© Symposion, 1, 1 (2014): 77-87 Skeptical Thoughts Concerning Explanationism and Skepticism Clayton Littlejohn Abstract: According to the explanationist, we can rely on inference to best explanation to justifiably believe familiar skeptical hypotheses are false. On this view, commonsense beliefs about the existence and character of familiar, medium-sized dry goods provides the best explanation of our evidence and so justifies our belief that we're not brains-in-vats. This explanationist approach seems prima facie plausible until we press the explanationist to tell us what the data is that we're trying to explain by appeal to our beliefs about external objects and how we could have access to it. Keywords: dogmatism, evidence, explanationism, inference to best explanation, knowledge, skepticism Introduction Please consider two hypotheses: BIV: Your body consists of nothing more than a brain that's currently housed in a vat of nutrients in a lab in Nevada. Scientists are conducting experiments on your brain to see whether it's possible to systematically deceive you about the nature of your surroundings and about the past. They cause you to undergo experiences that are indistinguishable from the experiences you're having right now and induce false memories to trick you into believing various things about the past. Hands: Your body consists of much more than just a brain. You have a pair of hands that you can see when held out in front of you. You know that these hypotheses cannot both be true. It's quite natural to think that you know that the Hands-hypothesis is true. It's also quite natural to think that you couldn't know the Hands-hypothesis to be true unless you were in a position to know that the BIV-hypothesis was false. Because of this, it seems quite natural to think that you're in a position to know that the BIV-hypothesis is false. Let's suppose that's right. The question that concerns us here isn't whether you can know that you're not a BIV, but how you could know this on the assumption that you can. Clayton Littlejohn 78 An increasingly popular explanation of how you could know that a skeptical hypothesis is false is the explanationist explanation.1 The gist of the explanationist view is that we can justifiably believe and know that we're not BIVs because the best explanation of our evidence (or features of our evidence) is an explanation that appeals to commonsense beliefs, such as the belief that you have hands.2 Assuming that we do indeed have hands and that we're not BIVs, it's an inference to best explanation that provides the justification we need to know that we're not BIVs. Some critics of this approach will criticize the idea that inference to best explanation provides justification or knowledge-level justification for our beliefs. For the purposes of this paper, let's bracket general concerns people have raised about the epistemic power of inference to best explanation. The question we shall focus on here is whether the explanationist view provides a satisfactory account of how we can know that a skeptical hypothesis like the BIV-hypothesis is false. To understand the explanationist view, it will be helpful to briefly discuss a familiar skeptical argument and some standard responses to it. Let's start with the argument from ignorance: The Skeptical Argument from Ignorance P1. You cannot know that you're not a BIV. P2. If you cannot know that you're not a BIV, you cannot know that you have hands. C. Thus, you cannot know that you have hands. You could simply accept the argument's conclusion for the reasons (or 'reasons') given. Some do have the strong intuition that we cannot know that we're not BIVs, so the skeptical view has something to be said for it insofar as it vindicates an intuition some of us surely have. The downside of skepticism, of course, is skepticism. Many of us think that it's at least possible to know things about the external world. Accepting the argument's conclusion is taken by many of us to be a significant cost. If you want to resist the skeptical argument, you could deny the argument's second premise. You might say that there are counterexamples to the closure principle and say that the case we're dealing with is a perfectly good counterexample to the general principle. The downside of this response is that the closure principle strikes many of us as being well motivated. While this view might vindicate the intuition that we can know that we have hands, it does so in a very costly way. Let's suppose we want to retain closure and want a view that allows for the possibility of knowledge of the 1 See BonJour 1999, Feldman 2001, Lipton 2004, Lycan 2002, McCain 2014, Moser 1988, and Vogel 1990 for sympathetic presentations of the explanationist responses to skepticism. 2 For a helpful discussion of explanationism that focuses on attempts to justify inference to best explanation, see Beebe 2009. Skeptical Thoughts Concerning Explanationism and Skepticism 79 external world. Setting contextualist views aside, let's consider the prospects of an explanationist view that denies the argument's first premise. If you deny the first premise of the skeptical argument, you'll face the nontrivial challenge of explaining how it could be false. I think it's helpful here to remember Pryor's 2000 advice. We shouldn't simply assume that the argument's first premise is correct. We should press those who accept the argument's first premise for an explanation as to why we should do likewise. One way to try to motivate it is by appeal to three ideas. The first is that we couldn't know that we're not BIVs unless we were justified in believing that we're not BIVs.3 The second is that we couldn't be justified in believing that we're not BIVs unless we had adequate experiential evidence for believing that we're not BIVs.4 The third is that we cannot have adequate evidence for believing that we're not BIVs.5 The first two points seem relatively unproblematic, but consider the third. Why shouldn't we say that our evidence is adequate for believing that the BIVhypothesis is false? Perhaps this is what we should say. If we do say this, we'll be pressed to explain how our evidence could be adequate for supporting this belief. As many epistemologists see it, we'd have the same evidence for our beliefs regardless of whether the Hands-hypothesis or the BIV-hypothesis is true.6 Doesn't that show that our evidence couldn't be adequate for believing the Hands-hypothesis and rejecting the BIV-hypothesis? Although there are epistemologists who will say that you couldn't have adequate evidence for believing that you're not a BIV unless you had evidence that wasn't available to a BIV, the explanationist view is supposed to explain how the evidence we have could be adequate for our beliefs even if it's just the evidence we'd have if we were BIVs.7 As they see it, the Hands-hypothesis provides the best explanation as to why our evidence is the way it is. If so, this explains why we have adequate evidence for believing the Hands-hypothesis and there would be no principled objection to rejecting the first premise of the skeptical argument. 3 This is controversial, but let's set this aside for the time being as I'm going to talk as if knowledge requires justification because it's convenient to do so. Nothing of importance here hangs on any controversial claims about the relationship between justification and knowledge. By speaking as if knowledge required knowledge-level justification, I can simplify the discussion and avoid having to talk about skeptical challenges that challenge different epistemic statuses. 4 For our purposes evidence will be understood as experiential or memorial. Let's assume for the purposes of this discussion that we don't have apriori justification for believing the BIVhypothesis is false. 5 See Pritchard 2012 and Pryor 2000 for discussion of this defense of the argument's first premise. 6 Cohen 1984 and Conee and Feldman 2004 defend the thesis that you and your deceived BIV counterpart share the same evidence. 7 See Littlejohn 2012, McDowell 1998, and Williamson 2000. Clayton Littlejohn 80 To flesh out the details of the explanationist view, the explanationist needs to answer two questions. First, by what criteria should we judge candidate explanations? Second, what is the Hands-hypothesis supposed to explain? The explanationist can recommend evaluating candidate explanations in terms of virtues like simplicity (i.e., the number and kinds of entities posited, the internal simplicity of the explanatory framework), fecundity (i.e., suggests further hypotheses that would be explanatorily useful), neatness (i.e., leaves fewer unanswered questions than rivals), or plausibility in terms of how well it coheres with our other justified commitments.8 As for the features of our evidence that the explanatory hypotheses purport to explain, the explanationist might take the Hands-hypothesis to figure in the best explanation of the following (alleged) features of our experiential evidence: F1: The coherence and regularity of experiences in a single sense modality. F2: The coherence and regularity of experiences across more than one sense modality. F3: It typically appears to us that external objects exist when we expect them to and these objects typically appear to be the way we expect them to be.9 The explanationist thinks that to justifiably believe or know that the BIVhypothesis is false, we have to know that our experiential evidence has some combination of these features and discern that the best explanation of some combination of (F1)-(F3) is best explained by appeal to commonsense beliefs such as the belief that you have hands. Explanationism vs. Dogmatism It wouldn't be surprising if most readers agreed that the Hands-hypothesis provides the best explains the relevant features of our evidence. It also wouldn't be surprising if most readers agreed that inference to best explanation is generally capable of conferring justification. The tricky question is whether we need to rely on inference to best explanation to justifiably reject the BIVhypothesis. As the view is understood here, the explanationist doesn't simply assert that inference to best explanation is one may amongst many to acquire justification for rejecting the BIV-hypothesis. The explanationist also thinks that rival views cannot provide an adequate account of how it is that we can justifiably believe that we're not BIVs. To evaluate the explanationist view, then, we should consider a rival approach. Consider Pryor's 2000 dogmatist view. Like the explanationist, Pryor's dogmatist wants to say that we can have experiential evidence that provides sufficient evidential support for believing that the BIV-hypothesis is mistaken. 8 See Lipton 2004 and Lycan 2002. 9 BonJour 2003, Feldman 2004, McCain 2014, and Vogel 1990 mention these kinds of features in their discussions of explanationism. Skeptical Thoughts Concerning Explanationism and Skepticism 81 Like the explanationist, Pryor's dogmatist doesn't think that the adequacy of our evidence for believing that we're not BIVs depends upon whether we have evidence that our BIV-counterparts do not. The disagreement between the dogmatist and the explanationist has to do with the power of particular experiences to justify the belief that we're not BIVs. It's possible, Pryor thinks, for a particular, one-off experience to justify the belief that you have hands. Once that belief is justified, you can justifiably infer that you're not a BIV, provided that you know that the BIV-hypothesis is incompatible with the Handshypothesis. Thus, on Pryor's view, you don't have to appeal to features like (F1)- (F3) to justify the belief that you're not BIV. On his neo-Moorean view, you can bypass that and justifiably infer that you're not a BIV by reasoning as follows: The Neo-Moorean Argument NM1: I have hands. NM2: If I have hands, I'm not a BIV. NMC: I'm not a BIV. The explanationist and the dogmatist can agree that your justification for believing NM2 is apriori. They can also agree that your justification for believing that NMC derives from experience. Their disagreement concerns the power of one-off experiences to provide justification for believing NMC via this sort of inference. As the dogmatist sees it, there's no principled reason to think that the one-off experience you have when you see your hands is incapable of justifying your belief in NM1. Once we've accepted that, the dogmatist will say that there's then no principled objection to the idea that that experience provides sufficient evidential support for believing NMC. It's this second point that's the primary point of contention in the debate between the dogmatist and the explanationist. If the one-off experience that you have when you see your hands is the sort of thing that could be sufficient to justify the belief that you have hands, the dogmatist thinks that it should also be sufficient to justify your belief that you're not a BIV. The explanationist thinks that the one-off experience cannot provide adequate evidential support for rejecting the BIV-hypothesis, but this puts them in a tricky spot, doesn't it? Let's consider two sufficiency claims: S1: The one-off experience you have when you see that you have hands can provide sufficient evidential support for believing that you have hands. S2: The one-off experience you have when you see that you have hands can provide sufficient evidential support for believing that you're not a BIV. The dogmatist can run the following argument against the explanationist view: The First Anti-Explanationist Argument FAE1: The one-off experience you have when you see that you have hands can provide sufficient evidential support for believing that you have hands regardless of whether your experiences have features (F1)-(F3). Clayton Littlejohn 82 FAE2: If your one-off experience as of hands can provide you with sufficient evidence to justifiably believe that you have hands regardless of whether your experiences have features (F1)-(F3), your one-off experience as of hands can provide you with sufficient evidence to justifiably believe that you're not a BIV regardless of whether your experiences have features (F1)-(F3). FAEC: Your one-off experience as of hands can provide you with sufficient evidence to justifiably believe that you're not a BIV regardless of whether your experiences have features (F1)-(F3). If this argument is sound, it would deliver a serious blow to the explanationist view as it would show that the ability to justifiably reject the BIV-hypothesis does not depend upon whether there's some feature of our experiential evidence that's best explained by appeal to commonsense beliefs like the belief in the Hands-hypothesis. Although the explanationist isn't committed to closure, we're exploring the possibility that the explanationist can rebut the skeptical argument without denying closure. It seems that if the explanationist accepts closure, they should accept (FAE2). The idea here isn't that the closure principle commits you to saying that (S2) follows from (S1). There are coherent views that accept closure, accept (S1), but reject (S2). These are views on which the justification for rejecting the BIV-hypothesis doesn't derive from (solely) experience but must be in place for experience to justify believing that you have hands.10 These views differ from the explanationist view on offer insofar as they deny that the justification for rejecting the BIV-hypothesis derives wholly from the justification provided by experience. The reason that the explanationist who accepts closure should accept (FAE2) is that if (F1)-(F3) are necessary for having justification to believe that the BIV-hypothesis is false, these are necessary for having justification to believe propositions that are known to entail that the BIVhypothesis is false. It looks like the explanationist will have to reject the argument's first premise, (FAE1). This doesn't come without intuitive costs. In terms of the phenomenology, it doesn't seem like your belief that you have hands is formed as the result of an inference that rests on multiple observations.11 It seems rather odd to think that the objects that are sitting in plain view are ens theoria. Wouldn't it take a powerful argument to show that the justification for believing 10 For discussion of such views, see Silins 2005 who accepts a liberal view on which (S1) is true that isn't committed to the dogmatist view on which both (S1) and (S2) are true. As he argues, it's possible for someone to accept Pryor's account of the justification of mundane beliefs like the belief that you have hands while accepting something like Wright's 2004 account of the justified rejection of skeptical hypotheses. For a critical discussion of Silins' proposal, see Kotzen 2012. 11 It's interesting that Feldman 2001, for example, insists that our evidence for rejecting the BIV-hypothesis is indirect since he seems to agree with Pryor in his 2004 that it's possible for particular experiences to provide non-inferential justification for the belief that we have hands. There seems to be a tension here because Feldman also endorses closure. Skeptical Thoughts Concerning Explanationism and Skepticism 83 in such things requires the kind of inferential work that's required for inferring that the existence of the thing provides the best explanation of our evidence? We shouldn't expect the explanationist to accept that this is a decisive counterexample to their view. Neutral parties might be put off by the idea that the justification for believing that you have the hands you seem to see before you really derives from an inference to best explanation, but perhaps the explanationist would reasonably claim that they have a good reason for rejecting (S1). They could say that we ought to reject (S1) because if we accept (S1) and accept closure, we'd either have to accept (S2) or we'd have to say that the justification for rejecting the BIV-hypothesis doesn't derive from our experiential evidence. They might admit that the rejection of (S1) is initially counterintuitive, but they might insist that it's a price worth paying in light of the fact that (S2) is so deeply counterintuitive. Is this a sufficient dialectical riposte? If the explanationist is offering a principled response here, it seems that the principle that they're relying on couldn't be this one: ISE: Every justified belief is justified by virtue of an inference to best explanation.12 While this impossibly strong explanationist principle supports the idea that the belief in the Hands-hypothesis could only be justifiably accepted on the basis of an inference to best explanation, the impossibly strong explanationist principle is impossibly strong. At some point, mustn't we have a non-inferential way of knowing about our evidence and various features of our evidence so that we have a kind of direct access to something that we can raise questions about? Similarly, if the inference to best explanation that generates justification is supposed to explain features of our evidence, it seems that we would need to have a way to form justified beliefs about these features of the evidence and at some point it seems we'd need a non-inferential way of knowing about some of the features of our evidence. The explanationist should appeal to a weaker principle, one that allows for the possibility of non-inferential knowledge and justification. The principle has to support the idea that the justification we have for believing the Handsand BIV-hypotheses is generated by inference to best explanation but allow for the possibility of non-inferential justification for believing various things about our evidence. This would do the trick: ME: For any proposition that's incompatible with a skeptical hypothesis (e.g., the BIV-hypothesis) to be justifiably believed, it has to be justified by an inference to best explanation. 12 An expalanationist view that incorporates ISE is even stronger than the view Lycan (2002, 417) dubs 'ferocious explanationism.' According to ferocious explanationism, the only ampliative inferences that generate justification derive their epistemic power from explanatory inference. This view allows for non-inferential justified judgments, but ISE appears to rule that out. Clayton Littlejohn 84 This modest explanationist principle supports the idea that you cannot justifiably believe that you have hands or that you're not a BIV unless the Handshypothesis (or something like it) is the something you see is part of the best explanation of your evidence. Unlike the impossibly strong explanationist principle, the modest principle doesn't tell us that you need to rely on inference to best explanation to justifiably believe that you have a headache or that it looks to you as if you have hands. To motivate the principle, the explanationist might say something along these lines. If things are going bad for us epistemically, we'll still have unproblematic access to our evidence. (We'd have to have this kind of unproblematic access since having such access is a necessary condition on possessing this evidence.) By appealing to such evidence and relying on inference to best explanation, we can justify beliefs about matters that go beyond this evidence. These matters are things that we could potentially be mistaken about even if our evidence is just the way that it is. ME is designed to capture the intuitive resistance to (S2). There are some matters that we can form justified beliefs about without relying on any further evidence and that is that which the vat operators cannot deceive us about. There are some matters beyond this that we have potentially problematic access to and we can only come to have sufficiently good access to such matters by thinking about the evidence we have to hand. While the explanationist might avoid the first line of objection (i.e., that it is implausible to think that the justification for believing the Hands-hypothesis must come from inference to best explanation), the maneuvers the explanationist would have to make steer them directly into a second line of objection. The explanationist rejects (S1) and (S2), but accepts the following sufficiency thesis: S3: The features of the experiences you have (i.e., (F1)-(F3)) can provide sufficient evidential support for believing that you have hands and that you're not a BIV via inference to best explanation. If your experiences as of material objects like hands are coherent and regular both within and across sense modalities and there's been a pattern of objects being where you'd expect them to be and appearing as you'd expect them to appear, you can appeal to (F1)-(F3) to justify your belief that you have hands and your belief that you're not a BIV. The view differs from dogmatism insofar as it denies that the one-off experience can do the trick. A run of experience with certain features is needed to justify a belief, according to the explanationist. The one-off experience isn't going to be fit for purpose. Assuming that your course of experience has the right features, it can provide the right kind of rational support for believing the Hands-hypothesis, provided of course that the experience is of a kind that's better explained by appeal to this hypothesis than a rival hypothesis such as the BIV-hypothesis. The trouble with the explanationist approach emerges when we think about your relation to (F1)-(F3). These aren't features of any particular, one-off Skeptical Thoughts Concerning Explanationism and Skepticism 85 experience. They couldn't be, the explanationist says. Not only do these features depend upon experiences had at different times, it's important for the explanationist to say that that these features aren't features of any particular, one-off experience since they accept (S3) but reject (S1) and (S2). Since they are features of a series of experiences that the subject had at different times, the explanationist has to say that these features aren't epistemically available to you in the way that they'd have to be to justify your beliefs: The Second Anti-Explanationist Argument SAE1: The truth of the proposition that your experiences have features (F1)- (F3) depends upon whether certain relations hold between present and past experiences, which means that the truth of the proposition that your experiences have features (F1)-(F3) is incompatible with the BIV-hypothesis. SAE2: If the truth of the proposition that your experiences have features (F1)- (F3) is incompatible with the BIV-hypothesis, you can only be justified in believing that your experiences have features (F1)-(F3) if such a belief is supported by inference to best explanation. SAE3: You cannot be justified in believing that your experiences have features (F1)-(F3) by means of an inference to best explanation. SAEC1: Thus, you cannot be justified in believing that your experiences have features (F1)-(F3). SAE4: If you cannot be justified in believing that your experiences have (F1)- (F3), the fact that your experiences have these features cannot provide rational support for believing that you have hands or that you're not a BIV. SAE5: If the fact that your experiences have these features cannot provide rational support for believing that you have hands or that you're not a BIV, you cannot justifiably believe that you have hands or that you're not a BIV. SAEC2: You cannot justifiably believe that you have hands or that you're not a BIV. The explanationist has to reject (SAEC2) since that's incompatible with (S3). Unless they can block the argument, they should not say that they are offering us a non-skeptical view. In support of the first premise, (SAE1), it should be noted that the BIVhypothesis does not simply target perceptual beliefs about your immediate surroundings, but also beliefs based on apparent memories about the past experiences you take yourself to have. Just as the vat operators have the power to trick a brain in a vat that's stored in a lab into believing that it's sitting on the beach, it can trick a brain in a vat that's been created in a lab only moments ago into thinking that it's been alive for years and that it's had just the sorts of experiences that we do when we see hands during that time. Thus, according to (ME), you cannot justifiably believe your experiences have features (F1)-(F3) unless you can believe this on the basis of an inference to best explanation. Unfortunately, the features of your experiences that you'd need to appeal to in Clayton Littlejohn 86 justifying beliefs about the experiences you've had are largely features of past experiences. They are epistemically off-limits until we have a story about how you could justifiably take your past experiences to have had the relevant features. Thus, so far as your beliefs about what your past experiences were like, it seems that you couldn't justifiably hold such beliefs without relying on inference to best explanation and it seems you don't have the right kind of access to the propositions about the explanandum for that inference to generate any justification. Once we see why the explanationist doesn't have the right to say that our beliefs about our past experiences are justified, we can see why the explanationist cannot plausibly defend (S3) while rejecting (S1) and (S2). The explanationist needs one-off apparent memories about your past experiences to be the sort of thing that can justify beliefs about these experiences so that you can appeal to features (F1)-(F3) to justify beliefs about the external world, but the explanationist denies that such one-off apparent memories are capable of providing that kind of justification. Conclusion The explanationist cannot have it both ways. If the possibility of deception and error are sufficient to show that one-off experiences are incapable of justifying beliefs about external objects, they should be sufficient to show that one-off apparent memories are incapable of justifying beliefs about past experiences. Without such justified beliefs about the character of past experiences, we cannot rationally appeal to features like (F1)-(F3) in the attempt to justify the belief that we're not BIVs. We can't get our hands on the data that we need for inference to best explanation. Thus, the features (F1)-(F3) cannot play any interesting role in any non-skeptical explanationist account of the justification of our beliefs about the external world. If, however, it's possible for one-off apparent memories to justify beliefs about past experiences in spite of the fact that our BIV counterparts could have these apparent memories without having had experiences with features like (F1)-(F3), the explanationist doesn't have any principled reason to think that (S1) and (S2) are mistaken. The skeptical pressures that they think undermine the dogmatist view undermine their view. The explanationist's failure to appreciate this reflects a failure to appreciate the non-trivial problem they face in understanding how we could have the right kind of access to a series of experiences for us to appeal to these features in trying to justify our beliefs. 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