Defeasibility and Memory Knowledge Andrew Naylor Mind, New Series, Vol. 91, No. 363. (Jul., 1982), pp. 432-437. Stable URL: http://links.jstor.org/sici?sici=0026-4423%28198207%292%3A91%3A363%3C432%3ADAMK%3E2.0.CO%3B2-K Mind is currently published by Oxford University Press.
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. Mind (1982) Vol. xcr, 432-437
Defeasibility and Memory Knowledge A N D R E W NAYLOR
Philosophers who devise fourth conditions in definitions of knowledge that p should investigate how their definitions might apply to cases where, if the subject did know thatp, that knowledge would be memory knowledge. Carl Ginet has done this.' More than this, by carefully developing a correlative four-part definition of memory knowledge that p, he has provided what may be the most nearly adequate traditional account of memory knowledge to have come along.2 I shall argue that, as a definition, the latter account fails-owing to the problematic way in which it incorporates the fourth condition in his general definition of knowledge.
According to that general definition, if a person, S , knows thatp, then (i)p, (ii) S is confident that p, and (iii) this confidence is supported by a disinterested justification that S has for it (pp. 12,80). Given my limited aim in this paper, I shall go along with Ginet's claim that (ii) and (iii) are requirements for knowledge that^.^ Thus when I assert or deny that S in some particular case knows thatp (or has memory knowledge thatp), indeed, whenever I use these terms, I shall always mean knowledge with justified confidence that p (or confident memory knowledge that p, where that confidence is appropriately justified as memory-confidence). T o these traditional requirements Ginet adds a defeasibility requirement, intending thereby to exclude cases in which, for every justification, J, in virtue of which (iii) is met, it is too much of an accident thatJ is a justification for a truth. On Ginet's definition, then, S knows thatp if and only if (i-iii) and (iv) there is no truth r such that, were S to have justification for believing that r and to retain every property entailed by his justification for being confident that p that is compatible with his having justification for believing I
2
3
Knowledge, Perception, and Memory (Dordrecht, 1975). Parenthetical pagereferences are to this book. By a 'traditional' account of memory knowledge I mean an account that locates whatever positive justification there may be for the confidence of that knowledge in a present memory-impression, whether this be an ostensible memory experience or (as in Ginet's case) a dispositional state of its seeming to one that he remembers. This claim is, of course, controversial. See, e.g., Colin Radford, 'Knowledgeby Examples', Analysis, xxvii (1966), pp. 1-11, and Hamlyn, The Theory of Knowledge (New York, London: 1970)) pp. 81-82, 96-97; also, Keith Lehrer, 'The Gettier Problem and the Analysis of Knowledge', in Justification and Knowledge, ed. George S . Pappas (Dordrecht, 1979)~ pp. 65-78, and Knowledge (Oxford, 1974).
that r, then that justification and those properties would be very far from justifying him in being confident that p (pp. 74, 80). Now a proposition r may be such that, for some cases, it would falsify (iii) if the subject actually possessed a justification for believing it, but would not falsify (iv) when the subject's justification for believing it is merely supposed in the manner which that condition specifies: r may be false, or r may be such that it would leave the subject still too close to being justified in being confident that p. By exploiting the latter possibility, Ginet's (iv) holds promise of avoiding the difficulty (of being too strong) that foils those early defeasibility theories that have fourth conditions essentially like (iv), but with 'would not justify' instead of 'would be very far from justifying'.' A second attractive feature of (iv) is its apparent relative simplicity compared to many of the fourth conditions put forth by more recent defeasibility theorists. And, third, there is Ginet's own very recent pronouncement that although some of the proposed fourth conditions of other defeasibility theorists (and of causal theorists as well) '. . . mav work for swecial kinds of knowledge (for example, knowledge by inference or memory knowledge or restricted kinds of perceptual knowledge), none of them applies in every kind of case'.2
Yet, however well Ginet's own definition employing (iv) may work for some of these kinds of knowledge, it does not work for memory knowledge.
S has [non-original] memory knowledge that p if and only if (1)
P,
S is confident that p, (3) this confidence is supported by the justification that (a) S has a strong memory-impression that p and (b) S has no other memory-impressions or sensations or infallible knowledge that would give S reason to be unsure that p despite his strong memory-impression that p, and (4) (a) there is no truth r such that were S to have justification for believing that r a n d retain those properties implied by (3) (a) and (b) that are compatible with his having justification for believing that r then that justification and those properties would be very far from justifying S i n being confident that p: (2)
I
2
See Carl Ginet, 'What Must be Added to Knowing to Obtain Knowing that One Knows?', Synthese, xxi (1970),p p. 173-175;Risto Hilpinen, 'Knowledge and Justification', Ajatus, xxxiii (1971),pp. 7-39; and Peter D. Klein, 'A Proposed Definition of Propositional Knowledge', Journal of Philosophy, lxviii (1971)) pp. 471-482;and, for an example exposing the difficulty, Keith Lehrer and Thomas Paxson, Jr, 'Knowledge: Undefeated Justified True Belief ', Journal of Philosophy, lxvi (1969),pp. 227-229. 'Knowing Less by Knowing More', Midwest Studies in Philosophy, v (1980), p.
159.
ANDREW NAYLOR: in particular the negation of the following proposition is not a truth: (b) . . . there was a time t such that S h a d non-memory knowledge thatp at t and S's present strong memory-impression thatp is memory-connected to his having known thatp at t (pp. I 53'54). Ih considering this definition, I first raise the question: Does the conjunction of (qa) with the other conditions listed above yield a sufficient condition for memory knowledge that p? It could do this, I then suggest, only if (qa) were not a necessary condition. In a situation where Scame to know thatp at t (cf. Ginet's ( I )and the first part of (4b)) solely by inference from q, S's present confidence that p (Ginet's (2)) may be supported by an appropriate memory-justification (Ginet's (3)) even though S has now forgotten that q and falsely but justifiedly believes that it was in some other way that he came to believe that p originally. At the same time, S's strong memory-impression that p (the one which meets (3a)) may be connected to his having known that p at t in the right sort of way for it to be a memory that p from t (thus meeting the second part of (4b)). All this could be true in a case where p and q had the values
(9)Professor X received a distinguished teaching award (q) The alumni magazine reported that p and the remaining details of the case were as follows. Case I . At no past time did S have any additional line of non-memory justification for believing that p. Nor at any past time did he have justification for believing a proposition r such that p cannot be nondeductively inferred with confidence from the conjunction of q and r. It was five months ago that he learned that p, and now, during a reception at his class reunion, he has brought up the subject of Professor X's award in the presence of an assistant editor of the magazine. The latter mentions the possibility that (r,) The copy (for the magazine issue which reported that p) had been sent to the printer shortly before the recipient of the award was announced, and a blank space had been left to be filled in during subsequent proof-reading; later Professor X's name had been added, but only because a student employed to read proof, who had no idea who had won the award, inserted the name of a personal favourite. Although r, is false (since there was no Gettier-type feature that infected the editorial process), the assistant editor, in what he goes on to say, provides S with justification for believing that (r,) An assistant editor of the magazine has just now said with apparent sincerity that, while he has more evidence against r, than he does for r,, his evidence for r, is such that, on the basis of all the evidence he has, it is reasonable for him to believe that not-r, with (only) a moderate degree of belief.
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(There is, in fact, no such evidence for r, other than the fabrications of the assistant editor himself on this one occasion, and only the few classmates who hear his remarks know that r,; there exists no other evidence to cast doubt on the reliability of the magazine report.) The assistant editor attests to the fact that p-so no question is raised about that, but only about whether one could come to know that p from reading the magazine. For S himself, however, no such question is raised about whether he previously knew that p. This, of course, is not because he is somehow justified in discounting r , as a reason for suspecting that r,. Rather, since he has forgotten that q and lacks any justification for believing that it was by inference from q that he originally came to believe that p, he fails to appreciate the force that r, would otherwise have by way of weakening his present memory-justification for p. Lacking reason to be unsure that p, he remains unshaken in his memory-confidence that p. Nevertheless, S does not have memory knowledge that p.' For, the justification he now has for believing that r , is a justification in the face of which his justification forp at t would now (assuming he now had the sort of justification which he had then) be insufficient to justify him in being confident that p. That a memory-impression cannot now give one knowledge unless one has had an original justification of a sort that could (if one had it now) now give one knowledge, is a principle whose denial would mean that our memories could sometimes be a source of knowledge in an unwelcome way. In Case I , Ginet's conditions (1-3) and (qb) are clearly met. Is there any truth r that falsifies (4a)?Well, there is a truth which, in accordance with the principle just mentioned, explains why S lacks memory knowledge that p: (r,) The only (past) non-memory justification that S h a d ever had for believing that p was an inferential justification whose premiss was q; and a justification of that sort'(if S had it now) would be insufficient-in the face of the justification S now has for believing that r,-to justify S i n believing thatp with greater than a moderate degree of belief. Yet it is not at all clear that this is a truth that will falsify (4a). This can be seen if, in accordance with (4a), we suppose both that S has justification for believing that r, and that he retains his strong memory-impression thatp as well as any other properties implied by (3) (a) and (b) that are compatible with his having that justification. Would he, in such a situation, be veryfar from justified in being confident that p on the basis of that memoryimpression? His (supposed) justification for r, would, of course, destroy the authority of this memory-impression as a basis for being confident that p. But why should this justification destroy the authority of the memoryimpression as a basis for believing that p with a lesser degree of belief? It would not wipe out altogether the belief-justifying force of his strong memory-impression; hor would it make it at all unreasonable for him to I
Reminder: the call here being made is that S does not have confident memory knowledge that p , and not that S does not have memory knowledge that pon less restricted uses of 'know', e.g., those adopted in the works cited in note 3, p. 432.
ANDREW NAYLOR:
436
continue on the basis of this memory-impression to believe that p with at least a moderate degree of belief. If, in this supposed situation, S would not be very far from justified in being confident thatp then (qa) is met, the truth r, notwithstanding. Faced with the prospect that Gjnet's definition is too weak, a would-be defender of the definition might respond: 'In the Case-I situation where S is considered to have a (supposed) justification for believing that r,, there is a considerable distance by which he would fall short of being justified in being confident thatp, and that distance is far enough to falsify (4a).' This response, however, faces an intractable problem. In a case which is like Case I except that S does not actually possess the evidence r,, S could have memory knowledge that p even though there is a truth r which, in accordance with (qa), would weaken S's memory-justification no less than .r, does in Case I . Case 2 . Swill not be attending the reunion. The plane she boarded to get there was hijacked. She is now held captive at a distant location. Unlike her Case-I counterpart who has come to have justification for believing that r,, S has no reason to doubt the reliability of the magazine report. Otherwise her situation from t through the present is like that of the subject in Case I , and all other 'background' facts are the same as in that case. Despite these similarities, S in this case has the memory knowledge that p which her counterpart lacks. The following truth that obtains in Case 2, were S to have justification for believing it, would definitely weaken her memory-justification for being confident that p: ( ~ 4 )(a) r2, and (b) the only (past) non-memory justification that S h a d ever had for believing that p was an inferential justification whose premiss was q, and if S should now have justification for believing that r,, then a non-memory justification of the sort that Shad in the past (if Shad it now) would be insufficientin the face of a justification on S's part for believing that r,to justify S in believing that p with greater than a moderate degree of belief. Were S to have justification for believing that r, while retaining those properties entailed by her (actual) memory-justification for being confident that p which are compatible with her having justification for believing that r,, that justification and those properties would justify her in believing that p with only a moderate degree of belief. Imagine now a hypothetical situation where the S of Case I , in the face of a (supposed) justification for believing that r,, believes that p (on the basis of his strong memoryimpression thatp) with that same moderate degree of belief thatp which the Sof Case 2, in the situation just described, would be justified in having. His moderate belief would be no less reasonable than hers. But, then, there can be no unround for holdinn in Case I but not in Case 2,that S would be too far from justified in being confident that p. Whatever judgement is made in Case I about whether or not (4a) is met must be made in Case 2 as well. The failure of Ginet's definition of memory
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437
knowledge that p is evident no matter how that judgement goes: if the judgement is affirmative, the definition is too weak-because all of its conditions would be met in Case I where Slacks memory knowledge that p; if negative, the definition is too strong-because S has memory knowledge that p in Case 2 where (4a) would not be met.
Is it worth adhering to the traditional view that there must be a memoryimpression or other justificatory device in the present for S's confidence to qualify as memory knowledge? Cases I and 2 may lead one to wonder. The primary question in cases like these is not whether there is an 'outside' truth r that defeats S's present memory-justification, but whether there is any truth r such that if S now had a justification of the sort that he had originally, r would defeat that justification. How much simpler the question of the defeasibility of a memory-justification would be if the positive part of that justification consisted in nothing other than elements of the original justification itself! We might then be able to say that S's confidence qualifies as memory knowledge just in case it is retained from the past and remains sufficiently and non-defectively justified on the basis of a subset of those elements alone.' Of course, we would still need an adequate account of what it is for a justification based on such elements to be non-defective, and this might or might not be an account in terms of defeasibility. INDIANA UNIVERSITY A T SOUTH BEND
I
This may be (but does not have to be) a proper subset. The suggested analysis is restricted to non-original memory knowledge thatp, where there was a past time at which S knew that p.
