Lehrer on Knowledge Gilbert H. Harman The Journal of Philosophy, Vol. 63, No. 9. (Apr. 28, 1966), pp. 241-247. Stable URL: http://links.jstor.org/sici?sici=0022-362X%2819660428%2963%3A9%3C241%3ALOK%3E2.0.CO%3B2-9 The Journal of Philosophy is currently published by Journal of Philosophy, Inc..
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up"; f o r a n occurrence, event, o r h a p p e n i n g is whatever occupies a segment of time; a n d n o t moving, a s well a s moving, takes time. A t a strict, mathematically dimensionless instant, changings a n d e n d u r i n g s a r e equally impossible. I n conclusion, a f e w w o r d s concerning t h e s t a t e m e n t b y R y l e quoted in t h e paper's footnote o n p a g e 699, t h a t "Motives a r e n o t happenings, a n d a r e n o t therefore of t h e r i g h t t y p e t o be causes." L e t us consider a concrete example ; say, t h e question : " W h a t w a s t h e boy's motive f o r s h a k i n g t h e a p p l e t r e e ? " a n d t h e a n s w e r : " H e desired a n apple, a n d believed t h a t s h a k i n g t h e t r e e would make one fall." I s u b m i t t h a t h i s desiring a n a p p l e was a "happening," a n event, a n occurrence, which occupied a p a r t i c u l a r span of t i m e whether s h o r t o r long, a n d t h a t so w a s h i s believing t h a t s h a k i n g t h e t r e e would make a n a p p l e fall. Thus, t h e motive a given person h a s f o r d o i n g w h a t h e does a t a p a r t i c u l a r time i s a happening a n d , therefore, R y l e notwithstanding, is "of t h e r i g h t t y p e " t o be a cause.4 C. J. DUCASSE BROWNUNIVERSITY LEHRER ON KNOWLEDGE
I
T is t e m p t i n g t o offer conditions like t h e following a s necessary a n d sufficient f o r S t o k n o w h : (i)
h (ii) S (iii) S
is true believes h is completely justified in believing
h
I f w e allow f o r various w a y s of s t a t i n g (iii), people so t e m p t e d m i g h t include J. 0. Urmson, A. J. A y e r , Roderick M. Chisholm, Douglas A r n e r , a n d J a a k k o Hintikka.l Recently, E d m u n d L. Gettier h a s shown t h a t these conditions a r e n o t sufficient, w h e n 4 The definitions of causally (as distinguished from logically) 'sufficient to' and its converse, 'necessitated by', and of 'necessary to' and its converse, 'contingent upon', are explicitly stated on pp. 54-57 of my Causation and the Types of Necessity. But no sign of acquaintance with these pages of the book appear in the paper. Those definitions are stated also on pp. 108-113 of my Carus Lectures, Nature, Mind, and Death, 1951. 1J. 0. Urmson, "Parenthetical Verbs," Mind, 61, 244 (October 1952) : 480-496; A. J. Ayer, T h e Problem of Knowledge (New Pork: St. Martin's, 1956); Roderick M. Chisholm, Perceiving: A Philosophical S t u d y (Ithaca, N.Y.: Cornell, 1957), p. 16; Douglas Arner, " On Knowing," Philosophical Review, 68, 1 (January 1959): 84-92; and Jaakko Hintikka, Knowledge and Belief (Ithaca, N.Y. : Cornell, 1962), pp. 19-20; whence these references.
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( f o r example) S h a s validly i n f e r r e d a t r u e conclusion f r o m false premises h e is completely justified in b e l i e ~ i n g . ~Gettier's article h a s l e d t o a n u m b e r of proposals concerning t h e correct analysis, if In h i s article, "Knowledge, T r u t h , a n d a n y , of "S knows h." Evidence," K e i t h L e h r e r h a s f o u n d defects in all of these proposals a n d h a s himself proposed a n interesting analysis (or, perhaps, first s t e p t o w a r d a n analysis) of 'know'. In t h e present p a p e r I a t t e m p t t o clarify Lehrer's analysis i n o r d e r t o a s k whether o r n o t it is correct. L e h r e r analyzes "S knows h " as t h e conjunction of (i)
h
is true
S believes h (iii) S is completely justified in believing h (iv c) If S is completely justified in believing any false statement p which entails (but is not entailed by) h, then S would be completely justified in believing h even if S were t o suppose that p is false (ii)
L e h r e r points o u t t h a t whether o r n o t S is completely justified in believing h depends u p o n w h y X believes h. H e notes (169), f o r example, "if a person h a s evidence a d e q u a t e t o completely j u s t i f y h i s belief, h e m a y still f a i l t o be completely justified i n believing w h a t h e does because his belief is n o t based on t h a t evidence." I t a k e it t h i s entails t h a t S c a n be completely justified i n believing h o n l y if h e actually believes h. I f t h i s is so, t h e n ( i v c ) m u s t b e modified slightly. Suppose t h a t S is completely justified i n believing h because h e is completely justified i n believing g a n d completely justified i n believing g -+ h and also because h e is completely justified i n believing f a n d completely justified i n believing f -+ h. Suppose these a r e t h e o n l y reasons S h a s f o r believing h ; a n d suppose also t h a t both g a n d f a r e false. T h e n S does n o t k n o w h. Consider whether o r n o t Lehrer's analysis is satisfied. Conditions ( i ) , ( i i ) , a n d (iii) a r e satisfied; b u t it would a p p e a r t h a t t h e r e is a relevant p falsifying ( i v c), n a m e l y : (f v g) & ((f v g) --t h). I f S were t o 2 Edmund L. Gettier, "Is Justified True Belief Enowledget", Analysis, 23.6, n.s. 96 (June 1963) : 121-123. Cf. Bertrand Russell, The Problems of Philosophy (New Pork: Oxford, 1912), ch. XIII, "Knowledge, Error, and Probable Opinion," especially 132 ff. 8 Besides Gettier's article containing his own suggestions, there are Michael Clark, "Knowledge and Grounds: A Comment on Mr. Gettier's Paper," Analysis, 24.1, n.s. 98 (December 1963) : 46-47; Ernest Sosa, "The Analysis of 'Knowledge that P'," ibid., 25.1, n.s. 103 (October 1964) : 1-3; and John Turk Saunders and Narayan Champawat, "Mr. Clark's Definition of 'Knowledge'," ibid., 25.1, n.s. 103 (October 1964) : 8-9. 4"Knowledge, Truth, and Evidence," Analysis, 25.5, n.s. 107 (April 1965) : 168-175.
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suppose this (false) statement to be false, then he would no longer be completely justified in believing h. And it may appear that S is completely justified in believing this statement, since it follows from statements S is completely justified in believing. However, S may fail to be completely justified in believing this statement, since he may fail to believe it or believe it for poor reasons. I n that case, Lehrer's analysis would be satisfied, although S does not know h. To avoid such a counterexample, (iv c) must be changed to ( i v d ) I f p is justified h, then were to
a false statement entailed by statements S is completely in believing such that p entails (but is not entailed by) S would be completely justified in believing h even if S suppose that p is false
In (iv d ) , as well as in (iv c), the parenthetical requirement on p, that p not be entailed by h, is superfluous, since h cannot be true and entail a false statement. Furthermore, the requirement that p entail h is also superfluous. Consider any false statement r that follows from statements S is completely justified in believing. Then r & h is also a false statement that follows from statements S is completely justified in believing; and r & h entails h. Therefore, if (iv d ) is to be satisfied, S must be completely justified in believing h even if he supposed that r & h was false. But to suppose this is to suppose either that r is false or that h is false, since "To suppose that the conjunction of PI and P2 is false, I need only suppose that one of the conjuncts is false" (174). But S would not be completely justified in believing h were he to suppose that h was false. Therefore, where r is any false statement following from statements S is completely justified in believing, then for (iv d ) to be satisfied S must be completely justified in believing h even if he were to suppose r false. This means that (iv d ) is equivalent to (iv e) I f p is a false statement entailed by statements S is completely justified in believing, then S would be completely justified i n believing h even if S were to suppose that p is false
Further simplifications are possible on certain assumptions. First, I assume that there is at least one false statement t that S is completely justified in believing. Then for any false statement r, t v r is a false statement entailed by statements S is completely justified in believing. So, if (iv e) is to be satisfied, S must be completely justified in believing h even if he were to suppose that t v r is false. Part of this supposition is the supposition that r is false, where r is an arbitrary false statement. Therefore, relative to the assumption that S is completely justified in believing some false statement, (iv e) is equivalent to
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Second, I assume that there is a statement that is (or means the same as) the disjunction of all false statements. This disjunction will itself be false. Since to suppose a disjunction false is to suppose that every disjunct is false, relative to the second assumption (iv f ) is equivalent to ( i v g ) S would be completely justified in believing h even if S were t o suppose false every statement t h a t is false
I see no reason for preferring condition (iv e) to (iv g). Furthermore, use of (iv g) permits still more simplification in the analysis of " S knows h." Thus, (iv g) entails (iii) S i s colnpletely justified in believing h
since, if S would be completely justified in believing h after making suppositions about the falsity of various statements, then he would be completely justified in believing h originally. We have already noted above that (iii) entails (ii) S believes h
since whether or not 8 is completely justified in believing h depends upon why 8 believes h. So (iv g), which entails (iii), also entails (ii). Furthermore, (iv g) entails (i)
h is true
since, if (i) is false, then h is a false statement such that, if 8 were to suppose it false, he would not be completely justified in believing h and then (iv g) must be false. Therefore, on the two assumptions mentioned above, Lehrer's analysis of " 8 knows h" reduces to the following: (1) S would be completely justified in believing h even if S were to suppose false every statement t h a t is false
I1
If 8 reasons from f & g to h by reasoning from f in a complicated way to h and then supposes that f is false (which it is), his supposing this may lead him to try to find an argument for h from g ; and, indeed, he may find one that is itself complicated and not at all parallel with his previous argument from f. But the fact that his supposition would get him to think up this second argument cannot be permitted to salvage the claim that he originally knew h. Thus, (1) must be so understood that this sort of salvage cannot happen. We might (begin to) make explicit the correct understanding of (1) as follows :
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( 2 ) S would be completely justSed i n believing h even if (without doing any further reasoning) S were to suppose false every proposition that is false
An obscurity in (2) [and in ( I ) ] is brought out by the following "proof" that there are no cases in which (2) is satisfied but S does not know h. Let p be the statement that S knows h. If S does not know h, then p is false. But S would not be completely justified in believing h if he were to suppose that p was false. Therefore, if S does not know h, (2) is automatically not satisfied. However, it now appears that the analysis involves a circularity in its application, if not in its statement. I n order to determine whether or not S knows that h is true one must determine whether or not it is false that S knows that h is true. But the "proof" depends on the assumption that S would not be completely justified in believing h were he to suppose it false that he knows h. Is this assumption true? I suggest, rather, that it is obscure and that this obscurity carries over to (2). Notice also that, for any statement p that is true or false, either p or its denial is false. I assume that to suppose that the denial of a statement q is false is to suppose that q is true. Therefore (2) is equivalent to the puzzling (3) S would be completely justified in believing h even if (without doing any further reasoning) S were to suppose of each statement that it has the truth value it, in fact, has
One might. think that, on making such a supposition, S would be completely justified in believing all and only those statements which are true. Then (3) would reduce to "h is true," which is obviously not a good analysis of " S knows h." I n trying to understand (3) one must remember that Lehrer points out (175) that "a man need not believe what he supposes to be true" and that "a man need not count as evidence all that he supposes . . . For [his] supposition might be entirely unjustified." This seems right and blocks the reduction of (3) to "h is true." But, for similar reasons, it also seems that a man may be completely justified in believing a proposition that he is at the same time supposing (for the sake of argument, say) to be false. This fact makes it difficult to see how any supposition S makes is going to affect what S is completely justified in believing. Or, rather, it again poses the question how we are to understand (2) and (3). Lehrer suggests to me (personal communication) the following : "The question of whether S would be completely justified in believing h if he were to suppose that p is false amounts to the question of whether S would be able to justify completely his belief that h without appealing to p or any other statement that
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could only be shown to support h by reasoning through p." he would read (2) as equivalent to
Thus
(4) S mould be able to justify completely his believing h. even if (with-
out doing any further reasoning) S mere to suppose false each statement that is false
I t is not obvious how one is to interpret the parenthetical remark in (4). It is meant to restrict 8 to giving justifications on which his belief is originally based and to prevent him from thinking up new justifications of his believing h in order to show (falsely) that he originally knew h. At best such new justifications show that 8 knows now. But this explanation of the parenthetical remark in (4) makes use of the notion that a belief is based on a certain justification, where the obvious interpretation of 'based on' is of necessity ruled out. Thus, one cannot explain 'based on7 by saying that 8's belief in h is based on a certain justification if and only if 8 would so justify his belief in h (if asked), since the request to S that he justify his belief may prod him into thinking up new justifications for previously unjustified or otherwise justified beliefs. Finally I would like to mention two ways in which (4) may turn out to be inadequate as analysis of "8 knows h." First, S will sometimes know h because he sees that h is true. If (4) is to apply, then 8's belief must be based on some justification; but what should this justification be taken to be? There seem to be two possibilities, each raising problems. On the one hand, 8's justification might be given by the argument "I see that h is true; therefore h." But then, to apply (4) in order to determine whether or not 8 knows h, one must know whether or not S, in appealing to the statement that he sees that h is true, is appealing to a false statement. Thus, to apply (4), one must know whether or not 8 sees that h is true; and, since seeing that h is true involves coming to know h by seeing, the application of (4) seems to be involved in circularity in at least some cases. On the other hand, 8's justification might be given by some other argument, e.g., with premises referring to how things look to S. But then, what is this argument, and in what sense can 8's belief be based on an argument he will, in all likelihood, be unable to state l Second, 8 may have forgotten why he came to believe h and may be quite unable to offer any argument for h, although this is not always enough to show that S does not know h. Much of
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one's knowledge was originally believed for reasons one no longer remembers. (Suppose h is, e.g., "The sun is approximately 93 million miles from the earth" or "Columbus arrived in America in 1492.") (4) cannot be applied a t all in such cases. One might think that in cases like this, X's justification is expressed by the argument, "I remember that h is true; therefore h." But, since to remember is in part to know, taking X's belief to involve this justification involves (4) in a circularity of application. Furthermore, it seems unlikely that any very good argument for h can be given from the premise that S seems to remember that h. GILBERT H. HARMAN PRINCETON
UNIVERSITY
NOTES AND NEWS Professor Jeanne Hersch, professor of philosophy at the Faculty of Letters of the University of Geneva, has been appointed director of the UNESCO Division of Philosophy. This new division was established following a resolution by UNESCO's General Conference in 1964, which gave it the task of studying "the sociocultural factors of development and the conditions of social progress which development should produce in man and in contemporary society." Professor Hersch, who is Swiss, studied first at Geneva and then a t the Sorbonne and Heidelberg. She was named to her professorship at the University of Geneva in 1956. She has also given courses at Pennsylvania State University and New Pork University. Messrs. Ramesh Patel, Upendra Trivedi, and Jyotindra Dave announce the founding of the Society for the Synthesis of Knowledge (prajnanam dhimahi), which aims, "in view of present trends toward overspecialization, resulting in the disintegration of knowledge, to synthesize the major heads of human knowledge on a flexible, intellectual, and valuational basis." The founders believe that "a dissective synthesis of the basic issues can, by elaboration and extension, eventually yield a suitable synthesis of human knowledge." They describe their organizing point of view as "dissective synthetism." The founders invite membership and correspondence, c/o Upendri Trivedi, 192 S. V. Road, Bombay 56, India.
