A Problem for Defeasibility Theories Deborah Scaduto-Horn The Journal of Philosophy, Vol. 79, No. 1. (Jan., 1982), pp. 40-45. Stable URL: http://links.jstor.org/sici?sici=0022-362X%28198201%2979%3A1%3C40%3AAPFDT%3E2.0.CO%3B2-I The Journal of Philosophy is currently published by Journal of Philosophy, Inc..
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fact that alternate-sequence interventions of the Frankfurt sort do not establish that the agent has the deliberate control required for responsibility. I developed a second strategy of response: this strategy concedes the dissociation of responsibility from control but argues that this dissociation needn't entail the consistency of determinism with responsibility. I have not argued for incompatibilism about determinism and responsibility; I have had the more modest project of showing how the incompatibilist is not forced into inconsistency by Frankfurt's examples. Both the compatibilist and the incompatibilist alike can unite in conceding that enough information is encoded in the actual sequence to ground our responsibility attributions; as philosophers we need to decode this information and see whether it is consistent with deterministic causation. JOHN MARTIN FISCHER
Yale University
COMMENTS AND CRITICISM A PROBLEM FOR DEFEASIBILITY THEORIESX
HAT all defeasibility theories of inferential knowledge have in common is the belief that Gettier and Gettierinspired counterexamples to the traditional definition of knowledge involve a defeater which prevents such cases from being true cases of knowledge. In order to say that S has inferential (or nonbasic) knowledge of some proposition, it is not enough that S have a justified true belief: S's justification must also not be defeated. Just what constitutes defeat has been the subject of much controversy, but underlying the various attempts that have been made at giving such a characterization, one intuition stands out-that a defeater is such that it is true and if a justified true believer were aware of it, then he would no longer be justified in believing whatever it is he believes (the reason being that the defeater undermines his original evidence for his belief). * I am indebted to llralter Horn, Ernest Sosa, James Van Cleve, Peter Klein, Carl Ginet, and the members of Ginet's 1980 Theory of Knowledge seminar for helpful comments on this topic.
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In its most general form, the defeasibility definition of inferential knowledge (which I will hereafter refer to as DK) says: S knows inferentially that h if and only if (i) h is true. (ii) S believes that h. (iii) There is some evidence e such that e justifies h for S. (iv) There is no defeater d such that (d and e ) fails to justify h for s.?
This definition has been shown to be too strong. T h e object of attack has been the controversial condition (iv); for cases of justified true belief that involve so-called "misleading defeaters" are not countenanced by DK as cases of knowledge; yet misleading defeaters are not considered to be obstacles to knowledge.' As a result of such criticism, much attention has been given to modifying DK in such a way as to distinguish between misleading defeaters and genuine defeaters. Fortunately, we need not concern ourselves here with amended variations of DK, for the line of attack in this paper comes from the opposite direction. What I aim to show is that DK is too weak; so all attempts to vindicate DK by weakening it are irrelevant for my purpose. T h e example by which I hope to show DK's weakness involves a necessary truth, and, in order for my case to be convincing, two things must be agreed upon from the outset: first, that we can have inferential knowledge of necessary truths and, second, that defeasibility definitions of knowledge should account for all types of inferential knowledge-even examples in which the proposition some believer is claimed to know is a necessary truth.
h his is the same definition that Peter Klein gives in his paper, "Knowledge, Causality, and Defeasibility," this JOLIRSAI., LXXIII, 20 (Nov, 18, 1976): 792-812, p. 802, before he revises it to account for misleading defeaters. I use Klein's original definition here because it seems to capture the general intuition behind all defeasibility definitions of inferential knowledge. Yet, by confining my discussion in this way, I don't mean to suggest that the example offered in this paper is limited to Klein's definition. It is my contention that the counterexample given here ranges over a number of defeasibility definitions of knowledge which have been recently proposed-David Annis's, Carl Ginet's, Ernest Sosa's (in particular, Sosa's definition of epistemic presupposition), and Peter Klein's revised definition, for instance. For purposes of brevity, I limit my discussion to Klein's original definition. See also David Annis, "Knowledge and Defeasibility," in George S. Pappas and Marshal Swain, eds., Essays on Knowledge and Justification (Ithaca, N.Y.: Cornell, 1978), pp. 155-159; Carl Ginet, Knowledge, Perception, and Memory (Boston: Reidel, 1975), p. 80; and Ernest Sosa, "Epistemic Presupposition," in Pappas, ed., Justificatzon and Knowledge (Boston: Reidel, 1979), pp. 79-92. The most popular example of a misleading defeater is, perhaps, Lehrer and Paxson's Mrs. Grabit case. See Keith Lehrer and Thomas Paxson, "Knowledge: Undefeated Justified True Belief," in Pappas and Swain, op. czt., pp. 15011.
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That a necessary truth can be known inferentially is, I think, easy to see. Just consider a case where a believer S is confronted with a complicated necessarily true proposition that he understands, but, because of its complex nature, does not see to be true immediately. There is, however, a proof accessible to S by which he comes to see the truth of the necessary proposition. I think we would want to say that S has acquired inferential knowledge of a necessarily true proposition in this case. As for the second matter, it has been said that "a defeasibility analysis can provide an adequate account of all that we know inferentially" (Klein, 793). Presumably, this includes our inferential knowledge of necessary truths. If, however, some defeasibility theorists maintain that their type of definition is not meant to range over examples involving necessary truths, then the defeasibility approach turns out to be inadequate in accounting for all types of knowledge and is to be restricted to inferential knowledge of contingent propositions. In any case, we will have shown that some other approach is needed to account for inferential knowledge of necessary truths. The case I have in mind goes as follows: Suppose that DK (i)-(iii) are satisfied, where h = Either, if i t is raining, then Jones is wearing a raincoat, or it is raining. e = Evidence for the proposition that if it is raining, then Jones is wearing a raincoat. (More precisely, in the past, whenever it has rained, Jones has worn a raincoat.)
[Generally speaking, the proposition that S is said to believe is of the form '(p 3 q ) v p' and S's evidence is evidence for the first disjunct.] Let me say a few things about our subject S. S is acquainted with some elementary rules of logic, but, in the above situation where h is involved, S applies his logical knowledge to all and only those propositions which appear in the epistemic framework of our example from which he could deduce h. He does not, however, apply any rules to h itself. That is to say, S avails himself of the rules of logic whenever he is trying to justify his belief that h by inference, and never avails himself of those rules when considering h itself. So S's justification for h is always a result of inference from another (or other) proposition(s). This is to be regarded as background information about S. Now in getting from e to h , S does not come to see that h is nec-
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essarily true. We may suppose, for instance, that S gets from e to h by applying the rule that says one can disjoin any statement to a true one and the resulting disjunction will be true. Perhaps this is not i n fact the method S uses to get from e to h , but it is a method that wouldn't force S to see the necessary nature of h , and, accordingly, is of the sort we're talking about here.' In any case, it is important to note that S has n o evidence for the proposition that it is raining. He has evidence only for the first disjunct of h.3 But now let us say that Jones is not wearing a raincoat, but it is raining. As it turns out then, it's not the case that if it is raining, then Jones is wearing a raincoat. In other words, S's evidence is faulty. I don't think we'd want to say S that knows that h in this situation. With the exception that a necessary truth is involved in the above case, so far my example is strictly analogous to Gettier's case in which the proposition the subject is said to know is that either Jones owns a Ford or Smith is in ~ a r c e l o n aThis . ~ Gettier example is considered to be a case of justified true belief without knowledge, and my example should be viewed in the same way-the status of the proposition S is said to believe should not be a factor in trying to decide whether or not S has knowledge of that proposition. It has already been stipulated above that DK (i)-(iii) are satisfied in the situation being presented here. It follows then that the only remaining explanation for S's lack of knowledge would be that condition (iv) is not satisfied. T h e problem is, (iv) is satisfied; i.e., according to DK there is n o defeater here. T o see this we need only consider what may be regarded as defeaters in this case, and I think there are only two candidates here, viz., (a) It's not the case that if it is raining, then Jones is wearing a raincoat, and (b) Jones isn't wearing a raincoat. It might seem to some that h is obviously necessarily true. But I think it will be agreed that h can be understood by a believer such as S without S seeing that it's necessarily true. 'By taking e to be evidence for the proposition that if it is raining, then Jones is wearing a raincoat, rather than that proposition itself, I am assuming that justification is transitive here. When I discussed a n earlier draft of this paper with Peter Klein, he illustrated the intransitivity of justification i n certain cases by pointing to a n example he gives i n his paper ( o p cit., p p . 805-807) and held that I cannot assume the transitivity of justification in my example either. I am inclined to agree with Klein that not all justification is transitive, but it is clear that e justifies h i n my case. 4 ~ e Edmund e Gettier, "Is Justified T r u e Belief Knowledge?" Analysis, xxrrr, 6 J u n e 1963): 121-123.
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Neither (a) nor (b) fits the role of a defeater as it is described in (iv), however. Take the supposed defeater (a).' If S conjoins ( a ) with his evidence e , his justification for h is not defeated. This is because an alternative proof for h can be got from (a), viz., evidence for the second disjunct of h (the proposition that it is raining). One way of seeing this is as follows: ( a ) is equivalent to the proposition that it is raining and Jones isn't wearing a raincoat. Using the rule of simplification, which allows one to deduce p from (pwq), one could get the proposition that it is raining. Then, using the rule about disjunctions, one could deduce from the proposition that it is raining, that h . Before turning to (b), let me stop to consider some possible objections to what I have said in discussing the supposed defeater (a). First, it might be said that although S has another proof of h available to him in conjoining (a) with e , there is n o guarantee that S w o ~ l l davail himself of that other proof, and, second, if S availed himself of that other proof, then it would seem that S would come to know that h is necessarily true. Let me take these u p in turn. First of all, it is true that having a n alternate proof available to one does not thereby guarantee that one would avail oneself of it. But in setting u p the counterexample, I have made it clear that S would apply his basic knowledge of logic in order to deduce h whenever it is possible to do so (i.e., deduce it from what's given in the situation at hand). So, in fact, we can be sure that S would avail himself of all the rules needed to see that the conjunction of e and (a) does not get in the way of his justification for h. T h e second objection can be clearly stated as follow^:^ if S sees that the proposition that it is raining and, therefore, h are deducible from (a), then S would see that the second disjunct of h is deducible from the negation of its first disjunct, and this is tantamount to S's seeing that h is necessary. I am in full agreement with this. I have already stressed that the counterexample guarantees that S would see that h is deducible from (a), so it follows that S would, in the end, come to realize that h is necessarily true. But this doesn't affect my example at all. It is still the case that S doesn't see the necessity of h until the supposed defeater (a) has been added to his epistemic framework. Where the question whether S has knowledge of h is concerned, S's belief that It should be clear that the conjunction of (a) and e is not a contradiction. e is a statement about the past from which S infers h ; so (a) isn't the negation of e. 1 am indebted to Carl Ginet for this formulation of S's coming to see the necessity of h .
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h remains unwarranted in virtue of the fact that it is raining but Jones isn't wearing a raincoat. ( b ) doesn't violate DK (iv) either. If we conjoin S's evidence e with (b), it does not follow that S is n o longer justified in believing h ; for ( b ) is merely the negation of the consequent of the first disjunct of h , and, as S well knows, a conditional is not shown to be false by the falsity of its consequent.' There is a case, then, in which DK (i)-(iv) are satisfied but there's no knowledge. This, of course, can mean either one of two things: (1) that there are in fact instances of undefeated justified true belief which are not cases of knowledge, or (2) that another defeasibility definition of knowledge is required to account for the situation presented here. DEBORAH S C A D U T O - H O R N
Brown University
BOOK REVIE\VS Transcendental Arguments and Science. Edited by PE.rER B I E R I , and LORENZ K R U G E R . Synthese Library. Dordrecht, Boston, and London: Reidel, 1978. viii, 314 p. $30.00. ROLF-PETER HORSTMANN,
I n this volume are assembled the papers, and the commenting papers, which emerged from a symposium on "transcendental arguments and the conceptual foundations of science," held in Bielefeld in the summer of 1977. There are twenty-two contributors in all. T h e three editors are included among the fourteen commentators on eight main papers. So the result is a substantial package-and one which leaves, on the mind of this reviewer, a slightly confused impression. T h e subjects discussed range from Kantian exegesis to the Copenhagen Interpretation of quantum theory. A multitude of banners wave. References, favorable and unfavorable, abound to: verificationism, pragmatism, naturalism, relativism, historicism, transcendentalism, skepticism, idealism, and at least three varieties of realism ("internal", explanatory, metaphysical). 'Another objection might be that ( a ) is in fact a defeater and moreover, satisfies the definition of a defeater given at the beginning of this paper-viz., a defeater is that which undermines one's original evidence for believing that h . Surely what I gave at the beginning of this paper was only a characterization of a defeater and not a definition. (There are reasons for not wanting to take it as a definition which I won't get into here.) ( a ) might be a defeater. T h e point of this paper is that (apparently) there is n o defeasibility definition of knowledge which takes (a) to be a defeater. 0022-362X/82/7901/0045~0.60
P 1982 T h e Journal of Philosophy, Inc.