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تاريخ التسجيل : 26/10/2009
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 | |  The Argument From Not (Easily) Knowable Propositions | |
Another anticlosure argument is that there are some sorts of propositions we cannot know unless perhaps we take extraordinary measures, yet such propositions are entailed by mundane claims whose truth we do know. Since this would be impossible if K were correct, K must be false. The same difficulty is sometimes discussed under the heading problem of easy knowledge, since some theorists (Cohen 2002) believe that certain things are difficult to know, in the sense that they cannot be known by deduction from banal knowledge. The argument has different versions depending on which propositions are said to be hard knowledge. According to Dretske (and perhaps Nozick as well), we cannot easily know that limiting propositions or heavyweight propositions are true. These resemble propositions Moore (1959) considered certainly true and that Wittgenstein (1969) declared to be unknowable (but Wittgenstein considered them unknowable on the dubious grounds that they must be true if we are to entertain doubts). Another possibility is that we cannot easily know lottery propositions. A special case of the argument from unknowable propositions starts with the claim that we cannot know the falsity of skeptical hypotheses. We will consider this third view in the next section. 4.1 The Argument from Limiting PropositionsDretske did not clearly delineate the class of propositions he called “limiting” (in 2003) or “heavyweight” (in 2005). Some of the examples he provided are “There is a past,” “There are physical objects,” and “I am not being fooled by a clever deception.” He appeared to think that these propositions have a property we may call “elusiveness,” where p is elusive for me if and only if p's falsity would not change my experiences. But being limiting does not coincide with being elusive. If there were no physical objects, my experiences would be changed dramatically, since I would not exist. So some limiting propositions are not elusive. As to whether all elusive claims are limiting, it is hard to say, because of the squishiness of the term “limiting”. Not-muleis elusive, but is it limiting?Can't we know limiting propositions? If not, and if we do know things that entail them, Dretske thought he had further support for his conclusive reasons view, assuming, as he did, that his view rules out our knowing limiting propositions (while allowing knowledge of things that entail them). However, this assumption is false (Hawthorne 2005, Luper 2006). We do have conclusive reason to believe some limiting propositions, such as that there are physical objects. Still, Dretske might abandon the notion of a limiting proposition in favor of the notion of elusive propositions, and cite, in favor of his conclusive reasons view, and against K, the facts that we cannot know elusive claims but we can know things that imply them.In order to rule out knowledge of limiting/elusive propositions, Dretske offered two sorts of argument, which we may call the argument from perception and the argument from pseudocircularity.The argument from perception starts with the claims that (a) we do not perceive that limiting/elusive claims hold and (b) we do not know, via perception, that limiting/elusive claims hold. Since it is hard to see how else we could know limiting/elusive propositions, (a) and (b) are good grounds for concluding that we just do not know that they hold.There is no doubt that (a) and (b) have considerable plausibility. Nonetheless, they are controversial. To explain the truth of (a) and (b), Dretske counted on his conclusive reasons analysis of perception. His critics may cite the safe indication account of perception as the basis for rejecting (a) and (b). Luper (2006), for example, argues against both, chiefly on the grounds that we can perceive and know some elusive claims (such as not-mule) indirectly, by directly perceiving claims (such as zeb) that entail them.Dretske suggested another reason for ruling out knowledge of limiting/elusive claims. He thought we can know banal facts (e.g., we ate breakfast) without knowing limiting/elusive claims they entail (e.g., the past is real) so long as those limiting/elusive claims are true, but we cannot then turn around and employ the former as our basis for knowing the latter. Suppose we take ourselves to know some claim, q, by inferring it from another claim, p, which we know, but our knowing pin the first place depends on the truth of q. Call this pseudocircular reasoning. According to Dretske, pseudocircular reasoning is unacceptable, and yet it is precisely what we rely on when we attempt to know limiting/elusive claims such as denials of skeptical hypotheses by deducing them from ordinary knowledge claims that entail them: we will not know the latter in the first place unless the former are true. The problem Dretske here raised was pressed earlier by critics of broadly reliabilist accounts of knowledge, such as Richard Fumerton (1995, 178). Jonathan Vogel (2000) discusses it under the heading bootstrapping, the procedure employed when, e.g., someone who has no initial evidence about the reliability of a gas gauge, comes to believe p on several different occasions because the gauge indicates p, and thereby knows p according to reliabilist accounts of knowledge, then infers that the gauge is reliable, by induction. By bootstrapping we may move—illegitimately, according to Vogel—from beliefs formed through a reliable process to the knowledge that those beliefs were arrived at through a reliable process. One may know p using a gauge in the first instance only if that gauge is reliable; hence, to conclude it is reliable solely on the basis of its track record involves pseudocircular reasoning.Theorists have long objected to knowledge claims whose truth depends on a fact that itself has not been established, especially if that fact is merely taken for granted. It is also standard to reject any knowledge claim whose pedigree smacks of circularity. Both worries arise if we claim to know that one proposition, q, is true on the grounds that it is entailed by a second proposition,p, even though the truth of q was taken for granted in coming to know that p is true. Many theorists will reject pseudocircular reasoning on precisely these traditional grounds. Dretske did not share the first worry but he did raise the second, the concern about pseudocircular reasoning. But there is a growing body of work that breaks with tradition and defends some forms of epistemic circularity (this work is heavily criticized, in turn, on the grounds that it is open to versions of traditional objections). Max Black (1949) and Nelson Goodman (1955) were early examples; others include Van Cleve 1979 and 2003; Luper 2004; Papineau 1992; and Alston 1993. Dretske himself meant to break with tradition, writing under the banner of ‘externalism.’ He explicitly said that most, if not all, of our mundane knowledge claims depend on facts we have not established. Indeed, he cited this as a virtue of his conclusive reasons view. Yet nothing in the nature of the conclusive reasons account rules out our knowing limiting propositions using pseudocircular reasoning, which leaves his reservations mysterious. A set of jar-ish experiences can constitute a conclusive reason for believing jar, a jar of cookies is in front of me. If I then believe objects, there are physical objects, because it is entailed by jar, I have conclusive reason for believing objects, a limiting proposition. (If objects were false, jar would be too, and I would lack my jar-ish experiences.)Dretske might have fallen back on the view that the conclusive reasons account rules out knowing elusive, as opposed to limiting, claims through pseudocircular reasoning, because we lack conclusive reasons for elusive claims no matter what sort of reasoning we employ. But this does not put Dretske's account at odds with pseudocircular reasoning. And even this more limited position can be challenged (adapting a charge against Nozick in Shatz 1987). We might insist thatp itself is a conclusive reason for believing q when we know p and p entails q. After all, assumingp entails q, if q were false so would p be. On this strategy we have a further argument for K: if Sknows p (relying on some conclusive reason R), and S believes q because S knows p entails q, Shas a conclusive reason for believing q, namely p (rather than R), and hence S knows q.Another doubt about knowing elusive claims deductively via mundane claims is that this maneuver is improperly ampliative. Cohen claims that knowing the table is red does not position us to know “I am not a brain-in-a-vat being deceived into believing that the table is red” nor “it's not the case that the table is white [but] illuminated by red lights” (2002: 313). In the transition from the former to the latter, our knowledge appears to have been amplified improperly. This concern may be due at least in large part to lack of precision in the application of entailment or deductive implication (Klein 2004). Let red be the proposition that the table is red, white the proposition that the table is white, and light the proposition that the table is being illuminated by a red light.Red does not entail anything about the conditions under which the table is illuminated. In particular it does not entail the conjunction, light & not-white. The most we can infer is that the conjunction, white & light, is false, and that gives us no information whatever about the lighting conditions of the table. One could as easily infer the falsity of the conjunction, white & not-light. No amplification of the original known proposition, red, has come about. 4.2 The Argument from Lottery PropositionsIt seems apparent that I do not know not-win, I will not win the state lottery tonight, even though my odds for hitting it big are vanishingly small. But suppose my heart's desire is to own a 10 million dollar villa in the French Riviera. It seems plausible to say that I know not-buy, I will not buy that villa tomorrow, since I lack the means, and that I know the conditional, if win then buy, i.e., tomorrow I will buy the villa if I win the state lottery tonight. From the conditional and not-buy it follows that not-win, so, given closure, knowing the conditional and not-buy positions me to know not-win. As this reasoning shows, the unknowability of claims like not-win together with the knowability of claims like not-buy position us to launch another challenge to closure.Let a lottery proposition be a proposition, like not-win, that (at least normally) is supportable only on the grounds that its probability is very high but less than 1. Vogel (1990, 2004) and Hawthorne (2004, 2005) have noted that a great number of propositions that do not actually involve lotteries resemble lottery propositions in that they can be given a probability that is close to but less than 1. Such propositions might be described as lotteryesque. The events mentioned in a claim can be subsumed under indefinitely many reference classes, and there is no authoritative way to choose which among these determines the probability of the subsumed events. By carefully selecting among these classes we can often find ways to suggest that the probability of a claim is less than 1. Take, for example, not-stolen, the proposition that the car you just parked in front of the house has not been stolen: by selecting the class, red cars stolen from in front of your house in the last hour, we can portray the statistical probability of not-stolen as 1. But by selecting, cars stolen in the U.S., we can portray the probability as significantly less than 1. If, like lottery propositions, lotteryesque propositions are not easily known, they increase the pressure on the closure principle, since they are entailed by a wide range of mundane propositions which become unknowable, given closure.How great a threat to K (and GK) are lottery and lotteryesque propositions? The matter is somewhat controversial. However, there is a great deal to be said for treating lottery propositions one way and lotteryesque propositions another.As for lottery propositions: several theorists suggest that we do not in fact know that they are true because knowing them requires believing them because of something that establishes their truth, and we (normally) cannot establish the truth of lottery propositions. There are various ways to understand what is meant by “establishing” the truth of a claim. Dretske, as we have seen, thinks that knowledge entails having a conclusive reason for thinking as we do. David Armstrong (1973, p. 187) said that knowledge entails having a belief state that “ensures” truth. Safe indication theorists suggest that we know things when we believe them because of something that safely indicates their truth. And Harman and Sherman (2004, p. 492) say that knowledge requires believing as we do because of something “that settles the truth of that belief.” On all four views, we fail to know that a claim is true when our only grounds for believing it is that it is highly likely. However, the unknowability of lottery propositions is not a substantial threat to closure, since it is not obvious that there are propositions that are both known to be true and that entail lottery propositions. Consider the example discussed earlier: the conditional if win then buytogether with not-buy. If I know these, then, by GK, I know not-win, a lottery proposition. But it is quite plausible to deny that I do know these. After all, I might win the lottery.Now consider lotteryesque propositions. We cannot defend closure by denying that we know any mundane proposition that entails a lotteryesque proposition since it is clear that we know that many things are true that entail lotteryesque propositions. To defend closure we must instead say that lotteryesque propositions are knowable. They differ from genuine lottery propositions in that they may be supportable on grounds that establish their truth. If I base my belief not-stolen solely on crime statistics, I will fail to know that it is true. But I can instead base it on observations, such as having just parked it in my garage, and so forth, that, under the circumstances, establish thatnot-stolen holds. | |
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