SORITES (Σωριτης), ISSN 1135-1349 http://www.sorites.org Issue # 21 - June 2008. Pp. 06-11 Evaluating Williamson's Anti-Scepticism Copyright © by Tony Cheng and SORITES EVALUATING WILLIAMSON'S ANTI-SCEPTICISM Tony Cheng 1. Epistemologists have different attitudes toward scepticism about knowledge, but no one can sensibly deny its central place in at least some branches of philosophy. We can trace its history back to ancient Greek, and nowadays there are still sceptics around us.1 It's fair to say that scepticism is a necessary ingredient of epistemology. Timothy Williamson's Knowledge and its Limits can be seen as a systematic response to scepticism.2 He starts with the slogan «knowledge first,» and elaborates it by arguing for the thesis that knowledge is a basic mental state: knowledge is basic in the sense that it cannot be analysed with more primitive terms (primeness), and knowledge is mental because it is a species of propositional attitudes that is externally individuated (broadness). These moves are anti-sceptic because knowledge essentially involves external conditions, and we cannot factorise knowledge into internal and external conditions.3 The anti-sceptic character of the book becomes more prominent when Williamson attacks the idea that we are always in a position to know our own mental states (anti-luminosity), a Cartesian way of thinking that often leads to scepticism. Williamson goes on to criticise another popular (maybe not so popular today) idea in epistemology, that in order to know something, we need to know that we know it (anti-KK principle). The idea under attack also leads to scepticism, for intuitively we do not know whether we are in sceptical scenarios or not. After setting up these main points against scepticism, Williamson begins to apply them to different topics, surprise exams 1. For a defence of global scepticism, see Peter Unger, Ignorance: A Case for Scepticism (USA: Oxford University Press, 1975). If we align sense-datum theories with scepticism, then Howard Robinson, Perception (Routledge, 1994) and Evan Fales, A Defense of the Given (Rowman & Littlefield Publishers, 1996) also offer positive cases for it. 2. Timothy Williamson, Knowledge and its Limits (USA: Oxford University Press, 2002). Philosophers have different readings of its main purpose; see extant reviews of this book. Among them Gilbert Harman, «Reflections on Knowledge and Its Limits,» Philosophical Review 111 (2002): 417-28 also emphasises its an-sceptic character. This complex piece allows for more than one reading. 3. The two moves do not always go hand in hand, so the conjunction here is crucial. Some philosophers concede that mental states are essentially individuated with the help of external conditions, but nevertheless hold the separability thesis about the internal and external factors. The internal factor is dubbed «narrow content.» We can say that these philosophers endorse broadness but deny primeness. For a recent defence of this view, see G. M. A. Segal, A Slim Book about Narrow Content (The MIT Press, 2000). For a reply to Williamson precisely on this point, see Ralph Wedgwood, «The Internal and External Components of Cognition,» in Contemporary Debates in Cognitive Science, ed. Robert Stainton (Blackwell Publishing Professional, 2006, 307-25). <http://www.sorites.org> - «Evaluating Williamson's Anti-Scepticism» by Tony Cheng 7 for example, and goes on to develop further elements in his overall project. The profoundness of the book is impressive.4 Williamson is not satisfied with the above treatments of scepticism. He is aware that some people argue for sceptical cases on the ground that normal people and their counterpart brains in vats (BIVs for short) share the same evidence. Williamson attempts to damp this line of thought by espousing an extreme thesis that evidence equals knowledge (E = K). If that is so, our counterparts and ourselves do not share the same evidence, for we have knowledge but they do not have. Williamson hunts the sceptics until their last breaths. As the above reconstruction shows, Williamson launches a range of arguments to repel scepticism. Some of them are centered on his conception of evidence. They will be the focuses of the present essay. I attempt to show that Williamson's notion of evidence begs the question against scepticism, that E = K is unnecessary as far as scepticism is concerned, that the argument based on E = K is incompatible with content externalism, and that «sameness of evidence» is not required by scepticism. Let me go through them in turn. 2. First of all, Williamson's stipulation of the notion of evidence begs the question. He introduces his notion of evidence in the following two passages: That one has the same evidence in the good and bad cases in a severe constraint on the nature of evidence. It is inconsistent with the view that evidence consists of true propositions like those standardly offered as evidence for scientific theories. (Knowledge and its Limits, 173) The communal case is needed: science depends on public evidence, which is neither the union nor the intersection of the evidence of each scientist. (Knowledge and its Limits, 185) Here we can find that Williamson has a specific conception of evidence in mind: only public, true propositions can be evidence. I think it is not correct even in scientific contexts: to think only true propositions can be counted as evidence is to presuppose the God-eye point of view. Scientists have to start with evidence before they know whether those propositions are true or not. But let me grant that point to Williamson for the sake of argument. Now, even the concession has been made, to stick to this allegedly scientific sense of evidence and say that it is inconsistent with sceptic's notion of evidence is not to the point, though it is true: they are indeed incompatible, but to simply invoke a notion from science and say that it is incompatible with scepticism does not damp the sceptical worry at all. It's just like saying that «look, that's just how science works, so scepticism is false.» If this can be a successful case for anti-sceptics, epistemology is not so hard (and interesting) a subject. What I am suggesting is the recognition of two different senses of evidence. The scientific sense is what Williamson has in mind (though it is not without problems), but it is irrelevant to the discussions of scepticism anyway: when a sceptic claims that a subject has the same evidence in the good and the bad cases, she is not saying that the subject has the same public, true propositions in the two cases. This is a nonstarter for scepticism. If we construe it this way, we cannot even make sense of it; we do not even have the slightest reason to believe it might be true. What the sceptic is driving at is that in both the normal case and the BIV scenario, the subject is not in a position to find any difference in her 4. This paragraph should not be seen as a comprehensive summary of Williamson's book. My selective reconstruction here is supposed to echo my main line in this essay – how Williamson deals with the notion of evidence in order to attack scepticism. I will explain this presently. <http://www.sorites.org> - SORITES Issue # 21 - June 2008 ISSN 1135-1349 8 experiences. It is experientially indistinguishable for her. Subjectively, it just makes no difference. The power of this point is that in daily life we really have indistinguishable hallucinations, though not very frequently.5 To stipulate the objective notion of evidence does not help here. We still want to know how to avoid scepticism and at the same time do justice to the possibility of experiential indistinguishability. Williamson takes issue with scepticism at this point by arguing against the phenomenal conception of experience, but only very old philosophical theories would hold that evidence consists in private sense-data or something like that even for science. The general problem here is that Williamson does not really confront scepticism in his arguments based on the notion of evidence. 3. Furthermore, to identify evidence with knowledge is excessive as far as scepticism is concerned. To see this, consider Williamson's claims about broadness and primeness. Williamson, like some other anti-sceptics, contends that the experiential indistinguishability does not imply that subjects in the good case and in the bad case share the same mental state: granted they have the same phenomenal feels, but the ontology of states should not be individuated by experiential sameness.6 That's what motivates Williamson's primeness claim. For if one is satisfied with broadness, the possibility that subjects in the good case and in the bad case share the same narrow content has not been ruled out. With this state externalism in hand, Williamson can legitimately claim that we have knowledge whereas BIVs do not. But then it is not clear why Williamson needs further steps. Given his state externalism about knowledge (that is, broadness plus primeness), scepticism based on experiential sameness has been refuted. Why do we still need to insist that they have different evidence? Williamson offers the following reason: A natural argument is by reductio ad absurdum. Suppose that one has different evidence in the two cases. Then one can deduce in the bad case that one is not in the good case, because one's evidence is not what it would be if one were in the good case. But even the sceptic's opponent agrees that it is consistent with everything one knows in the bad case that one is in the good case. Therefore, one has the same evidence in the two cases. (Knowledge and its Limits, 169-70) And he goes on to diagnose that «[t]he argument assumes that in the bad case one knows what one's evidence is...» (170). Williamson opposes to this, for he holds an objective notion of evidence, which consists in true propositions, therefore one does not have the same evidence in the two cases. But we have seen that to refute scepticism, state externalism about knowledge is sufficient. The motivation of objecting sameness of evidence is from his objective notion of evidence (and related thesis E = K). So it is fair to say that as far as scepticism is concerned, opposing sameness of evidence is ill-motivated. It is open to Williamson to reply that E = K is not especially relevant to his antiscepticism. Scepticism has been refuted in chapter eight and some earlier chapters of the book, but E = K is argued in chapter nine. It is self-sustaining and not presupposed in his arguments against scepticism. 5. For a delicate reconstruction of the argument from illusion and the argument from hallucination, see A. D. Smith, The Problem of Perception (Harvard University Press, 2002). He argues that even the possibility of illusion and hallucination will do. 6. Williamson himself appeals to John McDowell, «Criteria, Defeasibility, and Knowledge,» in his Meaning, Knowledge, and Reality (Harvard University Press, 1998), 369-94, as an ally. See McDowell's «Knowledge and the Internal» (ibid, 395-413) for further elaborations. <http://www.sorites.org> - «Evaluating Williamson's Anti-Scepticism» by Tony Cheng 9 Unfortunately, this line of reply is blocked by Williamson's own summary of his chapter eight. I quote the second half of it: Since sceptics have not refuted the equation of evidence with knowledge, they are not entitled to assume that we have no more evidence in ordinary cases than in their sceptical counterparts, for on the view against which they are attempting to argue we do have more knowledge in ordinary cases than in their sceptical counterparts. (Knowledge and its Limits, 15, my italics) Notice that E = K is invoked here, but it is argued later in chapter nine. For one thing, it makes the above putative reply unavailable to Williamson; for another, it betrays an oddity of the arrangement of the book: a crucial thesis is invoked before it is argued. What's more, sameness of evidence is not, pace Williamson's accusation, an assumption on sceptic's part. It is argued on the ground of the indistinguishability of the phenomenal. We can challenge this line of thought, to be sure. But we should not regard it as an assumption and thereby attribute the burden of proof to the sceptic. Quite the contrary. The burden of proof is on someone who proposes E = K, for it is not obvious at all. Now Williamson does offers substantial arguments for the equation, but as I have argued above, what he has in mind is the objective, public, scientific notion of evidence. So the sceptic can grant the equation and still launches her challenge. Williamson says the notion invoked by the sceptic is incompatible with the one he uses, but this only shows that he does not address the real worry of scepticism.7 4. My third claim is that the argument from E = K is incompatible with content externalism, a thesis accepted by Williamson himself. Consider the passage I just quoted from Williamson, and notice the thought behind the reasoning in those remarks: because evidence is factive thanks to E = K, the BIV does not share the same evidence with his normal counterpart, for the former has false, therefore fake evidence, the latter has true one. But by what standard the putative evidence of the BIV is false? When he uses «I have hands» as evidence to support his other beliefs, the putative evidence is false on the assumption that it is the same thought with the one entertained by his normal counterpart. But this is wrong according to content externalism. For example, according to certain version of content externalism, the content of BIV's thought is constituted by the stimulations he receives, so if there is certain corresponding relation between the thought expressed by «I have hands» and certain patterns of brain stimulations, the thought in question may well turn out to be true. Therefore, it becomes not clear that whether content externalism sides with Williamson or not.8 There are puzzles about assigning truth-values to the BIV's thoughts, to be sure, for there seems to be no objective ground to generate truth and falsity. Williamson can then argue that since «I have hands» is true in the good case but devoid of truth value in the bad case, sameness of evidence collapse anyway. However, there are a lot more to be said in taking this 7. In his review, Richard Foley echoes this passage by saying that «[w]hile envatted, John [the BIV] is severely deprived of knowledge of his environment, but because on Williamson's view, one's evidence is co-extensive with what one knows, John is also thereby severely deprived of evidence.» (721) 8. There is a crucial difference between the BIV case and the hallucinatory case here. It is relatively easier for Williamson to answer the present challenge if we construe it in terms of the hallucinatory case, for in the BIV case the normal subject and the BIV do not share the same thought when both of them entertain «I have hands.» Here I am indebted to Branden Fitelson. <http://www.sorites.org> - SORITES Issue # 21 - June 2008 ISSN 1135-1349 10 tack, so whether content externalism can be used to counter against scepticism remains an open question. 5. This brings us to the last point I would like to make. The above diagnosis points to the fact that Williamson does not fulfill his promise of substantially relating epistemology to philosophy of mind in his chapter on scepticism. Although Williamson's intention to connect these two subjects can be easily detected in many places in the book, and this is indeed admirable, he nevertheless only scratches the surface in this particular chapter. At the beginning of it, he briefly mentions content externalism and says: We assume for the sake of argument, perhaps over-generously, that the sceptic has some way of absorbing...implications of content externalism. (Knowledge and its Limits, 165, my italics) Here he writes as if content externalism is definitely a bad news for scepticism, but as my third point shows, this seems to be too quick. In what follows I will give a further reason (that is, my fourth point) why I think it is too quick. The line of thought in the quotation is this: the sceptic needs sameness of evidence, beliefs or perceptions or whatever, to establish her sceptical case. But given content externalism, the subject in the good case and the one in the bad case do not share most of their beliefs and (quasi-)perceptions, for their external environments are radically different. It seems that scepticism cannot get of the ground if content externalism is true. Now Williamson grants that maybe the sceptic can find a way out of this, but still, she will face some additional problems. That's the idea. But is the dialectic situation that simple? So the fourth point is this: given content externalism, and given that the sceptic needs sameness of evidence, the sceptical challenge evaporates right away. But is it true that sameness of evidence is required for the sceptic? I submit the negative answer. It is true that the skeptic needs something common to the good case and the bad case, but that something should be the support relations between evidence and hypotheses, not the evidence itself. If the normal subject and the BIV might be equally justified, but only the former has knowledge, then the sceptic is home and dry. Notice that the notion of «equally justified» is not interchangeable with the notion of «having the same evidence.» An analogy might help. Valid deductive arguments are equally valid, but they may well have different premises. It's the degree of supporting, not the ground of supporting, that is supposed to do the trick for scepticism. In this sense Williamson's whole argumentation against scepticism is beside the point. Think about content externalism. Assuming the sceptic in question champions this view herself. By her light, when both the normal subject and the BIV say the sentence «I have hands,» they are in fact expressing different thoughts despite the fact that the thoughts are instantiated by the same sentence. Now she grants Williamson's arguments against sameness of evidence, but argues that there is no obvious reason why the BIV cannot share the same degree of supporting with the normal subject: surely the ground of supporting in the BIV case may be bad, but what prevents this bad ground from supporting the hypothesis (i.e., the belief to be justified) in question well? Granted, they have different hypotheses thanks to content externalism, and they have different evidence for those hypotheses thanks to Williamson, but <http://www.sorites.org> - «Evaluating Williamson's Anti-Scepticism» by Tony Cheng 11 what on earth is supposed to establish the claim that the two subjects cannot have the same degree of supporting?9 It seems to me that Williamson does not address this issue at all. Let me adumbrate the points I have made before closing this short essay. First, Williamson's notion of evidence does not make any direct contact to scepticism. I am not saying that anti-sceptics need to invoke the notion of evidence adopted by the sceptics, but at least the former needs to address the latter's worry. It is not clear to me that Williamson is aware of this. Second, the role of E = K in the book is not clear. Because broadness and primeness are sufficient for rejecting scepticism, and because E = K is argued after the scepticism chapter, it seems that Williamson's anti-sceptic arguments can do without it. However, Williamson's own outline of that chapter suggests the other way around. The status of E = K is further undermined when we see that there is a tension between content externalism and it; this is the third point. And finally, the consideration of content externalism helps bring out the fact that sameness of evidence is a red herring as far as scepticism is concerned: if that were the locus of the debate, scepticism would be simply ruled out by content externalism; what should be at issue is sameness of the degree of supporting, not evidence. 6. Overall, Knowledge and its Limits presents not only a strong challenge to traditional epistemology, but also a solid ground for a systematic, positive project to pursue. Its treatments of scepticism, however, are not so satisfying because of the problems I discussed above. It is not that they cannot be answered by Williamson. The moral should be more positive: given the success of other parts of the book, we expect the book to do better when he takes issue with scepticism. His arguments against scepticism are as intricate as his arguments elsewhere, albeit the minor flaws I tried to point out above. I believe his case against scepticism can be more successful if he adjusts the thrusts along the lines I suggested in this critical notice. Acknowledgement This paper was written when I was a visitor of U. C. Berkeley, fall 2006. I would like to express my gratitude to Brandon Fitelson and Sherrilyn Roush, for their patience and helpful comments. For technical reasons the paper did not come out until recently, but I leave the paper as it was. Tony Cheng University of California, Berkeley h.cheng.12@ucl.ac.uk 9. Williamson might say that we cannot simply stipulate that they can share the same degree of supporting. He expresses his hostility to stipulations in the sceptical scenario by arguing that stipulation violates the requirement of constructing non-trivial connections between epistemic notions (169). But this begs the question against scepticism, for what it objects to is exactly substantial relations between epistemic notions. All the sceptic needs is the intuitive plausibility of conceiving sameness of supporting degree in the two cases.