth or fact. Later, we will also see that it does not entail (though it does not rule out) that our ignorance is chronic, that it cannot be overcome consistently with our contingent nature. Likewise, it does not entail (though it does not rule out) that our ignorance is categorical, that it concerns the categorical features of matter. Indeed, there may even be other possibilities. If there are, no harm will be done. For us, it is the fact of variety, and not the taxonomy of particular varieties, that is most important.

4.4.1. The Moths and the Beams Is it possible to construct an example analogous to the slug example but in which the background notion of ignorance is not basic-level but intermediatelevel? Yes—in contrast to the case of the slugs and the tiles, we also have the case of the moths and the beams. (This example is due in essentials to Karen Bennett.) Imagine an array of parallel light beams, completely constructed by red and green lights. The beams may, of course, be any color, so long as those colors are derived from an admixture of red and green, including in particular yellow; suppose for simplicity that there are only red, green, and yellow light beams. Now imagine a population of intelligent moths who live among the beams. The moths possess visual systems capable of detecting beams of red, green, and yellow lights. However, although they are cognitively sophisticated, the moths are ignorant of the principles whereby various lights combine to create different colored beams. Given their epistemological access to the array, it would be natural for these moths to think that its basic elements are three sorts of beams: red, green, and yellow. Of course, this is a mistake, but it would be a natural one in the situation. Now imagine further that among these moths there are some who begin to wonder about the array and formulate a synoptic vision of what it is like. For reasons that need not concern us, these moths take it that their yellowdetecting systems cannot tell them about the array in its most fundamental nature, and in consequence that yellow beams must not be fundamental or primitive; the yellow, they say, supervenes on the nonyellow. In particular, the moths think, the basic elements in the array are green and red beams; what the array consists of, one of them says, is a vast number of green and red beams set out in space, with every other beam being a construction of these. The moths now face what they call the problem of yellow: the yellowdetecting system tells them that there are yellow beams, and yet there is apparently no place for yellow beams in an array completely constructed from red and green beams. Just as the slug example provides us with a case of basic-level ignorance, the moth example provides us with cases of intermediate-level ignorance.

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Moreover, just as it is clear that the epistemic view is correct in the case of the slug example, it is likewise clear that it is correct in the case of the moth example. The moths face the problem of yellow because they are ignorant of a type of nonyellow truth that is nevertheless relevant to the nature of yellow; in particular, they are ignorant of the principles whereby green and red lights combine to produce yellow light. More generally, the ignorance hypothesis says that we are ignorant of a type of nonexperiential truth that is relevant to the nature of experience, but it is being left open whether we are in a position that is most like the slugs, on the one hand, or most like the moths on the other, or even some combination of the two situations.

4.5. Kinds of Modal Error We have so far examined what the ignorance hypothesis says and does not say. But something further is needed before we can turn our full attention to the central question of this chapter. We need an inventory of the sort of mistakes that may be made in trying to mount a modal argument. In my view, the recent literature on these issues suggests a basic division between three sorts of mistakes. I will call them proposition confusion, mode confusion, and neglecting to realize the existence of a defeater, or defeater neglect for short.

4.5.1. Proposition Confusion Suppose a person propounding a modal argument starts by asserting that a certain proposition p is conceivable and then reasons from this to the conclusion that p is possible. And suppose we know or believe (never mind why) that the argument is mistaken in the following sense: the proposition that is claimed to be possible in the conclusion of the argument is not in fact possible. Then the proponent of the argument has made a mistake—but what sort of mistake precisely has been made? One possibility is that there has been a confusion or conflation of two distinct propositions, p and q. The starting point of the argument is the claim that proposition p is conceivable, but perhaps all that is conceivable in fact is a quite distinct, but in the context harmless or uninteresting, proposition q. This is the mistake of proposition confusion: the proponent of the argument has confused the target proposition (as I will put it) with a contrasting proposition that is (in the context) unobjectionable. I take proposition confusion to be the main strategy under discussion by Kripke (1980, p. 142) when he says: ‘‘Any necessary truth, whether a priori or a posteriori, could not have turned out otherwise. In the case of some necessary a posteriori truths, however, we can say that under appropriate qualitatively identical evidential situations, an appropriate corresponding qualitative statement might have been false.’’

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4.5.2. Mode Confusion A different possibility is that the proponent of the argument has mistaken one mode of conceiving a given proposition for another mode. Notoriously, there are various different sorts of state properly called ‘‘conceiving,’’ and only some of these have evidential status with respect to modal beliefs. The idea behind mode confusion is that a proponent of the conceivability argument claims to conceive a certain proposition p and reasons from this to the thesis that is p is possible, and yet the argument goes wrong because the initial conceivability claim is plausible only if it is interpreted as one mode of conceiving rather than another. The mistake of mode confusion emerges in more detail if we distinguish two ways in which it might come about. The first appeals to a distinction between strong and weak conceivability discussed by Van Cleve 1983. The notion of conceiving that is at issue in modal arguments of the sort we are concerned with may be explained (though not analyzed) by saying that S conceives of p just in case it imaginatively appears to S that p is possible. Suppose we call this notion of conceiving—that is, the notion we have been using all along—‘‘strong conceivability.’’ We may then distinguish strong conceivability from a weaker variety that obtains just in case it does not appear to S that p is impossible. The distinction is as follows: (1) S strongly conceives that p just in case it imaginatively appears to S that p is possible. (2) S weakly conceives that p just in case (i) S entertains p and (ii) it is not the case that it imaginatively appears to S that p is impossible. Strong and weak conceivability differ from each other in two ways that are important for us. First, the slogan ‘‘conceivability is a guide to possibility’’ is plausible only when the notion of conceivability at issue is strong conceivability. If it visually appears to me that there is a lamp on the table, I seem thereby to be prima facie justified in believing that there is; hence, one might reasonably say being visually appeared to is a good guide to actuality. But suppose it is not the case that it visually appears to me that there is no lamp on the table. We would not normally say in such cases that I am thereby prima facie justified in believing that there is a lamp on the table. Perhaps if episodes of this kind were repeated often enough, I would have some sort of justification. But this is not what we mean when we say that perceptual experience is a guide to actuality. Likewise, while it is true that if I strongly conceive that p is possible, I am thereby prima facie justified in believing that p is possible, it is not true that if I do not conceive that p is not possible, I am thereby prima facie justified in believing that p is possible. Second, strong conceivability is epistemically more demanding than weak conceivability. One can strongly conceive a proposition—that is, it can appear to one in imagination that the proposition is possible—only if one has a sufficiently rich understanding of the proposition in question. But

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one can weakly conceive a proposition even in the absence of such understanding. Thus, for example, one cannot strongly conceive that there might be creatures with eyes that are not creatures with ears (a Van Cleve example) unless one has a sufficiently rich understanding of what it is to be a creature with eyes and a creature with ears. To take a different example, suppose the ontological argument is sound, and the honest and sincere atheist says that he can conceive of a Godless universe (see Yablo 2000). A conceivability report of this kind cannot be taken as a report of positive conceivability. If the ontological argument is sound, Godlessness is selfcontradictory; you cannot conceive that it is possible if you understand it. More generally, and returning to the idea of mode confusion, one may adopt the position that a proponent of a conceivability argument mistakes weak conceiving for strong conceiving, and as such the argument will not yield the conclusion. That is the mistake of mode confusion. A different way of developing mode confusion is by drawing a distinction between prima facie and idealized conceivability, a distinction discussed in detail by Chalmers (2002b, 147–149). Even if we suppose that there is a notion of conceivability in good standing, we should all agree that introspective judgments concerning the character and content of these conceivings are notoriously subject to influence. As Descartes says in the Meditations, to be clear that we are having the intuitions we say we are, we need to withdraw to a quiet place and meditate. To put it rather roughly, the idea of prima facie conceivability is the idea that something seems conceivable to you, but only at first glance or on first appearances. The idea of idealized conceivability is that the idea that it seems conceivable to you after you have really thought things through, considered all the factors that bear on it, and so on and so forth. Of course, the distinction here is a roughand-ready one, but it is real enough for all that. Moreover, the idealized– prima facie distinction crosscuts the weak-strong distinction. It might be the case that you ideally strongly conceive a proposition, that you ideally weakly conceive it, that you prima facie strongly conceive it, and that you prima facie weakly conceive it.

4.5.3. Mixed Confusion In distinguishing proposition confusion from mode confusion, I don’t mean to suggest that the two mistakes are incompatible. On the contrary, I take it that in reality a strategy alleging both is often the most persuasive way to defeat a modal argument. The reason is that the mixed strategy permits a response to an obvious reply by a proponent of a modal argument to the charge either of proposition confusion or of mode confusion. We may illustrate this by focusing on the relation between proposition confusion and the distinction between weak and strong conceivability. Suppose we pursue the strategy of proposition confusion by identifying a q that the proponent of the argument might be confusing with the target

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proposition p. The obvious response for the proponent of the argument is to concede that q is distinct from p, and even to concede that there is a tendency to confuse the two propositions. But it is nevertheless open to a proponent of the argument to insist that, once the two propositions have been distinguished, it becomes obvious that both propositions can be conceived. It obviously does no harm to the argument to conceive more things than you have to. In response to this move, it is natural to allege that the proponent of the argument is guilty, not just of proposition confusion, but of mode confusion. For if it can be argued that p cannot in the context be strongly conceived—say, because there is a failure to understand the proposition to a sufficient extent—the proponent of the argument cannot reply that both propositions are being strongly conceived, and this obvious response is blocked. In short, mode confusion may bolster proposition confusion. Similarly, suppose we pursue the strategy of mode confusion by claiming a proponent of the argument is confusing strongly conceiving p with weakly doing so. The obvious response for the proponent of the argument is to concede that p is weakly conceivable but to insist at the same time that it is also positively conceivable. There is, after all, no contradiction in supposing that a proposition may be both strongly and weakly conceivable. Moreover, if a proponent of the argument in good faith suggests that the introspective evidence is such that there is at least some strong conceiving going on, it is difficult to respond that there is none. On the other hand, if one can argue that the proposition p is being confused with another proposition q, and that there is in the context strong conceiving of q, then the objection can be met. In short, proposition confusion may bolster mode confusion.

4.5.4. Defeater Neglect I have so far discussed two sorts of mistakes that might be made in a fallacious piece of modal reasoning—proposition confusion and mode confusion—and noted that these mistakes might have different sources and might occur together. I turn finally to a third sort of mistake. This sort of mistake is the one identified and explained in Stephen Yablo’s discussion of these issues. Yablo writes: If X finds it conceivable that E, then she is prima facie justified in believing that E is possible. That justification is defeated if someone can provide her with reason to suspect the existence of a D such that (i) D is true, (ii) if D is true, then E is impossible, and (iii) that X finds E conceivable is explained by her failing to realize (i) and/or (ii). (2000, 121) It is clear that this mistake is different from the mistake of proposition confusion or mode confusion. In those cases, the focus is on the first stage of

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a modal argument, on the premise about what is conceivable. Here, by contrast, the focus is on the inference from conceivability to possibility. Someone may be innocent of proposition confusion and mode confusion, in other words, and nevertheless be guilty of defeater neglect. In the presentation to follow, I will for the most part concentrate on the mistakes of proposition confusion and mode confusion, rather than on the mistake of defeater neglect. I have three reasons for this: First, the notion of a defeater raises tricky issues in epistemology, and we can avoid those issues if we concentrate on the other mistakes. Second, according to some philosophers (e.g., Chalmers 2002b), conceivability entails possibility, and so presumably there is no possibility of making the mistake of defeater neglect; avoiding the issue of defeaters will permit us to avoid controversial issues about this aspect of the discussion. Third, so far as I am able to judge, it does not matter greatly to the plausibility of our position whether we operate with a background modal epistemology that favors one of these mistakes over others. Whatever I have to say about mode and proposition confusion would, I think, easily enough find a counterpart in the theories of those who prefer to talk in terms of defeat. The last point is important, for it permits us to note explicitly an important feature of the epistemic view—namely, that it is robust with respect to the background epistemology. We have just noted that the plausibility of our position will not be affected by whether one adopts a modal epistemology that emphasizes the possibility of a defeater. But more generally the plausibility of our position is not affected by whether one adopts a modal epistemology that emphasizes the notion of conceivability. As I noted briefly in chapter 3, some philosophers are modal skeptics on the ground that they are skeptical that the notion of conceivability can ever be spelled out. But, as Alex Byrne pointed out to me, a philosopher who is not a modal skeptic might nevertheless hold a related view—namely, that the proper formulation of arguments such as CA and KA would interpret them as starting, not from psychological claims about conceivability or imagination, but simply from tentative claims about what is or is not possible. This view is interesting and represents an apparently different approach to modal epistemology than the one adopted here. However, even if one held it, one could still hold the epistemic view, and for more or less the same reasons that I have set out. Even if one thinks about modal reasoning this way, it remains true that one needs to ask of any particular piece of reasoning whether it is successful; moreover, when one asks whether a piece of such reasoning is successful, it remains true that one would need to ask such questions as ‘‘What precisely is the proposition that is claimed to be possible at the start of reasoning?’’ and ‘‘Is the proposition that is claimed to be possible at the start of reasoning possible in fact?’’ Ignorance may play a role in answering these questions, just as much as it plays a role in answering the parallel questions that emerge when one thinks of modal reasoning as I have done here.

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4.6. Ignorance and Modal Reasoning: The Main Idea We have examined what the ignorance hypothesis says and does not say and also set out an inventory of mistakes that someone might make in advancing a modal argument. We are now in a position to state our basic reason for believing E1, the thesis that if the ignorance hypothesis is true, the problem of experience is solved. We may start with the observation that what we have said so far permits us to say in general terms what a response to a modal argument of any sort would look like. Suppose we call the inventory of mistakes that I have just introduced ‘‘the standard mistakes.’’ In abstract terms, a response to a modal argument is a consideration in favor of the idea that in advancing it we are making one (or a combination) of the standard mistakes. To put the same thing from the perspective of a critic, rather than a proponent, of a modal argument, a response to it is a plausibility consideration in favor of the idea that the proponent of the argument is making one (or a combination) of the standard mistakes. If we can pin one of the mistakes on a proponent of the argument, it would be a mistake to follow it through to its conclusion. Now, because it is clear what form a response to any modal argument would take, it is likewise clear what form a response to CA and KA in particular would take; that is, it would be a consideration in favor of the idea that in advancing either argument we are making one (or a combination) of the standard mistakes. On the other hand, the philosophical challenge presented by these arguments has always been that, although their conclusions seem objectionable, it is quite unclear that in advancing them we are making any of the standard mistakes. In fact, I think that many suggestions about what has gone wrong in these arguments can be seen as failed attempts to make it plausible that proponents of the arguments are guilty of these standard mistakes. It is at this point that ignorance enters the picture. If the ignorance hypothesis is true, it becomes immediately plausible that in advancing CA or KA we are indeed making one of the standard mistakes or a combination thereof. Moreover, if we are making one of these mistakes, the arguments for T3 collapse and the logical problem is solved. Putting these two points together, we arrive at E1: if the ignorance hypothesis is true, the logical problem is solved. It might be objected that to assert that we are making one of the standard mistakes because of ignorance is not to deny that we might be making these mistakes for some other reason as well. My reply is that this is no objection. I have claimed so far that if the ignorance hypothesis is true, the logical problem is solved. But I have not argued that there is no other way for it to be solved. In part III, I will indeed argue this, but the positive case for E1 does not prejudice this further issue. Alternatively, it might be objected that there might be two types of experience-relevant nonexperiential truth. It seems possible that we might

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be ignorant of one and not the other. But in that case, E2 seems false: we would be ignorant of a relevant type of truth, and yet the logical problem might be solved also in some other way. (Thanks to Brie Gertler for pointing this out.) My reply again is that this is no objection. I have claimed that the ignorance hypothesis is such as to solve the problem, but I have not argued— or yet argued; see part III—that there is no other way to solve the problem. Finally, it might be objected that to say that we are making one of the standard mistakes is not yet to characterize the mistake. But shouldn’t we characterize the mistake rather than simply saying that we have made one? My reply is that we have characterized the mistake, at least to this extent: we have said that it has its source in ignorance. This characterization is not empty because many philosophers suppose that our mistake, whatever it is, does not have its source in ignorance. Of course, it is true that there is a sense in which we have not characterized the mistake precisely, because we have not said precisely what we are ignorant of. We will return in chapter 8 to the question of whether this is a serious problem for our account.

4.7. Ignorance and Modal Reasoning: The Basic-Level Case I have suggested that E1 is plausible for the following reason: if the ignorance hypothesis is true, it is plausible that in advancing CA and KA we are making one of the standard mistakes. However, why is this latter claim plausible? We may approach the issue by looking again at the first of our two examples.

4.7.1. The Conceivability Argument Chez Slug The slugs, it may be recalled, advanced a conceivability argument to the effect that the circular truths fail to supervene on the noncircular truths. To formulate the argument, and at the risk of pursuing the analogy too far, let us introduce the idea of a zombie mosaic—that is, a mosaic identical to the actual mosaic in respect of all noncircular truths but different from it in respect of circular truths. With this notion in place, the conceivability argument may be formulated as proceeding from these two premises: CM1. CM2.

It is conceivable that there is a zombie mosaic. If it is conceivable that there is a zombie mosaic, it is possible that there is.

It is quite clear, for reasons that we have already considered, that if CM1 and CM2 are true, the circular does not supervene on the noncircular. On the other hand, it is equally clear that the reasoning here must be fallacious, for it is palpably impossible that the circular does not supervene on the noncircular. What, then, has gone wrong in the reasoning?

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A very plausible answer is as follows. The claim that there is a mosaic that matches the actual mosaic in respect of all noncircular truths but lacks circles may be interpreted in two quite different ways, depending on how its constituent quantifier phrase ‘‘all noncircular truths’’ is to be understood. On one reading, ‘‘all noncircular truths’’ includes both truths that pertain to triangles and those that pertain to pie pieces—for short, triangle truths and sector truths. On this reading, the basic proposition at issue in the argument is (4): (4) There is a mosaic identical to the actual mosaic in respect of all triangle and sector truths but which lacks circles. On a different reading, we confine attention when interpreting ‘‘all noncircular truths’’ to those that concern triangles. Then the basic proposition at issue in the argument is (5): (5) There is a mosaic identical to the actual mosaic in respect of all triangle truths but which lacks circles. Now, which of (4) and (5) is intended? This question sets up a destructive dilemma for a proponent of the argument. On the one hand, it is plausible that (5) is strongly conceivable: given their epistemic situation, there is no bar to it imaginatively appearing to the slugs that (5) is true. But (5) is not the target proposition of the argument. On the contrary, in the context (5) is unobjectionable; its conceivability would at most issue in a possibility that does not undermine the supervenience of the circular on the noncircular. On the other hand, it is plausible that (4) is the target proposition of the argument: its conceivability would issue in a possibility that undermines the supervenience of the circular on the noncircular. But (4) is not strongly conceivable. We saw that to strongly conceive a proposition demands a reasonable grasp on the proposition in question. But in an important sense the slugs don’t understand (4); they don’t know what pie pieces (or sectors) are. The most that can be said for (4) is that it does not appear to the slugs that (4) is impossible. But this claim of weak conceivability does not issue in possibility. Putting these points together, we arrive at the conclusion that the slugs are guilty of mixed confusion: they have confused (4) and (5); (5) is strongly conceivable but unobjectionable; (4) is objectionable but is at most weakly conceivable. That the slugs are guilty of mixed confusion is plausible. But the important point for us is that what makes it so plausible is that a version of the ignorance hypothesis is true of them: they are ignorant of a type of noncircular truth relevant to the truth about circles. In fact, this point might be brought out in two quite distinct ways. First, in the light of their ignorance, it is very plausible to say that the slugs are confusing (4) and (5); the important fact that distinguishes (4) and (5) is precisely something that is closed to them. Second, the fact that they are ignorant of the pieces of pie makes it plausible that they can only weakly conceive (4). On the other

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hand, their ignorance does nothing to stop them from imagining a situation in which (5) is true and hence believing that (5) is possible.

4.7.2. The Knowledge Argument Chez Slug As it is for the conceivability argument, so it is for the knowledge argument. Again, the general issue may be illustrated by considering the knowledge argument advanced by the slugs. In that case, the modal premise of the argument is KM1. KM1.

It is possible that a logically omniscient and conceptually sophisticated superslug knows all the noncircular truths and yet learns the circular truths on the basis of experience.

For reasons we considered in chapter 2, it is reasonable to suppose that, if KM1 is true, the circular does not supervene on the noncircular. However, it is equally obvious that the circular does supervene on the noncircular. What, then, has gone wrong in the reasoning? A very plausible suggestion is as follows. The basic claim at issue in this argument can be interpreted in two ways, depending on how ‘‘all the noncircular truths’’ is read. On one reading, we take the phrase to include both triangle and sector truths, as follows: (6) A logically omniscient and conceptually sophisticated superslug knows all the triangle and sector truths and yet learns the circular truths on the basis of experience. On a different reading, we take it to be restricted to only triangle truths: (7) A logically omniscient and conceptually sophisticated superslug knows all the triangular truths and yet learns the circular truths on the basis of experience. Once again, the distinction between (6) and (7) poses a destructive dilemma for a slugs’ knowledge argument. It is plausible to suppose that they can imagine (7) in the relevant sense, but (7) is also unobjectionable in that it does not give us reason to deny the supervenience of the circular on the noncircular. On the other hand, it is plausible to suppose that (6) is objectionable; indeed, this is the target proposition of the argument. On the other hand, (6) is not imaginable in the relevant sense, for to imagine (6) you would need to know, in a way that the slugs do not know, what pie pieces are. In short, the slugs are guilty of mixed confusion. Once again, what makes the charge of mixed confusion so plausible is the ignorance of the slugs. Finally, it is important to notice that our approach provides a unified treatment of CA and KA. The mistake in both arguments is explained by the fact that the ignorance hypothesis makes it plausible that in both cases we are guilty of one of the standard mistakes. This is quite different from a number of other approaches to these two arguments in the contemporary

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literature. For many philosophers, for example, the knowledge argument is mistaken insofar as it makes a mistake about the importance of novel experiences. In chapter 10, I will argue that it is quite implausible that any fact about novel experiences would undermine the argument, but at the moment I am making a different point. This is that many other accounts treat the arguments as very different from one another: the criticism applied to the knowledge argument could not in principle apply to the conceivability argument. Our own approach is therefore quite different.

4.8. Ignorance and Modal Reasoning: The Intermediate-Level Case In considering the impact of the ignorance hypothesis on modal arguments, we have assumed so far that the ignorance in question is basic-level. What if it is intermediate-level? In this case, the account proceeds slightly differently. To illustrate, let us reconsider the second of our toy examples.

4.8.1. The Conceivability Argument Chez Moth The moths, it may be recalled, advanced a conceivability argument to the effect that the yellow truths fail to supervene on the nonyellow truths. To formulate the argument, again at the risk of pressing the analogy, let us introduce the idea of a ‘‘zombie array’’—that is, an array of lights identical to the actual array in respect of all nonyellow truths but different from it in terms of yellow truths. With this notion in place, the conceivability argument may be formulated as proceeding from these two premises: CA1. CA2.

It is conceivable that there is a zombie array. If it is conceivable that there is a zombie array, it is possible that there is.

It is quite clear, for reasons that we have already considered, that if CA1 and CA2 are true, the yellow does not supervene on the nonyellow. On the other hand, it is equally clear that the reasoning here must be fallacious. It is palpably impossible that the yellow does not supervene on the nonyellow. What, then, has gone wrong in the reasoning? An initial thought is that we may tell an analogous story in the case of the moths to that we told in the case of the slugs. In particular, we might argue that the claim that there is an array that matches the actual array in respect of all nonyellow truths but lacks yellow beams may be interpreted in two quite different ways, depending on how its constituent quantifier phrase ‘‘all nonyellow truths’’ is to be understood. On one reading, the phase is interpreted broadly to mean not only truths about red and green beams but also truths about how these lights combine together—red truths, green truths, and truths about their composition. Then the basic proposition of the argument is (8):

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On another reading, we confine attention when interpreting ‘‘all nonyellow truths’’ to those that concern only red and green truths: (9) There is an array identical to the actual array in respect of all red truths and green truths but which lacks yellow beams. We might then try to argue that the moths are guilty of mixed confusion. They have confused (8) and (9): (9) is strongly conceivable but unobjectionable; (8) is objectionable but is at most weakly conceivable, in view of the fact that the moths are by assumption ignorant of the intermediatelevel truths. However, there is an obvious problem with this strategy. The problem is that if we concede that (9) is strongly conceivable, then this suggests very strongly that it is possible. But (9) is clearly not possible. If (9) were possible, then the yellow respects would fail to supervene on the nonyellow respects of the array, and this is not so. In short, to show what is wrong in the case of the moths, we need to do something different from what was attempted in the case of the slugs. So far, then, we have not managed to say with any precision what has gone wrong in the case of the moths. I think the way forward here is to concentrate in the first instance not on proposition confusion, as we have been doing so far, but on mode confusion. We have noted that it is implausible to think that the moths can strongly conceive (8) and so do not conceive (8) in the relevant mode. However, it is likewise plausible to suppose that they do not conceive (9) in the relevant mode either. In view of their ignorance, it is natural to think that they do not have a full appreciation of what it would be for an array to be identical to the actual array in all green and red respects but different from it in yellow respects. In particular, it seems natural to say that the moths only prima facie or weakly conceive (9), precisely because they don’t know all the truths it entails. On the other hand, if (9) is only prima facie or weakly conceived, nothing about its possibility will follow. In short, (9) is on all fours with (8): neither has been conceived in the relevant sense; the moths are guilty of mode confusion. Of course, as noted earlier, the suggestion that the moths are guilty of mode confusion invites the response that, although neither (8) nor (9) is strongly conceived, there is definitely some strong conceiving going on. To deal with this problem, we need to find a proposition that the moths are conceiving in the relevant mode. And in fact there does seem to be a candidate proposition here. It seems natural to say that, when they claim to imagine a zombie array, what the moths are really imagining is an array that is identical to the actual array except that it has the yellow lights removed. Of course, to remove the yellow lights is also to remove some nonyellow

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aspect of the array, for the yellow light is simply an admixture of green and red. But this is quite unknown to the moths. More particularly, one might say that the moths are strongly conceiving something like the following: (10) There is an array identical to the actual array in respect of most red and green truths but which is different from it in respect of some yellow truths. The fact that (10) is conceivable in the relevant sense is no problem, for it is unobjectionable. Two final points about our account of the conceivability argument and the moths should be noted. First, in suggesting that the moths strongly conceive (10), I am not saying that this alone is what answers the argument. What answers the argument is rather that there is no proposition here that is in any sense objectionable that is conceived in the relevant way. Mode confusion answers the argument. Proposition confusion is brought in only to answer an outstanding problem—namely, that there seems to be something here that is genuinely conceived. As I put it earlier, proposition confusion is brought in to bolster mode confusion, but mode confusion does most of the work. Second, that our approach is slightly different, depending on whether the type of ignorance at issue is basic-level or intermediate-level, brings out an important aspect of the discussion. If our focus is simply on the slugs, one might have thought that I am advancing some sort of recipe or algorithm for showing what is wrong with a modal argument. This is not what I am suggesting, and the difference between the moths and the slugs brings this out. There is no recipe here for generating a contrasting proposition or even for saying that there is one. The point is rather that reflection on cases makes plausible the idea that ignorance of a certain type makes it the case that in advancing modal arguments we are making one (or a combination) of the standard mistakes. But the characterization of the mistake we are making might be different in different cases.

4.8.2. The Knowledge Argument Chez Moth As it is for the moths’ conceivability argument, so it is for their knowledge argument. In that case, the modal premise that is at the heart of the argument is KA1. KA1.

It is possible that a logically omniscient and conceptually sophisticated supermoth knows all the nonyellow truths and yet learns the yellow truths on the basis of experience.

It is reasonable to suppose that if KA1 is true, the yellow does not supervene on the nonyellow. However, it is equally obvious that this is mistaken. What then has gone wrong? Well, taking our discussion of the moths’ conceivability argument as a model, the first thing to say is that the moths can conceive the target

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proposition of their knowledge argument only in a weak or prima facie sense. This is (11): (11) A logically omniscient and conceptually sophisticated supermoth knows all the red truths, green truths, and intermediate-level truths and yet learns the yellow truths on the basis of experience. When faced with the objection that there is some genuine conceiving going on in this reasoning, that something is being imagined, we might reply that what is genuinely being conceived is this: (12) A logically omniscient and conceptually sophisticated supermoth knows most of the red and green truths of the array and learns the yellow truths on the basis of experience. On the other hand, that (12) is imaginable causes no trouble, for it is in the context unobjectionable.

4.9. Conclusion The central points of this chapter may now be summarized as follows: If the ignorance hypothesis were true, we would be in the position of the slugs or the moths. If we were in the position of the slugs or the moths, it is plausible to suppose that, in advancing the modal arguments CA and KA, we are guilty of one (or a combination) of the standard mistakes. If we are guilty of one (or a combination) of the standard mistakes, it is mistaken to follow the modal arguments to their conclusion. But then the case for T3 collapses, and the first part of the epistemic view is true: if the ignorance hypothesis is true, the logical problem is solved. Of course, the second part of the epistemic view, the ignorance hypothesis itself, remains to be discussed. That is my next task.

5 General Plausibility

5.1. Introduction According to the ignorance hypothesis, we are unaware of a type of nonexperiential truth relevant to the nature of experience—an experience-relevant nonexperiential truth. If this is true, it is contingent. It depends on contingent facts about (a) the world and its complexity, (b) our cognitive powers and achievements, and (c) the relation between them. There is no possibility of proving the thesis logically. Nor is it possible for us to stand outside ourselves and say, ‘‘The truths of which we are ignorant are that . . . and that . . .’’ where the ellipses are filled in by an articulate statement of the truths in question. To do that would be to involve us in what philosophers sometimes call a pragmatic contradiction—that is, a proposition whose truth is inconsistent with its being rationally asserted in the relevant context. (The classic example of a pragmatic contradiction is the person who says in English, ‘‘I am not speaking English.’’) But while we can’t prove the truth of the ignorance hypothesis, or without pragmatic contradiction say what the truths are, it remains a sensible project to render it believable in an indirect way—to present a plausibility case, as I will put it. How should this case be organized? I think the considerations that render the ignorance hypothesis plausible may be divided into three: first, there are considerations that have their source in very general observations about ourselves and our place in the world and about the sort of philosophical predicament we are confronted with when we think about experience; second, there are considerations that have their source in philosophical reflection on the nature of matter; third, there are considerations that suggest considerable historical precedent for the idea 87

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that we are ignorant. In the next three chapters, I will take up these three considerations in turn. As will emerge more fully as we proceed, I don’t intend to suggest that these different considerations are or should be equally persuasive to all people. Rather, my aim is to show that we have a number of good, though nondemonstrative, reasons for thinking that the ignorance hypothesis is true. Before turning to these considerations, however, I should confess that, speaking for myself, the ignorance hypothesis is, although certainly contingent, really pretty obvious. Once we disentangle the hypothesis from other claims with which it might be confused, I think it is really very plausible that the hypothesis is true. In a sense, then, the more interesting question for me is not the truth of the hypothesis so much as why people regard it as irrelevant to the philosophical issues. In chapter 8, I will turn more directly to this aspect of the issue. For those who are inclined to agree with me about this, I would recommend skimming the next three chapters at least on first reading. You could perfectly well pick up the thread again later. Now that I have so confessed my feelings, we may turn to general considerations in favor of the ignorance hypothesis.

5.2. Excessive Optimism A convenient place to begin is the following passage from Frank Jackson: It is not sufficiently appreciated that Physicalism is an extremely optimistic view of our powers. If it is true, we have, in very broad outline admittedly, a grasp of our place in the scheme of things. Certain matters of sheer complexity defeat us—there are an awful lot of neurons—but in principle we have it all. But consider the antecedent probability that everything in the Universe be of a kind that is relevant in someway or other to the survival of homo sapiens. It is very low surely. But then one must admit that it is very likely that there is a part of the whole scheme of things, maybe a big part, which no amount of evolution will ever bring us near to knowledge about or understanding. For the simple reason that such knowledge and understanding is irrelevant to our survival. (1982, 135) Jackson makes this point in support of a certain version of dualism, epiphenomenalism, according to which nonphysical experiences are physically caused but lack physical effects; they are epiphenomena. What he is saying is that physicalists are too quick to dismiss this form of dualism because they have an overly optimistic view of our powers. Now, in fact, as I hope our previous discussion has made clear, there is no internal connection between physicalism and the sort of optimism that Jackson intends. But Jackson is certainly right that many influential physicalists—he has in mind Armstrong and Smart in particular—have held an optimistic version of physicalism. And he is also right that such optimism is really rather incredible. On any

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reasonable assessment of our epistemic situation, it is very improbable that we have a full grasp of our place in the (physical or nonexperiential) scheme of things. On the other hand, the point that physicalists have (or often have) an overly optimistic view of our powers has a straightforward application to our discussion. To put things in our terms, what Jackson is saying is, first, that physicalists are committed to the denial of the ignorance hypothesis and, second, that this is extremely implausible. Of course, this by itself does not entail the ignorance hypothesis. For all that has been said so far, one could correct for the optimism in physicalism by saying that we are ignorant of some types of truths but at the same time insist that that none of these are relevant to the nature of experience. But it at least makes clear that the hypothesis is a genuine possibility and cannot be dismissed.

5.3. Other Creatures Why is it so improbable that we have a full grasp of our place in the scheme of things? The simplest reason emerges from a comparison of our own epistemic achievements with those of other creatures. Jackson makes this point with his version of the story of the slugs with which we began: Suppose we discovered living on the bottom of the deepest oceans a sort of sea slug which manifested intelligence. . . . Despite their intelligence, these sea slugs have only a very restricted conception of the world by comparison with ours, the explanation for this being the nature of their immediate environment. Nevertheless, they have developed sciences which work surprisingly well in these restricted terms. They also have philosophers, called slugists. Some call themselves tough-minded slugists, others confess to being soft-minded slugists. (1982, 135) He goes on to say that, although the tough-minded slugists—the toughsoft distinction is due to William James—hold that in principle their sciences explain everything about their world, from our perspective this is clearly false. To put things in our terminology, there are types of truths concerning the nature of their environment of which the slugs are ignorant, and the claims of the tough-minded slugs to the contrary are quite unpersuasive. On the other hand, if we see ourselves as similar to the slugs—that is, as contingent creatures whose cognitive powers and achievements are limited—it is difficult to avoid the conclusion that we, too, are ignorant of types of physical or nonexperiential truths. And this consideration lends considerable plausibility to the ignorance hypothesis and considerable implausibility to its denial. Now Jackson himself develops the argument from other creatures by using an imaginary example (as, indeed, we ourselves have done in

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adapting his example in the introduction and also in introducing the moth example in chapter 4) and by mentioning evolutionary theory and cognitive closure—that is, the idea that the relevant truths are not simply unknown by us but unknowable in view of our psychological and biological nature. But these ideas are not essential to the main point and may make it appear more controversial than it is. To start with, the point works just as well with real creatures. We unhesitatingly think there is much that (e.g.) goats do not know, and moreover the things they do know are quite different in kind from the things they don’t. (Goats may know plenty about goats, but they don’t know much about the politics of Venezuela.) As regards evolution, it is controversial whether our cognitive powers (or all aspects of our cognitive powers) are relevant to our survival; they might instead be a by-product or side effect of something that is relevant to our survival. But that possibility by itself doesn’t alter the underlying point. Suppose our cognitive powers were a side effect either in whole or in part; it would surely remain implausible that we have a grasp of our place in the scheme of things. Finally, although the comparison between us and other creatures is certainly suggestive of cognitive closure, there is nothing here that entails it. It is improbable that we have a general sense of our place in nature, and this improbability is unaffected by the issue of whether this lies beyond our ken simply in fact or whether it does so as a result of our cognitive limits. The last point is important because of the widespread impression that cognitive closure is somehow essential to the epistemic view. For my own part, I don’t deny that we might be cognitively closed with respect to the relevant truths, and I also agree that emphasizing this possibility is important for gaining an appreciation of our position in the world—as ‘‘an antidote to excessive optimism,’’ as Jackson says. But there is no necessary connection here: cognitive closure is not entailed by our position. Indeed, as will emerge more fully when we turn in chapter 7 to historical precedents, there are plenty of cases in which people were, at a certain stage of human history, unaware of certain types of truths about the world and formulated on this basis modal arguments that proved later to be fallacious. But the mere fact that people at certain times lacked the concepts to understand certain truths does not mean that they were cognitively closed with respect to those truths; in fact, in the cases we will examine, things turned out very differently.

5.4. The Mysterian Version of the Epistemic View Although Jackson’s discussion suggests cognitive closure, it is not he who has championed this idea in contemporary philosophy. The champion is Colin McGinn (1989, 2004), and McGinn has developed on this basis a version of the epistemic view that I will call—following Flanagan (1992)—the mysterian version of the epistemic view. So at this point in our discussion, it

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is worthwhile taking the time to say explicitly what the differences are between this position and our own.

5.4.1. Chronic Ignorance versus Ignorance Simpliciter The issue might be approached by contrasting our own version of the ignorance hypothesis with McGinn’s, at least as I read him. Our ignorance hypothesis is that we are ignorant of or unaware of a type of truth relevant to the nature of experience. McGinn’s alternative—I will call it the chronic ignorance hypothesis—is that we are ignorant of a type of experience-relevant nonexperiential truth and chronically so, where to be chronically ignorant of a truth is to be cognitively closed with respect to it; that is, it is incompatible with the biological and psychological facts of human nature that we as a species will ever come to know the truths. The chronic ignorance hypothesis entails the ignorance hypothesis but not vice versa; they differ in point of view of logic. But they are also different from the point of view of empirical plausibility. The chronic ignorance hypothesis must at the end of the day appeal to some sort of speculation about the nature of human beings and the sorts of problems they are capable of solving. What McGinn is saying is that, given the psychological and biological nature of human beings, they will not be able to understand the relevant truths. However, in view of the infancy of serious scientific research into the psychological nature of human beings, this is a remarkably ambitious thing to say. It is one thing to say that our nature is such that there is a class of truths of which we chronically ignorant; it is another to say of this particular class of truths that our nature is such that we are chronically ignorant of them.

5.4.2. McGinn’s Argument Of course, McGinn does not simply say that the ignorance is chronic; he offers an argument that it is (1989). But in my view this argument is unconvincing. As I understand it, McGinn’s strategy is first to assume the ignorance hypothesis in our sense—that is, assume that there are nonexperiential experience-relevant truths of which we are ignorant—and then to present an argument that the ignorance in question must be chronic. The argument begins by dividing the truths that we are capable of knowing or understanding into three types. It then proceeds to say that the truths of which we are ignorant are not of these three types. Obviously, if the truths we are capable of understanding are of three types, and if the truths of which we are ignorant are not of these types, then our ignorance must be chronic, and the chronic ignorance hypothesis is true. What are the three types of truths that McGinn has in mind? The first type is the introspective truths—truths we can come to know or understand on the basis of introspection. Introspection certainly puts us in position to

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understand certain experiential truths. But the truths that we are after are nonexperiential, so introspection will not provide us an understanding of the relevant truths; hence: McG1.

The truths of which we are ignorant are not introspective.

The second type is the perceptual truths—truths we can come to know or understand on the basis of perception. Perception certainly puts us in a position to understand certain sorts of nonexperiential truths, for example, truths about shape. But the truths that we are after are experience-relevant, and, McGinn thinks, no truth that we might be in a position to understand on the basis of direct perception will permit us to understand any experience-relevant truths; hence: McG2.

The truths of which we are ignorant are not perceptual.

The third type is the theoretical truths—truths that, in McGinn’s (1989) phrase, are objects of thought. Theoretical truths certainly put us in a position to understand many nonperceptual nonexperiential truths. But according to McGinn, there is a deep similarity between perceptual truths and theoretical truths, and thus the point about perceptual truths holds good also for theoretical truths; hence: McG3.

The truths of which we are ignorant are not theoretical.

Clearly, if McG1, McG2, and McG3 are true, and if it is also true that McG4.

Any truth that humans are capable of understanding is introspective, perceptual, or theoretical,

then it is not simply the case that the ignorance hypothesis is true but that the chronic ignorance hypothesis is true as well; mysterianism follows. The basic problem with this argument is that it is irredeemably unclear about which truths the theoretical truths are supposed to be and what the dimensions of similarity are between them and perceptual truths. On a fairly relaxed interpretation, a theoretical truth is any truth at all that we might be caused to know or understand through a process of perception or observation. On this reading, McG4 is plausible. It is reasonable to think that any truth at all that humans are capable of understanding is such that we will understand it on the psychological or causal basis of perception. But equally, on this reading, McG3 is implausible; there is now no plausibility to the claim that theoretical truths exhibit some deep homogeneity with perceptual truths. To the contrary, it is difficult to see any similarity or homogeneity within the kind of truths we might be caused to have through observation or experiment. On a more constrained interpretation, a theoretical truth is a truth that is entailed by a perceptual truth. On this reading, McG3 is very plausible. It is reasonable to think that no truth that is entailed by a perceptual truth is likely to be relevant to experience, simply because of the gap between

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perceptual truths and introspective truths. But equally, on this reading, McG4 is implausible, for many truths that are objects of thought might not in that sense be entailed by perceptual truths. To think otherwise would be to think that the content of thought is a subset of the content of perception. But there seems ample reason for denying that. Of course, the fact that McGinn’s argument for cognitive closure is unsuccessful does not mean that its conclusion is false. If it is construed simply as a speculation about what might be the case, I have no objection; the chronic ignorance hypothesis might be true. But the important point is that there is no pressure on us to endorse it (or, for that matter, deny it). A proponent of the epistemic view need not be a mysterian.

5.4.3. The Irrelevance of Cognitive Closure I have concentrated so far on the logical and empirical differences between McGinn’s account and our own. But there is a further dimension of difference that is both less obvious and in a sense more important. This is that, although the idea of cognitive closure is obviously central to McGinn’s understanding of the issues, and I have so far been going along with this, for us the issue of cognitive closure is, strictly speaking, irrelevant. To see this point, let us focus again on why we, as opposed to others, are interested in ignorance in the first place. The reason that ignorance is important for us is that it makes plausible a response to the modal arguments; in particular, the ignorance hypothesis makes it plausible to say that in advancing the modal arguments CA or KA, we are making one (or a combination) of the standard mistakes. However, from this point of view, the chronicity or not of the ignorance is not to the point. What is important, rather, is the content of the ignorance—namely, what it is that we are ignorant of. Perhaps McGinn is correct that the ignorance is chronic, and perhaps he isn’t; either way, it doesn’t matter. Ignorance of a relevant type of truth will be sufficient to show that we are making the mistake of mode confusion or proposition confusion; the idea that the ignorance may not be surmountable consistent with our contingent nature is interesting, but it adds nothing to that assertion. The fact that the distinction between the chronic ignorance hypothesis and the ignorance hypothesis is irrelevant to the philosophical issues makes it something of a mystery why people are so drawn to this idea in the literature. I think this attraction may be explained in either of two ways: First, there is a tendency in these discussions to miss the distinction between scientific questions of consciousness and philosophical questions— between logical and empirical questions, as I put it in chapter 2. The idea of cognitive closure is highly relevant to the empirical question, because it is always worthwhile to ask whether a particular explanatory project has a chance of succeeding. But if our interest is the logical problem, it is much less clear why the chronicity of the ignorance should matter. On the other

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hand, if ignorance is relevant to the empirical problem, and if the problem is often or sometimes confused with the logical problem, it would be natural to conclude that chronic ignorance is relevant to the logical problem. (To be fair, McGinn himself certainly does emphasize the distinction between philosophical and scientific questions. However, that is not a distinction many have attended to in his work, and it was certainly not the central focus of his 1989 paper on the topic.) The second explanation of the emphasis on cognitive closure has to do with a tendency to associate the epistemic view with the idea that the truths of which we are ignorant are really very special. This tendency, I think, is on show in the quotation from Jackson with which I began this chapter. In this quotation, the assumption is that the exceptions to optimism are also exceptions to physicalism. But I think the tendency is also on show in McGinn’s position. Here the idea is that the truths of which we are ignorant are also such that we are cognitively closed with respect to them. But my own view is that there is no reason to assume that the truths of which we are ignorant are special in either of these ways. As against Jackson, they might be physical truths; as against McGinn, they might be truths that are knowable by us. Of course, the truths of which we are ignorant must be of a type different from any we do know; the structure of our view does depend on this. But apart from that, they might be quite mundane.

5.5. Optimism Defended? I have argued that reflection on other creatures provides one consideration in support of the ignorance hypothesis but that we should not interpret those reflections as committing ourselves to cognitive closure. I have also taken the time to distinguish our position from that of McGinn. How is one to respond to the idea that reflection on other creatures makes ignorance probable? One response is to grant the improbability of our having a full grasp of the scheme of things but to insist, nevertheless, that this is our position; unlikely things do sometimes happen after all. At one point, for example, Lewis writes that, while we don’t quite have it all, we are far enough along to suppose that completed physics will be very similar to what we have now: We have no a priori guarantee of it, but we may reasonably think that present-day physics already goes a long way toward a complete and correct inventory. Remember that the physical nature of ordinary matter under mild conditions is very well understood. And we may reasonably hope that future physics can finish the job in the same distinctive style. (1994, 292) Lewis is relying in part here on an influential paper by Feinberg 1966, in which it is argued that the physics of bulk matter is complete. (A similar

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position is defended by Smart 1978; it is positions such as these to which Jackson is referring in the passage we quoted at the beginning.) I will not attempt here to address how realistic a view about physics this is. Let me say only that, so far as I am able to judge, there is considerable scope for disagreement on the issue. The important point is that, even if what Lewis says is true, it is of limited value in the present discussion. As we noted in the previous chapter, the ignorance hypothesis is compatible with a wide variety of different kinds of ignorance. For example, our ignorance might be of a truth that is determined by physics but is not itself physical in the strict sense that Lewis has in mind. In that case, our ignorance would be of an intermediate-level rather a basic-level kind. It is quite consistent with this that physics is complete or nearly so. Moreover, even if our ignorance were basic, there is more than one way for this to come about. One possibility is that we are ignorant of some new element not described by contemporary or near-contemporary physics. But another is that physics does not tell the whole truth about the elements it already describes—a possibility I will discuss in detail in the following chapter. This, too, is consistent with the position described by Lewis. A different response to the argument from other creatures is to suppose that the empirical world has a rational nature—that is, a nature of the sort that can be explained by us. Rationalism of this sort might be developed in a number of ways: (i) it might be argued that God or some other superbeing has set up the world so that it is knowable by us; (ii) it might be argued that our intelligence is of a highly plastic sort, capable of meeting any challenge that the world throws up; (iii) it might be argued that a version of antirealism is true, according to which the contingent truths would not count as true unless they were capable of being understood by us. Once again, I will make no attempt to deal with these issues beyond asserting that in my view they are all of them less plausible than the starting point of our argument—namely, the comparison between ourselves and other creatures. Take, for example, the idea of general intelligence. This is extremely implausible from a comparative point of view. For example, consider: Goats either have general intelligence or they don’t. If they do have general intelligence, then presumably they can understand the politics of Venezuela, once we ignore inconvenient facts about the limitations of storage. But this is extremely implausible. On the other hand, if goats don’t have general intelligence, then there is a radical break between us and the goats. But this, too, is implausible, for it entails (assuming that there is nothing special about goats) that we are radically different from every other animal we know. Although I will not work them through, I think that similar remarks can be made in the case of suggestions (i) and (iii). Finally, it might be objected that optimism and rationalism are not to the point. The ignorance hypothesis is not simply the claim that we are unaware of a type of truth; it says, in addition, that the type of truth we are unaware of is relevant to the nature of experience. But this has not been

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shown. We may indeed be ignorant of many things; it does not follow that we are ignorant of truths relevant to experience. In response to this, we need to turn from other creatures to a different consideration: that as a matter of fact we are scientifically ignorant of the nature of experience.

5.6. Ignorance and the Empirical Problem What is the present state of our knowledge of conscious experience? Well, it is not quite true that we know nothing. We know a great deal about the basic biology of the brain, and we have some understanding of the computational models that underlie various forms of language understanding, errors in reasoning, vision, and so on. But that does not detract from the fact that—at least at the time of writing—we are almost completely ignorant about the issue of consciousness. The fact of the matter is that there is no framework for thinking about consciousness, as there is for thinking about some other sorts of psychological and related phenomena. Now, the fact that we are ignorant in this empirical sense is obviously not a solution to the empirical problems of experience. It is no solution to an empirical problem to be told that we are ignorant of the solution! On the other hand, our empirical ignorance of the nature of conscious experience is a fact, nonetheless. And if it is a fact, it is not something that can be reasonably denied by a philosopher. The options are not to ignore it or deny it but simply to accommodate it—that is, to present an account of the philosophical questions of conscious experience that is compatible with it. How, then, might one accommodate the fact of empirical ignorance? I think the most obvious thing to say is that reflection on our empirical ignorance of conscious experience lends considerable support to the ignorance hypothesis. It is natural to describe our empirical ignorance as being, or including, ignorance of a type of truth relevant to the nature of experience. But of course, if this is how we seek to accommodate the fact of our empirical ignorance, we have already adopted the ignorance hypothesis. It might be objected that, although our ignorance of conscious experience is ignorance of a type of truth relevant to the nature of experience, this is beside the point when it comes to the philosophical questions about experience. But this suggestion has two shortcomings: it concedes the ignorance hypothesis rather than denying it, and the claim that ignorance is beside the point is false, or so at any rate I will argue in chapters 7–10. Alternatively, it might be objected that it is a mischaracterization to say that our ignorance of conscious experiences is or includes ignorance of an experience-relevant nonexperiential truth. According to those who advance revelation—a thesis I will discuss in detail in chapter 11—if one has a conscious experience, then one knows the essence or nature of experience; the only things left to learn are certain nonessential or accidental features of experience. If revelation is true, the idea that we are ignorant of the nature of

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consciousness is a mistake. However, the problem with this suggestion is— as I argue in chapter 11—that revelation is false, or anyway unfounded. Finally, it might be replied that our ignorance of conscious experience is not ignorance of a type of truth but ignorance simply about how to arrange the truths already in our possession—ignorance of a particular truth rather than a truth of any sort or kind. But it hard to square this idea with the sense in which we are ignorant of the subject matter. Of course, if one held a version of rationalism or optimism of the sort discussed in the previous section, this position would make some sense. But, as we have just seen, these ideas are implausible, and the present idea is supposed to be an improvement on them. In summary, the comparison with other creatures and the ignorance of experience combine in support of the ignorance hypothesis.

5.7. The Explanatory Power of the Hypothesis I have argued so far that two general facts together make the ignorance hypothesis plausible: the fact that optimism in general is implausible (as shown by reflection on other creatures) and the fact that we are empirically ignorant of the nature of consciousness in particular. I now turn to a rather different general consideration in favor of the ignorance hypothesis: its explanatory power. We may start by noting an attractive feature of the primitivist or antiphysicalist position: it can explain a wide variety of philosophical data in a simple and unified way. Primitivism accounts not only for CA in all its forms but also for KA, and for a variety of other arguments as well. The primitivist looks at all of these arguments as so many symptoms of a single underlying cause—namely, that experiential truths do not supervene on nonexperiential truths. Of course, there are difficulties about squaring this claim with more general considerations, but the explanatory power of primitivism is surely a point in its favor. This feature of primitivism is also a feature of the epistemic view. The proponent of the epistemic view likewise may explain a wide variety of philosophical data in a simple and unified way. For a proponent of the epistemic view, all of these arguments are so many symptoms of a single underlying fact—namely, ignorance. Of course, there are difficulties about squaring this claim with more general considerations—though I would argue that the difficulties here are much less than with primitivism—but the explanatory power of the ignorance hypothesis is surely a point in its favor. To put the same point differently, the first part of the epistemic view is a reason to believe the second. E1—the first part—says that if the ignorance hypothesis is true, the logical problem is solved. If true, E1 is itself a reason to believe E2, that the ignorance hypothesis is true. Now, so far our discussion of the explanatory power of the ignorance hypothesis has been limited to an assessment of modal arguments. We have

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seen that, if the ignorance hypothesis is true, it becomes very plausible to say that we are making one (or a combination) of the standard mistakes. However, for many writers the central philosophical problems concerning experience do not revolve around modality but instead, or in addition, revolve around the quite different theme of explanation. In my view, discussions that emphasize the idea of explanation should be criticized on the ground that they tend to run together two issues better kept apart: philosophical questions about consciousness and scientific questions. As I noted in chapter 2, discussions of conscious experience are frustrated by a failure to state precisely what problem it is that needs to be solved; appeals to explanation and related notions seem to me to obscure, rather than clarify, the issue. However, having said that, there certainly are problems that involve the idea of explanation that are distinctively philosophical in character. But a brief examination of two of these problems makes it plausible that, just as the ignorance hypothesis provides a solution to the modal arguments, it likewise provides a solution to the arguments founded on explanation.

5.7.1. The Explanatory Gap The best-known example of such an argument is that developed over a number of years by Joseph Levine (1993, 2001). Levine’s starting point is the idea that nonexperiential truths do not explain the experiential truths in the way that we would expect them to do, given experiential supervenience. Knowledge of the nonexperiential truths, he thinks, does not make it intelligible that we have these experiential truths rather than some others or none at all. It is this absence of intelligibility that Levine calls ‘‘the explanatory gap.’’ Now, the fact that nonexperiential truths fail to render experiential truths intelligible does not by itself give us a reason to doubt supervenience; absence of intelligibility does not mean absence of entailment. On the other hand, if I can’t derive the experiential from the nonexperiential, I am in an epistemic position from which another ( better) epistemic position is clearly visible—that is, the epistemic position in which I can derive the experiential from the nonexperiential. And it is this fact that sets up the problem. In particular, the challenge posed by the explanatory gap might be put as follows: if you are in an epistemic position from which a better position is clearly visible, you are under an obligation either to attempt to move to that better position or else to show cause why this can’t be done. As I understand him, Levine’s suggestion is that this challenge is a good one but is yet to be met. Understood in these terms, however, the epistemic view easily meets the challenge, for it explains why we are in no position to move to the better epistemic position. The reason that we can’t see how to derive the experiential from the nonexperiential is that we don’t understand some of the

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relevant nonexperiential truths. Of course, one might imagine a slightly different version of the challenge, where the obligation is not to try to move to the better position or else show cause why it cannot be done, but simply to move to that better position. However, in this version, the best thing is to reject the challenge.

5.7.2. The Harder Problem A different argument based on the notion of explanation is Block’s (2002a, 2002b) so-called harder problem of conscious experience. Like Levine, Block begins with the assumption that we cannot see how to derive experiential truths from nonexperiential truths. But Block combines this with a different idea: that experiential truths are, or might be, multiply realizable in a particularly radical way. In our terminology, his suggestion is that two nonexperiential truths of completely different types both entail an experiential truth and yet have nothing further in common. With these two assumptions in place, Block then asks us to consider Commander Data of Star Trek, an android we may assume to be physically different from us. The question of whether Data is conscious makes perfect sense, and both negative and positive answers are permitted by our assumptions. But Block suggests that we have ‘‘no conception of a rational ground’’ for deciding the issue. In our case, we know that we are conscious, so there is no problem. But our own case gives us no help in asking about Data’s. We clearly cannot observe Data’s own experiences, and knowledge of his physical nature will not help us because it is epistemically possible both that this physical nature entails experience and that it doesn’t. Of course, Block does not deny that we have some reasons for saying that Data is conscious—functional or behavioral reasons, say. But in view of the distance from these facts to consciousness, there is still much that we do not know. He concludes, ‘‘Commander Data poses an epistemic problem whose solution we have no conception of’’ (2002b, 15). Once again, the ignorance hypothesis neatly explains this problem. The fact that we have no way to derive the experiential truths from the nonexperiential truths, on this view, is again a function of our ignorance. Similarly, the idea that two distinct nonexperiential truths might entail an experiential truth and have nothing further in common only seems plausible because of ignorance. Block himself sees the problem as being generated from a number of assumptions about consciousness that are widespread. But he does not explicitly mention the central assumption that makes the harder problem so hard—the assumption that the ignorance hypothesis is false and, in consequence, that we are in possession of the relevant types of facts. With that assumption in place, the harder problem forces us into a series of unpalatable options. But if we reject the assumption, the harder problem collapses.

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5.7.3. Block on the Epistemic View In saying that the ignorance hypothesis provides an answer to the harder problem, I am not suggesting that Block has missed this. On the contrary, Block himself notes (to put things in our terminology) that the epistemic view may solve the problem (2002b, 6). Speaking of ‘‘a time when the issue of how thought could be explained physically seemed as problematic as the issue seems today of how consciousness could be explained physically,’’ he draws attention to the following passage from the nineteenth-century scientist John Tyndall: Granted that a definite thought, and a definite molecular action in the brain, occur simultaneously; we do not possess the intellectual organ, nor apparently any rudiment of the organ, which would enable us to pass, by a process of reasoning, from the one to the other. They appear together, but we do not know why. (Tyndall 1868; quoted in Block et al. 1997, 48) Block goes on to say: ‘‘But now we have a glimmer of a conception of how thought could be explained physically’’ (2002b, 6). The obvious point is that Tyndall might well be advancing here ‘‘a harder problem of thought,’’ just as Block advances a ‘‘harder problem of consciousness.’’ Just as the response to Tyndall is a version of the epistemic view, similarly, a response to Block is a version of the epistemic view. However, although Block suggests this, he does not develop it further. In fact, when it comes to CA and KA, Block explicitly disowns the epistemic view in favor of the a posteriori entailment view I will consider in chapter 9. So the difference between Block’s position and our own turns on the question of how much of our philosophical predicament ignorance explains. Block thinks it helps, or would help, when the background issue concerns explanation, but it is no help at all when the background issues are modal. My own view, in contrast, is that that the ignorance hypothesis explains in a unified way all, or at least many, of the central philosophical problems about experience—and that is a major reason to believe it.

5.8. Structural Considerations The idea that both primitivism and the epistemic view explain in a unified way all, or many, of the central philosophical problems about experience is itself a fact that calls out for explanation. I think the explanation for this fact is a deep similarity between the epistemic view and primitivism. This deep similarity and the morals one may extract from it constitute the final consideration in favor of the ignorance hypothesis that I want to consider in this chapter.

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The deep similarity between primitivism and the epistemic view is this: both views are versions of what I will call—adapting Parfit’s (1984) famous terminology—a further fact view. By a further fact view, I mean in this context a view according to which there are more truths or facts than those usually doing business under the name ‘nonexperiential’.’’ The primitivist rather obviously presents a version of a further fact view; according to him, experiential truths are truths that are metaphysically distinct from nonexperiential truths. We might therefore say that the primitivist presents a metaphysical version of a further fact view. But the proponent of the epistemic view likewise thinks that there are more truths than those usually doing business under the label; it is simply that here the truths in question are further nonexperiential truths, which, in view of our ignorance, are hidden from us. We might therefore say that the epistemic view is an epistemological version of a further fact view. One might object that the epistemic view could not possibly be a further fact view without collapsing into primitivism. For many philosophers, there is a tacit equation of a further fact view with primitivism. However, this equation must be revised in the light of our discussion. If you have a convincing argument that a set of truths A does not intelligibly determine a set B, the most straightforward response is to suppose that there is a set C such that, when conjoined with A, does intelligibly determine B. This idea is common to both primitivism and the epistemic view; that is why both are versions of a further fact view. What divides primitivism and the epistemic view is the relation between C and A. For the primitivist, C is identical to the set B, so it is no wonder that the conjunction of A and C intelligibly determines B. For the proponent of the epistemic view, on the other hand, C is distinct from both A and B. It is just that in our ignorance we confuse the conjunction of A and C for A alone, and it is this that gives the impression that B is not intelligibly determined by anything else. Alternatively, one might object that only a particular version of the epistemic view could possibly count as a further fact view. In the previous chapter, we distinguished basic-level from intermediate-level ignorance and noted that the ignorance hypothesis itself is compatible with either form of ignorance. However, it might be argued that only if the relevant sort of ignorance is basic-level could it possibly be said that the epistemic view is a kind of further fact view. The guiding idea is that if the ignorance is merely intermediate-level, then the missing truths might supervene on basic truths of which we already have knowledge and so in that sense would not be further facts. However, this objection tacitly equates a further fact view with a metaphysical further fact view. It is true that both primitivism and the basic-level version of the epistemic view are both metaphysical further fact views. But it remains true that both basic- and intermediate-level versions of the epistemic view are epistemological further fact views. Moreover, it is in virtue of its being an epistemological further fact view that

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permits the basic-level version of the epistemic view to answer the modal arguments. Suppose, now, we agree that both the epistemic view and primitivism are versions of a further fact view; what follows? Well, one thing that follows is that we are now in the presence of a further general reason for supposing that the ignorance hypothesis is true, viz., that the basic structure of the philosophical problem of experience is suggestive of a further fact view, and in advancing the ignorance hypothesis, we are committing ourselves to one version of that position. We have already seen why it is true that committing ourselves to the ignorance hypothesis is committing ourselves to a further fact view, but why should it be that the basic structure of the logical problem of experience is suggestive of a further fact view? I will not try to prove that this is so. Rather, I will attempt to make it plausible by contrasting the logical problem of experience with a problem in metaethics with which it is superficially rather similar.

5.8.1. Philosophical Problems: Similar . . . It is often pointed out that a large number of problems in philosophy fall into a certain structure (see Van Cleve 1992, Harman and Thomson 1996). One begins by drawing a distinction between two classes of truths, A-truths and B-truths. One then draws attention to the presumed fact that we have reasons to believe each of the following (inconsistent) theses: S1. S2. S3.

There are A-truths. If there are A-truths, every A-truth is entailed by some B-truth (or set of B-truths). If there are A-truths, not every A-truth is entailed by some B-truth (or set of B-truths).

Obviously, the logical problem of experience represents one example of a problem of this kind: in this case, A-truths are experiential truths, and Btruths are nonexperiential truths. But it is not difficult to produce other examples, and one is the problem in metaethics, which, following Smith 1994, I will call the moral problem. In this case, the A-truths are moral or evaluative truths, and the B-truths are nonmoral or natural truths. Filling out the structure this way, S1 records our commonsensical conviction that there are moral truths, S2 is supported by the idea that moral truths supervene on nonmoral truths, and S3 by the ethical internalist idea that the apprehension of moral truths necessarily motivates one to action in a way that apprehension of nonmoral truths does not necessarily motivate one. Ethical internalism suggests that S3 is true, as supervenience suggests a route to the apprehension of moral truths that involves no motivation— roughly, the combination of the apprehension of nonmoral truths and inference.

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5.8.2. . . . but Different Although it is illuminating to notice this class of problems, it is important also to draw distinctions within the general class. One dimension of difference emerges when we consider the reasons that have been advanced for S2 and S3 in the two cases. In the experience case, as we have seen, the reasons for S2 are empirical, whereas the reasons for S3 are based on what, following Kripke, we called an appearance of contingency. In the moral case, things are different. To start with, it is usually supposed to be a conceptual matter rather than an empirical one that moral truths supervene on the nonmoral. So in this case the reasons for S2 are conceptual rather than empirical. Moreover, the reasons for S3 are not based on an appearance of contingency. The problem about motivation that I just mentioned has nothing to do with an appearance of contingency in the relation of moral and nonmoral truths. It emerges, rather, from the fact that if I can come to apprehend a moral truth by apprehending a nonmoral truth and drawing an inference, it is difficult to see how apprehending a moral truth could bear the internal connection to motivation that it apparently does bear. A different dimension of difference is that certain styles of solution have been thought to be plausible in the moral case but not in the experience case, and vice versa. In the moral case, a common solution is to deny S1, the claim that there are moral truths. This position is sometimes called expressivism. Expressivism is the view that moral judgments in general don’t express propositions and so are not true or false. Whether or not you think expressivism is true, you should at least admit it is a very serious position, one that has drawn considerable discussion in the moral philosophy literature. But now consider the counterpart of expressivism in philosophy of mind. This would be the view that experiential judgments, such as ‘‘Jones is in pain,’’ are not truth-evaluable. Although a position along these lines has occasionally been suggested (e.g., by Ryle 1949), I think very few people would think that this is a serious position at all, at least when it is construed as a general claim about experiential judgments. In short, in expressivism we have a position that is plausible in the moral case but not in the experience case. Is this a testament to the outright implausibility of expressivism? Surely not—it is testament only to the difference between problems about morality and problems about experience—namely, that one exhibits a tendency to expressivism and the other does not. In the experience case, by contrast, we have just seen that there is a tendency to some kind of further fact view. For example, whether or not you think a further fact view is true, everyone should agree in the case of experience that it is a serious position that has drawn considerable attention in the philosophical literature. But now consider a counterpart of the further fact view in moral philosophy. Although a position along these lines has occasionally been suggested (e.g., by Moore 1903b), I think very few

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people think that it is a serious position at all. In short, in the further fact view, we have a position that is plausible in the experience case but is not plausible in the moral case. Is this a testament to the outright implausibility of the further fact view? Surely not—it is a testament only to the difference between problems about experience and problems about morality—namely, that one exhibits a tendency to the further fact view and the other does not. What explains the fact that candidate solutions to some philosophical problems are plausible but counterparts of such solutions are not? No doubt, the reasons here are difficult, but I think in large part it can be traced to the different reasons for which people have advanced the various constituent theses, so the two dimensions of difference I just isolated are not independent of each other. To illustrate, consider again the fact that, in the case of the moral problem, S2 is often thought to be a conceptual truth. This fact is often thought to rule out a version of primitivism. Indeed, Smith argues (1994, pp. 23–24) directly that it does. He argues, for example, that in view of the conceptual connection between moral and nonmoral truths, it is a mistake to suppose that we are perceptually acquainted with moral truths (as primitivists are often thought to suppose). I am not here going to assess Smith’s argument for this claim. The important point for me is that he is clearly thinking about the supervenience of the moral on the nonmoral in such a way that it rules out on conceptual grounds any appeal to a further fact view. On the other hand, nothing similar is true in the experience case: the supervenience of the experiential on the nonexperiential is, even if true, empirical, and thus there is no conceptual reason to rule out a further fact view.

5.8.3. The Morals for Us These admittedly rather sketchy remarks about the structural similarity and difference among different philosophical problems, and about the internal dynamics of these problems, suggest a number of morals for our discussion. The first moral is that if it is indeed the case that the internal dynamics of the problem of experience is toward a further fact view, in a way that the internal dynamics of the moral problem is not toward a further fact view, we are in the presence of a slightly different argument for our position, for the epistemic view is itself a kind of further fact view. Hence, if the internal dynamics of the problem is toward a further fact view, then we are on strong ground in advancing such a view. The second moral concerns an objection that someone might advance against our account. It may be thought that our account badly overgenerates in the sense that any philosophical problem at all could be solved in this way. The differences and similarities among philosophical problems, however, suggest that the epistemic view is appropriate only in specific cases. In particular, the view is plausible only in cases in which we have an internal dynamic toward a further fact view. My claim is that in the case of the logical problem of experience, it is very plausible to suppose that some sort

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of further fact view is correct, but it is no part of my purpose to recommend a general strategy for solving philosophical problems. The final moral returns us to the difference between the problem of experience and the mind-body problem discussed in chapter 2. I noted there that discussion in philosophy about the mind-body problem tends to assume that there is a general problem about the relation between psychological truths and physical truths but that in fact it is difficult to see that there is any one problem that attaches to this contrast. What I have just said provides some substance to this comment. Although the problem of experience seems to be quite distinct from the moral problem, there are other problems about psychological phenomena that are more similar to the moral problem. One example is the problem of intentionality, at least as developed in the light of Kripke’s (1982) discussion of Wittgenstein on rule following. In this case, the A truths are intentional or semantic truths, and the B truths are truths about dispositions to use a word or think a thought. Kripke suggests that, according to the ordinary conception of meaning or intentionality, we must be able to ‘‘read-off’’ (p. 26) the intentional or semantic truths from these truths about dispositions. I take this to mean that it is a conceptual truth that if there are semantic or intentional truths, then every such truth is entailed by some relevant dispositional truth. To the extent that this claim about reading-off is true, a counterpart of the epistemic approach is extremely implausible in the Kripke-Wittgenstein case, for here it is an a priori assumption that we have full knowledge of the sort of truths on which the semantic facts supervene—that is, truths about dispositions. More generally, it seems reasonable to say that the Kripke-Wittgenstein problem is a problem about broadly psychological phenomena that has a close affinity with the moral problem. Hence, although I have been suggesting the experience problem is different in a number of important respects from the moral problem, this is not so with other problems that seem equally part of the traditional mind-body problem.

5.7. Conclusion We have so far argued that the ignorance hypothesis is plausible on four general grounds: it is a natural conjecture given reflection on other creatures; it is a natural conjecture given the fact of our empirical ignorance of conscious experience; it explains a wide variety of philosophical data; it is suggested by the basic structure of philosophical thinking about experience. One problem with these points, however, is that they are just that: general. They provide us with no guidance about what our ignorance might be like. Of course, as noted earlier, we are in no position to say outright what the truths of which we are ignorant are. But we might hope to render the hypothesis plausible by considering speculative proposals or models about what it might be like. In the next chapter, I explore one proposal along these lines.

6 Russellian Speculations

6.1. Introduction There is an obvious sense in which what we know about physical objects is incomplete; for example, the exact position and character of indefinitely many physical objects is unknown to us. But there is a famous philosophical argument, according to which what we know about physical objects is incomplete in a less obvious sense as well: there is a type of truth concerning physical objects of which we are completely ignorant. The type of truth in question concerns (what philosophers often call) the categorical or intrinsic nature of physical objects. Of course, these labels don’t convey all that much on their own. But just as a matter of terminology, let’s call the relevant truths ‘‘categorical truths,’’ and let’s call the argument that we are ignorant of them ‘‘the categorical argument.’’ With this terminology in place, what the categorical argument says is that we are ignorant of, or unaware of, the categorical truths about physical objects. The origin of the categorical argument goes back at least to Hume’s famous assertion in the Treatise on Human Nature (1.4.4) that ‘‘modern philosophy leaves us with no just or satisfactory idea of solidity; nor consequently of matter.’’ But the argument has been invoked in contemporary discussion in the context of a surprisingly wide variety of philosophical positions and projects. For some (e.g., Armstrong 1961, 1968), it is a central argument in the philosophy of matter. For others (e.g., Foster 1982), it plays a role in establishing a neutral monist or idealist metaphysics. For still others (e.g., Langton 1998), it provides the basis for an interpretation of Kant. For us, the important issue is not matter or neutral monism or Kant, but philosophy of mind. Here, too, there are connections to the categorical argument. 106

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These connections have been noted and discussed by a number of writers, including myself in earlier work (e.g., Stoljar 2001a, 2001b; see also Lockwood 1989, Maxwell 1978, Chalmers 1996, Unger 1998, Stubenberg 1997, Rosenberg 2004). But the key idea is, so far as I know, due to Bertrand Russell. In The Analysis of Matter, he wrote: A piece of matter is a logical structure composed of events; the causal laws of the events concerned, and the abstract logical properties of their spatio-temporal relations, are more or less known, but their intrinsic character is not known. Percepts fit into the same causal scheme as physical events, and are not known to have any intrinsic character which physical events cannot have, since we do not know of any intrinsic character which could be incompatible with the logical properties that physics assigns to physical events. There is therefore no ground for supposing that percepts cannot be physical events, or for supposing that they are never compresent with other events. (1927, 384) In the first part of this passage, Russell is asserting the conclusion of the categorical argument. A physical object (‘‘a piece of matter’’) is composed of events whose categorical (‘‘intrinsic’’) character is not known; hence physical objects themselves are items whose categorical character is not known. In the second part of the passage, he draws the connection to philosophy of mind: in view of this ignorance of the categorical nature of physical objects, there is no ground for supposing that experiences (‘‘percepts’’) are not physical. Now, Russell does not say here exactly what these putative grounds might be. But it is natural to interpret him as intending something like the modal arguments we have been discussing, CA and KA. Moreover, if we do interpret him this way, what we have here is not simply a connection between the categorical argument and philosophy of mind; what we have is nothing less than a version of the epistemic view. For consider, the categorical argument tells us that something like the ignorance hypothesis is true: we are ignorant of a type of physical or nonexperiential truth—namely, categorical truths. And what Russell seems to be suggesting is that once this hypothesis is appreciated, arguments such as CA and KA lose their force; hence, in our terminology, the logical problem is solved. My aim in this chapter is to set out and assess this Russellian version of the epistemic view—for short, the Russellian view. As will emerge, I think it is an elegant version of the basic epistemic view; to this extent, it is plausible. But it is not my intention to defend it outright. Instead, my interest is generated by two related considerations. First, as we noted at the end of the previous chapter, one way to make the ignorance hypothesis plausible is to explore a particular way in which it may be filled out. The Russellian view precisely provides such a way, for it provides a speculation about what our ignorance might be like that is more detailed than anything we have looked

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at so far. On the other hand—and this is my second reason for looking at the Russellian view—our discussion of it will demonstrate that there is no internal connection between the epistemic view and its Russellian incarnation; that is, there is no reason why a proponent of the epistemic view must be a Russellian. This fact is important for the plausibility of our overall position. Russell’s insight was that ignorance of the physical world plays a role when thinking about philosophy of mind. My aim is to show that this insight survives even if we detach it from the background metaphysical views that Russell used to express it. I will turn to the Russellian version of the epistemic view in a moment; first, what exactly is the categorical argument?

6.2. The Categorical Argument The categorical argument begins by dividing the truths of which we are not ignorant into three types. It then proceeds to say that neither these types nor any combination of them tells us the whole truth about physical objects. Clearly, if the types of truths about physical objects of which we are not ignorant do not tell us the whole truth, there must be some other type of truth of which we are ignorant. Conclusion: there is a type of truth concerning physical objects of which we are ignorant. (Note the structural parallel between this argument and the argument for cognitive closure discussed in the previous chapter.) What are these three types of truths, and why is it that they cannot tell us the complete story about physical objects?

6.2.1. Spatiotemporal Truths The first class concerns the spatiotemporal properties of physical objects— spatiotemporal truths, as I will call them. The spatiotemporal properties of objects include position in space and time and also shape and topography more generally. It is natural to say that any physical object will exhibit these properties, and so the story about physical objects will certainly include the spatiotemporal truths. But equally—a proponent of the categorical argument says—this can’t be the whole story. Having spatiotemporal properties is not a unique feature of physical objects, so there must be more truths that distinguish physical objects. Why are spatiotemporal properties not a unique feature of physical objects? We naturally think of physical objects as filling in space, not simply being in space: physical objects are not vacua (see Armstrong 1961). On the other hand, vacua may exhibit the very same properties of shape and position that a physical object can. Hence spatiotemporal properties are not unique to physical objects, and the spatiotemporal story about physical objects is not the whole story.

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6.2.2. Truths about Secondary Qualities The second class of truths concerns the secondary qualities of physical objects—secondary quality truths, as I will call them. Traditionally, secondary qualities of physical objects are their color, heat, smell, and so on, and these themselves can be thought of in various ways. But, however we conceive of secondary qualities—the proponent of the categorical argument continues—the truths about secondary qualities cannot tell us the full story about physical objects. The crucial consideration this time is that secondary qualities are not a universal feature of physical objects: there must be truths about physical objects that are not secondary quality truths. Why are secondary qualities not a universal feature of physical objects? Well, secondary qualities attach only to particulars that have a size and shape roughly congruent with our size and shape—that is, the size and shape of human beings. Objects that are very big (such as the universe itself) and very small (such as subatomic particles) do not have secondary qualities. What is the color of the universe, for example, and what is the smell of an electron? Secondary qualities, as we might put it, drain away as we move away from the sort of physical object that we humans normally deal with. That is why the secondary qualities of physical objects are not a universal feature of physical objects. So the secondary quality story about physical objects is not the whole story.

6.2.3. Truths about Primary Qualities The third class of truth concerns the primary qualities of physical objects— primary quality truths, as I will call them. Traditionally, the primary qualities include such properties as solidity and hardness, but in modern discussions the notion of a primary quality has been extended to include any property of physical objects that physical theory tells us about, such as mass and electrical charge. It is natural to say that any physical object will exhibit primary qualities in this broad sense, and so the story about physical objects will certainly include these truths. On the other hand—a proponent of the argument says—this can’t be the whole story. Having primary qualities is not an exhaustive feature of matter. Why is it that primary qualities are not an exhaustive feature of matter? This point emerges most clearly if we have two theses before us. The first is that physical theory tells us only about the dispositional properties of physical objects and so does not tell us about the categorical properties, if any, that they have. In the sense at issue here, a dispositional property is power to produce or bring about something in certain conditions. Hence fragility is a dispositional property of a vase because if a vase is fragile, it will break when struck. Similarly, being uncomfortable is a dispositional property of a chair. The notion of a categorical property is somewhat obscure—as noted earlier, the label ‘‘categorical’’ does not tell us much on

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its own—but for our purposes a categorical property is a nondispositional property whose instantiation is metaphysically sufficient for the instantiation of a dispositional property. Implicitly or explicitly, many philosophers hold the thesis that physical theory tells us only about dispositional properties. One is Simon Blackburn: When we think of categorical grounds, we are apt to think of spatial configurations of things—hard, massy, shaped things, resisting penetration and displacement by others of their kind. But the categorical credentials of any item in this list are poor. Resistance is par excellance dispositional; extension is only of use, as Leibniz insisted, if there is some other property whose instancing defines the boundaries; hardness goes with resistance, and mass is knowable only by its dynamical effects. Turn up the magnification and we find things like an electrical charge at a point, or rather varying over a region, but the magnitude of a field at a region is known only through its effects on other things in spatial relations to that region. A region with charge is very different from a region without. . . . It differs precisely in its dispositions or powers. But science finds only dispositions all the way down. (1990, 62–63) What Blackburn is saying here is that when we consider the properties of physical objects we normally think of as primary qualities—such as resistance, hardness, or having a certain charge—we find that such properties are dispositional. His final remark suggests that something more general is true and that in scientific theory—Blackburn means, I think, physical scientific theory—one only ‘‘finds’’ dispositional properties. It seems reasonable to summarize this by saying that physical theory tells us only about dispositional properties. The second thesis we need to consider is that the dispositional properties of physical objects do require categorical grounds; that is, for all dispositional properties, there must be a nondispositional property, or nondispositional properties, such that the instantiation of the latter is metaphysically sufficient for the instantiation of the former. For example, if a vase is fragile, there must be a nondispositional property, or nondispositional properties, whose instantiation makes it the case that the vase is fragile; if a chair is uncomfortable, there must be a nondispositional property, or nondispositional properties, whose instantiation makes it the case that the chair is uncomfortable. It might perhaps be thought that there is some conflict between this thesis and the first. But there is certainly no logical inconsistency here. Indeed, many (but not all) philosophers who hold the first thesis also hold the second. A prominent example is D. M. Armstrong, who in A Materialist Theory of the Mind holds that, because physical theory characterizes only the dispositional or relational nature of physical objects, it therefore ‘‘does not tell us’’ (1968, 282) about their categorical or nonrelational nature.

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With these two theses in place, it is easy to argue that having primary qualities is not an exhaustive feature of matter. Suppose a physical object x has a dispositional physical property F. From the thesis that dispositional properties require categorical grounds, it follows that x (or its constituents) must also have a further nondispositional property, which we may call G. But now let us ask: is G a primary quality or not? From the thesis that physical theory tells us only about dispositions, it follows that primary qualities are either dispositional or else supervene on dispositional properties. But neither is true in the case of G, so G itself is not a primary quality. Hence the primary quality story about physical objects is incomplete: there are truths— for example, truths concerning G —that escape the primary quality story. And this is what I mean when I say that primary qualities are not exhaustive. A complication with this argument derives from the fact that there are two different senses in which physical theory might fail to tell us about the categorical properties of physical objects. In the first sense, physical theory fails to tell us about a property just in case no expression of the theory refers to that property. Now, in this sense, the argument we just considered will not go through. Even if dispositional properties do require categorical grounds, it is still perfectly possible that the expressions of physical theory might refer to those grounds inter alia. But then G and its ilk will count as primary qualities in the broad sense that we have adopted: physical theory will tell us about them. But there is also is a second sense in which physical theory might fail to tell us about categorical grounds. In this sense, physical theory fails to tell us about categorical grounds just in case there might be two possible worlds w and w* such that (i) they are exactly alike in terms of their distribution of dispositional properties in that in both w and w*, x has F; but (ii) they are different in terms of their categorical properties because in w, x has G, but in w*, x has a quite distinct categorical property G*; and (iii) from the point of view of the theory, they are epistemically indiscernible—the two worlds are (in Kripke’s famous phrase) epistemically and qualitatively identical, though they might nevertheless be semantically different in the sense that in w, an expression of physical theory refers to G, whereas in w* the counterpart expression refers to G*. It is this idea that Blackburn and Armstrong are appealing to when they (respectively) say that science finds dispositions all the way down and that physical theory does not tell us about the categorical nature of physical objects. Similarly, it is this idea that is required by the argument we just considered that primary qualities are not an exhaustive feature of matter.

6.2.4. Combined Types The categorical argument says that none of these types of truth taken individually tells us the whole story about physical objects: spatiotemporal properties are not unique, secondary qualities are not uniform, and primary

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qualities are not exhaustive. It also says they do no better taken collectively. To see this, consider again the reason that primary quality truths cannot tell us the full story: that such truths constitute a dispositional story and that dispositional stories are not complete. Now, if either spatiotemporal properties or secondary qualities could be thought of as categorical, we could appeal to them to complete the dispositional story. On reflection, this idea is quite implausible. In the first place, spatiotemporal properties cannot be the categorical grounds of dispositions, for the fact remains that there is intuitively a difference between matter and empty space; spatiotemporal properties are not a unique feature of physical objects. In the second place, secondary qualities cannot be the categorical grounds of dispositions, for the fact remains that secondary qualities drain away; secondary qualities are not a universal feature of matter. In short, the argument leads to the same conclusion whether we are considering the three types of truths taken individually or taken collectively.

6.2.5. Conclusion If the known truths concerning physical objects can be divided into three classes, and if truths of these three classes do not tell us the whole story about physical objects, we arrive at the conclusion of the categorical argument; that is, there is a type of truth of which we are ignorant. How plausible is the categorical argument? It clearly contains a number of highly contentious assumptions. In the part of the argument that is supposed to show that spatiotemporal properties are not unique, for example, it was assumed that matter and space are distinct. But perhaps there are theories of matter that deny this. Descartes, for example, famously denied the distinction between matter and extension in space, and (as Eric Lormand suggested to me in conversation) perhaps contemporary physical theories can be interpreted in a slightly analogous way—namely, as connecting matter and space-time. Similarly, in the part of the argument that is supposed to show that primary qualities are not an exhaustive feature of matter, it was assumed, first, that dispositional properties require categorical grounds and, second, that physical theory only tells us (in the relevant sense) about dispositional properties. But these points are notoriously difficult to argue for in any systematic way. In view of the controversy surrounding the categorical argument, one might at this point attempt to develop the discussion by examining the presuppositions of the categorical argument in more detail and defending them. But this is not the direction in which I want to proceed. What is important for us is not the ultimate persuasiveness of the categorical argument; it is enough for our purposes to note that many people have found it persuasive. What is important, rather, is the conclusion of the argument and in particular—this is the thought that seems prominent in Russell’s discussion—the connection between the conclusion of the argument and the epistemic view.

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6.3. The Russellian View We have so far presented the categorical argument and noted that it is the conclusion of the argument, rather than the reasoning for that conclusion, that is important. The point to be developed now is that if we do accept the conclusion, we are rather close to the Russellian version of the epistemic view.

6.3.1. The Categorical Ignorance Hypothesis The issue might be approached by contrasting our own version of the ignorance hypothesis with the Russellian version, at least as I am interpreting it. Our ignorance hypothesis is that we are ignorant of or unaware of a type of truth relevant to the nature of experience. The alternative—I will call it the categorical ignorance hypothesis—is that we are ignorant of a type of experience-relevant nonexperiential truth that is categorical, where a ‘‘categorical truth’’ is one that concerns the categorical nature of physical objects. The categorical ignorance hypothesis entails the ignorance hypothesis but not vice versa; there is a clear logical difference here. But the categorical ignorance hypothesis is also more speculative than the ignorance hypothesis. It tells us something specific about the nature of the truths of which we are ignorant. In particular, it says that these truths are the very ones that are at issue in the categorical argument. Just as the categorical ignorance hypothesis entails the ignorance hypothesis but not vice versa, so, too, it entails the conclusion of the categorical argument but not vice versa. The conclusion of the categorical argument says only that we are ignorant of a type of nonexperiential truth—namely, categorical truths. The categorical ignorance hypothesis agrees that we are ignorant of a type of nonexperiential truth—namely, categorical truths—but it also says that these truths are relevant to experience. In making this claim of relevance, proponents of the Russellian view are moving beyond the conclusion of the categorical argument—though, of course, they might be doing so in a reasonable way. Even though these three theses—the ignorance hypothesis, the categorical ignorance hypothesis, and the conclusion of the categorical argument— are different from one another, there is also something that unites them. All three are united in asserting that we are ignorant of or unaware of a type of truth. In short, the conclusion of the categorical argument invokes, as the other two theses also do, the notion of being ignorant of, or unaware of, a type of truth. As I noted in chapter 4, Russell sought to explain this notion at least in part by drawing an analogy between our understanding of the physical world and a blind person’s understanding of color or light. Just as a blind person fails to understand a type of truth about colors and lights, so, too, if the categorical argument is sound, are we ignorant of a type of truth about physical objects.

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6.3.2. Categorical Ignorance and Chronic Ignorance We have identified the categorical ignorance hypothesis and distinguished it from both our own ignorance hypothesis and the conclusion of the categorical argument. We should also distinguish it from the chronic ignorance hypothesis discussed in the previous chapter. As we have seen, the chronic ignorance hypothesis says that we are ignorant of a type of nonexperiential experience-relevant truth and chronically so—‘‘chronically so’’ meaning that we cannot remedy the ignorance consistent with our biological and psychological nature. The chronic ignorance hypothesis and the categorical ignorance hypothesis are clearly logically distinct: on the face of it, our ignorance might be chronic without being categorical, and similarly our ignorance might be categorical without being chronic. Now, when discussing the chronic ignorance hypothesis, I made in effect two points: first, McGinn’s argument for the hypothesis failed, and hence the hypothesis is nothing more than a (perhaps plausible) speculation about the contingent limits of human knowledge; second, and more important for present purposes, the truth or not of the speculation is irrelevant to our main concern. Even if we suppose that the ignorance in question is chronic, this is not to the point when it comes to the assessment of CA and KA, the reason being that whether our ignorance is chronic is one thing, and what we are ignorant of—that is, the content of our ignorance—is another. The first of these points about the chronic ignorance hypothesis applies also to the categorical ignorance hypothesis: it, too, is a speculation that may or may not be true. But the second point does not apply. The categorical ignorance hypothesis does provide a speculation about the content of our ignorance. In particular, the categorical ignorance hypothesis speculates that we are ignorant of the categorical nature of physical objects and that this nature is relevant to experience. That the Russellian version of the epistemic view concerns the subject matter of our ignorance in a way in which the mysterian version of the view does not is one reason I have devoted relatively more space to the Russellian view.

6.3.3. Categorical Ignorance and Modal Error To illustrate how the categorical ignorance hypothesis involves a speculation that is relevant to the modal arguments, it is instructive to see how a Russellian would respond to these arguments. To this end, let us reconsider CA, which proceeds from these premises: C1.

C2.

It is conceivable that there is a situation identical to the actual situation in respect of all nonexperiential truths but different from it in respect of some experiential truth. If this is conceivable, it is possible.

These premises entail, for reasons we set out in chapter 2, the falsity of experiential supervenience. If C1 and C2 are true, the experiential conditional

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is contingent, but if the experiential conditional is contingent, experiential supervenience is false. The Russellian response to this argument assumes a form familiar from our discussion in chapter 4. The claim that there is a situation identical to the actual situation in respect of all nonexperiential truths may be interpreted in two quite different ways, depending on how its constituent quantifier phrase ‘‘all nonexperiential truths’’ is to be understood. On one reading, ‘‘all nonexperiential truths’’ includes both categorical and dispositional physical truths. On this reading, the basic proposition at issue in the argument is (1): (1) There is a situation identical in respect of all categorical and dispositional nonexperiential truths but different in respect of some experiential truth. On a different reading, we confine attention when interpreting ‘‘all nonexperiential truths’’ to those that concern dispositional physical properties. Then the basic proposition at issue in the argument is (2): (2) There is a situation identical to the actual situation in respect of all dispositional nonexperiential truths but different from it in respect of some experiential truth. Now, which of (1) and (2) is intended? Given what we have said so far, there is no bar to it imaginatively appearing to us that (2) is true. On the other hand, (2) is in the context unobjectionable. Its conceivability would not issue in a possibility that undermines experiential supervenience but only in a possibility that undermines the supervenience of the experiential on the dispositional, and this is a different matter. On the other hand, the conceivability of (1) would issue in a possibility that undermines experiential supervenience. But if the categorical ignorance hypothesis is true, (1) is not strongly conceivable. To strongly conceive a proposition demands a reasonable grasp of the proposition in question. But in an important sense we don’t understand (1) if the categorical ignorance hypothesis is true, for we don’t understand what these categorical truths are. In short, if the categorical ignorance hypothesis is true, there is no interpretation of the first premise of CA so that it is both true and yields the conclusion at issue. So the conceivability argument collapses. What applies to CA applies also to KA. As we have seen, the crucial premise of this argument may be expressed as follows: K1.

It is possible for a logically omniscient and conceptually sophisticated person to know every nonexperiential truth and yet learn some experiential truth on the basis of experience.

If the categorical ignorance hypothesis is true, there are two quite different ways to take both this premise and the reasoning that surrounds it. On one reading, ‘‘all nonexperiential truths’’ is interpreted liberally to mean ‘‘all

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dispositional and categorical truths.’’ Then the basic proposition at issue in the argument is (3): (3) A logically omniscient and conceptually sophisticated person knows every dispositional and categorical nonexperiential truth and yet learns some experiential truth on the basis of experience. On another reading, ‘‘all nonexperiential truths’’ is interpreted more restrictedly to mean ‘‘all dispositional nonexperiential truths.’’ Then the basic proposition at issue in the argument is (4): (4) A logically omniscient and conceptually sophisticated person knows every dispositional nonexperiential truth and yet learns some experiential truth on the basis of experience. But now the basic problem reemerges. On the one hand, (4) is or might be conceivable in the relevant sense, but it is unobjectionable; on the other hand, (3) is objectionable but is not conceivable in the relevant sense. Either way, if the categorical ignorance hypothesis is true, the knowledge argument collapses. We might summarize the situation by saying that, for the Russellian, our intellectual position when we confront the problem of experience is similar in outline to the intellectual position of the slugs when they confront the problem of the circle. We are ignorant of something that is intuitively a basic fact of the world—in the slugs’ case, it is ignorance of truths about pie pieces, but in our case it is ignorance of truths concerning the categorical nature of physical objects. And as a consequence of this ignorance, we make one of the standard mistakes that are made when fallacious modal arguments are advanced. In short, if the Russellian view is true, the problem of experience is solved.

6.4. Objections to the Russellian View The Russellian says that the categorical ignorance hypothesis is true and moreover that, if it is true, the problem of experience is solved. The motivation for the first thesis is the categorical argument—though, as we have noted, the conclusion of that argument does not entail the categorical ignorance hypothesis. And the reason for believing the second thesis is that if the categorical ignorance hypothesis is true, it becomes apparent that, in advancing CA and KA, we are making one (or a combination) of the standard mistakes. But how plausible is this view? I will not try to answer this question directly. Instead, I will consider some of the main objections that the Russellian view is thought to face. As I hope will become clear, on examination, these objections turn out to be much less forceful than they initially appear.

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6.4.1. The Grain Problem The first objection is often called the grain problem. Here is a statement of this problem taken from an important paper by Grover Maxwell in which he sets out a version of the Russellian view: The objection asks, for example, how it is that the occurrence of a smooth continuous expanse of red in our visual experience can be identical with a brain process that must, it would seem, involve particulate, discontinuous affairs such as transfers of or interactions among large numbers of electrons or the like. Surely being smooth is a structural property, and being particulate or discontinuous is also a structural property, one moreover that is incompatible with being smooth and continuous. This strongly suggests, the objection continues, that at least some mental events exemplify structural properties that not exemplified by any brain event. . . . It follows that the mental event and the brain event do not share all of their (structural) properties, and thus, the objector concludes, they cannot be identical. (1978, p. 398) Here Maxwell is concentrating on identity, and thus one might be tempted to argue that his objection does not threaten any version of physicalism that we would endorse. Of course, our claim is that experiential truths supervene on nonexperiential or physical truths, not that they are identical with them. However, I don’t think this reply is going to carry much weight with a proponent of the grain objection. The question can be stated without appealing to identity, as follows: how could a potentially noncontinuous and unsmooth myriad of physical properties combine together to entail a smooth, continuous expanse of red? Unless we can answer this more general question, the grain problem remains unsolved. If the grain problem cannot be answered by distinguishing between identity and supervenience, how can it be answered? There are number of proposals in the literature (e.g., Chalmers 1996, Lockwood 1992), but my own view is that the answer emerges when we focus on what precisely it is in Maxwell’s example that is supposed to be smooth and continuous. It seems plausible to say that it is the expanse that is smooth and continuous and also that the expanse is something that we represent in visual experience; that is, Maxwell’s example is an example in which we are having an experience that represents an expanse as being smooth and continuous. Of course, it does not follow from this that the experience itself is smooth and continuous. Consider: an experience of red represents something as being red, but it is not itself red. So the answer to the grain problem is that it gets the phenomenology wrong and mislocates the absence of grain: absence of grain is not a feature of experiences but a feature of something that experiences represent. One might object that it is obvious in introspection that one’s experience of a red expanse is itself smooth and continuous and not simply that it

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represents an expanse as being so. However, this is not obvious at all. As we noted in chapter 1, many philosophers have noted that many acts or states of experiencing seem in a certain respect ‘‘diaphanous’’ to introspection: introspection reveals the intentional objects of experiences to us but not the experiences themselves. To apply this to the case at hand, if we try to introspect the experience of a smooth and continuous expanse, all we see is the smoothness and continuity of the expanse; the other element—namely, the experience itself—is as it were diaphanous. If this account of the phenomenology of introspection is correct, it is by no means obvious that introspection reveals experiences to be smooth at all. What it reveals, rather, is that we often have experiences that represent things as being smooth and continuous. But that is a different matter.

6.4.2. Panpsychism A second objection to the Russellian view is that it entails or at least suggests a form of panpsychism. According to panpsychism, or at least to the sort of panpsychism that is relevant here, the categorical properties that underlie dispositional physical properties are psychological properties. It follows from panpsychism, therefore, that every physical object, and not just some physical objects, instantiates psychological properties. But why suppose that the Russellian view entails or suggests panpsychism? Well, it is often thought that the paradigm examples of categorical properties are phenomenal or experiential properties and in consequence that we derive the concept of a categorical property from reflection on experience; as Blackburn (1990, 65) puts it, ‘‘categoricity comes with the subjective view.’’ If every physical object instantiates categorical properties, and if categorical properties are paradigmatically phenomenal or at least involve the phenomenal in some deep sense, it is tempting to conclude that every physical object instantiates phenomenal properties. But there are three quite separate problems with this line of argument. First, even if one derives one’s concept of a categorical property from one’s concept of experience, it does not follow that all categorical properties are phenomenal or psychological. In Kripke’s (1982, 118) example, even if one derives one’s concept of a duck from the ducks in Central Park, it does not follow that the concept so derived does not apply to ducks not in Central Park. This means that one can at least speculate about a range of categorical properties that are both physical and nonpsychological: these are the properties that make up the categorical nature of physical objects. Unless there is something incoherent in the very idea of such a class of properties, we have no reason to suppose that the Russellian view will collapse into panpsychism. Second, it is quite unclear that we do derive our concepts of categoricity from reflection on experience—that is, that categoricity does come from the subjective view. As I noted previously, the notion of a categorical property

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is a bit obscure, but my own assumption is that categorical properties are by definition nondispositional properties on which dispositional properties supervene. If this definition or something roughly like it is right, there is no internal or logical connection between categoricity and consciousness. More particularly, the notion of a categorical property does not come with the subjective view, or anyway, it does not unless the notion of a dispositional property also comes with the subjective view—something I take to be quite implausible. Finally, it is quite unclear, contrary to what Blackburn seems to be assuming, that the categorical properties of which we are primarily aware are subjective or psychological. Take, for example, color properties. To the extent that categoricity is a feature of experiential properties, it is equally a feature of color properties. Likewise, to the extent that it is reasonable to suppose that the Russellian view is committed to panpsychism, it is equally reasonable to suppose that it is committed to pancolorism. Indeed, some have been tempted by such a position (e.g., Armstrong 1961). But, whatever else is mistaken about pancolorism—Armstrong 1968 takes back the suggestion made in Armstrong 1961—there is nothing panpsychist it. To suppose otherwise is to confuse a property of an experience with a property represented in experience, a confusion that we saw is at the heart of the grain problem.

6.4.3. Relevance A final objection to the Russellian version of the epistemic view is that we have been given no positive reason to believe that categorical truths are relevant to the nature of experience. As we have seen, what the categorical ignorance hypothesis adds to the conclusion of the categorical argument is the claim that categorical truths are relevant to experience. But why should we suppose that this is true? The point might be expressed by contrasting our situation as portrayed by the Russellian with the situation of the slugs (see Hohwy 2005). It is clear that the pie pieces are relevant to circles, but why should these categorical truths be relevant to experiences? One response to the relevance problem is to view the categorical features of matter as themselves somehow experiential or perhaps closely tied to the experiential. If the categorical truths are themselves experiential, then—one might think—it is easy (or easier, at any rate) to see how experiential truths can be entailed by categorical truths. This response is interesting in part because it connects the issue about relevance with the issue about panpsychism we have just discussed. As we have seen, it is not plausible to say directly that categoricity comes with the subject view, but perhaps it is plausible to say indirectly that if categorical truths are experiential, we have a solution to the relevance problem—though, of course, at the cost of committing ourselves to panpsychism. In fact, however, the suggestions that the categorical features of matter are themselves experiential does not solve the relevance problem, and we

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have no further reason here to adopt panpsychism. The suggestion implies that that it is easy (or, anyway, easier) to see how some experiential truths entail other experiential truths. In fact, this is far from obvious. As a number of philosophers have noted, it seems just as hard to see how one experiential truth can entail another as it is to see how a nonexperiential truth can entail an experiential truth. Ned Block, for example, asks us to imagine a race of humanlike creatures that are much smaller than our elementary particles: For reasons known only to them, they decide to devote the next few hundred years to creating out of their matter substances with the chemical and physical characteristics (except at the elementary particle level) of our elements. They build hordes of space ships of different varieties about the size of our electrons, protons, and other elementary particles, and fly the ships in such a way as to mimic the behaviour of these elementary particles. The ships also contain generators to produce the type of radiation elementary particles give off. (1980, 280) Block goes on to say that it is possible that we ourselves have these little creatures inside us or, anyway, that this could become so if we traveled to the part of the universe inhabited by them. If what Block describes is indeed a possibility, then, relative to that possibility, the truths concerning our experiences would presumably supervene, at least in part, on the truths about the experiences of these tiny creatures. In fact, a certain sort of limited panpsychism would be true—at least if the tiny creatures were successful enough in their scientific projects. On the other hand, it is clearly not the case that supposing this removes the relevance problem. On the contrary, it seems as reasonable as ever to ask, ‘‘Why are these truths about the tiny creatures relevant to our experiences?’’ Of course, this does not suggest that the relevance problem is not a problem, but what it does suggest is that it is a mistake to think that the relevance problem might be solved if one assumes that the categorical truths are themselves experiential. A second response to the relevance problem is to shift attention from categorical truths to noncategorical—that is, dispositional—truths. Are these truths relevant to experience or not? It is tempting to argue that they are not relevant. As we will see in chapter 7, a number of philosophers argue that no dispositional truth entails anything about experiences. So one might therefore suggest that while dispositional truths are not relevant but that some truths are, it would follow that categorical truths are. This gives us an indirect reason for supposing that categorical truths are relevant and so— one might think—to solve the relevance problem. But there are two problems with this way of dealing with the relevance problem. First, it helps itself to the idea that some nonexperiential truths are relevant, but in the context this assumption is illegitimate. Second, and more seriously, it is not at all clear that it is true that no dispositional truth

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entails any experiential truth (indeed, this issue will emerge in much more detail in chapter 7). In the first place, some experiential truths are themselves dispositional; in the second place, there is no bar in principle for dispositional truths to entail nondispositional truths. If we are not to respond to the relevance objection either by appealing to experiential truths or by switching attention from categorical truths to dispositional truths, how are we to respond to it? In my view, the relevance objection forgets that the Russellian view is at the end of the day a speculation about what might be going on. As Russell in effect said, we are in no position to deny that categorical truths are relevant to the nature of experience, or at least we are not if the categorical argument is sound. If we are ignorant of their nature, we are ignorant of whether they are relevant to experience or not. Hence we are entitled to speculate that they are relevant. To put it differently, the Russellian view is a hypothesis about what is going on that should be considered more in the light of its elegance, simplicity, and fruitfulness than as regards anything else. When we consider the Russellian view from this larger theoretical perspective, we find two main reasons to accept it: The first reason is that it solves the logical problem of experience. The second is that it unifies two quite disparate lines of thought. On the one hand, there is the line of thought about our ignorance of the nature of matter; this line is summarized in the categorical argument. On the other hand, there is the line of thought about our perplexity at the nature of experience; this line of thought is summarized in the logical problem. The Russellian view brings together these two areas of philosophical inquiry.

6.5. The Significance of the Russellian View So the Russellian view is, or contains, a hypothesis that would explain a number of data and unifies two apparently distinct lines of inquiry. Should we believe it? As I said at the beginning of this chapter, I am not going to positively recommend it here. The significance of the Russellian view lies rather in two facts: first, it provides one way in which the ignorance hypothesis can be developed; second, it provides us with a clear account of something that our overall position does not entail. The first point has in effect been our subject for the entire chapter. But we may bring out the second by demonstrating how, if we start with a Russellian view, we may proceed via a series of modifications to the more abstract, and so more conservative, version of the epistemic view that I want ultimately to advance. At stage 1, we imagine ourselves to hold the Russellian view; that is, we hold both that the categorical ignorance hypothesis is true and also that, if it is true, CA and KA are answered. As we have seen, the Russellian view involves a significant speculation about how things might be, a speculation

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that may not be true, and any proponent of the Russellian view must openly acknowledge this. At stage 2, we observe that the reference to categorical truths in the response of the Russellian to CA and KA is inessential. The reason the Russellian has a response to CA and KA does not have much to do with ignorance of categorical truths as such; rather, it has to do with ignorance of a type of truth relevant to the nature of experience. The Russellian view, of course, involves the idea that the type of truth in question is a categorical truth. But this is not necessary to the success of the view, construed as a response to the modal arguments. What does the work in responding to the arguments is the claim that we are ignorant of something; the claim that we are ignorant of something categorical is irrelevant. At stage 3, we articulate a more abstract position, a position that has the Russellian view as only one instantiation. To arrive at this more abstract position, we replace the categorical ignorance hypothesis with the ignorance hypothesis. Similarly, we connect the problem of experience not with the categorical ignorance hypothesis as such but with the ignorance hypothesis. The more abstract position is not inconsistent with the Russellian view; rather, the Russellian view is simply one way to spell it out. Moreover, there are many other ways in which it might be spelled out. For example, the type of truth in question might concern physics itself or something that supervenes on physics; it might be basic level or intermediate level, as I have put it. Similarly, it might concern dispositional physical properties rather than categorical physical properties. At stage 4, we notice that the more abstract position is vastly more plausible than its Russellian version—and the reason is precisely that it is so much less committal about the precise content of our ignorance. The claim that there is some type of truth relevant to the nature of experience of which we are ignorant is much more plausible than the claim that there is some type of categorical truth relevant to the nature of experience, because it permits vastly more possibilities about what the content of our ignorance might be. Obviously, it is this abstract position with which I have been operating all along. Of course, even if the Russellian view may by incremental changes be transformed into something more abstract and so more plausible, it remains true that the view itself is not for everyone. In consequence, it remains true that reflection on the Russellian view is going to have only so much weight when it comes to making the ignorance hypothesis plausible. In the next chapter, therefore, I turn to reasons to believe the ignorance hypothesis that have their source, not in the general considerations we considered in the previous chapter, nor in the metaphysical ideas we considered in this one, but in considerations of a more flat-footed variety.

7 Historical Precedent

7.1. Introduction If our project is to render the ignorance hypothesis plausible in an indirect way, an obvious strategy I have so far ignored is to appeal to historical examples. The guiding idea is that we have been here before: the situation we are confronted with when we think about experience is not unprecedented, and these precedents support the ignorance hypothesis. In this chapter, I consider two such examples, both extracted from the history of philosophy of mind. The first concerns Descartes’ presentation of dualism in the seventeenth century; the second concerns the relation between chemistry and physics as characterized by the early–twentieth-century philosopher C. D. Broad. The examples differ in a number of respects, but what unites them, and what is of interest to me, is that in both cases we have modal arguments undone by further knowledge. The suggestion of the epistemic view is that this is precisely how to think about the problem of experience.

7.2. Phenomenal and Intellectual Character It is a striking fact that contemporary philosophical discussion of the sort we are engaged in has focused so much on the phenomenal character of experience rather than on psychological properties that are more intellectual in nature, such as reasoning, speaking a language, and so on—on phenomenal rather than intellectual character, as I will say for short. This is not to say that issues associated with intellectual character have not been discussed; they certainly have. But these discussions have a structure and focus different 123

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from the discussions concerning phenomenal character. In the case of intellectual character, contemporary philosophers are not in the main concerned with whether the truths about intellectual character supervene on truths not about intellectual character; rather, they are concerned with explaining or vindicating a supervenience thesis that is agreed by all hands (well, most hands) to be true. This was not always the case. In the seventeenth century and in other periods as well, it was the intellectual character of human thought that most seemed to challenge physicalism and thus most seemed to suggest that dualism was true. This fact raises the possibility that we can make progress on the question of phenomenal character by asking how the analogous question was resolved in the case of intellectual character. A plausible answer, based on an important example, is that it was resolved by a gain in our knowledge.

7.3. The Machine Argument In xV of the Discourse of the Method, Descartes describes an imaginary world rather like our own and pursues the question of how much of that world can be explained from (what we would now call) the physicalist point of view. His answer is that most of the world can be so explained. Indeed, the only aspects of the world that cannot are various intellectual features that attach distinctively to humans. For the humans of that world, Descartes thinks, and of course for us as well, it is necessary to assume a rational soul. But for everything else—including in particular the plants and animals—one ought to be a thoroughgoing physicalist. In the course of discussing the contrast between animals and humans, Descartes says that because animals just are machines, there would be no way to distinguish between an animal and a suitably complicated machine. But in the case of human beings, there are two ways to determine the difference. The first is that humans speak a language, and neither machines nor animals do. The second has to do with the idea, as he puts it, that ‘‘reason is a universal instrument’’ and so could not be replicated in a machine. A number of issues arise in connection with both of these suggestions, issues taken up by many prominent writers (e.g., Gunderson 1964, 1971, Chomsky 1966, Wilson 1978, Cottingham 1986, 1992). I am not going to discuss these issues in detail. What is important for us is not so much Descartes’ views about animals or the contrast between animals and humans. What is important, rather, is the reason Descartes provides for the claim, central to his first way of distinguishing humans from machines, that machines don’t understand language. The reason emerges in the following famous passage: We can certainly conceive of a machine so constructed that it utters words, and even utters words which correspond to our bodily actions

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causing a change in its organs (e.g. if you touch it in one spot, it asks what you want of it, if you touch it in another it cries out that you are hurting it, and so on). But it is not conceivable that such a machine should produce different arrangements of words so as to give an appropriately meaningful answer to whatever is said in its presence, as the dullest of men can do. (VI 56: CSM II40) In the last sentence of this passage, Descartes says that it is ‘‘not conceivable that a machine should give an appropriately meaningful answer.’’ By this, I take him to mean that it is not conceivable (i.e., it is inconceivable) that a (mere) machine, however complicated, should speak a language. The conclusion I take him to be drawing from this—again, in our terminology—is that physicalism is false. In other words, in this and surrounding passages, Descartes is advancing an argument against physicalism, which I will call the machine argument. The premises of the argument are these: M1. M2.

It is inconceivable that a mere machine could speak a language. If it is inconceivable that a mere machine could speak a language, it is impossible that it could.

These premises entail that physicalism is false. If physicalism is true and we are mere machines, then, because we do in fact speak, it is actual and so possible that mere machines can speak. But if M1 and M2 are true, this is not possible; hence physicalism is false.

7.3.1. Conceivability and Inconceivability The first thing to say about the machine argument is that it is different from anything we have met before. Both CA and KA start off from somebody’s finding something conceivable. But in this case, we start off from somebody’s finding something inconceivable; Descartes’ is an inconceivability argument rather than a conceivability argument. And this presents a potential difficulty for our discussion. My aim is to focus on a historical situation that is similar in outline to our contemporary situation and to draw a moral from that similarity. The fact that the machine argument is an inconceivability argument, whereas our own arguments are conceivability arguments, might suggest that there is no relevant analogy here or, at any rate, none worth pursuing. I will come back to this issue in further detail later on. For the moment, it is sufficient to note that, although there are certainly differences between conceivability and inconceivability arguments, there are also similarities, and these are enough to get our discussion started. For one thing, both conceivability and inconceivability arguments are recognizably modal arguments in the sense we are discussing. As we have noted before, modal arguments begin with various imaginable or conceivable cases, draw interim conclusions about what is possible, and draw a final conclusion about the nature of the actual world. Inconceivability arguments likewise exhibit this

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threefold structure. The only differences are that such arguments start off from a claim about inconceivability rather than conceivability, and their interim conclusions are claims about impossibility rather than possibility. Moreover, the sorts of mistakes one could make in advancing an inconceivability argument parallel those one could make in advancing a conceivability argument. First, proposition confusion: it might be that a proposition p that is claimed to be inconceivable has been confused with another proposition q. Second, mode confusion: it might be that p is inconceivable only in the wrong way or mode. Third, defeater neglect: it might be that the inference from inconceivability to impossibility is subject to defeating considerations that have not been taken into account. So again, although conceivability and inconceivability arguments are different, it is the similarities that motivate our discussion.

7.3.2. Competence or Performance? One question about the machine argument concerns inconceivability; another concerns the interpretation of the claim that a mere machine could ‘‘produce different arrangements of words so as to give an appropriately meaningful answer to whatever is said in its presence.’’ I have taken Descartes here as saying that it is inconceivable that a mere machine could speak a language. But the idea of speaking a language oscillates uncomfortably between two rather different ideas. Is Descartes saying that no machine could understand a language, or is he saying only that no machine could exhibit the sort of behavioral flexibility that goes along with understanding a language? To adopt Chomsky’s (1965) famous terminology, does Descartes have in mind an idea of speaking that essentially involves competence, or does he have in mind an idea that is limited to performance? The distinction at issue here may be brought out by introducing a different example into the discussion, the blockhead example, due to Ned Block (1981; the name is due to Frank Jackson). Imagine a machine so designed that it mimics the linguistic dispositions of Ned Block’s Aunt Bubbles, but it operates only on the basis of a giant lookup tree. This is Aunt Bubbles’s blockhead twin or, for short, Blockhead Bubbles. If the mimicry is clever and complete enough, Blockhead Bubbles will be identical to Aunt Bubbles in terms of actual and potential behavior. But, as Block points out, if the causal transactions that mediate this behavior are of the wrong sort, Blockhead Bubbles, unlike Aunt Bubbles herself, will have no linguistic competence at all—‘‘the intelligence of a toaster,’’ as Block famously put it (1981, 21). But now let us ask: can Blockhead Bubbles speak a language or not? Well, she clearly cannot if we have the competence notion in mind: she understands nothing and so does not understand language a fortiori. On the other hand, she clearly speaks a language if one has the performance notion in mind. Her behavioral dispositions are exactly the same as Aunt Bubbles herself, and it is an assumption of the case that Aunt Bubbles exhibits

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whatever behavioral capacities accompany linguistic competence. We may summarize these facts by saying that Blockhead Bubbles speaks a language in the performance sense but not in the competence sense. Now, which of these senses does Descartes intend? According to one tradition of interpretation—a tradition influenced in particular by Chomsky’s (1966) famous remarks about this argument—Descartes intends to be talking about competence. And in fact I have been implicitly adopting this perspective in the presentation up to this point. I have been assuming that the psychological properties that are of interest to Descartes both here and throughout the Discourse are those that are associated with the intellectual character of thought. Linguistic competence is naturally classified in this way, but linguistic performance—I take it—is not. So a natural inference is that what Descartes has in mind is speaking a language in the competence sense. On the other hand, it should be acknowledged that the passage could perfectly well be read in the other way. In particular, it seems true of Blockhead Bubbles, just as much as of Aunt Bubbles herself, that she may produce different arrangements of words so as to give an appropriately meaningful answer to whatever is said in her presence—or its presence, as Descartes would put it. Having only the intelligence of a toaster, Blockhead Bubbles is much duller than the dullest of men, yet she satisfies the behavioral conditions for speaking a language that—on one reading— Descartes has in mind in this passage. Because there are two potential ways to interpret the idea of speaking a language, there are at least two potential ways to interpret the machine argument, which is built around that notion: on the one hand, Descartes might be arguing that no physical object could understand a language; on the other hand, he might be arguing that no physical object could behave exactly as language users behave. How do we deal with this? For the moment, I will continue to assume that Descartes intends the competence sense of speaking a language. Later I will consider in further detail how things would change if we interpreted the argument differently.

7.3.3. Mode Confusion and the Machine Argument We have so far set out the machine argument and made a number of comments about its nature and interpretation. The point to be developed now is that, when we reflect on what is wrong with the machine argument, we have a clear precedent for our current situation. My starting point is the assumption that the machine argument is mistaken and that its conclusion is untrue. We have no reason whatsoever to suppose that linguistic competence is at the end of the day a nonphysical matter. (Someone may disagree with this, but I will simply take it for granted in what follows.) Of course, to say that the machine argument is unsound is not to say that it seemed unsound to its proponents. Descartes presumably thought it sound at the time he wrote the Discourse. So a consequence of my

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starting point is that here we have an unsound argument that (mistakenly) seemed sound to its proponent. Now, if the machine argument is unsound, we need a plausible diagnosis of what has gone wrong with it. In the light of our discussion earlier, it is clear what form such a diagnosis would take. It would take the form of saying that, in advancing the argument, Descartes is making one (or a combination) of the standard mistakes; that is, he is guilty of one (or a combination) of mode confusion, proposition confusion, or defeater neglect. However, it is plausible to suppose that Descartes is making one of the standard mistakes. There are two points to make. First, the historical facts of this situation are (I assume) relatively uncontroversial. (Here I follow Gunderson 1964, 1971, Chomsky 1966, Wilson 1978; Cottingham 1986, 1992, and Haugeland 1985, among others.) Descartes was operating at a time when the idea of computation in anything like the modern sense was completely unknown or, at any rate, completely undiscussed. As a consequence, he did not realize something that seems natural to us—namely, that computational facts are relevant to the intellectual character of human thought and in particular to linguistic competence. In short, a counterpart of our ignorance hypothesis was true of the proponent of the machine argument: he was ignorant of a type of nonintellectual truth relevant to the nature of the intellect. Second, if this counterpart hypothesis is true in Descartes’ case, it becomes immediately plausible to say he was making one of the standard mistakes. One possibility, for example, is to draw a distinction between strong and weak inconceivability that is a counterpart to the distinction drawn in chapter 4 between strong and weak conceivability (see Van Cleve 1983, 44 n. 8.) This counterpart distinction is as follows: (1) p is strongly inconceivable for S just in case it imaginatively appears to S that p is impossible. (2) p is weakly inconceivable for S just in case (i) S entertains p; and (ii) it is not the case that it imaginatively appears to S that p is possible. In the light of this distinction, we might say that, in view of his ignorance, a mere machine’s speaking is not strongly inconceivable for Descartes. Hence the only notion of inconceivability that could be at issue here is weak inconceivability, and Descartes is guilty of mode confusion. Why is weak inconceivability the only notion of inconceivability that could be at issue? Well, the target proposition of the machine argument is, I take it, something like this: (3) There is a mere physical object that speaks a language. But it is implausible that (3) is strongly conceivable for Descartes. We noted when discussing strong conceivability that it is epistemically more demanding than weak conceivability and in particular that one could strongly

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conceive a proposition only if one had a sufficiently rich understanding of the proposition in question. A parallel point applies in the case of strong inconceivability: one can find a proposition strongly inconceivable only if one has a sufficiently rich understanding of the proposition in question. On the other hand, in view of his ignorance, it is implausible that Descartes could be credited with that sort of understanding. Hence it is implausible that for Descartes (3) is strongly inconceivable. Of course, it remains possible that (3) is weakly inconceivable. But from this nothing follows, for weak inconceivability is a poor guide to impossibility. After all, why should the failure of something to be conceived possible render the claim that it is impossible in any way plausible? A slightly different (but consistent) way to develop the charge of mode confusion emerges if we draw a distinction—likewise, parallel to one drawn in chapter 4—between what is inconceivable prima facie and what is inconceivable, all things considered. Once again, in view of his ignorance, it is reasonable to deny that, for Descartes, (3) is conceivable, all things considered. Of course, it remains possible that it is prima facie conceivable. But again, from this nothing interesting follows: prima facie inconceivability is a poor guide to impossibility.

7.3.4. Proposition Confusion and the Machine Argument On either of the two ways of identifying the mistake in the machine argument that we have just discussed, Descartes is guilty of mode confusion and is so because of his ignorance. However, as I noted in chapter 4, the charge of mode confusion may often be bolstered by a charge of proposition confusion. Accordingly, we may ask whether, in addition to the target proposition’s not being inconceivable for Descartes, there is also a contrasting proposition in the vicinity that does genuinely appear to be impossible. The answer is that there is, and we can see this if we look more closely at what is meant in these contexts by ‘‘machine’’ and by cognate words such as ‘‘mechanical.’’ So far I have been tacitly operating with an assumption that makes the argument proceed smoothly: that ‘‘machine’’ is to be understood along the lines of ‘‘physical.’’ However, while this is a natural interpretation, commentators on this passage typically suggest a second and very different idea. What they suggest is that what Descartes means by machine is something that is ‘‘a stimulus and response device’’ (Cottingham, 1992, 249) or a system of ‘‘reflex action’’ (Wilson 1978, 184). So at this point we have at least two interpretations of the relevant notion of machine. According to the first, my machine twin is something that is identical to me in all physical respects. According to the second, my machine twin is something that is identical to me in all (actual and potential) behavioral respects.

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These two accounts of what is meant by ‘‘machine’’ permit a distinction between two different propositions that might be at issue in the machine argument. As we have seen, the target proposition is (3): (3) There is a mere physical object that speaks a language. But in light of the ambiguities of ‘‘machine,’’ we also need to consider a contrasting proposition (4): (4) There is a mere stimulus and response device that speaks a language. We have seen that if Descartes claims to conceive the impossibility of (3), this can be true only in a sense that would not entail or make plausible its impossibility in fact. But it remains an option that he does conceive the impossibility of (4). Moreover, if he did in fact conceive the impossibility of (4), this would seem very plausible from our point of view, for the impossibility of (4) is something that is at least strongly suggested by the blockhead example. Earlier, I introduced that example to distinguish the competence sense of speaking a language from the performance sense. But Block (1981) himself uses it to mount a conceivability argument against behaviorism about linguistic understanding, an argument that is designed to be as similar as possible to Putnam’s perfect actor objection to behaviorism about experience that we considered in chapter 3. However, the example itself might be used equally to mount an inconceivability argument against behaviorism, whose target proposition would be (4). Putting these points together, we arrive at the idea that, first, (4) is inconceivable in the relevant sense and, second, that (3) only seems to be inconceivable in the relevant sense because it has been confused with (4). In sum, it is plausible to suppose that Descartes was ignorant of a certain type of nonintellectual truth relevant to the nature of cognition—that is, he was unaware that linguistic competence admits of a certain sort of computational explanation—and, second, that this fact about his epistemic situation explains his mistake in advancing the machine argument. Of course, in saying this, I am not saying that Descartes himself adopted the epistemic view; of course, he adopted some form of dualism. Nor am I denying one could imagine analogues of most of the positions that are advanced today in respect of the conceivability argument being advanced in response to Descartes’ argument. On the contrary, as Gunderson notes in a related context, ‘‘almost every major position which has been taken with respect to the current discussions has a counterpart in the seventeenth and eighteenth century’’ (1971, 6). What I am suggesting, rather, is that, with the great benefit of hindsight, we can see that none of these responses is the correct one. It is simply not true that an analysis was produced of the notion of linguistic competence in terms of concepts that would have been available to Descartes. Nor is it true—this point is, of course, an appalling anachronism— that there is some sort of necessary a posteriori relation between linguistic

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competence and the facts that Descartes was operating with. Nor is it reasonable to deny that people are able to give appropriately meaningful answers to whatever is said in their presence, as Descartes pointed out. What is reasonable, rather, is the epistemic view, or at least a counterpart of that view.

7.3.5. The Moral for Us The moral for our own position may now be summarized as follows: The intellectual predicament that confronts us when we formulate (e.g.) the conceivability argument is similar in outline to the intellectual predicament that confronts Descartes when he formulates the machine argument. Just as the machine argument was plausible to him, so the conceivability argument is plausible to us. Just as it is mistaken to follow the machine argument to its conclusion, so it is mistaken to follow the conceivability argument to its conclusion. Finally, just as Descartes was ignorant of a type of nonintellectual truth relevant to the nature of the intellectual, so, too, we are ignorant of a type of nonexperiential truth relevant to the nature of experience. In short, the Descartes example lends considerable plausibility to the ignorance hypothesis and so to the epistemic view in general. We may put the point slightly differently by saying that reflection on the machine argument makes it plausible to suppose that we are in the position of the moths from chapter 4. The moths illustrate the possibility of intermediate-level ignorance—namely, ignorance of a type of truth that is determined by the basic truths but that is not itself basic. If the historical assumptions of our discussion are correct, Descartes was in an analogous position. The kind of computational truths that are relevant to linguistic understanding but of which he was ignorant are precisely the truths that supervene on basic physics rather than being a part of basic physics. Ignorance of these computational truths is intermediate-level ignorance. Of course, to say that Descartes suffered intermediate-level ignorance is not to deny that he suffered basic-level ignorance, too. Descartes held a physical theory that did not survive the seventeenth century, so in that sense he was ignorant of various elements or basic facts of the world. However, the problems of Cartesian physics are irrelevant to the present discussion. Suppose, contrary to fact, that Descartes’ physics were true. The fact remains that he could still have mounted the machine argument; moreover, he would still have been wrong for the same reason.

7.3.6. Are Inconceivability Arguments Less Plausible Than Conceivability Arguments? I have argued that reflection on the machine argument affords a moral for our own situation. Of course, this conclusion is reasonable only to the extent that the machine argument really is analogous to the conceivability

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argument. I will close my discussion of this example by briefly considering three ways in which the two situations may be thought not to be analogous. The first has to do with the difference between conceivability and inconceivability. I said earlier that because—as I am assuming—the machine argument fails, we require a diagnosis of how it fails. I then offered a counterpart of the ignorance hypothesis as part of such a diagnosis. But it might be objected that there is no need to appeal to ignorance to explain the failure of the machine argument. The argument fails (one might say) for the simple reason that it is an inconceivability argument and, more generally, that inconceivability arguments as such are much less plausible than conceivability arguments as such. After all, doesn’t an inconceivability argument proceed from a claim that something is not conceivable, and aren’t claims about what is not conceivable of less epistemic value than claims about what is? (Thanks to David Chalmers and Yujin Nagasawa for this objection.) However, the idea that inconceivability arguments as such are less persuasive than conceivability arguments as such rests on a failure to draw the distinction, which we drew earlier, between weak and strong inconceivability. As we saw, a proposition is weakly inconceivable just in case— roughly—it does not imaginatively appear to us to be possible, and a proposition is strongly inconceivable just it case it imaginatively appears to us to be impossible. It is certainly true that weak inconceivability arguments proceed from a claim that something is not conceivable; likewise, it is true that arguments based on weak inconceivability are as a class less persuasive than arguments based on strong conceivability. But this observation does not tell us much about the general contrast between conceivability and inconceivability. For one thing, not all inconceivability arguments are weak inconceivability arguments. Indeed, as I have been interpreting it, the machine argument is precisely an inconceivability argument that is not a weak inconceivability argument, i.e. because it is a strong inconceivability argument. Moreover, the crucial question is not whether weak inconceivability arguments are more or less plausible than strong conceivability arguments; the crucial questions are, first, whether weak inconceivability arguments are less plausible than weak conceivability arguments and, second, whether strong inconceivability arguments are less plausible than strong conceivability arguments. Once the issues are raised in this form, I think it is clear that they receive, or ought to receive, negative answers. In general, inconceivability arguments seem to be epistemologically on all fours with conceivability arguments: weak versions of both are less plausible than strong versions of both, but it is not the case that inconceivability arguments as such are less plausible than conceivability arguments as such. The fact that inconceivability is epistemologically on all fours with conceivability lends further weight to the point I mentioned at the outset of our discussion of the machine argument. As I noted, the mere fact that the machine argument is an inconceivability argument might suggest that any attempt to draw analogies is misguided; indeed, the objection that we are

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currently considering is in a sense a version of this point. However, as we have just seen, the similarities between inconceivability arguments and conceivability arguments are rather striking. So it seems perfectly reasonable to suppose that we might motivate the ignorance hypothesis in our own case by examining inconceivability arguments from the past.

7.3.7. The Performance Interpretation of the Argument The second way in which our current situation might be thought to be different from Descartes’ has to do with the distinction, also noted earlier, between the competence sense of speaking a language and the performance sense. If one interprets the argument he is advancing in the second way, it proceeds, not from M1 and M2, but rather from: M1* M2*

It is inconceivable that a mere machine should exhibit the performance capacity that typically accompanies language understanding. If this is inconceivable, it is impossible.

These premises entail that physicalism is false. If physicalism is true and we are mere machines, then, because we do in fact exhibit the performance capacity that typically accompanies language understanding, it is actual and so possible that mere machines exhibit this capacity. On the other hand, it might be objected that if the argument is interpreted in this second way, the analogy between our own situation and that of Descartes is weaker than my presentation suggests. Part of what makes the Discourse case important for us is, as I noted, that although contemporary discussions of physicalism and dualism have focused on phenomenal character, many earlier discussions focused on intellectual character. I introduced the machine argument as an example of one such discussion. On the other hand, if the machine argument is concerned merely with performance capacity, behavioral flexibility, or something of the sort, it is hard to see it as concerning intellectual character; indeed, it is hard to see it as concerning something psychological at all. Are the connections, then, more remote than I have let on? The answer is ‘no’ and for two reasons. First, even if it is true that the machine argument should be interpreted so that it proceeds from M1* and M2*, it doesn’t follow that the argument has nothing to do with competence. On the contrary, it seems quite reasonable to suppose that performance in the sense at issue is necessary for linguistic understanding, even if it is not sufficient. If that is so, the conclusion that no physical object can behave in the way that language users behave entails the further conclusion that no physical object can understand a language. In short, we arrive at a conclusion about competence and so about intellectual character regardless of whether we start from M1 and M2, on the one hand, or from M1* and M2* on the other. Second, and more important, even if we did adopt the position that Descartes was not in this argument interested in a psychological property,

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this would not alter the underlying point of our discussion. True, the analogy between the machine argument and the conceivability argument is closer if in both cases the focus is on a psychological property. But the analogy remains even if the focus is not on a psychological property; indeed, I will go on in a moment to discuss one such nonpsychological case. Even if the machine argument did not concern a psychological property— something that seems to me to be quite unlikely—it remains true that it is a modal argument undone by further knowledge and as such is a precedent for our current situation. It is this latter fact that is most important for us.

7.3.8. Contrasting Propositions The final potential failure of analogy between our situation and that of Descartes has to do with the fact that, in discussing the machine argument interpreted so that it concerned linguistic competence, it was possible to identify two propositions that might be at issue—a target proposition and a contrasting proposition—and to suggest that Descartes was guilty of confusing these two propositions. More particularly, it is possible to partition the physical truths into two groups, the behavioral truths and the nonbehavioral truths, and to suggest, in effect, that the mistake Descartes makes is to confuse the behavioral truths with all the truths. However, what is the contrasting proposition in the case of the conceivability argument? It is not clear in the case of the conceivability argument that we have anything that plays the role of the behavioral truths in our analysis of Descartes’ argument. Now in one sense it is not required for our position that we do identify a contrasting proposition. It is only necessary to produce a contrasting proposition if one thinks that the mistake at issue is the mistake of proposition confusion. Our account does not entail that this is our situation. On the other hand, it is also possible in our own case to identify a contrasting proposition, and doing so brings out a plausible aspect of our position. The point might be developed by noting the connection between the traditional problem of other minds and the sort of problem we are dealing with here. Whether or not we are skeptics about other minds, we should all agree with the modal premise that sets up that problem. This premise is something like this: no amount of perceptually available physical information, nor any functional or computational information that is known to follow along with it, can by itself entail information about experience. I take it that this sort of information is the relevant sort when it comes to the conceivability argument. What this sort of information does is provide a class of physical or nonexperiential truths that underdetermine the experiential truths. According to the ignorance hypothesis, these truths do not constitute all of the physical or nonexperiential truths. So it is to these truths that we must look in answering the problem of the contrasting proposition.

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7.4. Physics and Chemistry Its focus on phenomenal rather than intellectual character is one striking feature of contemporary discussion. Another is its focus on psychological properties in general, rather than on properties that, although not physical in any strict sense, are not psychological either, properties of a biological or chemical nature. This was not always the case. In the nineteenth and early twentieth centuries and in other periods as well, the chemical and biological properties of physical objects presented difficulties that were clearly interpreted as analogous to those presented by psychological properties. This fact raises the possibility that we can make progress on the question of phenomenal character by asking how analogous questions were resolved in the case of biological or chemical properties. A plausible answer, based on a chemical example, is that they were resolved by a gain in our knowledge.

7.5. The Chemical Argument C. D. Broad’s The Mind and Its Place in Nature (1925) is not a work in chemistry or physics; it is a work, like this one, in philosophy of mind. But Broad is greatly concerned with the analogy between questions in philosophy of mind and questions about chemistry and biology. In particular, he is concerned with the question of whether arguments against (what we would now call) physicalism in philosophy of mind are similar to or different from arguments of a similar nature drawn from biology and chemistry, or at least from philosophical reflection on these. His overall suggestion is that reflection on these parallel cases suggests a certain style of antiphysicalist view, which he calls ‘‘the emergentist view,’’ not only in the psychological case but also in the biological and chemical cases. In the case of chemistry, Broad offers the following example: Oxygen has certain properties and Hydrogen has certain other properties. They combine to form water, and the proportions in which they do this are fixed. Nothing that we know about Oxygen by itself or in its combinations with anything but Hydrogen would give us the least reason to suppose that it would combine with Hydrogen at all. Nothing that we know about Hydrogen by itself or in its combination with anything but Oxygen would give us the least reason to expect that it would combine with Oxygen at all. And most of the chemical and physical properties of water have no known connexion, either quantitative or qualitative with those of Oxygen and Hydrogen. Here we have a clear instance of a case where, so far as we can tell, the properties of a whole composed of two constituents could not have been predicted from a knowledge of the properties of those constituents taken separately, or from this combined with a knowledge of other wholes which contain these constituents. (1925, 63)

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Broad goes on to say that the example of water, and of chemical compounds generally, shows not only that knowledge of constituents is insufficient for knowledge of the whole: it shows us something further. It shows us that, if we want to know the chemical . . . properties of a . . . compound, such as silver chloride, it is absolutely necessary to study samples of that particular compound. (1925, 64) For Broad, then, it is possible to know all the mechanical truths and then learn by experience what the chemical truths are. And the conclusion he draws from this is that physicalism (‘‘mechanism’’) is false. More generally, it is reasonable to interpret Broad as advancing a knowledge argument akin to the argument set out in chapter 2. The modal premise of the argument is as follows: Ch1.

It is possible for a logically omniscient and conceptually sophisticated person to know all the nonchemical truths about the world and to learn on the basis of experience the chemical truths.

This modal premise suggests that physicalism is untrue, for as Broad construes it, physicalism about chemistry entails that someone who knew all the nonchemical truths of the world would be in a position to know all the truths, but this (he thinks) is palpably not the case.

7.5.1. The Chemical Argument and the Knowledge Argument Actually, that Broad’s chemical argument is a (version of a) knowledge argument is unsurprising. A few pages later, we find a passage that notoriously anticipates the knowledge argument in its modern Jacksonian form. In describing the mechanistic theory of chemistry, Broad asks us to imagine ‘‘a mathematical archangel’’—that is, a being who is logically omniscient and who knows all the mechanistic truths about various chemical compounds. If mechanism about chemistry were true, the archangel would know all the chemical truths—but Broad takes it as obvious that he would not know absolutely all the truths: Take any ordinary statement, such as we find in chemistry books; e.g. ‘‘Nitrogen and Hydrogen combine when an electric discharge is passed through a mixture of the two. The resulting compound contains three atoms of Hydrogen to one of Nitrogen; it is a gas readily soluble in water, and possessed of a pungent and characteristic smell.’’ If the mechanistic theory be true, the archangel could deduce from his knowledge of the microscopic structure of atoms all these facts but the last. He would know exactly what the microscopic structure of ammonia must be; but he would be totally unable to predict that a substance with this structure must smell as ammonia does when it gets

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into the human nose. The utmost that he could predict on this subject would be that certain changes would take place in the mucous membrane, the olfactory nerves and so on. But he could not possibly know that these changes would be accompanied by the appearance of a smell in general, or of the peculiar smell of ammonia in particular unless someone told him so or he had smelled it for himself. If the existence of the so-called secondary qualities, or the fact of their appearance, depends on the microscopic movements and arrangements of material particles which do not have these qualities themselves, then the laws of this dependence are certainly of the emergent type. (1925, 71–72) In saying that the mathematical archangel could know all the physical truths and yet not know the truths about secondary qualities or their appearance, Broad is endorsing a version of a knowledge argument in the sense of chapter 2. His premise is that it is possible for someone to know all the nonexperiential or physical truths and yet learn some experiential truths on the basis of experience. And the conclusion he draws from this premise is that physicalism (‘‘mechanism’’) is false.

7.5.2. Broad’s Emergentism It is clear that Broad thinks there is a knowledge argument against physicalism to be developed both in the case of chemistry and in the case of experience and the secondary qualities. But what is the emergentism that he wants to contrast with physicalism? He characterizes emergentism as commitment to two theses. First, on the emergentist view: the properties of silver-chloride are completely determined by those of silver and of chlorine; in the sense that whenever you have a whole composed of these two elements in certain proportions and relations you have something with the characteristic properties of silver-chloride, and that nothing has these properties except a whole composed in this way. (1925, 64) In the contemporary literature, this is often interpreted as a sort of supervenience thesis (e.g., Kim 1993). So the first thesis characteristic of emergentism (interpreted in the chemical case) is that the chemical supervenes on the physical. It is this thesis that marks emergentism off from a more radical doctrine, according to which chemical facts ‘‘do not depend in any way on differences of structure or components’’ (54). This view Broad thinks ‘‘foolish,’’ even though ‘‘it was for many years the orthodox view of chemical elements’’ (54). The other distinguishing feature of emergentism is the idea that the properties of a whole cannot be deduced even in theory from the properties of its constituents: ‘‘the law connecting the properties of silver-chloride with those of silver and of chlorine and with the structure of the compound is, so far as we know, an unique and ultimate law’’ (64–65).

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This combination of features—supervenience and the denial of deducibility—goes some way to clarifying emergentism, but Broad’s position nevertheless remains obscure. The problem is that these commitments do not uniquely determine a position—or at least do not when examined from the vantage point of the contemporary scene. In particular, two quite distinct contemporary views may reasonably be characterized in these terms. The first is the a posteriori entailment view that we will discuss in chapter 8. According to this view, the supervenience of the experiential on the nonexperiential is combined with the idea that the experiential conditional is known only a posteriori. The second view is the primitivist view that we will discuss in chapter 11. According to at least one version of primitivism, the facts reported by experiential truths are metaphysically distinct from the facts reported by nonexperiential truths, and yet it is also true that the experiential truths supervene on the nonexperiential truths. This is a distinctive kind of primitivism because it asserts rather than denies experiential supervenience. The distinction between the a posteriori entailment view and this version of primitivism is elusive, but the main difference concerns the notion of metaphysical distinctness. As we have seen, the primitivist view holds that the facts expressed by experiential truths are metaphysically distinct from the nonexperiential truths; on the other hand, the a posteriori entailment view denies this. In my view, Broad’s emergentism is best interpreted as this form of primitivism, and for two reasons: (a) To interpret him as holding a version of the a posteriori entailment view is to read back onto Broad Kripke’s distinction between what is necessary and what is a posteriori, and this is quite anachronistic. (b) Although he certainly talks about deducibility, it seems clear that Broad regards emergentism as being a metaphysically different view from mechanism or physicalism, but the a posteriori entailment view need not be metaphysically different from a form of physicalism. Even if Broad is properly interpreted as advancing this kind of primitivism, however, a number of interpretative issues remain for his position, which for our purposes it is sufficient to mention rather than discuss in detail. First, it is controversial whether his style of primitivism, and so emergentism itself, is coherent or not. Broad seems to be committed to the view that experiential facts supervene on, but are metaphysically distinct from, nonexperiential truths or facts. This puts him in conflict with the Humean idea that there are no necessary connections between distinct existences. Second, there is an issue in squaring the emergentist claim that the knowledge argument is sound with his claim that experiential truths report facts that are metaphysically distinct from, but necessarily connected to, those reported by nonexperiential truths. As I have been interpreting them, both KA and CA seek to establish a contingent relation between experiential and nonexperiential truths and so, presumably, between the facts reported by those truths. But if Broad interpreted the knowledge argument in this way, he could not say both that it is successful and that there is a necessary

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connection between those facts. The result is that the emergentist cannot be interpreting them in the same way; for him, they are arguments not about modality but about metaphysical distinctness. Whether that interpretation of the arguments is a reasonable one is another issue raised by emergentism.

7.5.3. The Mistake in the Argument We have so far set out the chemical argument, noted its parallel to other arguments, and defended an interpretation of Broad’s response to the argument. The point to be developed now is that, when we reflect on what is wrong with the chemical argument, we have a clear precedent for our current situation. Once again, my starting point is the assumption that the chemical argument is mistaken and that its conclusion is untrue. We have no reason to suppose that chemical behavior is at the end of the day a nonphysical matter. (Someone may disagree, but I will simply take it for granted in what follows.) Of course, to say that the chemical argument is unsound is not to say that it seemed unsound to its proponents; Broad presumably thought it sound at the time he wrote the The Mind and Its Place in Nature. So a consequence of my starting point is that here we have an unsound argument that (mistakenly) seemed sound to its proponent. Now, if the chemical argument is unsound, we need a plausible diagnosis of what has gone wrong with it. Again, in the light of our discussion from chapter 4, it is clear that such a diagnosis would take the form of asserting that Broad is making one of the standard mistakes. However, it is plausible to suppose that Broad is making one of the standard mistakes. First, the historical facts of the situation are (I assume again) relatively uncontroversial (here I follow McLaughlin 1992; see also Horgan 1993). Broad was operating at a time when the quantum mechanical theory of chemical bonding was unknown or at least undiscussed. As a consequence, he did not realize something that seems natural to us—namely, that chemical facts follow directly from physical facts. In short, a counterpart of our ignorance hypothesis was true of the proponent of the chemical argument: he was ignorant of a type of nonchemical truth relevant to the nature of the chemistry. Second, if this counterpart hypothesis is true in Broad’s case, it becomes immediately plausible to say he was making one of the standard mistakes. One possibility, for example, is that in the first premise of the chemical argument, what is claimed to be conceivable is only prima facie conceivable but is not conceivable, all things considered. Broad claims to find it conceivable that a logically omniscient and conceptually sophisticated person might know all the mechanical truths and not know the chemical truths. But this is only prima facie conceivable for him. On this view, Broad is guilty of one version of mode confusion, and the argument collapses.

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7.5.4. The Moral for Us The moral for our own position may now be summarized as follows: The intellectual predicament that confronts us when we think about the knowledge argument is similar in outline to the intellectual predicament that confronted Broad when he thought about the chemical argument. Just as the chemical argument was plausible to him, so the knowledge argument is plausible to us. Just as it is mistaken to follow the chemical argument to its conclusion, so it is mistaken to follow the knowledge argument to its conclusion. Finally, just as Broad was ignorant of a type of nonchemical truth relevant to the nature of chemistry, so, too, we are ignorant of a type of nonexperiential truth relevant to the nature of experience. In short, the Broad example lends considerable plausibility to the ignorance hypothesis and so to the epistemic view in general. We may put the point slightly differently by saying that reflection on the chemical argument makes it plausible to suppose that we are in the position of the slugs. If the historical assumptions of our discussion are correct, as I think they are, Broad was himself ignorant of a certain elemental or basiclevel feature of the world, and it was this ignorance that led him to formulate the chemical argument as he did. Of course, in saying that Broad was in the position of the slugs and that his case provides a precedent for our own position, I am not claiming outright that we are in the position of the slugs. The point can be put more cautiously as follows: Historical examples make it plausible to suppose that we are ignorant of a type of nonexperiential truth relevant to the nature of experience. The precise nature of this ignorance—in particular, whether it is ignorance of a basic- or intermediate-level sort—is left an open question, as of course it should be.

7.6. Conclusion At the conclusion of his famous discussion of emergentism, McLaughin (1992, 90) writes: ‘‘its rise was not due to ‘philosophical mistakes,’ nor its fall to the uncovering of such mistakes. . . . Advances in science, not philosophical criticism, led to the fall of British emergentism.’’ One might question McLaughlin’s apparent suggestion that Broad and others were not making philosophical mistakes. If you are committed, as Broad seemed to be, to the view that there are necessary connections between metaphysically distinct existences, you are at the very least committed to something fairly controversial. But McLaughlin’s more general idea—that in many cases it is an increase in knowledge that leads to the downfall of various philosophical problems—is surely undeniable. Indeed, in a sense we have taken McLaughlin’s conclusion about emergentism as a model for our own case. For in essence, our suggestion is that it is not philosophical mistakes that lead us to suppose that CA and KA are plausible.

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To put matters a bit differently, what I have been suggesting throughout this chapter is that reflection on the past makes the ignorance hypothesis plausible. Of course, the discussion is inevitably somewhat open-ended. This is not only because the historical examples are vastly more complex than my presentation would suggest but also because there are many other examples that merit examination. For example, one might examine Goethe’s criticism of the Newtonian view of light (see Churchland 1996, 369), one might examine Samuel Clark’s anticipation of Block’s Chinese Nation example (see Guzeldere 1997, 64), and one might examine further Tyndall’s views about the relation between physiology and thought that we considered briefly in chapter 5; there might also be other cases. All of these cases bear analogies to our current situation, and all of them might afford various morals. Rather than pursue the issues further, however, I want at this point to bring to a close the project begun at the beginning of chapter 5, the project of making plausible the ignorance hypothesis. For you now have before you both the basic shape of the epistemic view and my reasons for believing it. As we have seen, the epistemic view is the conjunction of two theses, E1 and E2: E1. E2.

If the ignorance hypothesis is true, the problem of experience is solved. The ignorance hypothesis is true.

My reason for E1 is that, if we are ignorant in the way that the ignorance hypothesis says, it is very plausible to suppose that we are making one of the standard mistakes in advancing CA and KA. My reason for believing E2 is not that I have a proof of its truth; it is the nature of the case that E2 cannot be proven true. It is rather that different lines of argument seem to converge on the ignorance hypothesis. It is also true that when we distinguish the ignorance hypothesis itself from a number of closely related hypotheses—for example, the chronic ignorance hypothesis and the categorical ignorance hypothesis—it becomes quite clear (at any rate, it becomes clear to me) that it is an extremely reasonable hypothesis to hold. Of course, none of this would amount to much if it could be maintained on other grounds that the epistemic view is false or misses the point, or anyhow that we had better assume that it is false or misses the point. So it is to the case against the view that I now turn.

8 Objections and Replies

8.1. Introduction Objections to the epistemic view may be divided into three classes. According to the first, the view is misguided: a correct understanding of the problem we are discussing will reveal that ignorance of the kind I am interested in is irrelevant to its philosophical nature, and so can be ignored. According to the second, the view has a number of side effects (in some cases pointed to by proponents of the view themselves) that make it unpalatable. According to the third, the view is unnecessary: although the view is or may be possible, the problems at hand can be solved in a different and less costly way. To evaluate the last class of objections, we need to consider the alternatives to the epistemic view, and this is my task in part III. So in this chapter I concentrate on the first two. In the course of responding to them, I will take the opportunity to expand on some aspects of the previous discussion.

8.2. The Nature of Philosophical Problems I said in the introduction that most philosophers suppose, at least implicitly, that ignorance is not relevant to the problem we are discussing. They hold, or at least could be brought to hold, that—in Wittgenstein’s famous phrase— ‘‘the problems are solved, not by giving new information, but by arranging what we have always known.’’ Construed as a generalization about the contemporary scene, at least the last part of this is an exaggeration. Philosophers

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these days don’t think we have always known the facts relevant to the problem of experience, but the general idea that we are at least currently in possession of all the relevant facts, or types of facts, is extremely influential. Frank Jackson (1998, 5), to take one example, says of what he calls serious metaphysics—of which the logical problem would be one instance—that it is ‘‘discriminatory at the same time as being complete or complete with respect to some subject matter.’’ Similarly, John Perry describes his approach by saying that ‘‘it won’t be physiological or neurological, nor even . . . very phenomenological. [It] will be logical, semantical and philosophical’’ (2001, 118). As I read it, the suggestion implicit in the remarks of Jackson and Perry is that, in an important sense, all the relevant facts are in; we just need to think through those facts. In other respects, of course, Wittgenstein, Jackson, and Perry are about as different from one another as one can imagine, but on this point they speak with a single voice, or so anyway it seems to me. In philosophical matters, or at least a large class of philosophical matters, it is the case, as Wittgenstein (1960, 6) also put it, that ‘‘all the facts that concern us lie open before us.’’ Now to say that philosophical problems persist even if all the relevant facts are in is—as I understand it—to say that they arise not from ignorance but from how we are thinking of the facts in question, or perhaps how we are thinking of how we are representing those facts in speech and thought; for short, it is to say that the problems have a conceptual rather than an epistemic origin. So if this Wittgenstein-inspired view is true of philosophical problems in general, it is true of the problem of experience in particular, and the epistemic view is mistaken. But why believe the Wittgenstein-inspired view? No doubt some philosophical problems conform to the general picture; for example, perhaps the problems about moral objectivity do. But the idea that all do—or all must, or all of a certain important class do or must—seems to be something of a dogma. What happens if we drop the dogma? For one thing, a more variegated conception of philosophical problems comes more clearly into view; perhaps there is nothing to say in general about what a philosophical problem is like. But another thing that happens is that we lose this first reason for supposing that the epistemic view is misguided. Of course, one might at this point consider arguments that philosophical problems in general must take this form. But I am not going to take matters in this direction. For one thing, I don’t know what these arguments would be. More important, proposals about what philosophical problems are like in general should be driven by proposals about what particular philosophical problems are like, not the other way around. So if the Wittgenstein-inspired view is true of the problem of experience, we must have an argument for it that focuses on considerations, not about philosophical problems in general, but about this problem in particular. And do we?

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8.3. The Master Argument The answer is we have not just a potential argument here, but many. Moreover, these arguments may be organized as so many ways of filling out a general master argument. The master argument may be expressed as follows: ‘‘Of course, we may be ignorant of many things, but we at least know (MA1) that any relevant nonexperiential or physical truth is likely to have factor X. Moreover, (MA2) the problem will reemerge whenever you contrast truths that exhibit factor X with experiential truths; that is, arguments that have the persuasive force of CA and KA can be mounted about the relation between experiential truths and truths that exhibit factor X. Conclusion: the issue about ignorance can be ignored from the point of view of the philosophical issues.’’ If this master argument can be filled out in a plausible way, we may conclude that ignorance has no essential role in the problem, and so it can be ignored at least for the purposes of discussion. However, can the argument be filled out in a plausible way? It is clear that some suggestions concerning factor X are nonstarters. For example, consider the suggestion that X is the property of being nonexperiential. This suggestion renders MA1 trivially true, but it also renders MA2 question begging in the context. For the dialectical situation we are in is this. A proponent of the epistemic view has proposed an explanation of why CA and KA have whatever persuasive force they have, an explanation that presents itself as independently plausible. According to this explanation, these arguments seem persuasive because we are ignorant of some type of physical or nonexperiential truths. In response to this, it is no good to simply assert that, if we knew all the physical or nonexperiential truths, we would face the problem anyway; that is just to deny the epistemic view without having any independent reason for doing so. In short, if the master argument is to be developed in a convincing way, it had better not be founded on the suggestion that factor X is nonexperiential. However, although this suggestion is no good, others have considerable initial appeal. In the next four sections, I will examine four such suggestions. In each case, I will suggest that any initial appeal is merely that.

8.4. Structure and Dynamics The first candidate for factor X involves an appeal to the notions of structure and dynamics. This version of the master argument—I will call it the structure and dynamics argument—proceeds as follows: ‘‘Of course we may be ignorant of many things, but we at least know (MA1-sc) that any nonexperiential truth concerns structure and dynamics and (MA2-sc) that the problem will reemerge whenever you contrast truths that concern structure and dynamics with experiential truths.’’

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The structure and dynamics argument is prominent in the work of David Chalmers. In a recent criticism of a version of the epistemic view, he writes: The basic problem [is this]. . . . First: Physical descriptions of the world characterize the world in terms of structure and dynamics. Second: from truths about structure and dynamics, one can only deduce further truths about structure and dynamics. And third: Truths about consciousness are not truths about structure and dynamics. (2002a, 258) In this passage, Chalmers is saying that truths about structure and dynamics do not entail experiential truths at all. Now, this is something that a proponent of a version of our master argument might say: if nonexperiential truths do not entail experiential truths at all, then no unknown nonexperiential truth can entail experiential truths a fortiori. But a proponent of the argument need not say this. For the purposes of this argument, the important point is not so much that no truth about structure and dynamics entails any experiential truth. The important point is the weaker one, that the entailment of experiential truths by truths about structure and dynamics is just as controversial as the entailment of experiential truths by nonexperiential truths. To assess this proposal, we need to know what the relevant notions of structure and dynamics are. In explaining what he means by ‘‘structure,’’ Chalmers writes: basic physical systems are characterized by their spatiotemporal properties, and by properties such as mass, charge, and quantum wavefunction state. These latter properties are ultimately defined in terms of spaces of states that have a certain abstract structure . . . such that the states play a certain causal role with respect to other states. (2002a, 258) In effect, then, a structural property is one of two things: (a) a spatiotemporal relation or (b) a property of playing a certain causal role—what philosophers often refer to as a dispositional property. Moreover, in explaining what he means by ‘‘dynamics,’’ he writes: the states of these systems can change over time in accord with dynamic principles defined over the relevant properties. (2002a, 258) So a dynamics of a physical system is just the way in which it changes its dispositions and relations over time. In short, in speaking of structure and dynamics, what Chalmers means is that physical truths concern the relational and dispositional properties of various processes, including the way these properties change over time. The fact that by ‘‘structure and dynamics’’ Chalmers means to be talking about dispositional and relational properties permits us to formulate a related version of the argument he is advancing. In this related version, the argument is that nonexperiential or physical truths concern relations and

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dispositions, and arguments of the persuasive force of KA or CA will reemerge whenever you contrast truths concerning relations and dispositions with experiential truths. In what follows, I will mainly concentrate on the argument in its ‘‘structure and dynamics’’ version, but I will also use the ‘‘relations and dispositions’’ formulation on occasion. So far as I can see, the same points will apply in either case. More generally, in talking about ‘‘structure and dynamics,’’ Chalmers is saying that the subject matter of nonexperiential or physical truths conforms to a particular ontological category. But this suggests that the basic argument here might take a variety of forms, depending on which ontological category is at issue. In fact, arguments of this general style are widespread in the history of philosophy of mind. In some cases, the emphasis is on the fact that experiential truths concern intrinsic properties, whereas nonexperiential truths concern extrinsic properties. In other cases, the emphasis is on the claim that experiential truths concern categorical properties, whereas nonexperiential truths concern noncategorical properties. What the relationship is between all of these different kinds of ontological claims is controversial: is an intrinsic property the same as a nonrelational property, for example, and is a categorical property the same as a nondispositional one? I will not be going into the various interpretations of these notions here. Instead, I will concentrate on the structure and dynamics version of the argument. If this argument is unsuccessful, as I think it is, then it is reasonable to assume that other versions of the argument are likewise unsuccessful.

8.4.1. Experiential Structure and Dynamics But why is the argument unsuccessful? We may start with the observation that the notions of structure and dynamics are extremely general; that is, they apply to any domain whatsoever. In principle at least, we may speak of the structure and dynamics of physical and chemical processes, biological processes, and social and political processes. Moreover, this is no accident. If by ‘‘structure and dynamics,’’ Chalmers meant something quite specific, it would be implausible to suppose, as the first premise of the structure and dynamics argument does suppose, that any nonexperiential truth, known or unknown, concerns those features. In short, the generality of the feature Chalmers is focusing on is essential to the success of his argument. Now, the fact that the core notions of the argument are very general, and essentially so, makes it likely that, just as there are physical, biological, and social structures and dynamics, there are also experiential structures and dynamics. Indeed, a moment’s reflection reveals that this is so. First, experiential relations: some experiences are more vivid than others, for example, and one’s experiences seem to be unified both at a time and over time in a phenomenologically distinctive way (see, e.g., Bayne and Chalmers 2003). Second, experiential dispositions: one might have a pain that is such

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as to get worse if one moves too quickly; it is a phenomenological truth about the pain that it is disposed to get worse. Third, experiential dynamics: experiences might change their relational and dispositional properties over time, and this, too, might be a phenomenological aspect of the experience. So it is an undeniable fact that there are experiential structures and dynamics. On the other hand, this fact causes a problem for the argument we are considering, for it is now not true, or at least not true in general, that the problem will reemerge whenever one contrasts truths concerning structure and dynamics with experiential truths. If Mary, for example, knows all the truths about structure and dynamics, she will certainly know some truths about experiences, for some truths about experiences are themselves truths about structure and dynamics. Similarly, it is quite impossible to imagine a case in which all the truths about structure and dynamics obtain and no truths about experience do, for some truths about experience are themselves truths about structure and dynamics. To put the point slightly more directly, when Chalmers says, in the passage I quoted first, that ‘‘truths about consciousness are not truths about structure and dynamics,’’ this is false if taken literally: some truths about consciousness are truths about structure and dynamics because consciousness itself has structural and dynamical features. How might a proponent of the structure and dynamics argument respond? I see two possibilities. First, it might be argued that although there certainly are experiential structures and dynamics, these structures and dynamics are different from nonexperiential structures and dynamics, and that as a result, the observation is irrelevant. Second, it might be argued that, although there are experiential truths that are structural and dynamical, there are also experiential truths that are neither structural nor dynamical and that the objection I have advanced says nothing about them. The remainder of my discussion of the structure and dynamics argument will be devoted to demonstrating that neither of these two rejoinders succeeds. If I am right, we may conclude that the argument fails.

8.4.2. Experiential Structure versus Physical Structure The point that there are experiential structures and dynamics is undeniable. Does Chalmers deny it? Of course not. He says: Conscious states have structure: there is both internal structure within a single complex conscious state, and there are patterns of similarity and differences between conscious states. (2002a, 260) On the other hand, he goes on to say that this is irrelevant: But this structure is distinctively phenomenal structure, quite different in kind from the spatiotemporal and formal structure present in physics. (2002a, 260)

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The suggestion here is that, although there are experiential truths that are dynamical and structural, and there are nonexperiential truths that are dynamical and structural, these classes of truths are nevertheless so different from each other that the basic problem will reemerge whenever the two are contrasted. More simply, truths about physical structure and dynamics do not entail truths about phenomenal structure and dynamics. At this point, however, it is reasonable to ask what the basis is for this last claim. Why is it the case that truths about physical structure and dynamics do not entail truths about phenomenal structure and dynamics? The answer to this question cannot have anything to do with the fact that physical truths concern structure and dynamics and experiential truths do not. It has been conceded for the moment that both concern structure and dynamics. So the fact that one concerns structure and dynamics and the other does not in principle cannot be the thing that differentiates them. So again, when Chalmers says that physical structure is completely different from, and so does not entail, phenomenal structure, what is the basis for that claim? In my view, there are only two responses that might be made to this question. First, one might say that physical truths don’t entail phenomenal truths because of the modal arguments CA and KA. These arguments, if successful, would tell us that experiential truths are not entailed by nonexperiential truths; a fortiori they would tell us that experiential truths about structure are not entailed by nonexperiential truths about structure. But of course, if this is the reason for supposing that physical truths are different from phenomenal truths, then it is—in the context—no reason at all. As we have seen, to appeal to the modal arguments in this context is to beg the question. Recall again the dialectical situation. The proponent of the epistemic view has advanced the suggestion that CA and KA seem persuasive only because of our ignorance; the critic says that these arguments can be reformulated in such away that ignorance is irrelevant. Now, if the reformulation concerns the notion of structure and dynamics, this point has some appeal. On the other hand, if the reformulation amounts only to the assertion that the problems would reemerge even if we were not ignorant, then we have no reformulation here at all, and the objection collapses. More generally, if the difference is supposed to concern structure and dynamics, then it is not a difference; if the difference is supposed to concern being experiential, then the claim begs the question in the context. Second, one might respond that I have misread what Chalmers says about structure and dynamics. I am interpreting him as proposing that the subject matter of nonexperiential or physical truths conforms to a certain sort of ontological description; that is, it concerns dispositional and relational properties of various systems and how those dispositional and relational properties change over time. One might suggest that this puts the emphasis on the wrong place. Perhaps the emphasis should not be on the abstract ontology but rather on something tied more specifically to physics.

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In one of the passages quoted here, for example, Chalmers talks of ‘‘properties such as mass, charge, and quantum wavefunction state.’’ Perhaps, then, what he has in mind in talking about physical structures are properties of this quite specific sort? However, construed as a suggestion about how to fill out the master argument, this is quite implausible. It is true that if this is what is intended by ‘‘physical structures,’’ the second premise of the structure and dynamics argument—MA2-sd—is true, for truths about mass, charge, and quantum wavefunctions are such as to raise the problem of experience. However, the first premise of the argument—MA1-sd—is now false and palpably so. It is no longer clear that any sort of nonexperiential truths will concern structure and dynamics in the intended sense. Chemical or biological or social truths, for example, do not concern mass charge and quantum wavefunction state, and yet these truths are presumably entailed by physical truths. Indeed, the problem here is a variation on the problem we began with: it is quite crucial to the success of the structure and dynamics argument that the relevant notions are completely general. But if Chalmers means by ‘‘structure and dynamics’’ something like mass, charge, and quantum wavefunction state, his argument will not be general enough.

8.4.3. Intrinsic Properties So much, then, for the first way of responding to the objection that the notions of structure and dynamics apply as much to experience as to anything else—the suggestion that nonexperiential structures are different from experiential structures. What of the second way? The second way of responding points out that, although there certainly are experiential structures (i.e., experiential relations and dispositions), it is also true that there are features of experience that are nonrelational and nondispositional. Chalmers himself uses the word ‘‘intrinsic’’ as a label for these features, and we shall follow him in this. So another way to state this suggestion is this: ‘‘Of course we may be ignorant of many things, but we at least know that any nonexperiential truth concerns structure and dynamics, and because some experiential truths do not concern structure and dynamics and instead concern intrinsic properties, the problem will reemerge in that form.’’ To assess this suggestion, we need to ask, first, whether experiential truths do in fact concern intrinsic properties and, second, whether it matters that they do. The next two sections take up these questions.

8.4.4. Do Experiential Truths Concern Intrinsic Properties? It is clear that experiential truths concern some properties of experiences; for example, they concern the phenomenal character of experiences. So if

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the phenomenal character of an experience were an intrinsic property of that experience, it would be true that experiential truths concern an intrinsic property. But of course, this is correct only if phenomenal character is an intrinsic feature—and is it? One might think it is if by ‘‘intrinsic property of experience’’ one meant an essential feature of the experience. On this interpretation, the claim might be true. We noted in chapter 1 that phenomenal character is an essential feature of experiences in general; one might develop this by saying that its phenomenal character is an essential feature of a particular experience. However, while one might say this, it is also irrelevant. The crucial question is not whether its phenomenal character is intrinsic to an experience in the sense of being essential to it; the crucial question is whether its phenomenal character is intrinsic to an experience in the sense of being a nonrelational (or nondispositional) feature of it, and that is a completely different matter (see Humberstone 1996). Now the usual reason for supposing that phenomenal character is an intrinsic property in this sense is that reflection on our experience suggests that it is. Suppose I have an experience of a blue expanse before me. Isn’t it just obvious that my experience has some sort of quality, and isn’t it obvious that this quality is intrinsic to it? However, the answer to this question is ‘‘no, it is not obvious at all’’—and the reason is the so-called diaphanousness of experience, which we noted in chapter 1 and then again in chapter 6 (see also Harman 1990). When one has an experience as of a blue expanse, it is likely that one is confronted with a property that is intrinsic—namely, the blue of the expanse. But although that property is an intrinsic (nonrelational, nondispositional) property of the expanse, it is not a property of the experience. The expanse is not the experience but something that is represented by the experience. More particularly, from the true premise that, in having an experience, one represents an object as having an intrinsic property, the conclusion that experience itself instantiates an intrinsic property does not follow. Is there a way in which one could strengthen the premise or add to it in such a way that the conclusion does follow? So far as I know, there is only one suggestion in the literature about how to proceed from premise to conclusion here, and this is due to Sellars 1962. Sellars’s suggestion is that the way in which we understand the phenomenal character of an experience is, as he says ‘‘via an analogy’’ with the blueness of an object. Actually, the talk of analogy here is somewhat misleading; what Sellars intends, I take it, is that it is constitutive of the notion of the phenomenal character that we think of it on the model of the color of physical objects. The suggestion here is a parallel to Sellars’s notorious claim about thought and language—namely, that we understand thought ‘‘via an analogy’’ with language. In both cases, it is constitutive of various aspects of our psychology that they are understood on the model of external objects of one or another kind.

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Now, if the analogy suggested by Sellars holds, we do, indeed, seem to have a phenomenological argument for the idea that phenomenal character is an intrinsic property of experiences. If the colors of physical objects are intrinsic properties of those objects, and if we understand the phenomenal character of experience by analogy with colors, then phenomenal character is an intrinsic feature, too. But in fact it is quite unclear that the analogy does hold. One way to demonstrate this is to notice that being colored is not an essential feature of physical objects in general; even expanses of water might have been invisible, for example, and so might have lacked color (see Johnston 1992). So if we take the analogy seriously, the phenomenal character of experience should be likewise inessential. But as we have seen this is false; phenomenal character is essential to experience. Hence, we know that the analogy fails in respect of whether phenomenal character is essential. Why, then, should it not fail in respect of whether phenomenal character is intrinsic? Of course, in suggesting that phenomenology doesn’t decide the issue of the intrinsicness of phenomenal character, I am not insisting that it is not intrinsic. The point, rather, is that the phenomenological considerations leave the issue open: if someone wanted to deny that phenomenal character is intrinsic, they would not be making any phenomenological mistake. So our conclusion is that we have no reason to believe the thesis that the phenomenal character is a nonrelational or intrinsic feature of experience.

8.4.5. Why Does Intrinsicness Matter? In any case—and in fact this is the more important point—why should it matter? Suppose we agree that the phenomenal character of an experience is an intrinsic property of an experience, in the sense that it is a nonrelational or nondispositional property of that experience. How is it supposed to follow that the problem of experience will reemerge whenever you contrast experiential truths with truths about structure and dynamics? As I understand it, the reason it is supposed to follow is, as Chalmers says, that ‘‘from truths about structure and dynamics, one can only deduce further truths about structure and dynamics.’’ If it is true that from structural (relational, dispositional) truths one can only deduce further structural (relational, dispositional) truths, then the structure and dynamics argument may be resuscitated. In particular, if phenomenal truths at least sometimes concern intrinsic features, if nonexperiential truths never do, and if nothing that does not concern an intrinsic feature entails anything that does, then any claim to ignorance is beside the point. However, the problem with this development of the argument is that it is hard to see why its central claim is true. Suppose we call the thesis that from truths about structure, one can only deduce further truths about structure the from-structure-only-structure thesis. The simplest way to see

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that the from-structure-only-structure thesis is false is to note that one can derive the instantiation of an intrinsic property from a relational one just by shifting what thing you are talking about. For example, being a husband is a relational property of Jack Spratt, and being a wife is a relational property of his wife. But being married is an intrinsic property of the pair (or the sum) of Jack Spratt and his wife. To take a different example, it seems plausible to say that I have the property of having a hand intrinsically, but my having this property obviously follows from a relation between my hand and the rest of my body, and that the truth concerning this is a relational truth. If any of these examples are successful, the from-structure-only-structure thesis is not true. Why does it seem true to its proponents? My hypothesis is that it seems true only because it has been confused with a much more cautious thesis. The cautious thesis is that the full story about the relational properties of a thing will not entail the full story about the intrinsic properties of that very thing; for short, the relational profile of x does not entail the intrinsic profile of x. But from this, the from-structure-only-structure thesis does not follow. It remains possible that the full story about the relational properties of a set of things x1, x2, . . . x3 does, entail the full story about the intrinsic property of a further thing y. Indeed, it is precisely this sort of case that the examples we just considered exploit. On the other hand, the more cautious thesis will not help a proponent of the structure and dynamics argument, even assuming that phenomenal character is an intrinsic property of experience. Anyone who is attracted to experiential supervenience in the first place is likely to suppose that experiences themselves are complex items in some sense built out of more primitive items. (My thanks to Karen Bennett, Andy Egan, and L. A. Paul for discussion on these issues.) In sum, the from-structure-only-structure thesis is false, and no weaker thesis will have the effect that the structure and dynamics argument requires. What might a proponent of the argument say at this point? What they will say, I think, is that although in some cases relational truths entail intrinsic truths, the case at hand is not one of those cases, for here we are comparing experiential intrinsic truths with nonexperiential relational truths. But, again, in response to this suggestion we are entitled to ask why this is supposed to be so. The answer to this question cannot have anything to do with the from-structure-only-structure thesis, for, as we have seen, this is not true. So the answer must have something to do with the nature of the experiential: the experiential and the nonexperiential are so different that nonexperiential relational truths don’t entail experiential intrinsic truths. However, at this point, the proponent of the structure and dynamics argument seems simply to be asserting that any nonexperiential truth is such as to the raise the problem. But as we have already noted, although that assertion certainly contradicts the epistemic view, we have been given no reason to make it.

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8.4.6. Conclusion The response I have offered to the structure and dynamics argument is complex, but the basic idea is simple. The basic idea is that the notions of structure and dynamics (relational, dispositional, intrinsic, etc.) are very general, and so it can’t be these that distinguish the experiential from the nonexperiential. Nor do these taken alone constitute any bar to the experiential being entailed by the nonexperiential. On the other hand, if we go on to ask why there should be a bar to such an entailment, or why such an entailment should be controversial, the only answer that seems to be forthcoming is that the first truths are experiential and the second are not. But this claim amounts in the context only to a denial of the epistemic view; it does not amount to a reason for that denial. A final point: in criticizing Chalmers’s argument, I have nowhere objected to his claim that physical truths concern structure and dynamics. But he himself notes that one might do this and, moreover, that the result of doing so is a version of the epistemic view that in chapter 6 I called the Russellian version of the epistemic view. So if the structure and dynamics argument were not faulted on other grounds, it would provide a further reason to adopt the Russellian view, and we would need to revisit our discussion of that view. But I have suggested that it is to be faulted on other grounds, and so no revisiting is necessary.

8.5. Objectivity The second candidate for factor X emerges from an appeal to the notion of objectivity. This version of the master argument—I will call it the objectivity argument—proceeds as follows: ‘‘Of course we may be ignorant of many things, but we at least know (MA1-o) that any nonexperiential truth is objective and (MA2-o) that the problem will reemerge whenever you contrast truths that are objective with experiential truths.’’ This line of argument is prominent in Thomas Nagel. A feature of Nagel’s work over many years has been the idea, to put it in slogan form, that physical truths are objective truths (1974, 1986, 2002): ‘‘whatever else may be said of the physical, it has to be objective’’ (1974, 527 n. 15). The correlative concepts of objectivity and subjectivity can obviously be spelled out in a number of ways, but the dominant one for Nagel, or so it seems to me, is an idea about understanding. A subjective truth is one that can be understood only from a single point of view, and an objective truth is one that is not subjective. Of course, this explanation of the subjective-objective contrast leaves the notion of a point of view unexplained. But I take it that what Nagel has in mind is that sometimes understanding a truth depends largely on quite specific facts about what sort of psychological resources are available to one and what sort of circumstances one finds oneself in; in contrast,

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sometimes understanding a truth does not depend—at least not to the same extent—on those specific sorts of fact. As he (1986, 5) notes, the contrast here is really a matter of degree and so, too, is objectivity itself on this account, but we can set aside this aspect of the issue in what follows. If we assume, therefore, a notion of objectivity that is explained in terms of a point of view, we have the objectivity argument. How plausible is the argument? Its first premise—that any nonexperiential truth is objective— certainly is plausible. Nonexperiential truths, or at least nonexperiential truths of the kind we are interested in, do indeed seem to be the sort of truth that one could understand from a number of points of view; that is, understanding them does not depend on specific facts about the psychological capacities and circumstances of particular creatures. Likewise, experiential truths are subjective in Nagel’s sense. To understand such truths, one would have to take up a point of view; that is, one would either have had a certain experience or else be in the sort of cognitive state that people are in when they have had such experiences. So the first premise of the argument is plausible; what of the second? The second premise of the argument is that the problems at hand will reemerge whenever you contrast experiential truths with objective truths. We may bring out the line of thought in favor of this premise by introducing a famous example into the discussion: Nagel’s bat. Nagel (1974) observes that in view of the difference between bats and us—that is, between the point of view of a bat and our own point of view—we will never know what it is like to be a bat. On the other hand, there seems to be no problem in principle in our coming to know any or all of the objective truths about a bat. These points together add up to a claim I will call Nagel’s thesis. According to Nagel’s thesis, even if I learned every objective truth about bats, I would not thereby know every truth about bats. The reason is there are some subjective truths specifying what it is like to be a bat that I do not even understand, because I cannot take up the relevant point of view; on the other hand, if I cannot understand them, I cannot know that they are true. Now, with Nagel’s thesis before us, the step to the second premise of the objectivity argument—that the problems will reemerge whenever you contrast experiential and objective truths—looks very short indeed. On the one hand, the truth or falsity of Nagel’s thesis is independent of what anybody in fact knows. Suppose we point out to Nagel that we don’t know some of the objective truths about bats; perhaps we tell him that the scientific description of bats is in its infancy, that we should not be too optimistic about our epistemic position, and so on and so forth. Nagel’s response, I think, would and should be: true but irrelevant. His basic point is that, in view of the obvious difference between bats and us, we don’t know what it is like to be a bat. This point is unaffected by the true (or, at any rate, plausible) claim that we are ignorant of some of the objective facts about bats.

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On the other hand, although Nagel’s thesis is independent of what anybody in fact knows, it also seems to lie at the heart of the two arguments we have been focusing on, CA and KA. It is natural to suppose that if Nagel’s thesis is true, there will be (in Kripke’s phrase) an appearance of contingency in the relation between the objective truths about bats and the subjective truths about them—that is, the truths, whatever they are, that state what it is like to be a bat. And both CA and KA may reasonably be construed as different attempts to make that appearance of contingency explicit. But then it seems the problem will reemerge if you contrast experiential and objective truths, just as the second premise of the argument (MA2-o) says. For if Nagel’s thesis is independent of what anybody in fact knows, and if Nagel’s thesis is at the heart of the CA and KA, the problem presented by these arguments will persist whether we are ignorant in the relevant sense or not. As Nagel himself puts it at one point, ‘‘if the facts of experience— facts about what it is like for the experiencing organism—are accessible only from one point of view, then it is a mystery how the true character of experiences could be revealed in the physical operation of that organism’’ (1974, 522). In my view, it is difficult to underestimate the influence of the objectivity argument on contemporary philosophy of mind. There are echoes of it in Lewis’s point about the target of the knowledge argument we considered in chapter 3, there are echoes of it in McGinn’s argument for cognitive closure we considered in chapter 5, and it is present also in the claims about phenomenal concepts that we will consider in chapters 9 and 10. For present purposes, however, I will concentrate, not on these further connections, but simply on the fact that here we have a version of the master argument in which both premises seem compelling and whose conclusion is inconsistent with our position. Should we abandon the epistemic view in the face of it? I think not: although the considerations in favor of the second premise of the objectivity argument seem compelling on the surface, this impression collapses on closer inspection.

8.5.1. The Structure of the Crucial Reasoning The second premise of the objectivity argument is MA2-o: The problem will reemerge whenever you contrast truths that are objective with experiential truths. Now, as we have noted a number of times, in the formulations we have adopted, both CA and KA focus on the experiential conditional—that is, the conditional ‘‘if N then E,’’ where N is a statement summarizing the complete nonexperiential facts of the world and E is a statement summarizing the experiential facts. In the light of this conditional, the crucial reasoning in favor of MA2-o proceeds in three stages. At the first stage, it is asserted that, where N is objective and E is subjective:

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(1) Even if you were to know N, you would still not thereby know E. It is should be clear that (1) is simply Nagel’s thesis generalized from the bat example and adapted to our own theoretical framework. At the second stage, it is inferred from (1) that: (2) Even if you were to know N, there would still appear to you to be an element of contingency in the relation between N and E. Of course, (2) is not claiming that even if you were to know N, there would be still be an element of contingency in the relation between N and E. The appearance of contingency might, for all (2) says, be illusory. But what (2) does suggest is that the appearance of contingency is not going to be made to go away if somehow our ignorance of the relevant facts were removed. To put it differently, according to (2), the appearance of contingency survives, or would survive, the acquisition of knowledge. On the other hand, this appearance of contingency is precisely what is at issue in CA and KA, and this rather straightforwardly yields a conclusion that is tantamount to MA2-o: (3) Even if you were to know N, it would still be possible to formulate versions of CA and KA that have the persuasive power of the original arguments. According to this conclusion, our ignorance of N is irrelevant to the philosophical nature of the argument, and the epistemic view is mistaken. In short, the argument for MA2-o moves from (1) to (2) and then finally to (3), and (3) just is (MA2-o). How do we respond? One possibility is to deny (1) and by implication Nagel’s thesis as well. However, on reflection, this denial is quite implausible. In fact, given the assumptions that N is objective and E is subjective, (1) is not only true, it is analytic. For consider: to say that N is objective is to say that it is understandable from more than one point of view, and to say that E is subjective is to say that it is understandable from at most one point of view. Suppose now I come to know N and so understand it. Obviously, I do so from some point of view or other. However, because I can come to know E and so understand it from only one point of view, it is always possible that the point of view I adopted to understand N is not the one required of me to know or understand E. But this is just to say that if N is objective and E subjective, the mere fact that I know and so understand N does not entail that I know and so understand E, and this is precisely what (1) says. So there is no possibility at all of denying (1). However, even if there is no possibility of denying (1), it remains possible that the reasoning I have just set out for MA2-o fails for a different reason. And this is what I will argue. In my view, the reasoning for the second premise of the objectivity argument fails because the inference from (1) to (2) is illegitimate. It is certainly the case that even if I were to know N, I would still not thereby know E. But it does not follow from this that if

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I were to know N, there would appear to me to be an element of contingency in the relation between N and E.

8.5.2. Counterexample To illustrate the failure of the inference from (1) to (2), consider first a statement such as (4): (4) John is in pain. It is clear that (4) is subjective in Nagel’s sense if anything is. Now consider a negation of (4), namely (5): (5) John is not in pain. Because (5) contains the same constituents as (4) and (4) is subjective, then so, too, is (5). But now consider the conditional (6): (6) If John is a number, then he is not in pain. It is clear that (6) is a necessary truth; in fact, one might say that John’s being a number entails that he is not in pain. On the other hand, the antecedent of (6)—namely, (7)—is quite clearly an objective truth, by Nagel’s lights: (7) John is a number. In short, what we have in (6) is an example in which an objective truth entails a subjective truth. But now let us consider the following inference, which is designed to mimic the one from (1) to (2): (8) Even if I were to know that John is a number, I would not thereby know that he is not in pain. (9) Even if I were to know that John is a number, there would still appear to me to be an element of contingency in the relation between John’s being a number and his not being in pain. Any inference from (8) to (9) is invalid, for (8) is true and (9) is false. If I knew that John is a number, I would not thereby know that he is not in pain. The reason is that I may come to know that John is a number and still not have taken up the point of view required to understand the claim that he is not in pain; that is, I may not understand what pain is. So it is true, as (8) says, that merely knowing that John is a number does not put me in a position to know he is not in pain. On the other hand, (9) is false. It is false that if I were to know that John is a number, it would appear to me that there is an element of contingency in the relation between John’s being a number and John’s not being in pain. On the contrary, in this particular case there is no element of contingency at all, and no appearance of one. In sum, the inference from (8) to (9) is a failure; moreover, because that inference parallels the one from (1) to (2), the inference from (1) to (2) must be a failure as well.

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It might be objected that (6) is linguistically strange or odd or objectionable in some way. If you think this, you may substitute for (6) a statement like: (6*) If John does not exist, then he is not in pain. (I am indebted to Eric Lormand here.) There is nothing analytically odd or questionable about (6*), and yet it is clear that here we have an objective truth entailing a subjective one. Alternatively, it might be objected that (5) is not subjective—why should the negation of a subjective statement be itself subjective? However, to say this is to forget that, as Nagel (1986, p. 4) says, ‘‘objectivity is a method of understanding.’’ In talking in this context about subjective and objective, we are talking about what it takes to understand certain statements and their constituents. On the other hand, if some statements or constituents of statements meet a condition of understanding, then so do compound statements formulated from these constituents. To understand a compound statement, you must understand each of its constituents.

8.5.3. Diagnosis The reasoning behind MA2-o—that is, the second premise of the objectivity argument—proceeds from (1) to (2), and then to (3): (1) Even if you were to know N, you would still not thereby know E. (2) Even if you were to know N, there would still appear to you to be an element of contingency in the relation between N and E. (3) Even if you were to know N, it would still be possible to formulate versions of CA and KA that have the persuasive power of the original arguments. My objection to this reasoning is not that (1) is false—in the relevant sense, (1) is analytic—but rather that the step from (1) to (2) is illegitimate. If this step is illegitimate, the reasoning for MA2-o collapses, and the version of the master argument we are considering—the objectivity argument— fails. But at this point one might reasonably ask for a response to the argument that does not proceed by counterexample. Perhaps the material I have introduced shows that something is wrong here—but what exactly? My answer is that there is confusion in the objectivity argument between two closely related properties that a conditional can have. (For further discussion of this distinction using different terminology, see Stoljar 2005b.) One property that a conditional of the form ‘‘If A then B’’ can have is that it is necessary, where: (10) ‘‘If A then B’’ is necessary if and only if in every possible world in which A is true, B is true—for short, if and only if A entails B.

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Another property that a conditional can have is that it is—as I will put it— synthesizable, where: (11) ‘‘If A then B’’ is synthesizable if and only if in every possible world in which S understands A, then S understands (or is in a position to understand) B—for short, if and only if understanding A entails understanding B. Clearly, synthesizability is not necessity; these are distinct properties. In particular, a conditional that fails to be synthesizable may for all that still be necessary. To illustrate, consider (12–14): (12) If x is rectangular, then x has some property or other. (13) If x is colored, then x is extended. (14) If x is red, then x is not green. It is obvious that (12)—to concentrate on it, though parallel points apply in the other cases, too—is necessary if true. In every possible world in which x is rectangular, x has some property or other. But (12) is not synthesizable. To understand the consequent of (12), one would need to have the ontological concept of a property, as well as the concepts involved in quantification over properties. To understand its antecedent, on the other hand, one needs to have only the concept of a rectangle. But possessing the concept of a rectangle is not at all sufficient for possessing the concept of a property. A different example in which failure of synthesizability is not failure of necessity is one we have already met: (6) If John is a number, then he is not in pain. As we noted before, (6) is necessary: that John is a number entails that he is not in pain. Yet (6) is not synthesizable: (6) is a conditional whose antecedent entails its consequent, and yet understanding its antecedent does not entail understanding its consequent. Having distinguished synthesizability from necessity, we are now in a position to explain why the reasoning from (1) to (2)—and so the objectivity argument itself—fails. Consider (1) again: (1) Even if you were to know N, you would still not thereby know E. The reason that (1) is true is that the experiential conditional is (in the terminology we have introduced) not synthesizable, or at any rate is not synthesizable on the assumption—which we are making—that N is objective and E is subjective. If N is objective and E is subjective, then understanding N does not entail understanding E. And this is just to say that ‘‘if N then E’’ is not synthesizable. However, once it is appreciated that (1) is true because the experiential conditional is not synthesizable, it becomes quite obvious that (1) does not entail (2):

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(2) Even if you were to know N, there would still appear to you to be an element of contingency in the relation between N and E. On the intended interpretation, what (2) says is that regardless of what you know, it will appear to you that the relation between N and E is not necessary. But, in view of the difference between the two properties, it is clearly a fallacy to suppose that because something is not synthesizable, it will therefore appear to you to be not necessary. We might put the point more generally by drawing a distinction between two ways in which the experiential conditional might appear to be contingent. First, there might be an appearance or impression of contingency in the relation between understanding N, on the one hand, and understanding E on the other; second, there might be an appearance or impression of contingency in the relation between N and E themselves. What the objectivity argument shows quite conclusively is that, if N is objective and E is subjective, no matter what we learn, there will always be an appearance of contingency in the relation between understanding N and understanding E. The reason for this is quite straightforward: the relation between understanding N and understanding E is in fact contingent; that is, understanding N does not entail understanding E where the first is objective and the second subjective. Because the relation between understanding N and understanding E is in fact contingent, it is not surprising that it appears so. However, from the fact that there is an appearance of contingency in the relation between understanding N and understanding E, it does not follow that there is also an appearance of contingency in the relation between N and E—and it is, of course, this that needs to be shown if the epistemic view is to be challenged. As our distinction between necessity and synthesizability shows, a conditional can fail to be synthesizable and yet not fail to be necessary; a fortiori, a conditional can appear not to be synthesizable while both being necessary and appearing so.

8.5.4. Replies and Rejoinders The proponent of the objectivity argument says that while we might be ignorant of many things, we know that any nonexperiential truth is objective and that the problems will reemerge whenever you contrast experiential truths with objective ones. If this argument is persuasive, the problem of experience does not have an epistemic origin, and our position is mistaken. But my suggestion has been that it is not persuasive, for we have been given no reason to suppose that the problems will reemerge whenever you contrast experiential truths with objective ones. As I understand matters, to say that the problems will reemerge is to say that if N is objective and E is subjective, then the experiential conditional would appear contingent, even if the kind of ignorance I am interested in were taken away. But this has not been

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shown. What has been shown is that if N is objective and E subjective, the experiential conditional would appear nonsynthesizable, even if the kind of ignorance I am interested in were taken away. But this is an entirely different matter. How might a proponent of the objectivity argument respond to this criticism? First, it might be objected that if the experiential conditional appears not to be synthesizable—that is, if it appears that understanding N does not entail understanding E—then it will likewise appear to not be necessary— that is, it will appear that N does not entail E. However, our examples show conclusively that this is not the case. Take (13), for example: (13) If x is colored, then x is extended. (13) is clearly not synthesizable and so presumably appears not to be synthesizable. But it is not true that (13) appears contingent. On the contrary, it notoriously appears to be necessary. Again, in light of the distance between necessity and synthesizability, it is quite unclear that a conditional that lacks or appears to lack the first will lack or appear to lack the second. Second, it might be objected that even if the experiential conditional does not appear contingent because it appears nonsynthesizable, it might appear contingent for another reason; for example, it might appear contingent because of the modal arguments CA and KA, or perhaps because of the examples and thought experiments that prompt those arguments. However, this suggestion begs the question in the context. As we have already noted, the proponent of the epistemic view has suggested that the experiential conditional appears contingent only because of our ignorance or the relevant facts. The critic says that the appearance would persist even if the ignorance were taken away. If the appearance in question has something to do with objectivity, and so understanding, then the critic’s suggestion has some degree of plausibility. But if the claim is simply the bald one that the problems would persist even if the ignorance did not, all we have against the epistemic view is assertion and not argument. Third, it might be argued that, if the criticism of the objectivity argument that I have offered works at all, it works too well. What I have said naturally suggests a strategy for explaining away the appearance of contingency in the experiential conditional that is quite different from the strategy of the epistemic view. This alternative strategy begins by pointing out the two relations I have distinguished: first, the relation between understanding N and understanding E; second, the relation between N and E themselves. It then suggests that the second appears contingent only because it has been confused with the first, which is in fact contingent. However, this strategy of responding is a version of a position we will consider in chapters 9 and

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10, the phenomenal concept strategy. As I will argue there, the strategy is mistaken.

8.5.5. Conclusion As in the case of the structure and dynamics argument, my discussion of the objectivity argument has been complex. But again, the basic idea is simple. The basic idea is that the argument confuses the thesis that one truth entails or fails to entail another with the thesis that understanding one truth entails or fails to entail understanding another. And in fact, on reflection, it ought to be quite unsurprising that this is so. Once it is clearly appreciated that appeals to objectivity in contemporary philosophy of mind are appeals to ideas about what it is to understand various claims, it is hard to see how these ideas will play any role in explaining questions about the modal properties of those claims, which on their face have not much to do with understanding. We may summarize the situation by looking again at Nagel’s remark previously quoted that ‘‘if the facts of experience—facts about what it is like for the experiencing organism—are accessible only from one point of view, then it is a mystery how the true character of experiences could be revealed in the physical operation of that organism.’’ Nagel’s claim here is a conditional, and in the antecedent of the conditional, he is pointing out that the facts of experience are subjective (and presumably he means, too, that the nonexperiential or physical facts are objective). In the consequent of the conditional, he says that the relation between experience and the physical is a mystery; the clear implication of what he says is that the mystery in question has its source in the contrast between the subjective and the objective. If Nagel were right, the epistemic view is mistaken, for that view suggests that problem of experience has a quite distinct source. But I have argued that he is not right. The only mystery that would follow from the subjectivity of experience is that the phenomenal character of experience is not synthesizable from the physical nature of the world. But if this is a mystery at all—something that seems to be quite unlikely—it is plainly not the mystery we are discussing. The mystery we are discussing arises from the idea that the phenomenal character of experience is not necessitated by the physical facts. On that problem, the subjectivity of experience has no bearing. Only a confusion of necessity with synthesizability would lead you to suppose the opposite.

8.6. Perceptual Availability The third candidate for factor X is the suggestion is that it is—to put it vaguely at first—perceptual availability. This version of the master argument—I will call it the perceptual availability argument—proceeds as follows: ‘‘Of course, we may be ignorant of many things, but we at least know (MA1-pa) that any nonexperiential truth is perceptually available and (MA2-pa) that the

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problem will reemerge whenever you contrast perceptually available truths with experiential truths.’’ In fact, no contemporary philosopher that I am aware of has advanced the perceptual availability argument, at least not in this form. But it is certainly a natural line of thought to consider. To illustrate, take the Cartesian idea that matter is extension. Intuitively, extension is a perceptually available property. This is not to say that all instances of the property are such that we could detect them; some things are just too small or large for us to see. The point, rather, is that truths about extension are of a type that is perceptually available to us. On the other hand, it seems equally clear that truths about extension by themselves are not sufficient for experience or, indeed, for thought, just as Descartes argued. In effect, this version of the master argument takes the Cartesian equation of matter and extension as its exemplar and generalizes. However, although the perceptual availability argument is initially natural, it is not persuasive. For what does ‘‘perceptually available’’ mean? On the one hand, it might mean something like ‘‘available to perception in an unaided way.’’ Then MA2-pa is very plausible; that is, it is very plausible that no truth of the sort that is available to perception in an unaided way is likely to entail any experiential truth. Indeed, this is precisely what makes the problem of other minds a problem: it has its source precisely in the idea that no truth about a person of the sort that we might arrive at by direct perception is of a sort that entails experience. On the other hand, it is equally obvious that, on this interpretation, MA1-pa is false, and there are many nonexperiential truths that are not perceptually available. For example, truths concerning all manner of entities discovered by science, plus the truths about the causal relations and laws that they instantiate, are nonexperiential and yet not perceptually available to us, at any rate not available to our perceptual faculties in an unaided way. Someone might dispute particular examples here. Some philosophers suppose that causation is perceptually available; others deny the reality of theoretical entities; still others say that experiences are the subject of direct perceptual observation. But regardless of the analysis of particular examples, I think we have a very general reason to deny MA1-pa in the sense we are considering. To suppose it true is to suppose a version of the rationalist position considered briefly in chapter 5. Rationalism, as we considered it there, is the claim that the world has a nature, at least in its nonexperiential aspects, that is understandable by us, that is available to our cognitive faculties. Here the claim is not only that the world is such that it can be understood by us but also that the world is such that it can be seen by us— that is, available to our perceptual faculties. It seems quite obvious that many truths are not available in this sense. Of course, it is possible that ‘‘perceptually available’’ does not mean ‘‘available to perception in an unaided way.’’ Perhaps, instead, it means something like ‘‘can be known through inference from observation and

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experiment.’’ On this interpretation, MA1-pa might be true, but there is now no reason to believe MA2-pa, for it is plainly false that no truth of the sort we might infer through observation and experiment should entail an experiential truth. Suppose that, on the basis of close examination of your behavior, I form the belief that you are in pain, a belief that, as it happens, is true. This is a truth I come to know through inference from observation; on the other hand, it certainly entails an experiential truth—for it is one itself. Alternatively, perhaps ‘‘perceptually available’’ means something like ‘‘essentially perceptually available’’—that is, can be known only through inference from observation and experiment. (Brie Gertler made this suggestion.) This avoids the objection I just made; the claim that you are in pain is such that it can be known through inference from observation and experiment, but it is not such that it can be known only through inference from observation and experiment, for presumably you yourself may know it, but not through any such inference. However, adopting this suggestion means the argument fails for another reason. What the second premise of the argument—namely, MA2-pa—now says is that the problem will reemerge whenever one contrasts truths that are not essentially perceptually available with experiential truths, and the reason for this, of course, is that the problem will reemerge whenever one contrasts truths that are not essentially perceptually available with truths that are. However, the problem will not reemerge whenever one contrasts truths that are essentially perceptually available with truths that are not—or at any rate we have been given no reason to suppose so. To the extent that it is true of experiences that they are not essentially perceptually available, it is also true of other psychological events, such as judging or thinking, and also of psychological states such as believing or desiring. On the other hand, it is implausible that other events and states present exactly the same sort of problem as experiences: notoriously, a version of CA that substitutes thought or judgment for experience lacks any persuasive power. It might be objected that episodes of judgment have phenomenal character somewhat in the way that experiences do (see Pitt 2004). However, although this might be so, in my view it is not to the point in the present context. First, whatever is true of judgments, it remains implausible that beliefs have phenomenal character, if only because beliefs may persist despite loss of consciousness. But for many philosophers (e.g., Shoemaker 1996), beliefs are not essentially perceptually available in the sense we are intending. Second, that judgments have phenomenal character does not entail that the phenomenal character of judgments presents the same sort of problem as the phenomenal character of experiences. What it might suggest, instead, is that there are various kinds of phenomenal character. One sort is such as to motivate arguments like CA and KA; another sort is not. But if this is so, the problem of experience that we are considering cannot really have its source in the contrast between truths that are essentially perceptually available and those that aren’t. So the argument from perceptual availability collapses.

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8.7. Expressibility The final suggestion I want to consider is that factor X is expressibility in language. This version of the master argument—I will call it the expressibility argument—proceeds as follows: ‘‘Of course, we may be ignorant of many things, but we at least know (MA1-e) that any nonexperiential truth is expressible in language and (MA2-e) that the problem will reemerge whenever you contrast linguistically expressible truths with experiential truths.’’ Now, in the history of philosophy of mind, the idea that various aspects of experience are not expressible is a common one. However, the problem with it has always been that it is quite unclear what the language, relative to which experience is inexpressible, is supposed to be. One extreme possibility is that the language is—to adopt some terminology introduced by David Lewis (1986, p. 145)—Lagadonian, where a Lagadonian language is one in which objects are names for themselves and properties are predicates that express themselves. On this interpretation, however, while MA1-e looks to be plausible, there is no reason at all why MA2-e is true, for experiential truths themselves are presumably expressible in a Lagadonian language. No truth will be inexpressible in language if the language in question is Lagadonian. A different possibility is that the language in question is something with which we are very familiar—modern English, say. On this interpretation, it is quite unclear that either premise is true. In the first place, MA1-e now says that any nonexperiential truth is expressible in English, but, in view of the technical language required in most sciences, this is quite implausible. In the second place, MA2-e seems to presuppose that experiential truths are not expressible in modern English—a claim that is also unlikely, in light of the fact that philosophers of mind conduct their inquiries mostly in modern English and seem perfectly well able to convey (somehow!) the phenomenal character of experience to each other (see Thau 2002). Of course, one might attempt to escape these difficulties by articulating constraints on the language in question. For example, one might insist that the language in question be objective or that it concern only perceptually available properties or structural and dynamical properties. However, to say something like this is to reveal that the expressibility argument is really not an independent argument from the ones we have been discussing.

8.8. Naturalization The objections to the epistemic view I have considered so far are all attempts to show, at least with respect to the problem of experience, that the Wittgenstein-inspired view of the problem is right and, in consequence, that all the facts or types of facts that concern us lie open before us. As we have seen, philosophers who hold this view can usefully be viewed as advancing one or another version of the master argument set out in 8.3. But what I have

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argued is that no version of the argument is correct. If I am right, the idea that the epistemic view misconstrues the philosophical nature of the problem of experience is without foundation. I want now to close our discussion of this kind of objection by considering the idea that, properly understood, the problem of experience is an instance of what is sometimes called a naturalization problem. As I understand it, a naturalization problem starts by distinguishing the ordinary or commonsensical point of view on a certain subject matter from the scientific or theoretical point of view on the same subject matter, or what is intuitively the same subject matter. The problem assumes, reasonably, that the scientific point of view has some sort of epistemic authority with respect to how the subject matter should be conceptualized or explained, and the intellectual challenge presented by the problem is to see how much, if any, of the commonsense point of view can be accounted for or accommodated from within the scientific point of view, and if so, what form that account might take. A good example of such a problem is the question of what the relationship is between language as we ordinarily imagine it to be and language as modern linguistics imagines it to be. Ordinarily, we take language to be a social phenomenon—‘‘language is a social art,’’ as Quine (1960) famously put it. But contemporary linguistics is often interpreted as viewing language as determined by facts about individual speakers, as neither an art nor social (see, e.g., Chomsky 2000). The picture is roughly as follows: We are all born with a switch box in our heads, and possible settings on the switch box are the possible human languages. Learning a language is a matter of fixing a setting on the switch box—in fact, the ordinary talk of ‘‘learning’’ is highly misleading—but there is no easy inference from setting to outward expression. For example, from the ordinary point of view, it is true that George and Tony speak the same language, but from a theoretical point of view, this question is interpreted as the question of whether George’s switch box is in the same configuration as Tony’s—something that, given their vastly different experiences and histories, appears unlikely. There is much to say about problems of this sort in general, and about the language case in particular. But the important point for our purposes is that appealing to our ignorance with respect to the subject matter seems not to the point. In the naturalization problem about language, for example, the parameters of the problem are set by comparing the picture of language produced by modern linguistics with the ordinary picture, and it is not really relevant that modern linguistics might have a missing chapter. This is obviously not to say that modern linguistics does not have a missing chapter; obviously, it may. It is rather to say that the question of comparing language-as-linguisticsimagines-it and language-as-we-ordinarily-imagine-it generally presupposes, or presupposes for the purpose of discussion, that the two pictures are at least roughly complete in their own terms. In general, then, naturalization projects make the methodological, if not the factual, assumption that all the facts are in.

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It follows that if the experience problem is a naturalization problem, we may similarly assume full disclosure of the relevant facts. However, the response to this objection is straightforward: the problem of experience is not a naturalization problem in this sense. Naturalization projects are problems that arise at quite specific moments of scientific inquiry. They don’t emerge from the very general considerations that we began with in spelling out the problem of experience. They emerge, instead, from a much more specific consideration of what the scientific truths are likely to be in a certain domain. But it is not reasonable to suppose that in the case of experience we have attained any similar point of scientific inquiry. Of course, this is not to deny that we have attained this position in other cases— the case of language, say—and it is not to deny that we might attain it in the future in the case of experience. The point is rather that the problem we are concerned with, the logical problem, is not this sort of problem. It follows that there is no reason to suppose that the problem presupposes full disclosure of the relevant nonexperiential facts. It might be responded that either philosophical problems are naturalization problems or they are nothing. However, even though some philosophers seem to hold something like this, it is not my view. So far as I can see, the development of sciences like linguistics poses certain problems that are quite different in rhythm and structure from other problems. Many philosophical problems are not naturalization problems in this sense. Why, then, should the problem of experience be a naturalization problem?

8.9. Side Effects I have been concerned with the idea that a proper understanding of our problem rules out the epistemic view. I turn now to the second of the three kinds of objection distinguished at the beginning of the chapter—namely, that the epistemic view has a range of potential side effects that make it unpalatable. Some of these side effects have already been pointed out and discussed. For example, the epistemic view need not involve a claim about cognitive closure or about the intrinsic features of matter. In what follows, therefore, I will concentrate on different potential side effects, as well as on some other problems that are harder to classify. In addressing these objections, it is convenient to proceed in a ‘‘parry and riposte’’ style.

Objection 1 Isn’t the epistemic view just too quick and easy a response to a philosophical problem? Couldn’t one simply respond to any philosophical problem in this way, and—because this is implausible—doesn’t this suggest that there is something deeply implausible about your position? Put

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differently, the objection is that your account badly overgeneralizes and so should be rejected.

Reply Well, as we saw in chapter 5, there are various sorts of philosophical problems, and the epistemic view is plausible only for some of them. More generally, the fact that a certain solution is plausible in one case and not in another is a commonplace of philosophical discussion.

Objection 2 Your response to the previous objection doesn’t get to the heart of the issue. The worry about overgeneralization is not merely that the epistemic view would account for every philosophical issue; it is that it would account for every conceivability argument. For example, take the conceivability argument against behaviorism that you are so impressed by. A behaviorist might say in response that we are ignorant of a certain type of behavioral truth and that as a result those arguments fail. So, contrary to your own intentions, your position hands the behaviorist the tools to respond to the arguments against behaviorism. Putting it differently, your own account fails the condition of adequacy laid down in chapter 3.

Reply Behavioral truths are, and are intended by the behaviorist to be, truths that we can establish on the basis of direct perception: behavioral dispositions, or at any rate their manifestations, are supposed to be available to perception. That was the basic rationale of the behaviorist program. But it is very plausible that no truth of that sort will be of any help in thinking about the perfect actor objection. In essence, then, I think a version of the master argument we considered earlier is successful when we are thinking about behaviorism and not successful in our own case. The underlying reason for that is that behavioral truths are of a certain sort, and no truth of that sort will account for experiences.

Objection 3 Your response to the objection about behaviorism is inconsistent with other things you have said. For example, you emphasized that our ignorance might be of a level intermediate between psychology and basic physics. Why couldn’t a behaviorist say something similar? For example, he or she might say that we are ignorant of some type of truth that concerns a level intermediate between behavior and psychology. (I am indebted to Gideon Rosen and Josh Brown for this objection.)

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Reply Behaviorism was initially advanced as a translational doctrine. In view of that, it seems to be quite impossible that a behaviorist of any normal sort could take the line you propose. But I don’t deny that some sort of nonstandard behaviorism might be advanced in the way you suggest. Would such a view constitute a problem for me? I don’t think so, for two reasons. First, your initial objection was that the epistemic view would defeat any view. This is clearly not true, for standard behaviorists cannot avail themselves of the position, and so it is not true that the strategy is available to everyone. I am not claiming that the view might not be used in other cases, only that it cannot be used in every case. Second, it is not enough to say that it is possible that we might be ignorant in this way; you have to make it plausible that we are. There is no logical reason that I can think of why a behaviorist could not take the line you propose, but that doesn’t make it plausible that they could.

Objection 4 Aren’t you yourself saying that it is possible that we are ignorant? And wouldn’t this be enough to defeat any conceivability argument? In short, isn’t the epistemic view just a version of skepticism about modal reasoning in disguise?

Reply Of course, the mere possibility of ignorance is not enough to defeat a conceivability argument. But I am not saying that our ignorance is merely possible, and that is why the epistemic view is not committed to skepticism about modal reasoning (see chapter 3). What I am saying is that we have good, though not demonstrative, reasons for believing that we are in fact ignorant. And this means that we have good, though not demonstrative, reasons for believing that CA and KA fail.

Objection 5 Aren’t you saying that we need a new type of truth to account for experiential truths, and isn’t this just primitivism? Aren’t you just stretching the notion of the physical so that it may include primitive experiences?

Reply This suggestion rests on a misunderstanding of my position. As we noted earlier, there are positions that combine the idea that experience is irreducible with the further idea that the concept of the physical should be

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extended to them. As I understand it, this is Searle’s (1992) view. But this position is not ours. To see this, notice that Searle’s position is consistent with the falsity of the ignorance hypothesis; indeed, he accepts the traditional dualist conception of the situation and simply redescribes it in his own terms. One might object that he has hijacked the term ‘‘physical,’’ but as I don’t think that word plays any essential role in our discussion, I will set this aside. The crucial point for our purposes is that this view is very different from ours.

Objection 6 Aren’t you just saying that there must be some response to the logical problem and you don’t know what it is? Isn’t yours a ‘‘there must be a reply’’ reply (Braddon-Mitchell and Jackson 1996) or a version of ‘‘fingers-crossed’’ physicalism (Tye 1999)?

Reply There is certainly an element of this in our account. I am saying that we know that there is a mistake in the argument but we are not quite in a position to characterize precisely the nature of the mistake. However, this is not really what is meant by the ‘‘there must be a reply reply’’—at least as I understand matters. The crucial consideration is that I am saying something quite specific about what the source of the problem is. In my view, the mistake in these arguments is the presupposition that we are in possession of all the relevant physical or nonexperiential facts. But others think that the mistake is really elsewhere. To illustrate this, imagine a person who is convinced that the mistake in CA lies in some aspects of the special features of phenomenal concepts—say, in a feature of how they come to be possessed in normal cases. Such a person might also say that there is a mistake in CA, without saying exactly what the nature of the mistake is. But they would not on that ground be advancing a ‘‘there must be a reply reply.’’

Objection 7 Isn’t your view at the end of the day a wild speculation about the future course of science?

Reply Someone might defend the epistemic view by making a speculation about the future course of science, but this is no part of the position I am advancing. Given the incredible complexity of the institution of science, speculations about its future course are ill advised. The crucial thing for me is what to believe now, not what will happen in the future.

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Objection 8 Your response to the previous objection ignores the fact that philosophers who have advanced views like yours have made such speculations.

Reply That’s true, but much of this speculation seems to me to be separable from the epistemic view. I think it is reasonable to say that we are ignorant of a type of truth relevant to the nature of that experience. Whether that type of truth concerns basic physics (as Sellars 1962 seems to suggest) or intrinsic features of matter (Russell) or truths that are forever beyond our ken (McGinn) seems to me to be a further question on which we need take no stand.

Objection 9 Imagine I am trying to convince you that numbers are colored. When you point out to me that numbers don’t seem to be the sort of things that are colored, it is no good my saying that there are or might be numbers of which we are ignorant. Unknown numbers are still numbers, after all; hence our ignorance of some numbers is irrelevant to the assessment of my position.

Reply True, but not analogous to anything I have said. Our ignorance of numbers is irrelevant to whether they are colored because (a) no number is extended in space, but (b) everything colored is extended. In effect, reasoning analogous to that represented by the master argument considered earlier is plausible in this case. But as I have argued, no similar argument is plausible in the case of experience.

Objection 10 Your suggestion doesn’t solve anything and doesn’t advance the debate. How does it help to be told we are ignorant? It’s fair enough to be ignorant, but don’t pretend that being ignorant solves anything. At the very least, it is false advertising to be told that the epistemic view constitutes a solution to the problem of consciousness.

Reply Whether our account solves anything depends on what problem it is designed to solve. If one is mainly interested in the empirical problem, then obviously the ignorance hypothesis doesn’t solve the problem. But that isn’t what I am interested in, at least not in this book. What I am interested in is solving the

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philosophical problem that experience seems to be distinct from everything else. For that problem, ignorance is helpful. The crucial arguments that suggest that experience is distinct from everything else presuppose the ignorance hypothesis is false. If that hypothesis is true, as I think it is, the arguments collapse. It is in this sense that ignorance solves the problem.

Objection 11 I am not talking about the empirical problem, and I don’t deny that what you have said undermines some arguments against experiential supervenience. But doesn’t a philosophical approach to consciousness need to tell us something positive?

Reply The demand for a positive account betrays a certain understanding of what the problem consists in. When philosophers ask for a positive account, they often have in mind a positive account of how we conceive of experience or how we conceive of our thought and talk about experience. The implicit suggestion here is that CA and KA go wrong precisely because they operate with the wrong picture or theory of experience or our talk and thought about experience. In the next part of our discussion, I will argue this is quite implausible; in my view, experiential truths are not conceptually distinctive (apart from their subject matter). For the moment, let me simply point out that if our issue is ‘‘What, if anything, is wrong with the reasoning illustrated by CA and KA?’’ it is a substantial proposal that what is wrong is a mistaken view either of experience or of our thought and talk about experience. That might be the case, but it need not be. What might be wrong instead is that we are ignorant of the relevant facts.

8.10. Conclusion We are now in a position to summarize the main points of part II. At the start of chapter 4, I undertook to explain and defend both parts of the epistemic view. This I have now done. In chapter 4, I argued that if the ignorance hypothesis is true, the logical problem is solved. In chapters 5–7, I defended the plausibility, and so the truth, of the ignorance hypothesis. And then in this chapter, I considered various objections to the epistemic view. Of course, it might be said that I have so far neglected to answer the most serious objection to our account. The most serious objection is not that our position is impossible; it is that it is unnecessary. That is, although there is no inconsistency or implausibility in the epistemic view, the view is not needed because it is possible to solve the problem without postulating a lack of knowledge on our part. In the rest of our discussion, I argue there is no alternative.

PART III THE ALTERNATIVES

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9 A Posteriori Entailment

9.1. Introduction In the introduction, we distinguished four alternatives to the epistemic view: eliminativism, primitivism, the a priori entailment view, and the a posteriori entailment view. Eliminativists reject T1, the thesis that there are experiential truths. Primitivists reject T2, the thesis that if there are experiential truths, those truths are entailed by nonexperiential truths. And both the a posteriori entailment view and the a priori entailment view reject T3, the thesis that if there are experiential truths, those truths are not entailed by nonexperiential truths. The aim of part III is to argue that these views either are less plausible than the epistemic view or else do not represent genuine alternatives.

9.2. A Framework for Discussion We may begin by drawing a distinction between eliminativism and primitivism, on the one hand, and a priori entailment and a posteriori entailment on the other. The eliminativist and primitivist views are clearly distinct from the epistemic view, at least as we have been developing it here. As against eliminativism, the epistemic view accepts T1; as against primitivism, it accepts T2. Again, the epistemic view denies that the arguments for T3 are successful in any sense, whereas the primitivist accepts them, and the eliminativist accepts them, modulo the condition that there are experiences, a condition then denied by eliminativism. However, although the contrast with primitivism and eliminativism is clear enough, the contrast with a priori and a posteriori entailment is more 175

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elusive. To illustrate, let us look more closely at the difference between a priori entailment and a posteriori entailment. This emerges from a consideration of the experiential conditional introduced in chapter 2: the truthfunctional conditional whose antecedent summarizes the physical truths and whose consequent summarizes the phenomenal truths. We saw that if experiential supervenience is true, the experiential conditional is necessary. Both the a posteriori and a priori entailment views agree that the conditional is necessary; the difference is that the first says it is a posteriori, and the second says it is a priori. However, if this is the difference between the a priori and a posteriori entailment views, the relation between them and the epistemic view is puzzling. Presumably, either the experiential conditional is a priori or it is not, and presumably not being a priori is just being a posteriori. Therefore, it is a logical truth that either the experiential conditional is a priori or it is a posteriori. But then in turn it is a logical truth that if the experiential conditional is necessary, it is either a priori or a posteriori. So it looks as if, in differentiating themselves from these two views, proponents of the epistemic view are forced into denying a logical truth! How, then, can the epistemic view represent any alternative? To solve the puzzle, we need to distinguish two questions.



What, if anything, is the mistake in the arguments for T3? Is the experiential conditional a priori or a posteriori?

The difference between a posteriori and a priori entailment focuses our attention on the second of these questions, but the epistemic view focuses our attention on the first. It says that what has gone wrong in these arguments is that we have presupposed full knowledge of the relevant facts or types of facts. So, to clarify the contrast between the epistemic view and the a posteriori and a priori entailment views, we need to ask, first, what the a posteriori and a priori entailment views say about the first question and, second, what the epistemic view says about the second. I am going to postpone discussion of what our view says about the epistemic status of the experiential conditional until the end of this chapter. For the moment, let us concentrate on the first issue. What, then, do the a posteriori entailment and a priori entailment views say about the first question? I think the correct answer to this question is ‘‘nothing.’’ Taken alone, the idea that the experiential conditional has or does not have a certain epistemic status does not tell us what, if anything, is wrong with the arguments for T3. Of course, this is not to deny that people who hold these views have made proposals about how to answer this question; they have. But in making these proposals, they have supplied material that is, strictly speaking, separate from the views themselves. For example, it is common for the proponent of the a priori entailment view to say that, in reflecting on these arguments, we haven’t really thought the cases through. When we think the cases through, they say, we will see that the cases either are badly described or else contain a hidden contradiction or

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both. Later we will consider the plausibility of this idea in some detail. For the moment, the thing to notice is that, plausible or not, this suggestion does not follow from the claim that the experiential conditional is a priori. It is something extra, something that a proponent of the a priori entailment view may or may not agree to. What other factor may be introduced to answer the argument? There are a number of possibilities here, but the salient one for our purposes is the epistemic view. There is no inconsistency in the package that includes a priori entailment and the epistemic view; it is simply not the typical package. The typical package combines the a priori entailment view and the idea that we have not thought things through. Similarly, it is common for a proponent of the a posteriori entailment view to say that when we think about these arguments, we have neglected to take into consideration the special features of phenomenal concepts. Later we will consider the plausibility of this idea in some detail. But for the moment the thing to notice is that, plausible or not, this suggestion does not follow from the claim that the experiential conditional is a posteriori. It is something extra, and something the proponent of a posteriori entailment may or may not agree to. What other factor may be introduced to answer the argument? As before, there are a number of possibilities here, but the salient one for our purposes is the epistemic view. There is no inconsistency in the package that includes the a posteriori entailment view and the epistemic view; it is simply not the typical package. The typical package—or at least a typical package—combines a posteriori entailment with an appeal to the distinctive features of phenomenal concepts. The fact that the a posteriori and a priori entailment views do not on their own answer the arguments for T3 is important when it comes to the assessment of the epistemic view. What it suggests is that in criticizing these views, we are not required to argue that they are false. All we need to argue is that the most plausible versions of the positions are indistinguishable from versions of the epistemic view. In the light of this, our discussion in part III may be organized as follows. In this chapter, I will discuss a posteriori entailment. I will argue that this view alone does not answer the arguments and that when we go on to consider ways in which the view might be amplified or added to, the result is something that is either implausible or indistinguishable from the epistemic view. In chapter 10, I advance a parallel argument in the case of a priori entailment. And then in the final chapter—chapter 11—I discuss our genuine rivals, primitivism and eliminativism, and summarize the overall discussion.

9.3. Kripke on Heat and Pain I have said that the a posteriori entailment view does not on its own answer the arguments for T3. But for some this will be a surprise. Isn’t it just obvious that this idea answers the arguments? I think this is not obvious at all and

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that the best way to illustrate this is to look again at Kripke’s (1980) seminal discussion in Naming and Necessity.

9.3.1. Kripke’s Overall Position In lectures I and II of Naming and Necessity, Kripke set out and defended, among other things, the notion of a necessary a posteriori truth. A truth is a priori just in case one can come to know or justifiably believe it independently of experience, and a truth is necessary just in case it is true at all possible worlds. Traditionally, it was assumed that these two features are coextensive: all and only a priori truths are necessary. But what Kripke and others showed is that it is possible to have a truth that is both necessary and a posteriori. (It was also argued, more controversially, that it is possible to have truths that are contingent and yet a priori; we will set aside this idea in what follows.) One example he gave is the identity statement ‘‘heat ¼ molecular motion.’’ This statement, according to Kripke, is true at all possible worlds (or, at any rate, at all possible worlds at which heat exists), and yet it is also a posteriori in the sense that one could not come to know or justifiably believe it independently of experience. Of course, any example is controversial, and this one is no different. But it greatly simplifies matters if we have an example of a necessary a posteriori truth before us, and so in what follows I will simply agree with Kripke that ‘‘heat ¼ molecular motion’’ is a necessary a posteriori truth. In lecture III, Kripke went on to consider—again, among other things— the application of this idea to philosophy of mind and, in particular, to (what we would call) the conceivability argument. You might have expected him to defend the a posteriori entailment view and say that the notion of a necessary and a posteriori truth is going to have a major impact on CA. In fact, the reverse is true. Instead, what Kripke argued is that the notion of the necessary a posteriori cannot be exploited to answer this argument. From our point of view, this suggests that an examination of Kripke’s position on this issue will yield the result that the a posteriori entailment view will not on its own answer the conceivability argument. What, then, was Kripke’s argument? In the following, I will present a statement of his argument that, while faithful to his main ideas, is nevertheless adjusted to connect more easily with our discussion.

9.3.2. The Pain Argument and the Heat Argument We may begin by considering two arguments I will call ‘‘the pain argument’’ and ‘‘the heat argument.’’ The pain argument proceeds from the premises (1) and (2): (1) It is conceivable that there are c-fibers firing in me, and I am not in pain.

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(2) If this is conceivable, then it is possible. If these two premises are true, the following conditional—I will call it ‘‘the pain conditional’’—is at best contingent: (3) If there are c-fibers firing in me, then I am in pain. So far as the a posteriori entailment view is concerned, (3) is a stand-in for the experiential conditional, and the pain argument is simply a more specific version of the conceivability argument. In short, for the a posteriori entailment view, in the pain argument we have the problem of experience in microcosm. Why is the pain argument only a microcosm as far as the a posteriori entailment view is concerned? Why isn’t it a microcosm tout court? The answer is that, whatever one’s views about the experiential conditional, it is surely plausible that the pain conditional is a posteriori; hence, if is necessarily true, it is a necessary and a posteriori truth. But then, for the proponent of a priori entailment view, there is the following difference between the pain conditional and the experiential conditional: the first is a posteriori; the second isn’t. The reason for the difference, roughly, is that the experiential conditional implicitly contains vastly more nonexperiential truths in its antecedent than the pain conditional. On the other hand, for the proponent of a posteriori entailment, this difference does not affect the a posteriori nature of the conditionals, and the two conditionals are epistemologically on all fours. So, when I say that the pain argument is the problem of experience in microcosm, this is, strictly speaking, true only from the vantage point of the a posteriori entailment view. Of course, because it is the a posteriori entailment view that I am talking about in this chapter, this simplification does no harm. Turning now to the heat argument, the premises of this argument are (4) and (5): (4) It is conceivable that there is molecular motion in the poker and there is no heat in the poker. (5) If this is conceivable, then it is possible. If these two premises are true, then the following conditional—I will call it ‘‘the heat conditional’’—is at best contingent: (6) If there is molecular motion in the poker, then there is heat in the poker. It should be obvious that the heat argument is in structure identical to the pain argument. It should be equally obvious, at least given our assumptions, that the heat argument is unsound, for we are assuming, with Kripke, that ‘‘heat ¼ molecular motion’’ is a necessary truth. However, if ‘‘heat ¼ molecular motion’’ is necessary, (6) is necessary. But if (6) is necessary, there must be something wrong with any argument that seems to show that it is contingent.

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We are now in a position to introduce the a posteriori entailment view in something like the form that Kripke discusses it. A proponent of this view advances the following argument: P1. The heat argument is unsound. P2. The heat argument is analogous to the pain argument. C. Therefore, the pain argument is unsound. The significance of this argument, of course, is that the pain argument is simply a version of the conceivability argument. So, if the pain argument is analogous to the heat argument, and if the heat argument is unsound, we have a very good reason for rejecting the conceivability argument. Of course, this line of reasoning would not show in itself that the knowledge argument is unsound, and so the idea would undercut only one of the arguments for T3. But it is natural to imagine an extension of the argument that would apply to KA. After all, it is natural to assume that, just as we can construct a conceivability argument for both heat and pain, we could also construct a knowledge argument for both. In any case, for the purposes of this chapter I am going to assume that what we say about the conceivability argument would apply to the knowledge argument, too.

9.3.3. Kripke’s Rejection of the Analogy So that is the basic suggestion of the a posteriori entailment view; what is Kripke’s objection? Kripke agrees that the heat argument is fallacious, but he thinks that this has no implications for the pain argument. The reason is that when we identify the mistake in the heat argument, we find that that mistake (or an analogous mistake) could not possibly be the mistake in the pain argument. So Kripke’s view is that P2 is false: there is no relevant analogy between the pain argument and the heat argument. What is the mistake in the heat argument? Well, as we saw in chapter 4, when something goes wrong in a modal argument, it is often because the proponents of that argument are guilty of proposition confusion; that is, they have confused the proposition that is mainly at issue in the argument— the target proposition—with a contrasting proposition that is in the context unobjectionable. In the case of the heat argument, Kripke says, this sort of response is plausible. Here the target proposition is (7) and the contrasting proposition is (8): (7) There is molecular motion in the poker, and there is no heat in the poker. (8) There is molecular motion in the poker, and there is nothing in the poker that produces heat sensations. The heat argument threatens to show that (7) is possible, and if (7) is possible, (6) is contingent. But according to Kripke, (7) is necessary and could not possibly be imagined to be contingent. What is possible is rather (8)—that is,

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it is possible that the poker has molecular motion in it but this fact doesn’t produce heat sensations in me. (Perhaps I am physically different in that world and something else—pistachio ice cream, for example—is the only thing that produces heat sensations.) But in the context (8) is unobjectionable, for the possibility of (8) does not entail that (6) is contingent. In short, says Kripke, the proponent of the argument has confused (7) for (8) and is therefore guilty of proposition confusion. So much for the mistake in the heat argument—what Kripke now argues is that if we attempt to tell the same story in the case of the pain argument, we confront a major difficulty. If we try to tell a story about pain that parallels the story about heat, we would inevitably arrive at the suggestion that the proponent of the pain argument has conflated the following two propositions: (9) There are c-fibers firing in me, and there is no pain in me. (10) There are c-fibers firing in me, and there is nothing in me that causes pain sensations. But the problem here is that it is quite unclear what (10) says. On one view, saying ‘‘there is nothing in me that causes pain sensations’’ is just a longwinded way of denying that I am in pain. But then (10) is just a long-winded way of saying (9), and there is no possibility that (10) is contingent while (9) is necessary. In other words, (10) is just as objectionable as (9), and so there is no point in advancing the idea that the proponent of the argument has conflated them. On another view, saying ‘‘there is nothing in me that causes pain sensations’’ might simply be a way of ruling out any internal cause of my pain. Then what (10) says is that there are c-fibers in me, and so I am in pain, but nothing in me causes it. But from this, the natural conclusion is that something outside of me causes pain sensations—tight shoes, for example. Understood this way, (10) is clearly modally distinct from (9). It is surely a contingent fact that nothing in me causes my pain. But there is also no possibility of its being confused with (9). On this interpretation, (10) concerns the causes of pain, whereas (9) concerns what pain is. It is hard to see how a proponent of the pain argument would have confused one for the other. What explains the fact that it is impossible to duplicate the story about heat when one turns to pain? For Kripke, the difference is explained by a more basic difference between heat and pain. In the case of heat, we may distinguish between heat and sensations of heat. In the case of pain, no such distinction is possible. Moreover, in the case of heat, there is a genuine contingency in the connection between heat and sensations of heat. This genuine contingency can be confused for the apparent contingency in the connection between heat and molecular motion. But in the case of pain there is no contingency at all in the connection between pain and sensations of pain; this connection is just identity. Conclusion: if there is no genuine

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contingency here, it cannot be confused with any apparent contingency between pain and c-fibers firing.

9.3.4. The Situation So Far The proponent of a posteriori entailment offers the suggestion that the pain argument is analogous to the heat argument and is therefore mistaken. Kripke responds that there is no analogy. Hence his conclusion concerning the a posteriori entailment view is the negative one that the view does not answer the pain argument. It might be objected that Kripke’s conclusion is not simply a negative one about a posteriori entailment; rather, it is a negative one about physicalism or experiential supervenience in general. However, only a cursory reading of what Kripke says suggests he is an antiphysicalist or primitivist. His official conclusion is that the issue is ‘‘wide open and extremely confusing’’ (1980, 155). This is very far from a primitivist position; primitivists on the contrary tend to think of the issue as open and shut. Moreover, whatever Kripke’s own views, he evidently does present a line of argument against the a posteriori entailment view, and it is this line of argument that we are currently assessing. It might also be objected that Kripke’s conclusion is of limited value to us. As we noted previously, our main objective is to show, not that a posteriori entailment is false, but rather two things: first, that unless it is supplemented with further material, the a posteriori entailment view has no answer to the conceivability argument and, second, that the most plausible candidate for this further material is provided by some version of the epistemic view. How can what Kripke says help us secure this objective? The answer is that what his discussion shows is a version of the first point. It is an assumption of his discussion that what has gone wrong in the heat argument is not simply that the heat conditional is necessary and a posteriori. What has gone wrong is explained by the additional fact that the proponent of the argument is guilty of proposition confusion. It is this additional fact that seems to be unavailable in the case of the pain argument. So what Kripke shows is that the most obvious way—or, anyway, an obvious way— of developing the a posteriori entailment view so that it may answer the pain argument is unsuccessful. He does not show that there is no way to do so at all.

9.3.5. Moving Forward So far we have been following in Kripke’s footsteps. Suppose now we ask how the argument might be developed further. In particular, how is the a posteriori entailment theorist who wishes to circumvent Kripke’s objection to proceed at this point? There would appear to be four options:

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(i) Deny the difference between pain and heat: if, contrary to what Kripke says, pain and heat are on all fours, parity between the pain argument and the heat argument would be restored. (ii) Find a different way to implement the proposition confusion strategy: Kripke makes a persuasive case that (9) is not being confused with (10). But it doesn’t follow that (9) is not being confused with anything; maybe we can identify another proposition with which (9) is being confused. (iii) Find a strategy of response to the pain argument that is different from the proposition confusion strategy. The idea of proposition confusion seems to be one compelling way of defeating a conceivability argument, but it is not the only way. So perhaps there are other ways of defeating a conceivability argument that Kripke does not consider. (iv) Reject outright the demand that the a posteriori entailment view must provide an answer to the pain argument. It is an assumption of Kripke’s discussion that both the pain argument and the heat argument are prima facie compelling and thus that we need to answer them. Perhaps this concedes too much to the arguments. Perhaps the real lesson of the necessary a posteriori is that these arguments are much less compelling than they appear. I want now to consider these options in turn. My suggestion will be that each option is either implausible on its own terms or else collapses into the epistemic view. If I am right, we may conclude that the a posteriori entailment view offers no solution to the logical problem that is both distinctive and plausible.

9.4. Parity Restored? The first option of the four just distinguished was this: ‘‘Deny the difference between pain and heat: if, contrary to what Kripke says, pain and heat are on all fours, parity between the pain argument and the heat argument would be restored.’’ Initially, this option looks hopeless. Surely Kripke is right that heat is distinct from heat sensations and that pain is not likewise distinct from pain sensations. But then surely he is right that heat and pain are disanalogous. But there is more to be said on this issue. Suppose we agree that there is no distinguishing pain and sensations of pain. It obviously remains true that on occasion we come to know that we are in pain and, because these are equivalent, come to know that we are having sensations of pain. How do we come to know this? Well, let us first ask how we come to know—as we obviously also do on occasion—that various objects (pokers, for example) are hot. The answer—at least in the usual case—is that we come to know that a poker is hot by noticing that it produces sensations of heat and by

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inferring on this basis that the poker is hot. In the case of heat, in other words, we tell a story that commits us to what Kripke calls a psychological ‘‘intermediary’’—that is, a sensation of heat that stands between hot pokers and us. But consider now the suggestion that we come to know that we are in pain in an analogous way—that is, in virtue of a psychological intermediary that stands between our pains and us. There is nothing in our review of Kripke’s position so far that rules out this possibility. In particular, the point that there is no distinction between pain and sensations of pain does not rule it out. All it rules out is the identification of any supposed intermediary with a sensation of pain. It does not rule out the existence of such an intermediary in the first place. Now, if Kripke’s point about heat and pain does not rule out the possibility of a psychological intermediary between us and our pains, it likewise does not rule out the possibility that the first option of the four listed might be resuscitated. ‘‘True enough,’’ you might argue, ‘‘heat and pain are not analogous insofar as one can distinguish heat from heat sensations and no parallel distinction is available in the case of pain. But heat and pain are nevertheless analogous insofar as we come to know about both in virtue of an intermediary. Moreover, this analogy may be exploited to answer the pain argument, as follows: There is a genuine contingency in the relation between heat and the psychological intermediary in virtue of which we find out about heat. This genuine contingency can be mistaken for an apparent contingency in the relation between heat and molecular motion. In a parallel fashion, there is a genuine contingency in the relation between pain and the psychological intermediary in virtue of which we find out about pain. This genuine contingency can be mistaken for an apparent contingency in the relation between pain and c-fibers firing.’’ Of course, the cogency of this move depends on how friendly we are to the possibility that psychological intermediaries are involved in our coming to know that we are in pain. And some positions in philosophy of mind—in particular, those influenced by perceptual or observational models of selfknowledge or introspection—might well be open to this possibility. On the other hand, there seem also to be a number of reasons for ruling out this possibility. In my view, the most interesting one derives from the idea, which we noted in chapter 1, that experience is apparently self-presenting— that is, that if one is in pain, one is thereby in a position to know that one is in pain (see Shoemaker 1996). Self-presentation in this sense is inconsistent with the postulation of intermediaries. What it suggests is that, at least on occasion, we come to know that we are in pain, not by having some inner psychological appearance that one is in pain, but simply by being in pain. But this means that there need be no intermediary. On the other hand, if there is no psychological intermediary at all, there is a fortiori no contingency in the relation between it and one’s pain. It might be replied that this argument against psychological intermediaries ignores the fact that self-presentation is itself controversial. Timothy

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Williamson (2000), for example, has notoriously argued that there might be cases in which a particular experience is so faint that you cannot reliably tell whether you have it or not. If so, although it is true that you are having the experience, it is not true that you are in a position to know that you are. Williamson’s discussion of this point raises a number of epistemological issues we cannot take up here. However, even if successful, I don’t think what Williamson says affects the substance of our position. In the first place, even if Williamson’s argument is successful against self-presentation, it is harmless against a related idea—namely, that if one is in extreme pain, one is in a position to know that one is in pain. To avoid the problem Williamson raises, we could simply adopt the policy of assuming that, throughout our discussion of Kripke, talk of pain should be interpreted as talk of extreme or definite pain. So far as I can see, nothing else would need to change. (I am indebted to Andy Egan for this point.) In the second place, Williamson himself is as hostile to the idea of a psychological intermediary as is any proponent of self-presentation; to that extent, then, it is unlikely that his discussion is going to recommend itself to a friend of the observational model of introspection. Alternatively, it might be replied that my emphasis on psychological intermediaries is misleading. Suppose there is an intermediary of any sort between my pain and me—a causal or nomic relation, say. Presumably, the relation between the intermediary and the pain will be as contingent as anything else; hence it remains possible to confuse this genuine contingency with a merely apparent one. However, at this point we need to remind ourselves that Kripke is interested not only in there being some contingency in the relation between pain and something else but also in the idea that this contingency can plausibly be confused with an apparent contingency between pain and c-fibers firing. But the invocation of nonpsychological intermediaries is no help in this regard. Suppose in good faith I claim to imagine myself instantiating c-fibers firing and not being in pain. Is it really plausible to suggest that what I have in fact imagined is myself being in pain but not bearing a particular causal or nomological relation to the pain? For one thing, this attributes to me a confusion between imagined pain and imagined nonpain, but at least in most cases it is very unlikely that I am going to make such a confusion. More generally, I may not know anything about the causal or nomological relation in question; how then is it plausible to suggest that I have mistaken it for pain in the course of my imagining? There is also a more general point that can be made here about the relation between heat and pain. I think it is a datum that our psychological relation to pain is completely different from our psychological relation to heat; in consequence, although it is plausible in certain cases that we might confuse something that is hot for something that isn’t, it is vastly less plausible that we might confuse something that is pain for something that isn’t. It is natural to read Kripke’s discussion as associating this psychological claim with a number of other considerations of a more philosophical

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kind: the metaphysical claim that there is no distinction between pain and sensations of pain, the epistemological claim that pain is or appears to be self-presenting at least in clear cases, and the claim in philosophy of mind that the observational model of introspection is mistaken. To some extent, of course, all these philosophical points—particularly the last two—are controversial. But it is a mistake to think that Kripke’s distinction between heat and pain is likewise controversial. It is the psychological difference between heat and pain that makes it the case that the response to the heat argument cannot be replicated when one turns to the pain argument. To respond to Kripke’s distinction between heat and pain, then, you would need to deny not only the various philosophical ways of explaining the psychological difference but also the psychological difference itself. And this, I think, is extremely hard to do. We will return in chapter 11 to the distinction between heat and pain and to the issue of self-presentation. For the moment, let me conclude my discussion of this first way of responding to Kripke’s argument by saying that in my view there is no way to restore parity between heat and pain. Hence, if we want to respond to Kripke’s argument about a posteriori physicalism, we must look elsewhere.

9.5. Proposition Confusion Differently Implemented? The second option of the four distinguished earlier was this: ‘‘Find a different way to implement the proposition confusion strategy: Kripke makes a persuasive case that (9) is not being confused with (10). But it doesn’t follow that (9) is not being confused with anything; maybe we can identify another proposition with which (9) is being confused.’’ It should be clear from our previous discussion that this second option is not something that can be dismissed. Indeed, in discussing the epistemic view earlier, we have examined a different implementation of the proposition confusion strategy. So it is possible for the a posteriori entailment theorist to take a leaf out of the epistemic view’s book and say that because of ignorance, two propositions are being confused. On the other hand, if this is how the position is developed, there is no longer any difference between it and the epistemic view. Here, then, we see one version of the a posteriori entailment view indistinguishable from the epistemic view. Another way of implementing the proposition confusion strategy is to suggest that we have simply not thought things through and that our descriptions of the cases are mistaken. But this way of developing the view makes it indistinguishable from the version of the a priori entailment view that I will discuss in the next chapter. There I will argue that the idea that one has failed to think the cases through either will fail to answer the argument or is indistinguishable from the epistemic view. So we need to postpone discussion of this point until then.

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Is there a way in which the proponent of the a posteriori entailment view can develop the strategy of proposition confusion and not collapse into the epistemic view? I know of two proposals in the literature, the first made some time ago in an important critique of Kripke by Boyd 1980, the second by Stalnaker 2002. (Stalnaker’s proposal is similar to that in Hawthorne 2002 and Braddon-Mitchell 2003; I will concentrate on Stalnaker.)

9.5.1. Boyd Boyd’s suggestion starts from the observation that although pain is or might be self-presenting, having c-fibers firing presumably is not. So we may suppose that in the typical case we find out that our c-fibers fire by noting that some relevant instrument or instruments are whizzing and whirring. This suggests that, rather than saying that (9) is being confused with (10), one might instead say that (9) is being confused with (11): (11) There is something in me causing our instruments to whiz and whir, and there is no pain in me. It should be clear that (11) is contingent and so is unobjectionable in the context. So, if it is plausible to suppose that the proponent of the pain argument has confused (9) with (11), we have a position that is a variant on the one that Kripke discusses but is not vulnerable to the objection he raises to that position. As an abstract possibility, what Boyd says is surely correct, but it does not follow that his response to Kripke is successful. The problem is that it is implausible that any proponent of the argument has confused (9) with (11). Suppose I imagine the firing of a neuron in something like the way it is discussed in a neurology textbook, and I am told that this neural event is identical with the onset of my pain. Suppose, too, I report in good faith that it nevertheless seems to me to be perfectly possible that this neural event is not the onset of my pain. What Boyd is saying is that in this case I have confused a proposition about the neural event with another one—namely, the proposition that the cause of the whizzing and whirring is not the onset of my pain. In response, I will surely grant that this contrasting proposition seems possible, and I may even grant that I have a tendency to confuse the two propositions in my thinking (though in fact this is quite unlikely). But what I will not grant is that this has any tendency to make me think that I have not conceived the original proposition. It still seems possible that the neural event is not the onset of my pain. The fact that it also seems possible that the cause of this whizzing and whirring is not the onset of my pain is neither here nor there. (The point at issue here is the weakness in proposition confusion that we noted in chapter 4. If you try to argue that a proponent of a modal argument has confused one proposition with another, you must be ready for the response that both propositions are conceivable.)

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Of course, it might be that Boyd’s point could be developed to meet this objection. For example, one might say that, strictly speaking, one cannot conceive the proposition about the neural event because one is ignorant of some of the relevant facts about the event in question. However, if this is the way in which Boyd’s point is to be understood, his proposal is no longer distinct from our own. In short, we arrive at a point in the discussion at which Boyd’s version of the alternative proposition confusion strategy collapses into the epistemic view.

9.5.2. Stalnaker Turning now to Stalnaker’s position, this starts with the observation that one possible course of the history of science is that the caloric theory is true and that the phenomenon we call ‘‘heat’’ would in that case be explained in terms of that theory. (Stalnaker’s main example concerns water, rather than heat, but I will adapt what he says for the sake of continuity.) It is plausible to suppose that, if the caloric theory had turned out to be true, we would have used the word ‘‘heat’’ roughly as we do, except that it would refer to some substance defined by the caloric theory. Similarly, Stalnaker says, it is an empirical fact, if it is a fact, that primitivism is false. Moreover, it is plausible to suppose that, if primitivism had turned out to be true, we would have used the word ‘‘pain’’ roughly as we do now; it is only that we would have referred to some primitive event or state or property. These considerations prompt a slightly different interpretation of the proposition confusion strategy as it is applied to both the heat argument and the pain argument. The target propositions are as before, but the contrasting propositions are, for Stalnaker, the following: (12) In a caloric world considered as actual, there is molecular motion in the poker and there is no heat in the poker. (13) In a primitivist world considered as actual, there are c-fibers firing in me, and I am not in pain. The phrase ‘‘world considered as actual’’ is due to an important paper by Davies and Humberstone 1980 and has a technical meaning within twodimensional modal semantics, a topic to which Stalnaker has made seminal contributions. The details of these ideas are difficult, but I think there is no harm in the present context to interpret what is intended as follows: (12*) There is molecular motion in the poker, and there is no heatas-the-caloric-theory-understands-heat in the poker. (13*) There are c-fibers firing in me, and I am in not in pain-as-theprimitivist-understands-pain. On this interpretation, what Stalnaker is suggesting is that in the heat argument we confuse the target proposition with (12*) and in the pain argument we confuse the target proposition with (13*). The significance of this

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suggestion is that both (12*) and (13*) are in the context unobjectionable. It is not impossible that the caloric theory is true, so it is not impossible that the poker instantiates heat as the caloric theory understands heat. But heatas-the-caloric-theory-understands-heat is only contingently related to real heat (i.e., molecular motion). The same thing applies, Stalnaker says, in the pain case, and so the argument collapses. Stalnaker’s suggestion is ingenious, but it faces a number of problems. For one thing, like Boyd’s suggestion, Stalnaker’s is vulnerable to the reply that one can imagine or conceive both of the propositions he distinguishes. Let us agree with Stalnaker that we can imagine c-fibers firing without painas-the-dualist-conceives-of-pain. How is it supposed to follow that we cannot imagine c-fibers firing without pain sans phrase? Moreover, and more important, Stalnaker’s account fails the condition of adequacy formulated in chapter 3. As I formulated it there, that condition went like this: ‘‘if you think you have isolated a factor that constitutes the mistake in CA or KA, check to see if that factor is present in parallel arguments you accept; if the factor is present in a modal argument you accept, consign your proposal to the flames.’’ That Stalnaker’s suggestion fails to meet this condition emerges if we look again at the perfect actor objection to behaviorism. That argument proceeds from the premises, first, that it is conceivable that I have a behavioral duplicate that is phenomenally distinct from me and, second, that what is conceivable is possible. The conclusion of the argument is that behaviorism is false, for behaviorism entails that behavioral truths entail the psychological truths. As I have said, I take it to be quite obvious that this argument is successful. But unfortunately Stalnaker is in no position to say this. There is no reason at all that the behaviorist might not respond to these arguments in precisely the way that he recommends we respond to the conceivability argument. In particular, there is nothing in Stalnaker’s account to prevent a behaviorist from responding as follows. ‘‘The perfect actor argument fails because it confuses pain with pain-as-the-antibehaviorist-understands-it. Everyone agrees that pain understood that way could come apart from behavior, but if you assume that this is what pain is, you have begged the question against me. The question is whether pain-as-we-ordinarilyconceive-it can come apart from behavior, and this the argument does not show.’’ I take it that there is something seriously wrong with the idea that a behaviorist might respond to the perfect actor argument in this way, and so there is likewise something seriously wrong with Stalnaker’s proposal. One might reply by pointing out that there are many other reasons to resist behaviorism—empirical reasons, say. True enough, but irrelevant: I am not denying that there might be other arguments against behaviorism; of course, there are. Nor am I saying that Stalnaker’s position commits him to behaviorism; of course, it doesn’t. What I am saying is that Stalnaker’s response to the conceivability argument has the bad consequence that a good argument against behaviorism turns out to be a bad argument. His response

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provides the materials to respond to Putnam’s perfect actor argument, but because we know that the latter argument is a good one, there must be something mistaken about his response. (For further discussion of Stalnaker, see Stoljar forthcoming.) Of course, that neither Boyd nor Stalnaker has managed to produce alternative versions of the proposition confusion strategy does not prove that there is no possible proposal along these lines. Nevertheless, the material I have introduced makes that hypothesis very plausible. So I think at this point we should turn our back on the second way of responding to Kripke’s argument, and examine options three and four.

9.6. Alternative Strategies? The third option of the four distinguished previously was this: ‘‘Find a strategy of response to the pain argument that is different from the proposition confusion strategy. The idea of proposition confusion seems to be one compelling way of defeating a conceivability argument, but it is not the only way. So perhaps there are other ways of defeating a conceivability argument that Kripke does not consider.’’ Once again, it should be clear from what we have said so far that strategies other than the proposition confusion strategy cannot be ruled out. We have so far been concentrating on proposition confusion, but it is possible that what has gone on here is defeater neglect or mode confusion. On the other hand, it is also difficult to keep these strategies apart from each other in practice, and so we must be alert to the possibility that a mistake that starts off as the mistake of proposition confusion ends up being a mistake of mode confusion. As we noted, in many cases it is a combination of these mistakes that is at issue. There is, however, a common strategy in the contemporary literature that does seem to be genuinely different from anything we have met before. This is to appeal to what are sometimes called phenomenal concepts. A phenomenal concept is the concept of a specific type of perceptual or sensory experience where the notion of experience is understood in accordance with the phenomenal conception. So, for example, the phenomenal concept ‘‘red sensation’’ is the concept of the specific type of sensation one gets from looking at red things such as British pillar boxes or the Chinese flag. Proponents of the phenomenal concept strategy—as I will sometimes call it—suggest that phenomenal concepts have various ‘‘special features’’ that distinguish them from nonphenomenal concepts and that the proponent of CA has neglected the difference. There are a number of different versions of this strategy on offer in the contemporary literature, but in what follows I will concentrate on the version advanced by Christopher Hill, both on his own (1997) and in collaboration with Brian McLaughlin (1999). A distinctive feature of Hill’s discussion is that he makes two proposals, the first focusing on a distinction between

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two types of imagination and the second focusing on a distinction between two types of concept. I will discuss first what he says about imagination and then turn to the issue of concepts. In both cases, I will suggest, Hill’s strategy does no better than the suggestions we have already considered.

9.6.1. Two Types of Imagination? The starting point of Hill’s discussion of imagination is the famous footnote 11 in Nagel 1974, in which two types of imagination are distinguished, sympathetic and perceptual imagination. (Nagel also talks of ‘‘symbolic imagination,’’ but, following Hill, I will set that aside here.) Sympathetic imagination occurs when one imagines oneself undergoing a certain experience—being in pain, say. In such cases, Nagel says, one puts oneself in a position that ‘‘resembles’’ the pain itself. Perceptual imagination occurs when one imagines oneself perceiving (or seeming to perceive) some event in the world. In such cases, Nagel says, one puts oneself in a position that ‘‘resembles’’ seeing the event in question. Hill goes on to say that, when we imagine ourselves having c-fibers firing and not being in pain, we combine these two types of imagination. As a result, he says, the connection between pain and c-fibers will appear contingent even if it is not. Hill’s proposal is a generalization of this idea. As it stands, Nagel’s suggestion is limited to cases of direct perception; Hill says that one can legitimately talk of indirect perception. (The issues are obviously related to the issues of perceptual availability that we considered in chapter 8.) If the generalization is accepted, we arrive at Hill’s central claim: that the proponent of CA blends the two types of imagination together and that in cases in which this is so, we are not permitted to move from conceivability (or imaginability) to possibility. If this claim is correct, we have an answer to CA that, on the one hand, does not require the postulation of ignorance but that, on the other, explains what is wrong with the argument in a way that comports with the a posteriori entailment view. How plausible is this answer? One objection is that it seems, as Hill points out himself, to be in the first instance a view about what happens psychologically when someone imagines, say, c-fibers firing and no pain; it does not seem to be a view about the epistemic status of those imaginings. As it is sometimes put, Hill’s view seems to be an explanation of the intuitions that are central to CA, but it does not explain them away (see Chalmers 1999). In response to this, Hill says that his account would apply in cases in which the intuitions are unreliable. However, this does nothing to answer the objection. The objection is that the psychological facts Hill is appealing to will be in place, whether or not the arguments are successful. Pointing out that they might be in place in cases where the arguments are unsuccessful is not a response. A second objection is that it is mistaken, or at any rate extremely misleading, to say that we have two types of imagination here. Properly

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understood, the difference concerns, not types of imagination, but types of things imagined. In the one case, one imagines oneself to be in pain; in the other case, one imagines oneself to perceive (or apparently perceive) that such and such is the case. Another way to make the same point is this: to imagine oneself perceiving or apparently perceiving that such and such is the case is to imagine oneself being in a conscious state. So imagining oneself perceiving something is sympathetic imagination, and there is no difference in type between perceptual and sympathetic imagination. On the other hand, if there is no difference in types of imagination, it cannot be illegitimate to blend those two types together. It might be replied that Hill’s basic suggestion can be recast to avoid this objection. In particular, it might be claimed that what Hill is suggesting is that the first premise of the pain argument is false. It is not true that it is conceivable or imaginable that there are c-fibers firing in me, and I am not in pain. Rather, two things are true: first, that it is (perceptually) imaginable that there are c-fibers firing in me and, second, that it is (sympathetically) imaginable that I am not in pain. In short, Hill’s suggestion is that we have two things imagined here rather than one, and that is enough to defeat the argument. However, this version of the proposal runs into a problem that is familiar from our previous discussion. Perhaps it is true that each of those things is imaginable separately, but why is it not also true that they are imaginable together? Again, the mere fact that a certain thing is imaginable does not make it less likely that something else is not imaginable; why should the fact that a certain two things are imaginable make any difference? Of course, Hill might respond that this is to illegitimately blend the two types of imagining. But again, it is mistaken or misleading to say that there are two types of imagination here. My final objection is that Hill’s proposal overgenerates in exactly the way that Stalnaker’s does: it, too, fails our condition of adequacy. Consider again the perfect actor objection. There is nothing in Hill’s proposal to stop a behaviorist from responding to this argument as follows: ‘‘When you claim to imagine yourself instantiating certain dispositions to pain behavior and yet not being in pain, this blends together two types of imagination. All that is true is that you can perceptually imagine yourself instantiating certain dispositions to pain behavior while you can sympathetically imagine yourself not being in pain. So the argument fails.’’ Because, as I have said, I think the perfect actor argument is a good argument against behaviorism, there must be something wrong with Hill’s proposal.

9.6.2. Two Types of Concept? Hill’s discussion of imagination does not afford any response to the modal arguments; what, then, of his discussion of the special features of phenomenal concepts? Here the idea is that phenomenal concepts are distinct from other concepts in virtue of their ‘‘justification conditions.’’ In

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particular, Hill says, when one is justified in applying a phenomenal concept to a particular psychological event or state, it is often the presence of that very state that constitutes one’s justification. This idea is obviously very close to the idea of self-presentation discussed earlier. What Hill is saying is that phenomenal concepts are special in that the states and events that fall under them are self-presenting, whereas the states and events that do not fall under them are not self-presenting. Moreover, he says—in our terminology— that in cases in which the target proposition of a conceivability argument brings together concepts that have the justification conditions of phenomenal concepts and concepts that do not have those justification conditions, it is illegitimate to infer from conceivability to possibility. We might put the central point differently by saying that when a statement brings together concepts of these kinds, it will appear contingent and a posteriori, even if it is necessary. For that reason, it is illegitimate to infer from conceivability to possibility. As Hill and McLaughlin put it: ‘‘Given these differences between sensory [i.e. phenomenal] concepts and physical concepts, a sensory state and its nomologically correlated brain state would seem contingently related, even if they were necessarily one’’ (1999, 449). But this proposal faces serious objections, too. First, take an example that we considered in chapter 8 when considering Nagel’s views on objectivity repeated here as (14): (14) If John is a number, then he is not in pain. It is obvious that the concept in the consequent of this is phenomenal and the concept in the antecedent is not. But then (14) should appear to be contingent or a posteriori. On the other hand, (14) does not appear to be either contingent or a posteriori. On the contrary, (14) is palpably necessary and a priori. It might be replied that the concept in the consequent of (14) is not selfpresenting because it occurs embedded in a negation. However, if this is so, then Hill has no answer to the pain argument. In that argument, the proposition at issue is precisely that there are c-fibers firing in me and I am not in pain. Alternatively, it might be suggested that Hill’s proposal is intended to apply only to cases that involve the necessary a posteriori. (Hill suggests something like this in his 1997.) But that is a statement only of the intended scope of his proposal; it says nothing about its actual scope. The basic point is that there is nothing in the proposal that stops it from having the result that (14) should appear either contingent or a posteriori. Because it appears neither of those things, Hill’s proposal is mistaken. A second objection is that what Hill says about phenomenal concepts overgenerates in the way that is now familiar. There is nothing in their position to prevent a behaviorist from responding as follows: ‘‘Phenomenal concepts are self-presenting, and behavioral concepts are not. Given these differences between phenomenal concepts and behavioral concepts, a phenomenal state and its nomologically correlated behavioral state would seem

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contingently related, even if they were necessarily one. Hence the conceivability argument against behaviorism is mistaken.’’ If it is accepted, as I think it should be, that this is not a successful response on the part of the behaviorist, then I think it should likewise be accepted that Hill and McLaughlin’s version of the phenomenal concept strategy is also unsuccessful. In fact, this observation about Hill’s position permits us to make a criticism of the phenomenal concept strategy more general than any we have discussed so far. We have seen that any version of the strategy—not simply Hill’s version—says that the conceivability argument can be disarmed by considering the special features of phenomenal concepts vis-a`-vis nonphenomenal or theoretical concepts. The differences between the various versions of the strategy emerge only when we ask what these special features are: some say that phenomenal concepts exhibit a special sort of possession condition, others say they are a special sort of indexical, and still others that they have special epistemological features. However, whatever factor precisely is supposed to set phenomenal concepts apart from theoretical concepts, that factor must likewise set phenomenal concepts apart from behavioral concepts, for behavioral concepts are a subclass of theoretical concepts. (Clearly, if a class of concepts C is distinct in some respect from another class C*, it is likewise distinct in that respect from a third class C#, if C# is a subclass of C*.) From this it follows that any version of the phenomenal concept strategy will have the consequence that the conceivability argument against behaviorism is not a good argument. But as we have seen, it is very implausible that this is so. (For some further discussion of the phenomenal concept strategy, see Stoljar 2005b.) So our conclusion about this third way of responding to Kripke is identical to the conclusion in the case of the second: we have not so far found a development of the a posteriori entailment view that is both plausible and distinct from the epistemic view.

9.7. The Necessary A Posteriori and the Notion of Conceivability The final option of the four distinguished above was this: ‘‘Reject outright the demand that the a posteriori entailment view must provide an answer to the pain argument. It is an assumption of Kripke’s discussion that both the pain argument and the heat argument are prima facie compelling, and thus that we need to answer them. But perhaps this concedes too much to the arguments. Perhaps the real lesson of the necessary a posteriori is that these arguments are much less compelling than they appear.’’ It should be evident that this position is a version of the skepticism about modal reasoning considered in chapter 3. There we rejected skepticism on the ground that modal reasoning is used throughout philosophy. But in this

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context, we cannot be so quick. According to this suggestion, the real lesson of the necessary a posteriori is that modal arguments always fail when the target proposition involves a necessary a posteriori truth. In short, what we are facing here is a sort of limited skepticism about modal arguments. But why should the mere existence of the necessary a posteriori have this consequence for modal arguments? As I understand it, the basic suggestion can be divided into three stages. First, one advances a certain definition of what ‘‘it is conceivable that p’’ means. According to this definition, ‘‘it is conceivable that p’’ in the relevant sense just means ‘‘it is not a priori that not p.’’ Second, one points out that, if this account is correct, the premises of (e.g.) the pain argument are properly understood as follows: (15) It is not a priori that there is molecular motion in the poker and there is no heat in the poker. (16) If this is conceivable, then it is possible. But third, one points out that these premises give you nothing interesting because (16) is false, and moreover we know that it is false because of the existence of the necessary a posteriori. And that, one concludes, is the real lesson of the necessary a posteriori. There is no point denying that ‘‘it is conceivable that p’’ has a reading according to which it means ‘‘it is not a priori that not p.’’ The notion of conceivability can be legitimately spelled out in a number of different ways; this is one of those ways. But the idea that, in the specific context of the conceivability argument, this is what ‘‘it is conceivable that p’’ means is quite another matter. When Putnam tells us about perfect actors, I don’t think he means to be saying merely that it is not a priori false that there are perfect actors. I think he means to be saying that a certain case appears to be possible or (if this is different) is imaginable. On the other hand, talk of what seems to be possible or of what is imaginable is prima facie different from talk of what is or is not a priori. It might be replied that although this is true prima facie, it is not true all things considered, and in particular, ‘‘it is imaginable that p’’—to focus on this notion for the moment—itself just means ‘‘it is not a priori that not p.’’ However, I think this last equivalence is decidedly implausible (see Yablo 1993). Consider any of the standard examples of necessary a posteriori truth—say, ‘‘water is H2O.’’ It is clear that it is a posteriori that water is H2O, and so of course it is not a priori that water is H2O. Is it likewise imaginable that water is not H2O? I think not. As Kripke argued, it is not at all clear that we can imagine water not being H2O. Of course, we can imagine related things. For example, we can imagine water not producing perceptions as of water. But this is not, strictly speaking, imagining that water is not H2O. More generally, therefore, the idea that ‘‘it is imaginable that p’’ just means ‘‘it is not a priori that not p’’ is open to counterexample. More generally still, the idea that the premises of the pain argument should be interpreted as (15) and (16) is implausible.

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9.8. Conclusion Earlier we reviewed Kripke’s criticism of (what we are calling) the a posteriori entailment view and noted four options for those who want to circumvent that criticism. We have now considered those options and found them wanting. Hence we have an answer—at least so far as a posteriori entailment goes—to the first of the two questions distinguished in section 9.2: ‘‘What, if anything, is the mistake in the arguments for T3?’’ The answer to this question is that a posteriori entailment on its own tells us nothing about what is wrong with the arguments, and that if the view is embellished so that it does say something about this, the results are either implausible or indistinguishable from the epistemic view. I want to close the chapter by returning to the second of the two questions left over from section 9.2: ‘‘Is the experiential conditional a priori or a posteriori?’’ This is a question that has drawn a considerable amount of attention in the literature. In particular, a number of philosophers have argued that, although Kripke may be right that there are examples of the necessary a posteriori, it is unreasonable to suppose—to put things in our terminology—that the experiential conditional is one of them, at least if experiential supervenience is true. For example, (i) Jackson (1994, 1998) argues that if a statement is necessary and a posteriori, it can be derived a priori from some further contingent statement. In turn, if the experiential conditional is a posteriori, it, too, must be derived from some further contingent statement. On the other hand, if experiential supervenience is true, there is no other contingent truth from which the experiential conditional can be derived. For supervenience aims at completeness: any contingent truth must already be included in the antecedent of the experiential conditional. So, Jackson concludes, if experiential supervenience is true, the experiential conditional is not only necessary but also a priori. (ii) Chalmers (1996, 2002a) suggests that every necessary a posteriori statement is associated with two distinct propositions. In his terms, these are its primary intension, which is contingent, and its secondary intension, which is necessary. This idea creates trouble for the a posteriori entailment view in two ways. First, if the experiential conditional is necessary and a posteriori, it must be associated with two propositions, one of which is contingent and the other necessary— but the contingent proposition here is already inconsistent with supervenience. Second, Chalmers suggests that in the case of the experiential conditional, these two intensions coincide. But then it could not be that the conditional is necessary a posteriori: either it is contingent and a posteriori or else it is necessary and a priori. (iii) White (1986)—following a suggestion of Smart 1959; for recent discussion, see Block forthcoming—suggests that if any statement is necessary and a posteriori, this is to be explained by the fact that the referent of at least one of its constituent terms instantiates two distinct properties. But, White argues, this general principle eventually

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commits the proponent of a posteriori entailment to a kind of property dualism or primitivism. But then, White concludes, if physicalism is true, the experiential conditional is not a posteriori. If any of these arguments is sound, the analogy between the experiential conditional and the pain conditional is misguided from the start. Although the pain conditional might be necessary and a posteriori, the experiential conditional could not be. Moreover, if any of these arguments is sound, there is no need to consider all the material I have just considered—no need to examine Kripke’s discussion, or the relation of pain to heat, or pain as the primitivist understands pain, or phenomenal concepts, or different conceptions of conceivability. Why, then, did I not simply avail myself of these arguments at the outset? The question is made all the more acute when we consider that some proponents of the epistemic view (e.g., McGinn 2001) have certainly availed themselves of arguments of this style. Why have we not followed suit? The answer is that the arguments of Jackson, Chalmers, and White are controversial in a number of different senses. First, they are controversial in the sociological sense that many people don’t agree with them. If we relied on them, we would be in danger of losing our audience. Second, they are controversial in the rational sense that it is not very clear how to decide whether the views are correct or not. Jackson’s position, for example, relies overtly on the description theory of reference. But it is quite unclear—at any rate, it is quite unclear to me—how to decide between the extremely sophisticated, ultramodern description theory that Jackson advances and the extremely sophisticated, ultramodern antidescription theory advanced by philosophers such as Stalnaker (2003a). Finally, the sources of these controversies seem to have nothing in particular to do with the distinctive subject matter of philosophy of mind; they have nothing to with the notion of experience, for example. They seem rather to do with modal epistemology and philosophy of language. Given the controversial nature of these arguments, it seems to be good policy to remain neutral on them in the course of our discussion. So, what is the answer to the second question? Is the experiential conditional a priori or a posteriori? For us, the issue remains open. For one thing, it is unclear how to close it; more important, whether it is closed or open, it is has no impact on the plausibility of our position.

10 A Priori Entailment

10.1. Introduction We argued in the previous chapter that when it is considered alone, the a posteriori entailment view answers neither the conceivability argument (CA) nor the knowledge argument (KA) and that when it is conjoined with further material, the resulting package is either implausible or indistinguishable from the epistemic view. In this chapter, I argue that the same things apply, mutatis mutandis, in the case of the a priori entailment view, the thesis that the experiential conditional is necessary and a priori. We may begin with the observation that, in the case of the a priori entailment view, it is uncontroversial that it alone does not answer these arguments. In this respect, the situation is different from the a posteriori entailment view. Of course, if one thinks that the experiential conditional is necessary and a priori, one is committed to there being a mistake in the arguments somewhere. If one thinks the conditional is necessary at all, one is committed to there being a mistake in the arguments somewhere. But one is not committed to there being any mistake in particular, and it is the identification of a particular mistake or sort of mistake that is at issue when one asks for a diagnosis of what has gone wrong. What, then, do proponents of the a priori entailment view say about where the arguments go wrong? Some (e.g., McGinn 2001) appeal to ignorance, but of course that would not provide us with a version of the a priori entailment view that is distinct from our position. Others appeal to ideas we have already met in the course of discussing a posteriori entailment. For example, it is quite consistent with the a priori entailment view to say that we are confusing pain, on the one hand, and pain-as-the-primitivist-understands-pain, 198

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on the other, or else that we have confused two types of imagination or that we have not properly assimilated the special features of phenomenal concepts. But we have already seen that these suggestions are unpersuasive. Rather than develop the discussion in these directions, therefore, the suggestion I want to concentrate on is this: in an important sense, we have failed to think the relevant cases through. But what is it to fail to think things through?

10.2. Failing to Think Things Through Suppose we are marooned on a desert island. I promise you that, if you die and I alone return to civilization, I will spend the bag of money buried under your house to promote the local racing club. Suppose I do get back to civilization and that, instead of carrying out my promise, I spend the money on something else—helping the underprivileged, say. In this case, if we pretend (unrealistically!) that promoting the racing club and helping the underprivileged are the only possibilities, my action clearly promoted the most good of those available to me. Yet it looks like this action is not the right one, for the right one is to keep the promise. This example is one of a large number advanced by critics of utilitarianism, the claim, roughly, that the right action is the one that in the circumstances promotes the most good. How does the utilitarian respond? The usual answer is that the critic hasn’t thought things through. ‘‘You think you can imagine a case in which the right action is not the one that promotes the most good,’’ the utilitarian says, ‘‘but think harder. Is it really true that keeping the promise is the right action in the circumstances? Of course, by and large, keeping promises is the right thing to do, but in this special case perhaps things are different. Alternatively, is it really true that helping the underprivileged promotes the most good in the circumstances? Perhaps keeping promises is so important as to outweigh even this admittedly beneficent action.’’ According to the a priori entailment view, we should approach the cases that lie behind the arguments for T3 in an analogous way. ‘‘You think you can imagine a case on which to mount versions of the conceivability or knowledge arguments,’’ the proponent of the a priori entailment view says, ‘‘but think harder. For example, in the case of CA, is the situation you are imagining really one in which all the same nonexperiential truths obtain? And in the case of KA, is the situation you are imagining really one in which the subject knows all the nonexperiential truths and then learns some experiential truths? Unless we are satisfied that these are the correct ways to describe the relevant situations, we have no reason to follow the arguments to their conclusion.’’ In the terms of chapter 4, this failure to think the cases through is what makes it plausible that in advancing CA and KA we have committed one (or a combination) of the standard mistakes.

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Of course, the proponent of the epistemic view may also be described as saying we have failed to think the cases through. What then is the difference between our position and that of the sort of a priori entailment theorist I am considering? The difference is that the sort of a priori entailment theorist I am concerned with in this chapter accepts that we are in a position of full disclosure of the relevant facts or types of facts. Our analogy to utilitarianism helps to bring this out. When the utilitarian responds to critics that they have failed to think things through, the idea is not that the critic is ignorant of, or is unaware of, a type of truth concerning the nature of the good that is relevant to the nature of rightness; this is quite implausible in the situation. It is rather that the critic has not thought through all the truths or types of truths that all parties to the dispute agree to be common knowledge. More generally, the claim is not that we are missing some information; it is that we have not thought hard enough about the information already in our possession.

10.3. The Robustness of the Intuitions But how plausible is the proposal that we have not thought hard enough about the information already in our possession? Its initial problem is that we have thought hard enough, or at any rate so it appears. In particular, when we look in detail at various proposals about where the mistake in our description of the cases might lie, it is always possible to adjust things to avoid the problem. To illustrate this, I want now to consider two proposals, one about the Mary example and one about the zombie example. These are not the only ones that have been or could be made, but they do convey the general tone and may serve as our exemplars.

10.3.1. Novel Experiences When Mary comes out of her room, the experience she has when (e.g.) looking at a ripe tomato is novel; that is, she has never had this experience before. But it is often suggested that novel experiences are special and, moreover, that this specialness makes it mistaken, or at least not obligatory, to describe the Mary example as one in which someone who knows all the nonexperiential or physical truths comes to know a new truth. This suggestion may be developed in one of at least three ways. First, for proponents of the so-called ability hypothesis (Nemirow 1988, Lewis 1988), the novel experience confers on Mary a new ability that she did not have before, an ability to imagine, recollect, and think about experiences. We may, if we like, describe this as a certain sort of knowledge. But for the proponent of the ability hypothesis, the knowledge is not of a truth that she failed to know before: it is know-how rather than know-that, to put the point in terms of the contrast introduced by Ryle 1949. On this view, therefore, the

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modal premise of the knowledge argument, repeated here as (1), has been confused with (2): (1) It is possible for a conceptually sophisticated and logically omniscient person to know all nonexperiential truths and to learn its consequent on the basis of experience. (2) It is possible for a conceptually sophisticated and logically omniscient person to know all nonexperiential truths and to gain, on the basis of experience, abilities to imagine, recollect, and think about experiences. From the point of view of the ability hypothesis, (1) is a possibility that would impact on the experiential conditional, but only (2) is supported by the Mary example, and this is in the context unobjectionable. Second, for proponents of the so-called acquaintance hypothesis (Churchland 1985, 1996, Conee 1994, Dretske 1999), the novel experience makes it the case that Mary is aware of, or acquainted with, a property that she was not acquainted with before. Once again, we can, if we like, describe this as a certain sort of knowledge. But for the proponent of the acquaintance hypothesis, the knowledge is not of a truth that she failed to know before: it is knowledge of a property, rather than knowledge that such and such is the case. On this view, therefore, (1) has been confused not with (2) but with (3): (3) It is possible for a conceptually sophisticated and logically omniscient person to know all nonexperiential truths and, on the basis of experience, become aware of, or acquainted with, properties of experience. From the point of view of the acquaintance hypothesis, (1) is a possibility that impacts on the experiential conditional, but only (3) is supported by the Mary example, and this is in the context unobjectionable. Finally, the idea of novel experiences suggests a slightly different implementation of the phenomenal concept strategy that we considered in the previous chapter (see Harman 1990, Byrne 1999, Tye 1999). On this view, the novel experience confers on Mary a new concept, and this concept allows her to understand the consequent of the experiential conditional, whereas previously she could not understand it, or at least not in the relevant sense. On this view, (1) has been confused not with (2) or (3) but with (4): (4) It is possible for a logically omniscient person to know all nonexperiential truths and to learn some experiential truth on the basis of experience. The difference between (4) and (1) is that (1) requires the person in question to be conceptually sophisticated and (4) makes no such requirement. According to this version of the phenomenal concept view, (1) would impact on the experiential conditional, but only (4) is supported by the Mary example, and this, too, is unobjectionable.

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These suggestions are different from one another in various ways and face different sorts of challenges. However, for our purposes, the important point is that, even if they were right, they would not defeat the knowledge argument. The reason is that all of these suggestions focus on a particular example, the Mary example, and in fact on a particular feature of that example—that is, that it involves novel experiences. But it is not difficult to spell out similar examples that make no reference to novel experiences but nevertheless permit a formulation of the knowledge argument. One of these is (what I will call) the example of Experienced Mary. (This example is similar to one discussed in different contexts by Lewis 1988 and by Nida-Ru¨melin 1995. See Stoljar 2005b for further discussion.) Experienced Mary is exactly like Mary for the first part of the story. Both grow up in the black-and-white environment, and both eventually escape to have experiences. The difference is that Experienced Mary is unfortunate enough to be recaptured and returned to her room. Not only that, but the nature of her capture is such that she develops partial amnesia. She loses none of the purely nonexperiential knowledge that she knew so impressively before her release. Nor does she forget all of her experiential knowledge—she remembers, for example, what red sensations are like—hence it is plausible to say, with the phenomenal concept view, that she does not lose any phenomenal concepts. What she forgets, however, is experiential knowledge of another sort—knowledge of cases in which these phenomenal concepts are correctly applied. Thus what she forgets are truths of the form ‘‘Fred’s arthritis causes him pain’’ and ‘‘Looking at Granny Smith apples causes green sensations.’’ In forgetting these truths, it is not that Experienced Mary does not know (e.g.) what pain is like, nor is it that she could not imagine a possibility in which Fred’s arthritis causes him pain. It is simply that she does not and cannot know or deduce that Fred’s arthritis does cause him pain. Nothing she knows, for example, rules out the possibility that his arthritis might cause nausea or perhaps nothing at all. Now, it is perfectly possible to develop the knowledge argument on the basis of the example of Experienced Mary rather than on the example of Mary. For Experienced Mary is someone who knows the antecedent of the experiential conditional; she knows all the physical truths about Fred, for example, and about Granny Smith apples. What she does not know before being released the second time, and comes to learn on being released, is the consequent of the experiential conditional. The consequent of that conditional summarizes all the experiential truths of the world, including truths such as seeing red is like such and such and also truths such as Fred’s arthritis causes him pain. However, because Experienced Mary does not know these latter truths, she does not know the consequent of the conditional. At this point, however, the argument proceeds as before. If we can imagine someone, Experienced Mary, who knows the antecedent of the experiential conditional but who learns the consequent on the basis of experience, then—says the proponent of the knowledge argument—the best

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explanation is that this conditional is either contingent or false. But then experiential supervenience is false, for it entails that the experiential conditional is necessary. Now it is quite plain what the problem is for any response to the knowledge argument that focuses on novel experiences. In the case of Mary, it is plausible to say that (1) has been confused with (2–4) or at any rate that there is nothing to choose between these alternatives. But in the case of Experienced Mary, this is no longer plausible. For by assumption Experienced Mary has had the relevant experiences, and, if she has had the relevant experiences, you cannot argue that what happens to her is that she gains an ability or a new state of acquaintance or a new concept. Experienced Mary has the abilities, is acquainted, and possesses the concept. On the other hand, Experienced Mary is a good case on which to mount the knowledge argument, for Experienced Mary presents a case in which someone knows the nonexperiential truths and yet comes to learn further truths on the basis of experience. More generally, once we see that the knowledge argument can be divorced from the particular details of the example of Mary, it is clear that the idea of novel experiences is quite irrelevant to the soundness of that argument.

10.3.2. Constitutive Connections Turning now to the zombie case, the most influential suggestion here—it is due to Shoemaker 1975 (see also 1999)—is that the usual description of the case fails to recognize the sense in which there are constitutive connections between experience and certain sorts of beliefs that one might call phenomenal beliefs—that is, beliefs of the form ‘‘I am in pain,’’ ‘‘I am having a red sensation,’’ and so on. But these connections—so the argument goes— render the zombie hypothesis incoherent. My zombie duplicate is supposed to be someone who is functionally and physically identical to me but who lacks experience. But if he lacks experience, he must also lack phenomenal beliefs, in view of the constitutive connections between experience and belief. On the other hand, if he lacks phenomenal beliefs, he will be functionally and so physically different. Once again, this suggestion may be developed in a number of different ways. In some cases, the emphasis is on the epistemological difficulties that would result if the constitutive connection between experience and experiential belief is broken (Shoemaker 1975, Chalmers 1996). In other cases, the development of the issue is dialectically more complex. For example, Balog 1999 argues that if the zombie case were possible, a zombie could advance a conceivability argument in much the same way that real philosophers do now. She thinks that the counterpart argument that a zombie would produce is fallacious and draws the conclusion that the actual argument is likewise fallacious. Alternatively, McGeer 2003 argues that if zombies are possible, it is also possible that there be a zombie Mary. McGeer

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suggests that our description of zombie Mary would parallel that of genuine Mary, but because the argument based on the example of zombie Mary is fallacious, the argument based on the example of Mary is likewise fallacious. There is much to say about these suggestions, but for us the important point is that what is under attack here is the zombie example in particular and not CA in general. Hence, even if these suggestions were right, the proper response is to develop CA on the basis of a different example. However, as we noted in chapter 2, there are a number of different examples available. For one thing, as Shoemaker himself makes clear in his discussion, we could instead appeal to the spectrum inversion example. But this, too, is a controversial idea in many ways, because the notion of spectrum inversion requires a phenomenal space that instantiates a number of controversial properties (see Byrne 2004). So, to minimize controversy, consider the hypothesis that there is a situation in which everything is exactly as it is but is increased or decreased slightly on a certain phenomenological dimension: all the colors or experiences of color are just marginally duller, for example, or the tastes are just that little bit more vivid. That hypothesis would be sufficient to develop the conceivability argument, and yet it is not touched by the observation that there are constitutive connections between experience and experiential belief.

10.3.3. A Catalogue of Defeat? Does the failure of these suggestions about Mary and zombies represent an inevitable catalogue of defeat or a series of cases growing ever closer to the truth? It is difficult to say in the abstract. But our continual failure to nail down any errors in the way we describe the cases behind KA and CA is remarkable and calls for explanation. From the perspective of the epistemic view, however, the explanation is straightforward. We can’t see what is wrong with these cases because we are missing certain facts crucial to doing so. So in effect, reflection on these cases provides support, not for the versions of the a priori entailment view that I have been considering, but for the epistemic view.

10.4. An Alternative Strategy The prospect of going through the examples one by one and suggesting that in each case our description involves a mistake or misrepresentation looks grim. But there is another way that a proponent of the a priori entailment view might attempt to secure the claim that we have failed to think things through. Even if it is difficult to defeat every example, it might be possible to produce an argument that there must be a mistake in the way we describe those cases, even if we cannot say in each case just where the mistake lies.

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Now, as before, the proponent of the epistemic view might also be described as defending this indirect strategy and being in the business of arguing that there is a mistake or misrepresentation in our description of the cases, even if we don’t know what it is. As before, however, I am considering in this chapter the a priori entailment theorist who insists also on the idea that we have full knowledge of the relevant facts or types of facts. For such a person, it remains possible to argue that there is a mistake in the way that we are thinking these cases through, even if we can’t say precisely where. How, then, might this strategy be implemented? I think the most plausible line of argument here turns in one way or another on a central idea in philosophy of mind known as functionalism. So in the next part of our discussion, I will look at this in some detail.

10.5. Functionalism Introduced It often happens that when we try to define a certain term, it turns out that the term in question is one of a family of terms, and it is impossible to define one without defining all the others. Terms such as ‘‘husband’’ and ‘‘wife’’ provide a simple example. Try to define what a husband is, and you will find this impossible unless you have the notion of a wife and perhaps, too, the notion of marriage already at your disposal, for you will almost certainly end up saying that a husband is someone married to a wife. On the other hand, try to define what a wife is, and you will end up with same problem in the opposite direction. At the heart of functionalism is an idea about how to circumvent this problem. The precise development of this idea is difficult and need not concern us. (For the seminal presentation in the context of philosophy of mind, see Lewis 1972.) But speaking very roughly, the key suggestion is that, in the first instance, we may define (not terms but) vocabularies. So, in this example, if we permit ourselves to distinguish matrimonial from nonmatrimonial vocabulary, we may say that a husband and wife are a pair of people who stand to each other in such and such a complicated way W, where W is specified in terms drawn from the nonmatrimonial vocabulary. In addition, it is possible to transform such a definition of vocabularies into a definition of particular terms. In this example, we may say that a person S is a husband just in case there is a pair of people x and y such that x and y stand to each other in way W and S is the first person in this pair. Again, the details are difficult, but the important point is that functionalism is a highly sophisticated approach that permits the formulation of a definition of the following form: ð1Þ

x is a husband ¼ def x has D.

In this definition, ‘‘D’’ stands in for a no doubt complex expression that contains no expression like ‘‘husband’’ and no expression like ‘‘wife’’ or ‘‘marriage’’ that is of the same family.

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Functionalism in philosophy of mind is the application of this general idea to psychological vocabulary. Psychological terms plausibly form a family somewhat in the way that matrimonial terms do: it is impossible to define any term without defining all the others. But here, too, we may explore the possibility of defining in the first instance not terms but vocabularies. So, to adopt an absurdly simplified example, we might say that pain, belief, and action are a trio of states that stand to each other in such and such a way W*, where W* is specified in terms drawn from a nonpsychological vocabulary. In addition, it is possible to transform this definition of vocabularies into a definition of particular terms. So, for example, we may say that a person S is in pain just in case there are a trio of states x, y, and z such that x, y, and z stand to each other in way W* and S is in state y. Once again, the important point here is that functionalism is a highly sophisticated approach that permits the formulation of a definition of the following form: ð2Þ

x is in pain ¼ def x has D*.

Again, in this definition, ‘‘D*’’ is a stand-in for a no doubt complex expression that contains no expression like ‘‘pain’’ and no expressions like ‘‘belief’’ or ‘‘action’’ that intuitively come from the same family.

10.6. Functionalism and A Priori Entailment Functionalism in philosophy of mind—I will refer simply to functionalism from now on—is a simple but remarkably interesting proposal. It permits a number of different kinds of variation and development, and it raises many questions. But for us, the crucial thing is its connection to the a priori entailment view and, in particular, to the idea that there is a plausible version of the a priori entailment view that is distinct from the epistemic view. We may bring out this connection by concentrating on an argument from functionalism to the falsity of the epistemic view. Its first premise is simply an assertion of functionalism: F1. Functionalism is true. It should be clear that if functionalism is true, then, for every mental term, there is a definition that has the form of (2). So, taking ‘‘pain’’ again as our example, the second premise of the argument is: F2. If functionalism is true, there is a definition of ‘‘pain,’’ even if we have not managed to articulate that definition. The final premise of the argument connects the existence of a definition with the denial of the epistemic view:

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F3. If there is a definition of ‘‘pain,’’ even if we have not managed to articulate the definition, then the epistemic view is false. The intuitive idea behind F3 is that definitions of the sort that exist if functionalism is true are the kind of thing we can come to know through armchair reflection on concepts we already have: the ignorance hypothesis is not to the point. But if that is so, we know that there is a definition of the term ‘‘pain,’’ and the epistemic view is false. One response is to deny that functionalism is true in any form. For example, philosophers who are a posteriori entailment theorists would deny that there are any definitions such as (2). They might, of course, allow that statements like (2) are necessary, but they would not allow that there are any statements like (2) that are necessary and a priori. (I assume that a definition is essentially necessary and a priori. Someone might deny this and say that some definitions are necessary but not a priori. If so, we may restate the point by distinguishing between a priori definitions and others.) However, although one might respond to the argument by appealing to a posteriori entailment, this is not available to us. For we are being neutral on the issue of whether a priori or a posteriori entailment is true. So we can hardly appeal to the truth of a posteriori entailment to dismiss the possibility of functionalism. A better response, from our point of view, starts by pointing out that functionalism can be understood in a variety of ways. One dimension of difference concerns exactly how the nonpsychological vocabulary that the functionalist appeals to is to be understood. On a very liberal interpretation, this vocabulary might contain any possible term at all so long as it is nonpsychological. Let’s call the resultant version of functionalism liberal functionalism. On a conservative interpretation, this vocabulary might contain any nonpsychological term, so long as it is in our current or near current repertoire—that is, so long as we understand it now or perhaps in the near future. Let’s call the resultant version of functionalism conservative functionalism. Clearly, these versions of functionalism are different: conservative functionalism might be false, and liberal functionalism true. But both are permitted by the basic structure of functionalism. A different dimension of difference concerns how exactly to understand definitions of the form of (2). We have seen that any definition, and so (2), must be a priori. But even so, we may draw a distinction between the claim that a definition is merely a priori and the stronger claim that it is a priori and analytic. As I have been using the term, a statement is a priori just in case one could come to know it or justifiably believe it independently of experience. On the other hand, a statement is analytic just in case understanding its constituent terms is sufficient for knowing that it is true. Clearly, if something is analytic, then it is a priori, but the reverse does not hold: it is possible that statement might be such that one could know it or justifiably believe it independently of experience, and yet it is not the case

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that merely understanding it puts one in a position to know that it is true. In view of this distinction, one might draw a further distinction between a version of functionalism that requires only that definitions of psychological terms along the lines of (2) are a priori (we might call the resultant version of functionalism a priori functionalism) and a version of functionalism that requires that the definitions of psychological terms along the lines of (2) are analytic (we might call the resultant version of functionalism analytic functionalism). It should be clear that these two are distinct doctrines: a priori functionalism might be true while analytic functionalism is not. But again, both are permitted by the basic structure of functionalism. Putting these two distinctions together, we have four varieties of functionalism, as indicated in the following table: Table 10.1.

Liberal Conservative

Some Varieties of Functionalism Merely A Priori

Analytic

A C

B D

Now, which variety of functionalism in the table is at issue in the reasoning from F1 to F3? As I will now argue, this question presents a dilemma for a proponent of the argument. In particular, if position A, B, or C is at issue, then the third premise of the argument—that is, F3—is false: it may be the case that there is a definition of ‘‘pain’’ that we have not articulated, but this is not something that a proponent of the epistemic view need deny. On the other hand, if position D is at issue, then the first premise of the argument—that is, F1—is false or, at any rate, not established. For CA and KA themselves suggest that this kind of functionalism is implausible. To illustrate this problem in more detail, let us suppose first that what is at issue in the argument is liberal functionalism of either the analytic or the merely a priori variety—that is, position A or B. The problem with this supposition is that liberal functionalism, just like the a priori entailment view itself, is not inconsistent with the epistemic view. The epistemic view is not denying that one might define experiential terms in nonexperiential terms, nor, more generally, is it denying that one might define psychological terms in nonpsychological terms. On the other hand, if there is no inconsistency between liberal functionalism and the epistemic view, the appeal to functionalism in this context loses all interest. If liberal functionalism is true, it remains possible that we don’t see any mistake or misrepresentation of these cases, not because we haven’t thought hard enough about the information already in our possession but because we are missing some of the relevant information. To put it differently, if liberal functionalism is the kind of functionalism at issue, then F3 is false and the argument collapses.

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So much for liberal functionalism. Suppose now that the functionalism at issue is conservative a priori functionalism: position C. According to Ctype functionalism, there is a definition of ‘‘pain’’ that is a priori but not analytic. Once again, however, this possibility is not inconsistent with the epistemic view, the reason being that it is not inconsistent with versions of the epistemic view that postulate an intermediate-level ignorance. Such views do not or need not deny that there is an a priori definition of phenomenal truths into (say) physical truths. What they do deny is that such definitions are analytic. The reason, roughly, is that on such views one can understand both the physical truths in question and the phenomenal truths, and yet the definitions appear contingent or false because of our ignorance of an intermediate truth. To put the point in terms of conditionals rather than definitions, the proponent of this kind of epistemic view thinks— where N summarizes the physical truths, E the phenomenal truths, and I some intermediate truths of which we are ignorant—that ‘‘If N then I’’ is necessary a priori and ‘‘If I then E’’ is necessary a priori. If these two claims are true, it is reasonable to think also that ‘‘If N then E’’ is likewise necessary a priori. But it is not reasonable to think it is analytic, for one may understand ‘‘If N then E’’ and nevertheless think it is either contingent or false for the reason that one is ignorant of I. In short, if conservative a priori functionalism is true, it remains possible that we fail to find any mistake or misrepresentation in the cases that generate CA and KA only because we are missing some intermediate information; in fact, that is precisely what the epistemic view on one of its versions predicts. Finally, let us suppose that what is at issue in the argument from functionalism is conservative analytic functionalism: position D. In this case there is indeed trouble for the epistemic view, and F3 is true. If the sort of functionalism that is at issue is conservative analytic functionalism—D-type functionalism, as I will say for short—there must be a mistake here, even if we can’t say what it is, and this has nothing to do with our being ignorant of the relevant facts or, at any rate, not in the intended sense. In short, if D-type functionalism is true, the epistemic response to CA and KA is mistaken. However, although D-type functionalism is inconsistent with the epistemic view, it is quite unclear that it is true. To illustrate, consider a simple version of conservative analytic (i.e., D-type) functionalism, commonsense functionalism. Commonsense functionalism, as I understand it, restricts the vocabulary in which one defines psychological terms to nonpsychological commonsense vocabulary and assumes also that the definitions of psychological terms are analytic. Now, CA and KA are normally taken to be, if successful, arguments against commonsense functionalism. So it is no good to appeal to commonsense functionalism in the course of responding to these arguments. Moreover, because the problem with commonsense functionalism is likely to recur with any sort of D-type or conservative analytic functionalism, it is not much good to appeal to that form of functionalism in the course of responding to these arguments.

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In sum, the dilemma faced by a proponent of the a priori entailment view is this. If either liberal functionalism or conservative a priori functionalism is what it at issue, functionalism might well be true, but we have no version of a priori entailment that is distinct from the epistemic view. If conservative analytic functionalism is what is at issue, then we do have a version of a priori entailment that is distinct from the epistemic view, but it is now implausible that functionalism is true.

10.7. Functionalism and Intentionalism How is the proponent of the a priori entailment view to respond to this dilemma? So far as I can see, the only way to develop the argument at this point is to provide an independent reason for supposing that conservative analytic or D-type functionalism is true. If D-type functionalism were true, or if we had good reason to think it true, we would in turn have very good reason for thinking that there is a mistake or misrepresentation in our description of the examples that generate CA and KA, even if we can’t isolate that mistake, and moreover that this has nothing to do with our ignorance of the relevant types of facts. But how is one to argue that this kind of functionalism is true? The recent literature seems to me to present only two possibilities here. The first appeals to what is often called intentionalism (or representationalism; I will use these expressions interchangeably in what follows). In chapter 1, we took note of the idea that experiences have intentionality; that is, they represent the world as being in a certain way. One way to develop this idea is to advance the thesis of intentionalism, according to which phenomenal or experiential truths are entailed by intentional truths—that is, truths that concern the representational aspects of psychological states. Just which intentional truths is a matter of some dispute. Some intentionalists hold (what is sometimes called) first-order intentionalism. According to this development of the view, the phenomenal character of an experience is to be accounted for in terms of what that very experience represents. Other intentionalists hold (what is sometimes called) higherorder intentionalism, according to which the phenomenal character of an experience is to be accounted for by appealing to the way other psychological states represent it. In what follows, I will concentrate on first-order intentionalism, but what I have to say will, I think, have fairly straightforward application to higher-order intentionalism. (For some recent defenses of higher-order intentionalism, see Carruthers 2000 and Lormand forthcoming.) But how is the argument from intentionalism to D-type functionalism to be developed? Its first premise is simply a statement of intentionalism: I1. Every phenomenal truth is entailed by some intentional truth.

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The second premise of the argument is a thesis about intentional truths— namely, that such truths may be given a D-type definition in physical or nonexperiential terms and so follow from truths that may be given such a definition. If we call such truths ‘‘D-type functional truths,’’ the second premise might be formulated as follows: I2. Every intentional truth is entailed by some D-type functional truth— that is, some truth that admits of a conservative analytic functional definition. The motivation for this premise is the idea that intentionality itself can be accounted for in causal, informational, or teleological terms. This idea was widely promoted in discussion of philosophy of mind and language in the 1980s, including in particular Fodor 1987 and related work. Although many find the details of these proposals controversial, many people have found the general idea that there is some definition along these lines to be very plausible; hence, many have thought I2 to be plausible. Now, from I1 and I2 we may obviously derive a conclusion—namely, I3. Every experiential truth follows from some D-type functional truth. And in turn, I3 is at least close to the view that experiential truths have an analytic conservative functional definition. In short, if intentionalism is true, and if a plausible thesis about intentional truths is true, it follows that every experiential truth has an analytic conservative functional definition. Hence there must be some mistake or misrepresentation in the cases that generate CA and KA, even if we can’t put our finger on what it is; moreover, this fact has nothing to do with our ignorance. One objection to this line of argument is that even if I3 were true, it would not show that experiential truths themselves admit of a conservative functional definition. For example, one might hold that following from truths that have conservative functional definitions is one thing, and having a conservative functional definition is quite another. However, although it is true that there is a distinction here, I am not going to pursue matters in this direction. Presumably, a proponent of the argument would say that one truth follows from another just in case the conditional formed from these truths is analytic. But if so, the step from following from truths that have such and such a definition to having such and such a definition is very short indeed. A different objection points out that, just as functionalism may be interpreted in different ways, so, too, may the notion of an intentional truth, and so intentionalism itself. On one way, the intentional truths may themselves be understood in nonphenomenal terms. Operating with that conception of intentional truths results in a particular version of intentionalism I will call reductive intentionalism. On the other way, the intentional truths may not themselves be understood in nonphenomenal terms. Operating with that conception of intentional truths results in a particular version of intentionalism I will call nonreductive intentionalism. Now which of reductive

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or nonreductive intentionalism is at issue in this argument? As in the case of functionalism, this question poses a dilemma for a proponent of the argument we are considering. (I have developed this argument in more detail elsewhere; see Stoljar 2005a; see also Chalmers 2004.) Suppose first that nonreductive intentionalism is at issue. Then I1, and so intentionalism itself, is true—indeed, obviously so. On the other hand, on this interpretation, the claim that intentional truths can be given a D-type functional definition is no more plausible than the claim that phenomenal character can be given a D-type functional definition. But as we have seen, it is plausible to say that CA and KA are precisely arguments that no sort of definition can be given. On this interpretation, in other words, the premise of the argument, I2, is no more plausible than its conclusion, I3. But then the argument could not possibly be used to establish I3 with any degree of persuasiveness. Of course, it remains true that many philosophers have advanced reasons for thinking that something like I2 is true. As I have indicated, many philosophers take the debates in philosophy of mind and language in the 1980s to make this premise quite plausible. However, in my view suggestions of this sort fail to take note of the fact that the typical debate in the 1980s surrounding intentionality has a focus slightly different from the debate about experience. The debates about intentionality are typically focused on the idea that intentional truths might be as a class irreducible—as it is sometimes put, that there is no way to break out of the intentional circle. To put things in the framework we have been adopting, these debates are driven by the idea that no intentional truth is entailed by any truth that admits of a Dtype definition. But the negation of that idea is not I2 but instead the closely related I2*: I2* Some intentional truth or other is entailed by some D-type truth—that is, some truth that admits of an analytic conservative functional definition. Obviously, I2* is a different thesis from I2; the first is about whether some intentional truths follow from conservative functional truths; the second is about whether all do. Moreover, even if I2* is true, and even if I1 is true, it scarcely follows that I3 is true. The intentional truths that make I2* true might simply be quite different from the ones that make I1 true. To put it differently, the debates about intentionality from the 1980s make it plausible that I2* is true, but they do not make it plausible that I2 is true, and it is I2 that is required by the argument we are considering. I have been concentrating on the idea that the notion of an intentional truth, and so of intentionalism itself, should be interpreted as a nonreductive thesis. Suppose now that reductive intentionalism is at issue; that is, suppose that intentional truths can be understood in nonphenomenal terms. Then the situation is the reverse of that we encountered when thinking about nonreductive intentionalism. In particular, it now seems that I2 is

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true or, at any rate, could perfectly well be. On the other hand, on this interpretation, the claim that phenomenal truths are entailed by intentional truths is no more plausible than the claim that phenomenal truths are entailed by physical truths. On this interpretation, in other words, the first premise of the argument, I1, is no more plausible than its conclusion, I3. But again, in that case the argument could not possibly be used to establish I3 with any degree of persuasiveness. In drawing the distinction between reductive and nonreductive intentionalism, and in suggesting that this distinction scuppers any attempt to infer D-type functionalism from intentionalism, I have not really entered into the debate about the status and plausibility of intentionalism. For present purposes, however, there is no reason to examine this complicated debate further. Our interest in intentionalism has been driven by the idea that it might provide an independent reason for supposing that D-type functionalism is true, and our interest in D-type functionalism has been driven by the idea that, if it is true, we have a very good reason for supposing that a nonignorance-based response to CA and KA is available. What we have been led to, however, is the opposite conclusion. Appealing to intentionalism does not in any way change the basic shape of the problem for the a priori entailment view, for intentionalism itself provides no persuasive reason for thinking that D-type functionalism is plausible.

10.8. Functionalism as a Theory of Understanding The second way of responding to the dilemma I presented for the use of functionalism starts off by noting a slightly different way in which functionalism may be understood. So far, I have been presenting functionalism as a thesis about the definitions of words or concepts. But functionalism is sometimes thought of not (or not only) as a thesis about the definitions of various words or concepts but rather as a thesis about what it is to understand those words or concepts (e.g., in Lewis 1994). On this development of the view, to understand a term is to understand its conservative analytic or D-type functional definition. Now, with this account of understanding in place, we confront a new argument for conservative analytic functionalism. Taking ‘‘pain’’ as our example, the picture of understanding just reviewed yields U1. U1. I understand the word ‘‘pain’’ if and only if I tacitly know its D-type functional definition; that is, its conservative analytic functionalist definition. If we permit ourselves the obvious truth that I do indeed understand the word, we may infer: U2. I tacitly know the D-type functionalist definition of ‘‘pain.’’

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But if U2 is true, ‘‘pain’’ must indeed have a conservative functionalist definition, so we may infer: U3. The word ‘‘pain’’ has a D-type functionalist definition. However, from U3, the version of a priori entailment view that we are interested in follows directly. If ‘‘pain’’ has a folk psychological definition, ‘‘pain’’ is definable in nonexperiential terms that we do understand and, in particular, in terms of causation and behavior-in-circumstances. But then there must be a mistake in CA and KA, even if we cannot put our finger on where it is. There is obviously nothing wrong with the validity of this argument, and the assumption that we understand the word ‘‘pain’’ is, I take it, a datum. On the other hand, U3 is false. As we have just seen, it is implausible that mental terms, such as ‘‘pain,’’ have D-type definitions in the sense we have introduced. At any rate, it is implausible to suppose so in the course of responding to CA or KA, for those arguments, if successful, precisely refute the idea that there is such a definition. Moreover, if U3 is false, then so, too, is U2: If the word ‘‘pain’’ has no conservative functionalist definition, then it can’t be that I tacitly know the definition—you can’t know x if x doesn’t exist. Of course, the mere suggestion that both U3 and U2 are false is not enough to dispose of this argument. For both follow from the theory of understanding articulated in U1, together with the obvious fact that I understand the word ‘‘pain.’’ In short, we have arrived at the idea that the view about understanding embodied in U1 is false, and our response to the argument will not be complete unless we can at least gesture at an alternative. One possibility is that to understand ‘‘pain’’ is to tacitly know its definition but not its conservative analytic functional definition—its liberal functional definition, say. Now, there is no objection to there being such a definition, at least none that I have given. Nevertheless, it can’t be that understanding ‘‘pain’’ is knowing its liberal functional definition. For the fact is that we can understand ‘‘pain’’ and not know its liberal definition. Indeed, it is this suggestion that lies at the heart of the epistemic view. According to that view, we are ignorant of some of the terms in that definition—if, that is, it has a definition at all. A more plausible possibility is that one can understand ‘‘pain’’ without knowing any definition at all. In Naming and Necessity (1980), Kripke discusses the suggestion that one could fix the reference of ‘‘pain’’ by saying ‘‘let ‘pain’ pick out this experience,’’ where the demonstrative picks out pain itself. One might develop what Kripke says here into an account of what it is to understand the word ‘‘pain’’ that would take the following form (I assume again that the demonstrative refers to pain itself): U1* I understand the word ‘‘pain’’ if and only if I know that it picks out this experience.

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One interesting feature of this account is that it incorporates a de re or externalist element into the idea of understanding ‘‘pain.’’ Here we are using pain itself to characterize the state of understanding the word ‘‘pain’’; indeed, this is a point I will come back to in the following chapter. Another interesting feature is that if this picture of what it is to understand ‘‘pain’’ is right, one could understand it without knowing its conservative analytic functional definition. It might be objected that on this account of what it is to understand the word ‘‘pain,’’ you do indeed understand a definition, for you know that pain is this experience, and that claim can itself be thought of as a definition. But it is quite implausible that ‘‘pain is this experience’’ is a definition of pain; for one thing, it is a posteriori, and no definition is a posteriori, at least as I understand matters. However, even if I am wrong about this, it is possible to finesse this point rather than confront it directly. Whether or not ‘‘pain is this experience’’ is a definition of ‘‘pain,’’ it is clearly not its conservative analytic functional definition. Hence the point remains that U1* is a view about what it is to understand ‘‘pain’’ that is distinct from U1. And it is only U1 that entails that ‘‘pain’’ has a conservative analytic functional definition and so is a threat to our position. Alternatively, it might be objected that all I have done is sketch some possibilities. One possibility is U1; this possibility is inconsistent with the epistemic view. Another possibility is U1*; this possibility is not inconsistent with the epistemic view. But what I have not done is go into detail about which possibility is the right one and why. These are questions that I am going to make no attempt to answer here. It is enough for our purposes to say that the account of understanding that is set out in U1 is not mandatory. If that is right, the argument we are considering is unpersuasive.

10.9. Conclusion We have been pursuing the idea that what has gone wrong in the arguments for T3 is that we have failed to think through the relevant cases, not in the sense that we may be missing some information but in the sense that we have not thought through the information already in our possession. I began by considering a straightforward implementation of this idea. I then considered a less straightforward implementation, wherein one appeals to functionalism to show there must be some mistake or misrepresentation in our description of the cases, even if we cannot say exactly what it is. I think both versions of the approach are unpersuasive and that, as a result, we have failed to find a version of the a priori entailment view that is both plausible and distinct from the epistemic view. We are now in a position to summarize the project I began at the beginning of the previous chapter. The starting point of that project was to distinguish the question ‘‘what, if anything, is wrong with CA and KA?’’ from the question ‘‘what is the epistemic status of the experiential conditional?’’

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Obviously, the a priori and a posteriori entailment views give contrasting answers to the second question, but my suggestion is that they give no answer at all to the first question. On the other hand, if one adds further material to both views so that they do or may answer the first question, the result is either something that is implausible or something that is no different from the epistemic view. At this point, however, I should acknowledge a weakness in our discussion, a weakness that I am sure some readers have noticed: I have considered the a priori and a posteriori entailment views in a rather piecemeal fashion. In particular, I have criticized various proposals but have offered no direct argument that nothing here can work. I want to close this chapter by briefly offering such an argument. We may begin by returning again to the point that neither the a posteriori entailment view nor the a priori entailment view on its own tells us what has gone wrong in CA and KA, assuming for the moment that something has gone wrong. To do that, one must embellish these positions by adding further material. What further material can be added? Well, one possibility, as I have mentioned, is to appeal to ignorance, and so to appeal to the position we have been advancing. However, suppose that we set ignorance aside. Suppose, in other words, that we are assuming that all the relevant types of facts are in. Under that supposition, it is reasonable to divide into two broad categories the sorts of consideration that might be added to either a priori or a posteriori entailment. On the one hand, one might attempt to argue that CA and KA presuppose a mistaken account or picture of what experience is. This sort of approach is typical of those we examined in this chapter, approaches that are either functionalist or developments thereof. In effect, the proponents of these views say: ‘‘Look, you have a mistaken basic picture of what an experience is. If you adopt my picture, the correct picture, you will see that the arguments are mistaken.’’ This strategy is often combined with a commitment to the a priori entailment view, but as I hope my previous discussion indicates, there is no necessity in this connection. On the other hand, one might attempt to argue that CA and KA presuppose a mistaken account of our thought and talk about experience. This sort of approach is typical of the various approaches we examined in the previous chapter, approaches that focus on phenomenal concepts or terms rather than on what those concepts or terms denote. In effect, proponents of these views say: ‘‘Look, you have a mistaken basic picture of the behavior of the words or concepts we use to describe experiences. If you adopt my picture, the correct picture, you will see that the arguments are mistaken.’’ This strategy is often combined with a commitment to the a posteriori entailment view, but as I hope my previous discussion indicates, there is no necessity in this connection. So the first premise of the direct argument I am constructing is this: If one wants to claim that there is a mistake in CA and KA, and if one wants to

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claim that the mistake has nothing to do with the ignorance hypothesis, there are two strategies available, both of which we may refer to as conceptual strategies. The first says that the arguments presuppose a mistaken picture or account of experience; the second says that the arguments presuppose a mistaken picture or account of ‘‘experience’’—that is, of thought and talk about experience. The second premise is that neither conceptual strategy works. The difficulty with suggesting that the problem has its source in a mistaken conception of experience is, as we noted in chapter 1, that the conception of experience that generates the problem is a minimal one. It is not as if the notion of experience that is presupposed by CA or KA is a particularly loaded one. We might put the point differently by saying that in a certain sense we don’t have much of a conception of experience. It is rather that we have certain experiences and find ourselves liable to react to them in various ways. The difficulty with suggesting that the problem has its source in a mistaken conception of our thought and talk about experience is that what makes this thought and talk distinctive is really its subject matter. It is true, of course, that experience is associated or seems to be associated with a distinctive epistemology. But the problem is that this distinctive epistemology is not unique to experiences. For example, to the extent that it is plausible to say that experiences are self-presenting, the same thing seems to be true for thoughts or beliefs. But psychological states or episodes of this kind do not generate persuasive arguments such as CA and KA. If neither of the conceptual strategies works, and if these are the two strategies available to us if we set aside the epistemic view, we may conclude that no view short of the epistemic view will be able to say what, if anything, is wrong in the arguments for T3. There is no conceptual solution to the problem of experience.

11 Genuine Rivals, Revelation, and Concluding Remarks

11.1. Introduction The logical problem of experience presents us with three theses that on reflection we have reason to endorse but that are jointly contradictory: T1. T2. T3.

There are experiential truths. If there are experiential truths, every experiential truth is entailed by some nonexperiential truth. If there are experiential truths, not every experiential truth is entailed by some nonexperiential truth.

The intellectual project we have undertaken is to decide which course of action to adopt in the face of this inconsistency. In pursuing this project, my attention has been occupied so far wholly with the arguments for T3— namely, CA and KA. I have presented and defended one view about how these arguments go wrong, the epistemic view, and criticized a number of apparently alternative views of the same issue. As we have seen, these views are either not plausible or not alternatives. I want now to close our discussion by doing three things. First, I will briefly evaluate both the eliminativist suggestion that T1 is false and the primitivist suggestion that T2 is false. As noted at the beginning of part III, these are genuine alternatives to the epistemic view, and I have so far said little that is negative about them. Second, I will discuss an argument in favor of this pair of views that is equally an objection to the epistemic view—an argument based on the recently notorious doctrine of revelation. Third, I will draw out some general morals from our discussion.

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11.2. Initial Comparisons How should the critique of eliminativism and primitivism proceed? The first thing to say is that there is nothing a priori false about these views; there is no way to refute them. Rather, the issue turns on whether the balance of probabilities goes with the epistemic view or, alternatively, with one of eliminativism or primitivism. Of course, this in turn depends on what one’s own prior convictions are. But speaking for myself and I think for many others, the epistemic view is more probable, at least as an initial assessment. There are three related points to make. First, much of the motivation for both eliminativism and primitivism derives from CA and KA. What unites them is the idea that these arguments are successful in establishing T3. What divides them is how to respond to this idea: eliminativists reject T1, and primitivists T2. On the other hand, if what I have been saying is correct, CA and KA are not successful in establishing T3. Of course, it might be said about the epistemic view that its motivation derives from its ability to answer CA and KA. But the epistemic view advertises itself as also having independent motivation; that is, it is independently plausible both that the ignorance hypothesis is true and that if it is true, CA and KA are unsuccessful. Hence, in the absence of independent arguments in favor of the alternatives—I will consider one proposal in a minute—it is more plausible to endorse the epistemic view. Second, it is implausible to reject either T1 or T2. In talking about the reasons for T1, we took note of its obviousness, and in introducing the phenomenal conception of experience, we took note of its being a minimal conception; that is, it avoids many of the controversies that one can raise in thinking about experience. This makes it most probable that T1 is true. Similarly, in talking about the reasons for T2, we distinguished two arguments, the argument from physicalism and the argument from manifest supervenience. As we noted, the argument from physicalism is certainly controversial, in part because it is unclear precisely what being physical amounts to. But even if that is so, the argument from manifest supervenience remains plausible. It might be objected against manifest supervenience that primitivism can be advanced as an empirical thesis, akin to vitalism in biology. In my view, however, appeals to vitalism in this context should be approached with considerable caution. It is certainly a conceivable empirical speculation that there are two (or more) sorts of fundamental stuff in the world and, moreover, that one of these sorts is more fruitfully described employing standard mental vocabulary than standard physical vocabulary. Indeed, a proposal along these lines emerged in chapter 3, when we considered Lewis’s suggestion that KA, if successful, would refute not only physicalism but also a certain form of dualism. But the form of dualism that Lewis has in mind is not relevant to the sort of primitivism that is important for us. What is being

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considered here is that the experiential as we currently understand it is primitive—that is, does not supervene on the nonexperiential. It is not easy to make sense of this idea being incorporated into any scientific or naturalistic inquiry, precisely because of manifest supervenience. So the analogy to vitalism is a weak ground on which to base one’s primitivism. Alternatively, it might be objected that one may endorse manifest supervenience and still be a primitivist. In chapter 7, we considered Broad’s emergentism and noted that this was a distinctive form of primitivism in that it combined primitivism with a commitment to experiential supervenience. In particular, the emergentist holds that experiential truths supervene on nonexperiential truths, and yet the facts reported by experiential truths are metaphysically distinct from the facts reported by the nonexperiential truths; it is the latter commitment that marks the emergentist as a primitivist. Presumably, an emergentist like Broad could accept manifest supervenience while at the same time being a primitivist; how, then, could the truth of manifest supervenience be used against primitivism? However, although Broad could certainly endorse the letter of manifest supervenience, it is much less clear that he may endorse its spirit. As we noted in chapter 7, the emergentist is committed to the denial of the Humean dictum that there are no necessary connections between metaphysically distinct existences. The questions of whether Hume’s dictum is true and what precisely it means are difficult; however, as we have also noted, even if the dictum is false, it would not make the various arguments and theses that constitute the logical problem of experience disappear. It would mean only that they should be reformulated so that they are arguments and theses explicitly about metaphysical distinctness, rather than about modality. We made use of this point when considering the apparent problem that Broad endorses KA and yet is committed to there being a necessary connection between the experiential and the nonexperiential. We may also make use of it when thinking about the relation between Broad’s emergentism and manifest supervenience. In particular, for someone who denies Hume’s dictum, manifest supervenience should be interpreted as saying not that the manifest truths supervene on scientific truths but, rather, that the facts expressed by manifest truths are not metaphysically distinct from the facts expressed by scientific truths. This latter thesis seems to precisely capture the idea that is expressed by manifest supervenience—though presumably it should not be named ‘‘manifest supervenience’’—and yet it is inconsistent with primitivism of any sort, for primitivism of any sort entails that the experiential is metaphysically distinct from the nonexperiential. The final point to make by way of initial comparison of our view, on the one hand, and primitivism and eliminativism, on the other, is that these latter views, at least insofar as they rely on KA and CA, implicitly deny the ignorance hypothesis. It is hard to see how primitivists can confidently say that experiential truths are distinct from nonexperiential truths unless they are in a position to say with confidence just which truths the nonexperiential

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truths are; mutatis mutandis for eliminativists and their claim that, because no experiential truths are entailed by any nonexperiential truths, there are no such truths. In the context, however, to say just which truths the nonexperiential truths are is to deny the ignorance hypothesis. As we have seen, however, there is considerable reason against this denial. At least at a superficial level, therefore, things look rather bad for the genuine alternatives to our position and correspondingly good for the epistemic view. Of course, this situation would change if there were independent arguments in favor of eliminativism or primitivism, where by ‘‘an independent argument’’ I mean one independent of the issues surrounding the evaluation of the modal arguments, CA and KA. Are there such arguments? Well, there are certainly independent arguments against eliminativism and primitivism. For example, some say that eliminativism is incoherent, on the grounds that whether there are experiences is a contingent matter of fact and that one needs to rely on experience in order to establish a contingent matter of fact. Similarly, some say that primitivism is false, on the ground that it is inconsistent with, or cannot give a proper account of, the facts of mental causation—the fact that we sometimes act because we are in pain or have a blue sensation. Both of these arguments raise controversial and interesting issues, but I will not pursue them here. For one thing, they have been extensively discussed elsewhere, and I have nothing much to add to what has been said. More important, even if they were persuasive, it would not affect our main suggestion. A further argument against eliminativism and primitivism would give us no reason to change our initial assessment of the relative merits of the epistemic view and its alternatives.

11.3. Revelation There is, however, at least one independent argument in favor of these alternatives that we do need to consider, an argument whose starting point is a notorious thesis in philosophy of mind called ‘‘revelation.’’ Moreover, this argument is important for another reason as well: It constitutes a straightforward objection to the epistemic view that I have so far been ignoring. So in what follows, I will set out the basic idea of this argument and respond to it.

11.3.1. The Basic Idea According to the thesis of revelation, having an experience puts you in a remarkable epistemic position: you know all the essential properties of the experience; the only thing left to learn are its nonessential or accidental properties. Suppose, for example, I have an itch in my toe. If revelation is true, I know every essential property of the itch and in this sense know its nature or essence. The only things left to know are various facts about the distribution of something with this essence or nature; for example, whether

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other people have similar itches, and when, and what having such itches causes and is caused by. Does the chair of the department have a similar itch? Did he have it last Wednesday during the faculty meeting? Did it last the whole meeting? Of course, questions of this sort raise further philosophical issues. For example, skeptics about other minds will say that I cannot know or justifiably believe that the department chair has a similar itch. But skepticism about other minds is not to the point when it comes to revelation. Revelation says only that having an experience puts you in a position such that you have only the accidental truths about the experience left to learn. Whether you will learn those truths in fact is irrelevant. This epistemic position—the one that, according to revelation, I am in with respect to this itch, if I have it—is to be contrasted with the epistemic position I am typically in with respect to other things. Suppose, for example, I have a diamond in my pocket. It does not begin to follow that I know every essential property of the diamond or its essence or nature, or that the only things left to know are various facts about the distribution of things with this essence or nature—whether other people have similar diamonds, etc. For one thing, merely having a diamond in my pocket puts me in no epistemic position whatsoever. I may have a diamond in my pocket and have no idea what diamonds are. Moreover, even if I know what diamonds are, I may be ignorant of some of their essential properties. For example, I may be quite ignorant of the chemical nature of diamonds, and thus ignorant of something essential to them. And yet, I know what diamonds are in the ordinary sense that most of us do; that is, I am able to reliably to pick out the diamonds at a jeweler’s, distinguish diamonds from other stones, and so on. So according to proponents of revelation, having an itch puts one in an epistemic position with respect to itches in a way that having a diamond does not put one in with respect to diamonds. I am in a position with respect to itches (and experiences more generally) such that the only thing left to learn are accidental truths. But I am not in that position with respect to diamonds. Revelation has been held to be plausible both about experiences themselves and for properties that experiences are intimately connected to, such as colors. In fact, it is the literature on color that contains the largest discussion of revelation (see Johnston 1992, Strawson 1989, Lewis 1995, 1997; the terminology is due to Johnston). In the version that pertains to color, the thesis says that having an experience as of (e.g.) red puts you in a remarkable epistemic position with respect not to the experience of red but to red itself. In particular, you know all of the essential features of red and in this sense know its nature or essence. The only thing left to learn are accidental features. Whether revelation is true for colors in addition to experience as of color, and to experiences in general, is an interesting issue that raises some questions that do not arise in the experience case. For the most part, however, I will concentrate here on experiences themselves rather than what experiences are of.

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11.3.2. Revelation and Self-Presentation To say that revelation is true of experiences is in effect to advance one principle about the relation between experience, on the one hand, and knowledge or justified belief, on the other. It is to say that if you have an experience, then you are in some sort of epistemic position with respect to it. But there is a whole class of different principles along these lines (see Alston 1971), and revelation is a fairly extreme principle within that class. For example, consider another principle about the relation between experience and knowledge or justified belief that we have already considered at some length—namely, self-presentation. According to self-presentation, having an experience puts you in a position to know or justifiably believe that you are having the experience. But self-presentation is neither necessary nor sufficient for revelation. Self-presentation is not sufficient for revelation because it is possible to be in a position to know that a property is instantiated without being in a position to know the essence of that property. Suppose I know perfectly well that there is a diamond in my pocket, and so I know that the property of being a diamond is instantiated in my pocket. If I know there is a diamond in my pocket, I am in a position to know it: Trivially, if you know something, you are in a position to know it. Am I in a position to know the essence of diamonds? Surely not—knowing the essence of diamonds would involve at least knowing their chemical composition and maybe a good deal more besides. But chemical ignoramus that I am, I know nothing of such things. All I know is that I have a diamond in my pocket. So I am in a position to know there is a diamond in my pocket but not in a position to know the essence of diamonds. Self-presentation is not necessary for revelation because knowledge of the essence of a property does not entail knowledge that you yourself instantiate it. As an illustration, suppose that revelation is true and that on having an experience I do indeed know the essence of the experience. To know the essence of the experience is not to know its accidental features. So it is consistent with revelation that I fail to know every accidental feature of the experience. However, that I myself have the experience is one accidental feature of the experience; after all, it is not part of the essence of any experience that I have it. But then it is possible that I know the essence of the experience and not know that I myself have the experience.

11.3.3. The Argument from Revelation So much, then, for what revelation says; what does it matter if it is true? Well, as I indicated earlier, one reason it matters is that if revelation is true, we have a direct argument for either primitivism or eliminativism. The argument proceeds by pointing out that when revelation is combined with an agreed-on fact, it is inconsistent with the denial of both eliminativism and

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primitivism. The primitivist uses this inconsistency to argue for primitivism; the eliminativist uses it to argue for eliminativism. Why is it that, when revelation is combined with an agreed-on fact, it is inconsistent with the denial of eliminativism and primitivism? The inconsistency can be presented in straightforward fashion as follows: (1) If Jones has an experience of type E, then for every essential truth T about E, Jones knows, or is in a position to know, T. (2) Jones has an experience of type E. (3) The following is one essential truth about E: there is a physical condition of type C such that C entails E. (4) Jones does not know, and is not in a position to know, that there is a physical condition of type C such that C entails E. It should be clear, first, that these four claims are inconsistent. If (1) and (2) are true, then Jones knows every essential truth about E. But if (3) and (4) are true, Jones does not know every essential truth about E—that is, because he does not know at least one essential truth, namely, the truth that physical condition C is metaphysically sufficient for E. On the other hand, (1) follows from revelation, (2) follows from (or is an instance of something that follows from) the denial of eliminativism, (3) follows from (or is an instance of something that follows from) the denial of primitivism, and (4) is a statement of fact about Jones that we can assume or at least stipulate to be true— this is the agreed-on fact I mentioned earlier. If (1–4) are inconsistent, one of them is false. Setting aside (4), the only options left are to deny (1), (2), or (3). Primitivists and eliminativists say that because (1) is true, our options are either primitivism or eliminativism and then draw the conclusion that is appropriate for their position. That is the argument from revelation to the disjunction of primitivism and eliminativism.

11.3.4. The Significance of the Argument The thesis of revelation is interesting because it suggests a straightforward argument for either eliminativism or primitivism. But it is also of interest for the further reason that, if revelation is true, the epistemic view is false. One way to bring this out is to notice again that, as we have been developing it here, the epistemic view is inconsistent with primitivism or eliminativism. Hence, because the argument from revelation is an argument for primitivism and eliminativism, it is equally an argument against the epistemic view. More generally, the basic epistemic posture of someone attracted to revelation is quite different from the basic epistemic posture of someone attracted to the epistemic view. Throughout our discussion, I have taken for granted that we are ignorant of consciousness, ignorant of its nature, and so on. I have insisted that this is a fact and, moreover, that there is no reason that philosophy of mind might not draw on this fact as much as anyone else.

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But—as I noted briefly in chapter 5—for a proponent of revelation, there is something deeply wrong with this point of view. If revelation is true, we are not ignorant of the nature of conscious experience. Of course, it might be the case that we are ignorant of some accidental facts about conscious experience, but the idea that we are ignorant about any necessary or essential truths about it is anathema. To put the point slightly differently, I said that (4)—the claim that Jones does not know or is not in a position to know that C entails E—is (or can be taken to be) an agreed-on fact. In saying this, I meant that we could perfectly well imagine a person Jones for whom it is the case that (4) is true. However, if the epistemic view is true, Jones is not simply a person for whom this might be true; he is everyman, an exemplar for all of us. In short, the argument from revelation is on a collision course with the epistemic view.

11.4. Essential Truths and Necessary Truths How then to respond? The first response I want to consider focuses on a distinction between an essential truth, on the one hand, and a necessary truth on the other. Kit Fine (1994), for example, famously argues that it is necessary that Socrates is a member of his singleton set—that is, the set that has only Socrates as a member—but it is not essential to Socrates that he is a member of this set. As Fine also says, it is similarly necessary that Socrates is such that 2 þ 2 ¼ 4, but it is not essential to Socrates that he is. Armed with this distinction, one might argue that (3) is false: (3) The following is an essential truth about E: there is a physical condition of type C such that C entails E. It is no part of the essence of E, one might argue, that C entails it; at any rate, there is no reason that anyone who denies primitivism needs to be committed to this. What is plausible, rather, is (3-n): (3-n) The following is a necessary truth about E: there is a physical condition of type C such that C entails E. But if that is true, the argument collapses: what is plausible is not (1–4); what is plausible is only (3-n), (1), (2), and (4). But these four present no contradiction. Of course, if one should distinguish (3) from (3-n), one should likewise distinguish (1) from (1-n), as follows: (1-n) If Jones has an experience of type E, then for every necessary truth T about E, Jones knows, or is a position to know, T. Moreover, if (1-n) is true, we have the contradiction back again. However, the proponent of the objection that I am imagining will respond that (1-n) is false. Revelation is the doctrine that if one has an experience, one knows the

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experience in its essence. It is not the doctrine that if one has an experience, one knows every necessary truth about the experience. In short, if we may draw a distinction between essential truths and necessary truths, we may respond to the argument from revelation with the assertion that there is no genuine contradiction here. However, although this response is in some ways attractive, it has two defects. The first defect is that it is difficult to know how to control the distinction between essential and necessary truths. Proponents of the argument from revelation might be impressed by Fine’s discussion of Socrates and nevertheless doubt its application to the present case. In particular, they might simply insist that while (3-n) is plausible, so to is (3). It is hard to know how to respond to this sort of insistence. The second defect is that some philosophers who hold that experiential truths supervene on nonexperiential truths do so because they hold that the facts or properties or conditions reported by experiential truths are numerically identical to the facts or properties or conditions reported by nonexperiential truths; they hold, as I shall say, an identity version of experiential supervenience. For these philosophers, however, the distinction between essential and necessary truths is no help when it comes to the argument from revelation. To illustrate this, suppose one held an identity version of experiential supervenience. Then (3) in the preceding argument should be properly replaced with (3-i): (3-i) The following is an essential truth about E: there is a physical condition C of type C such that C is identical to E. Likewise, (4) should be replaced with (4-i): (4-i) Jones does not know, and is not in a position to know, that there is a physical condition of type C such that C is identical to E. It should be clear that (1), (2), (3-i), and (4-i) present a contradiction, just as the original quartet did. But this time there is no possibility of appealing to the distinction between essence and necessity to escape the problem. It is implausible to deny that being identical to C is part of E’s essence. Perhaps it is no part of Socrates’ essence that he is a member of his singleton set, but presumably it is part of his essence that he is Socrates. So shifting to an identity version of experiential supervenience means that the necessityessence distinction cannot be used to disarm the argument from revelation. ‘‘So much the worse for identity versions of experiential supervenience,’’ one might say, ‘‘and for the philosophers who hold them.’’ But this is not the approach I will take here. Early on in our discussion (in chapter 2), I noted that there was a considerable literature on how exactly to formulate physicalism—and, related to this, experiential supervenience—and that some philosophers prefer identity- or realization-based accounts rather than supervenience-based accounts. I also said that I was setting this complication

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aside because it would have no effect on what we have said. In the light of this, it would be bad form to appeal to an identity version of experiential supervenience, especially at this late stage in our discussion. So for me at least, there is no choice but to consider a second response to the problem presented by (1–4).

11.5. Revelation and Understanding The argument from revelation threatens to show that either primitivism or eliminativism is true and, related to this, that the epistemic view is false. The first response to this argument that I considered was to draw a distinction between essential truths and necessary truths. The problems with this response are, first, that it is controversial whether the distinction applies in the present case and, second, that the response is unavailable to a person who thinks that the facts reported by experiential truths are identical to the facts reported by nonexperiential truths. The second response I want to consider looks more closely at the reasons for believing the thesis of revelation in the first place.

11.5.1. Lewis on the Part-Whole Relation We may approach this issue by considering a comment Lewis made in his discussion of these issues that is initially extremely strange. Lewis rejects revelation as it pertains both to experience and to color, but he also says: ‘‘maybe revelation is true in other cases—as it might be for the part-whole relation’’ (Lewis, 1997, 353 n. 21). This is unexpected. As we have noted, revelation is normally thought to apply to experiences or perhaps to properties that are by reputation intimately connected to experiences, such as colors. How, then, could revelation be true of the part-whole relation? We don’t have experiences as of the part-whole relation! The way forward here is to notice that there are two slightly different theses doing business under the label ‘‘revelation.’’ The first, which I will call e-revelation, is a thesis about what happens when you have an experience. This is, or for our purposes may be assumed to be: (1) If Jones has an experience of type E, then for every essential truth T about E, Jones knows, or is a position to know, T. Obviously (1) is the thesis with which we have been operating so far, so we may say that the preceding argument exploits e-revelation. But e-revelation needs to be set apart from a related thesis, which I will call u-revelation. This concerns what happens not when you have an experience but rather when you understand what an experience is. This is, or for our purposes may be assumed to be: (5) If Jones understands what an experience of type E is, then for every essential truth T about E, Jones knows, or is in a position to know, T.

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Obviously, (5) is different from (1). To say that having an experience puts one in an epistemic position is not the same as saying that understanding experience does. More generally, e-revelation is not u-revelation. On the other hand, although e-revelation is not u-revelation, the two are closely related. For notice that there is a third thesis that, when combined with (1), will generate (5). This third thesis is: (6) If Jones has an experience of type E, he thereby understands what an experience of type E is. Like both revelation and self-presentation, (6) is one of a class of theses about experience, on the one hand, and about knowledge or justified belief, on the other. But it is a fairly plausible principle within this class. Surely, it is plausible that if you have an itch, then at the very moment that you have the itch, you understand what itches are. Of course, you may forget a second later. And you may not know the word for ‘‘itch’’ in English or any other language; your understanding may be in an important sense subverbal or nonconceptual. But surely you know what itches are and so understand them in any normal sense. So the two points we have isolated are these: first, e-revelation is distinct from u-revelation; second, e-revelation follows from u-revelation together with a plausible further principle, according to which if you have an experience of a certain type, then you understand what that experience is. These two points suggest a third about the relation between e-revelation and u-revelation—namely, that it is reasonable to regard u-revelation as the basic doctrine here and, correlatively, to assign e-revelation a derived status. The basic doctrine at issue here is u-revelation; e-revelation is something that follows from this basic doctrine, together with the view that if you have an experience, you understand it. This array of points permits us to explain Lewis’s initially odd remark about whole and part. When Lewis says that revelation is or might be true of the relation of whole and part, he does not mean to be invoking e-revelation and therefore claiming that having an experience of the relation of whole and part puts you in a position to know the essence of that relation. This claim lacks clear sense because it is unclear what it is to have an experience of the whole and part relation. Rather, he is invoking u-revelation and means that if you understand what the relation of whole and part is, you know the essence of the relation. More generally, because u-revelation is a thesis about understanding and is not a thesis about experience, it might be applied without oddity to domains, such as whole and part, in which experience has no role.

11.5.2. The Problem with the Argument We have used Lewis’s comment about whole and part to motivate and introduce the distinction between u-revelation and e-revelation. With this

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distinction in hand, we are in a position to make our objection to the argument from revelation. To begin with, if e-revelation really is a derived thesis, then it is plausible only to the extent that the more basic doctrine of u-revelation is plausible. That is, (1) is plausible only to the extent that (5) is: (1) If Jones has an experience of type E, then for every essential truth T about E, Jones knows, or is a position to know, T. (5) If Jones understands what an experience of type E is, then for every essential truth T about E, Jones knows, or is in a position to know, T. However—and here is the objection—(5) is not plausible; at any rate, a rival thesis is equally plausible. In the previous chapter, we noted that, although one might say that understanding ‘‘pain’’ involves tacit knowledge of a definition, it is at least equally plausible to say instead that to understand ‘‘pain’’ is to know that it refers to this experience (where the demonstrative in question picks out pain). Something similar is true when we turn to the question of what it is to understand not the word ‘‘pain’’ but pain itself and, more generally, experience itself. In particular, instead of holding (5), we could perfectly well hold: (7) If Jones understands what an experience of type E is, then he knows that E is this type of experience (where the demonstrative picks out an experience of type E). This account of what it is to understand experience is clearly different from u-revelation. In particular, I can know that a certain experience is this type of experience without knowing the essence of the type of experience in question: (7) can be true without (6) being true. It might be objected that if (7) is true, then understanding what an experience is does entail a kind of knowledge of essence after all. It is natural to say that if you know that E is this type of experience, then you know of this type of experience, that it is E. Moreover, if you know of this type of experience that it is E, then you know of something, which in fact has a certain essence, that it is E. However, although this may be true, it is not revelation within the terms of the act. Revelation is not the doctrine that if you understand experience, you know of something, which in fact has a certain essence, that it is such and such. Revelation is rather the doctrine that if you understand what experience is, you know that experience has a certain essence. To put the point in terms of the distinction between de re and de dicto knowledge, revelation says that if you understand what experience is, you have a certain kind of de dicto knowledge about the essence of your experience. It does not say that if you understand what experience is, you have a certain kind of de re knowledge, even if that de re knowledge is of the essence of your experience (see Lewis 1995). Alternatively, it might be objected that all I have done is sketch some possibilities. One possibility is (6): this possibility is inconsistent with the

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epistemic view. Another possibility is (7): this possibility is not inconsistent with the epistemic view. But what I have not done is go into detail about which possibility is the right one and why. However, these are questions that I am going to make no attempt to answer here. It is enough for our purposes to say that the account of understanding set out in (6) is not mandatory, for, if that is so, the argument from revelation is unpersuasive.

11.6. Heat and Pain Again We have presented two objections to the argument from revelation. The first was that the argument confused necessary with essential properties. This objection ran aground on the possibility of an identity version of experiential supervenience. The second was that the argument failed to distinguish two kinds of revelation and that u-revelation is implausible when set against a rival thesis that involves no knowledge of essence. It is on the basis of this second objection that I conclude that the argument from revelation fails. In a sense our discussion might end now, but there is one further matter that should be dealt with. In addition to the remark about whole and part, Lewis also says that revelation is implicit in what Kripke says about pain. He writes: Kripke seems to be relying on the identification thesis in Naming and Necessity when he writes that ‘‘pain is picked out by its immediate phenomenological quality.’’ (Lewis 1995, 328 fn. 3) Because, in Lewis’s terminology, ‘‘the identification thesis’’ simply is revelation, what Lewis is saying is that Kripke seems to be relying on revelation. But relying on revelation for what purpose? At this point, it is a little hard to interpret exactly what Lewis has in mind. One possibility is that he thinks that Kripke is relying on revelation when he says that ‘‘pain’’ is a rigid designator; as we saw in chapter 2, there is a dispute between Kripke and Lewis on this point. In fact, however, it is hard to see why revelation would play a role here. The question of whether a term is a rigid designator is an empirical question, the answer to which follows from, or is made plausible by, various semantic judgments about how the term functions in various modal contexts. It is not clear that revelation plays an essential role in these judgments. A second possibility is that—according to Lewis—Kripke is relying on revelation when he distinguishes heat from pain; indeed, Kripke is doing this in the passage that Lewis quotes. If this is Lewis’s suggestion, and if he is right, our discussion would be in trouble. For while we have agreed with Kripke that there is a distinction between heat and pain, we have also agreed with Lewis that revelation is false. However, why suppose that the distinction between heat and pain does presuppose the truth of revelation? As we saw in chapter 9, this distinction might be associated with a number

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of other claims; in particular, it might be associated with self-presentation. But—as we saw earlier in this chapter—self-presentation is not revelation. To put it differently, pain may be different from heat, but it scarcely follows that it is similar to whole and part! A final possibility is that Lewis is suggesting that Kripke is relying on revelation when he defends, as he does in Naming and Necessity, the plausibility of the conceivability argument. Once again, if this is Lewis’s suggestion and if he is right, our discussion would be in trouble. We, too, have emphasized the plausibility of CA (and KA, too) and suggested that to respond to both arguments one must assume that we are ignorant of some of the relevant facts. If these arguments presupposed revelation, one could presumably dispose of them in a vastly more economical way—that is, by rejecting revelation. But once again, it is unclear that CA and KA do presuppose revelation. Both arguments certainly assume that phenomenal character is an essential property of an experience. Perhaps, too—though in fact this is not obvious— they rely on the idea that if one understands what experience is, one knows that it is a kind of psychological event or state that essentially has phenomenal character. But this entails at most that in understanding experience one knows one essential truth about it. It does not entail that one knows every essential truth about experience, as the thesis of revelation requires. In short, neither CA nor KA presupposes revelation.

11.7. Conclusion We are now in a position to summarize the main points of part III—indeed, our entire discussion—and to draw some general morals. In part I, we saw that the problem of experience presents us with three incompatible theses, each of which we have reason to believe. We also saw that various reasons for rejecting the problem are less persuasive than they initially appear. In part II, I presented a solution to this problem, the epistemic view. We saw that the view can be divided into two parts and that our epistemic attitude to these two parts should be different. The first part—the thesis that if the ignorance hypothesis is true, the logical problem is solved—can be defended in a relatively a priori way. The second part—the thesis that the ignorance hypothesis is true—can be defended on the basis of plausibility considerations. We also saw that various philosophical objections to the view are unpersuasive. In particular, we saw that appeals to the ideas of structure and function, on the one hand, and objectivity, on the other, turn out to be misguided. And here in part III, I argued that there was no satisfactory alternative to the epistemic view. It is usual to distinguish four views: primitivism, eliminativism, the a priori entailment view, and the a posteriori entailment view. The second two of these do not represent clear alternatives to the

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epistemic view, and when they are developed in such a way that they are alternatives, the results are implausible. The first two do represent clear alternatives, but we have seen that, although they are not a priori false, there is no positive reason to believe them and that on balance the epistemic view is preferable. We also saw that a main positive reason to advance either primitivism or eliminativism—revelation—is not true about experience or at least may be coherently denied. So that is the epistemic view, or anyway a much longer sketch of the epistemic view. What morals should be drawn from our discussion? I will close by briefly drawing out three that, although contained in what has gone before, are sufficiently important to be formulated explicitly. First, we tend to articulate our epistemic position in extremely optimistic terms. In some cases, this tendency is driven by a simple optimism about the present state of science; in some cases, it is driven by philosophical ideas such as the versions of rationalism mentioned in chapter 5; in still other cases, it is driven by the idea that there are certain kinds of high-level description of what we know, such that anything else we learn will be similar in respect of these to what we already know. In my view, this tendency is one factor that drives the problem of experience. If we suppose that what we know about the nature of the physical or nonexperiential world exhausts what there is to be known about it—if not in detail, then in outline—we will feel the force of the problem of experience extremely keenly. It is a great merit of the epistemic view that it teaches us to overcome this tendency. Second, we tend to view philosophical problems as problems that are solved not by providing new information but by rearranging what we already know—that is, as conceptual problems. We have seen this idea voiced by Wittgenstein, but it also is prevalent in contemporary discussion. Moreover, this idea about what philosophical problems consist in encourages a range of ideas about what solutions to these problems will look like. If one thinks that philosophical problems in general have this character, one will be inclined to suppose that a contribution to the problem will be conceptual: we have a mistaken picture either of the subject matter under discussion or of our thought and talk about the subject matter. I think the tendency to think this way about philosophical problems is another factor that drives the problem of experience. It is a great merit of the epistemic view that it teaches us to overcome this tendency. Third, it is natural to view the questions that are characteristic of the discussion in philosophy of mind about experience as being driven by these two tendencies operating in tandem. In the light of our tendency to discount our own ignorance, we are inclined to feel the force of the problem of experience incredibly keenly. In the light of our tendency to view philosophical problems as problems whose solutions do not involve new information, we are inclined to look around for a conceptual solution to the problem of experience. But this package of commitments places us in an

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intellectual predicament from which there is no escape: there is no conceptual solution to the problem of experience. It is again a great merit of the epistemic view that it teaches us to avoid this intellectual predicament. Philosophy of mind can be thought of broadly as a subject matter, but it can also be thought of more narrowly as an intellectual program—that is, as an interrelated series of methodological suggestions about how to deal with the subject matter. For much of the past hundred years, the program of philosophy of mind, even in its more naturalistic phases, has been to use broadly conceptual machinery to answer the metaphysical problems of mind and the problem of experience in particular. If what I have been saying is correct, philosophy of mind in this narrow sense is a failure. But the failure is instructive, for it points us toward a more realistic account of our place in the world, a more variegated conception of philosophical problems, and of course an answer to the logical problem of experience.

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Index

access consciousness, 22 alien experiences, 38 Alston, W., 223 a posteriori entailment view, 9, 175–197, 231 and conceivability arguments, 180–197 a priori entailment view, 9, 175–177, 198–217, 231 and functionalism, 206–210 Armstrong, D. M., 51, 88, 106, 108, 110–111, 119 Aunt Bubbles, 126–127 Ayer, A. J., 49 Balog, K., 203 Bayne, T., 146 behaviorism, 46, 52–53, 71, 130, 168, 189, 192, 193–194 Bennett, K., 73, 152 Berkeley, G., 51 Blackburn, S., 110–111, 118–119 blind sight, 24 Block, N., 18, 99–100, 120, 126, 130, 141, 196 on the epistemic view, 100 Blockhead, 126–127, 130 Bloom, P., 45

Boyd, R., 187–188, 190 and proposition confusion, 187–188 Braddon-Mitchell, D., 170, 187 Broad, C. D., 123, 135–140, 220 Brown, J., 168 Byrne, A., 38, 78, 201, 204 CA. See conceivability argument caloric theory of heat, 188–189 Campbell, K., 37 Carruthers, P., 210 Cartesian physicalism, 33 categorical argument, 106–112, 119–121 categorical grounds, 112 categorical properties, 109, 118–119, 146 categorical truths, 69, 106, 113, 115 Chalmers, D., 9, 37, 63, 76, 78, 107, 117, 132, 144–149, 191, 196–197, 203, 212 chemical argument, 135–140 and knowledge argument, 136–137 Chinese nation example, 141 Chomsky, N., 44, 50, 54–56, 58, 60, 124, 126–128 243

244

Index

Churchland, P., 50, 60, 141, 201 Clark, S., 141 cognitive closure, 6, 10–11, 90, 155 and epistemic view, 10–11, 90 and ignorance hypothesis, 93–94 Commander Data, 99 competence/performance, 126–127 compound truths, 27, 158 computation, 128, 130–131 conceivability idealized, 76 and inconceivability, 125–126, 131–133 positive, 77 and possibility, 50–54, 74–78 prima facie, 76, 86 strong, 75–76, 81, 84 weak, 75–76, 81, 84, 86 conceivability argument, 33, 37–38, 52–54, 75, 79–82, 83–85, 107, 114–115, 134, 140–411, 169, 189, 191, 198 and inconceivability arguments, 125–126, 131–133 and knowledge argument, 41 and moths, 83–85 and slugs 80–82 conditionals necessary /synthesizable, 158–162 Conee, E., 201 contingency, appearance of, 40–41, 158–161, 181–182 Cottingham, J., 124, 128, 129 Crane, T., 55 Cummins, R., 44 Davies, M., 188 Descartes, R., 17, 33, 45, 76, 112, 123–134 Devitt, M., 57 diaphanousness of experience. See transparency of experience dispositional properties, 109–111 dispositional truths, 109, 115 Dretske, F., 201 dual aspect theory, 6

dualism, 21, 45–46, 49, 53, 61–62, 88, 124, 133, 197 Duhem-Quine thesis, 43–44 Egan, A., 152, 185 eliminativism, 9, 71, 175, 218–219, 231–232 emergentism, 135, 137–139, 140–141, 220 and supervenience, 137–138, 220 empirical problem of experience, 42–44 entailment, 27–28 modal notion of, 27 and relevance, 70 epiphenomenal ectoplasm, 36 epiphenomenalism, 88 epistemic view, 4–7, 9–11, 67, 78, 97, 205, 206–207, 231–233 formulated, 6 and functionalism, 208–210 master argument against, 144 expressibility version, 165 objectivity version, 153–162 perceptual availability version, 162–164 structure and dynamics version, 144–153 and modal skepticism, 169 mysterian version, 90–94, 114 Russellian version, 106–122, 153 essential properties, 225–227 ethical internalism, 102 experience machine, 51–52 experiential conditional, 34–37, 38, 114–115, 158–160, 176–177, 179–180, 196–197, 198, 201–203 experiential supervenience, 28, 34–41, 98, 114–115, 182, 196, 220 as contingent thesis, 34 identity version, 226–227 and modal arguments, 34–35 and necessary entailment, 35 experiential truths, 24, 92 explanatory gap, 98–99 expressivism, 103 extrinsic properties, 146

Index Farrell, B. A., 19, 23, 49 Feinberg, G., 94 Fine, K., 225 Flanagan, O., 90 Fodor, J., 211 Foster, J., 106 from-structure-only-structure thesis, 151–152 functionalism, 205–215 analytic functionalism, 207–208 and a priori entailment view, 206–210 a priori functionalism, 207–208 A-type, 208 B-type, 208 commonsense functionalism, 209 conservative functionalism, 207–210, 211–213, 214–215 C-type, 208, 209 and definition of pain, 206–207, 211–213 D-type, 208, 209–214 and intentionalism, 210–213 liberal functionalism, 207–210, 214–215 as theory of understanding, 211–213 further fact views, 101–104 Gendler, T. S., 51 Gertler, B., 80, 164 Gillet, C., 29 Goethe, J. W., 141 grain problem, 117–118 Gunderson, K., 124, 128, 130 Gu¨zeldere, G., 141 harder problem of conscious experience, 99–100 Harman, G., 23, 102, 150, 201 Haugeland, J., 128 Hawthorne, J., 51, 187 heat argument, 178–183 hedonism, 51–52 Hempel, C., G., 55 Hill, C., 190–194 Hohwy, J., 119 Horgan, T., 28, 36, 139 Horwich, P., 57

245

Humberstone, L., 188 Hume, D., 106 Humean dictum, 138, 220 idealism, 46 identity, 56–57 Leibniz’s law, 56–57 personal identity, 56–57 identity statements, 35–36 ignorance, 72–4 basic-level, 6, 72–73, 80–83, 95, 101, 131 categorical, 113–116 chronic, 91–94, 114 and empirical problem, 96–97 intermediate-level, 72–73, 95, 101, 131, 209 and modal reasoning, 79–86 ignorance hypothesis, 6–7, 67–74, 79, 81, 87–105, 207, 220–221 categorical ignorance hypothesis, 113–116, 119–121 chronic ignorance hypothesis, 91–94, 114 explanatory power of, 97–100 imagination perceptual, 191–192 sympathetic, 191–192 See also conceivability inconceivability all things considered, 129 and conceivability, 125–126, 131–133 prima facie, 129 strong, 128–129, 132–133 weak, 128–129, 132–133 intellectual character, 123–124, 133 intentionality, 21–22, 46, 105, 210–213 intentionalism, 210–213 first-order, 210 higher-order, 210 non-reductive, 211–213 reductive, 211–213 intrinsic properties, 107, 146, 149–152. See also categorical truths introspection 5, 117–118 introspective truths, 91–93

246

Index

INUS condition, 70 inverted spectrum, 37–8 Jackson, F., 4, 19, 36, 38–40, 88–89, 94, 95, 126, 143, 170, 196–197 James, W., 89 Johnston, M., 151, 222 KA. See knowledge argument Kant, I., 106 Kim, J., 28, 137 knowledge argument, 33, 38–41, 52–54, 61, 79, 82–83, 85–86, 107, 115–116, 136–138, 140–141, 155, 169, 189, 198, 200–203 and ability hypothesis, 200–201 and acquaintance hypothesis, 201 and conceivability argument, 41 and moths, 85–86 and open question argument, 39–40 and slugs, 82–83 Kripke, S., 7, 13, 35–37, 40, 50, 74, 103, 105, 111, 118, 138, 177–197, 214, 230–231 on heat and pain, 177–183, 230–231 and pain argument, 178–182 Lagadonian language, 165 Langton, R., 106 language and linguistics, 166 language use and machine argument, 124–134 See also competence/ performance Leeds, S., 57 Leibniz, G. W., 110 Leibniz’s law, 56–57 Levine, J., 98–99 Lewis, D., 35–36, 57, 60–62, 71, 94–95, 155, 165, 200, 202. 205, 213, 219, 222, 227–230 Lockwood, M., 107, 117

Loewer, B., 29 logical problem of experience. See problem of experience logicism, 46 Lormand, E., 112, 158, 210 Lycan, W., 35 machine, definition of, 129–130 machine argument, 124–134 competence interpretation, 127–133 and mode confusion, 127–129 performance interpretation, 133–134 and proposition confusion, 129–131 Mackie, J., 70 manifest image, 31–32, 60 and scientific image, 31–32, 60 manifest supervenience, 31–33, 59–61, 220 and experiential supervenience, 32, 59 and physicalism, 32–33 Mary example, 38–39, 41, 61, 146, 200–203 experienced Mary example, 202–203 zombie Mary example, 203 See also knowledge argument Maxwell, G., 107, 117–118 McGeer, T., 203–204 McGinn, C., 6, 90–94, 114, 155, 171, 197, 198 McLaughlin, B., 139–141, 190, 193–194 mechanism, 29 Mellor, D. H., 55 Meno, 71 mental causation, 221 metaphysical distinctness, 9, 138–139, 220 mind-body problem, 17, 20, 45–47, 48 minimal conception of experience. See phenomenal conception of experience modal arguments, 7, 34 and ignorance, 7

Index skepticism about, 49, 50–54, 78, 194–195 See also conceivability argument; knowledge argument modal error, 74–78 and categorical ignorance, 114–116 defeater neglect, 77–78, 190 mixed confusion, 76–7, 81, 84, 126 mode confusion, 75–76, 84–85, 93, 126, 190 standard mistakes, 79, 98, 116, 139 proposition confusion, 74, 84–85, 93, 126, 180–183, 186–190 Moore, G. E., 23, 39–40, 46, 63, 103 and unanalyzable properties, 46 moral problem, 102 moths and beams, 73–74, 83–86, 131 mysterianism, 90–94, 114 Nagasawa, Y., 132 Nagel, T., 8, 19–20, 24, 61, 153–158, 162, 191, 193 bat example, 154, 156 thesis, 154–157 naturalization problems, 165–167 necessary a posteriori truths, 178, 196–197 and conceivability, 194–195 Nemirow, L., 200 neodescriptivism, 40, 197 Newton, I., 141 neutral monism, 46 Nida-Ru¨melin, M., 202 Nozick, R. 51–52 objectivity, 8, 153–162, 193 ontological argument, 76 open question argument, 39–40 pain, as rigid designator, 35, 230 pain argument, 178–197 panpsychism, 118–120 parapsychology, 61–62 Parfit, D., 57, 101 part-whole relation, 227–228

247

Paul, L. A., 152 perceptual availability, 162–164, 191 perfect actors, 52–53, 71, 130, 168, 189–190, 192, 195 Perry, J., 143 phenomenal beliefs, 203–204 phenomenal conception of experience, 17–24 as minimal conception, 20–24, 217, 219 phenomenal concepts, 190–194, 202, 216 as indexical concepts, 194 and justification conditions, 192–193 possession conditions of, 194 phenomenal concept strategy, 160–161, 190–194, 201 phenomenal properties, 118–119 as intrinsic, 149–152 phenomenal structure, 144–153 physical, definition of, 29–30, 49, 54–56 inessential role in problem of experience, 56–62 and paradigm physical object view, 29 physicalism, 21, 28–31, 45–46, 49–50, 54–62, 125, 133, 182, 197 and experiential supervenience, 31, 59, 182 fingers crossed physicalism, 170 and manifest supervenience, 32–33 and optimism, 88–89 role in logical problem of experience, 58–62 and supervenience, 28–29 Pitt, D., 164 Platonism, 32 primitivism, 9, 34, 60, 71, 104, 138–139, 175, 182, 197, 218–221, 231–232 and epistemic view, 97–102, 175 Prior, A. N., 27 primary qualities, 109–112

248

Index

problem of evil, 51 problem of experience, 5, 6, 18, 48–49, 67, 105, 232–233 as conceptual 8–9 empirical problem, 48 logical problem, 26, 67, 79, 232–233 skepticism about, 48–64 methodological version, 49, 50–54 conceptual version, 49, 54–58 traditional mind-body problem, 48–49, 105 proposition confusion. See modal error psychological intermediaries, 184–186 Putnam, H., 52–53, 71–72, 130, 190, 195 quantum mechanics, 10, 139 Quine, W. V. O., 43–44, 166 rationalism, 95, 163 realism, 57–58, 63 reductionism, 46 representationalism, 210–213 Restall, G., 27 revelation, 21, 96, 218, 221–5, 227–232 and color, 222 e-revelation and u-revelation, 227–230 and self-presentation, 223–224, 228 and understanding, 227–230 and argument for primitivism, or eliminativism, 223–225, 228–230 rigid designation, 35–36 Rosen, G., 168 Rosenberg, G., 107 Russell, B., 8, 12, 69, 106–122, 171 Russell, G., 27 Russellian view, 106–122 Ryle, G., 49, 103, 200

Searle, J., 48, 55, 59, 170 secondary qualities, 109, 111–112, 137 self-presentation, 21, 184–186, 192–193, 217, 228, 231 sense-data, 23, 41 Sellars, W., 31–32, 59, 150, 171 Shoemaker, S., 38, 164, 184, 203 skepticism, about other minds, 134, 222 slugs, 3–7, 69–72, 80–83, 89, 116, 140 slugists, 3–4, 89 Smart, J. J. C., 88, 95, 196 Smith, M., 102, 104 Soames, S., 57 spatiotemporal truths, 108, 111–112 Sprigge, T., 19 Stalnaker, R., 187, 188–190, 197 proposition confusion, 188–190 Star Trek, 99 structural properties, 117 Stubenberg, L., 107 Strawson, G., 55, 222 structure and function, 9 structure and dynamics, 144–153 subjective, 8, 153–62 supervenience, 27–37 and entailment, 27 and emergentism, 137–138, 220 manifest, 28, 31–33, 59–61, 220 See also experiential supervenience Thau, M., 165 theoretical truths, 92–93 Thomson, J. J., 102 transparency of experience, 23, 118, 150 truth, 57–58 and realism/anti-realism debate, 57–58 type of, 70–71, 102 two-dimensional modal semantics, 188–190 Tye, M., 170, 201 Tyndall, J., 100, 141

Index Unger, P., 107 Utilitarianism, 199–200

Wittgenstein, L., 8, 19, 23, 105, 142–143, 165, 232

Van Cleve, J., 75–76, 102, 128 vitalism, 219

Yablo, S., 51, 76, 77, 195

what it is like, 19 White, S., 196–197 Williamson, T., 185 Wilson, M., 124, 128, 129

Zombies, 37, 203–204 zombie array, 83, 84 zombie Mary, 203–204 zombie mosaic, 80–82 zombie world, 37

249