If the reliability of a source of testimony is open to question, it seems epistemically illegitimate to verify the source’s reliability by appealing to that source’s own testimony. Is this because it is illegitimate to trust a questionable source’s testimony on any matter whatsoever? Or is there a distinctive problem with appealing to the source’s testimony on the matter of that source’s own reliability? After distinguishing between two kinds of epistemically illegitimate circularity—bootstrapping and self-verification—I argue for a qualified version of (...) the claim that there is nothing especially illegitimate about using a questionable source to evaluate its own reliability. Instead, it is illegitimate to appeal to a questionable source’s testimony on any matter whatsoever, with the matter of the source’s own reliability serving only as a special case. (shrink)

I focus on a key argument for global external world scepticism resting on the underdetermination thesis: the argument according to which we cannot know any proposition about our physical environment because sense evidence for it equally justifies some sceptical alternative (e.g. the Cartesian demon conjecture). I contend that the underdetermination argument can go through only if the controversial thesis that conceivability is per se a source of evidence for metaphysical possibility is true. I also suggest a reason to doubt that (...) conceivability is per se a source of evidence for metaphysical possibility, and thus to doubt the underdetermination argument. (shrink)

Some philosophers argue that we are justified in rejecting skepticism because it is explanatorily inferior to more commonsense hypotheses about the world. Focusing on the work of Jonathan Vogel, I show that this “abductivist” or “inference to the best explanation” response rests on an impoverished explanatory framework which ignores the explanatory gap between an object's having certain properties and its appearing to have those properties. Once this gap is appreciated, I argue, the abductivist strategy is defeated.

The first step in responding to the challenge of external world skepticism is to get clear on the structure of the skeptic’s argument. The most prominent varieties of skeptical arguments either rely on closure principles or underdetermination principles. The relationship between these two sorts of arguments is contentious. Some argue that these arguments can independently motivate skepticism. Others argue that they are really equivalent. I argue that although these two arguments are distinct, their independence is not as obvious as some (...) have thought. The fact that these arguments are not equivalent is important because skeptical arguments that appeal to underdetermination principles cannot be refuted by simply denying closure. So, the strategy for responding to skepticism offered by Nozick/Dretske does not seem an adequate solution. (shrink)

Abductivists claim that explanatory considerations (e.g., simplicity, parsimony, explanatory breadth, etc.) favor belief in the external world over skeptical hypotheses involving evil demons and brains in vats. After showing how most versions of abductivism succumb fairly easily to obvious and fatal objections, I explain how rationalist versions of abductivism can avoid these difficulties. I then discuss the most pressing challenges facing abductivist appeals to the a priori and offer suggestions on how to overcome them.

The concept of evidence is among the central concerns of epistemology broadly construed. As such, it has long engaged the intellectual energies of both philosophers of science and epistemologists of a more traditional variety. Here I briefly survey some of the more important ideas to have emerged from this tradition of reflection. I then look somewhat more closely at an issue that has recently come to the fore, largely as a result of Williamson's Knowledge and Its Limits: that of whether (...) one's evidence supervenes on one's non-factive mental states. (shrink)

Defenders of pragmatic theories of knowledge (such as contextualism and sensitive invariantism) argue that these theories, unlike those that invoke a single standard for knowledge, comport with the intuitively compelling thesis that knowledge is the norm of assertion and practical reason. In this paper, I dispute this thesis, and argue that, therefore, the prospects for both “high standard” approach, and contend that if one abandons the thesis that knowledge is the norm of assertion and practical reason, the most serious arguments (...) against it lose force. (shrink)

The abductivist reply to skepticism is the view that commonsense explanations of the patterns and regularities that appear in our sensory experiences should be rationally preferred to skeptical explanations of those same patterns and regularities on the basis of explanatory considerations. In this article I critically examine Laurence BonJour’s rationalist version of the abductivist position. After explaining why BonJour’s account is more defensible than other versions of the view, I argue that the notion of probability he relies upon is deeply (...) problematic, that he incorporates an implausible double-standard concerning a priori and a posteriori justification, and that his view is vulnerable to skepticism about the a priori. I suggest that some of these problems are due to idiosyncratic commitments BonJour makes and that abductivists would be better off without them. I conclude with some suggestions about how to improve BonJour’s abductivist response to skepticism. (shrink)

An important line of response to scepticism appeals to the best explanation. But anti-sceptics have not engaged much with work on explanation in the philosophy of science. I plan to investigate whether plausible assumptions about best explanations really do favour anti-scepticism. I will argue that there are ways of constructing sceptical hypotheses in which the assumptions do favour anti-scepticism, but the size of the support for anti-scepticism is small.

The following thesis discusses a range of central aspects in Timothy Williamson’s so-called «knowledge-first» epistemology. In particular, it adresses whether this kind of epistemological framework is apt to answer the challenges of scepticism.

In the first experiment, I exhibit unreliable judgment about the primeness or divisibility of four-digit numbers, in contrast to a seeming Excel program. In the second experiment, I exhibit an imperfect memory for arbitrary-seeming three-digit number and letter combinations, in contrast to my seeming collaborator with seemingly hidden notes. In the third experiment, I seem to suffer repeated defeats at chess. In all three experiments, the most straightforward interpretation of the experiential evidence is that something exists in the universe that (...) is superior in the relevant respects – theoretical reasoning (about primes), memorial retention (for digits and letters), or practical reasoning (at chess) – to my own solipsistically-conceived self. (shrink)

In this paper I introduce a problem regarding whether there are good reasons to accept fallibilism about justified belief. According to this species of fallibilism, one can be justified in believing a proposition on the basis of reasons that do not justify certainty. Call such reasons “fallible reasons.” The problem is this: can one justifiably believe fallibilism on the basis of fallible reasons? To do so would seem to beg the question. If you are undecided as to whether you should (...) accept anything on the basis of fallible reasons, then you should also be undecided as to whether you should accept fallibilism on the basis of such reasons. In this paper I consider several possible responses to this problem. I argue that the most appealing is to grant that good but fallible reasons on behalf of fallibilism are possible, and that this shows that one’s basic rational commitments cannot be defended in a non-circular fashion. (shrink)

In this paper I argue that Cartesian skepticism about the external world is self-defeating. The Cartesian skeptic holds that we are not justified in believing claims about the external world on the grounds that we cannot rule out the possibility of our being in a radical skeptical scenario. My argument against this position builds upon a critique of Wilson in Analysis, 72, 668–673. Wilson argues that the Cartesian’s skeptical reasoning commits him to mental state skepticism and that this undermines his (...) ability to claim that he is truly skeptical about the external world. I show that Wilson’s argument does not succeed. She is correct that the Cartesian is committed to mental state skepticism. However, she is mistaken in thinking that there is anything incoherent about combining the Cartesian position that one ought to doubt external world claims with doubt about whether one is in fact such a skeptic. I propose an alternative explanation as to why mental state skepticism proves to be the Cartesian’s undoing. I suggest that mental state skepticism leads to epistemic skepticism and that this undermines the Cartesian’s position that belief about the external world is unjustified. (shrink)

External world skeptics are typically opposed to admitting as evidence anything that goes beyond the purely phenomenal, and equally typically, they disown the use of rules of inference that might enable one to move from premises about the phenomenal alone to a conclusion about the external world. This seems to bar any a posteriori resolution of the skepticism debate. This paper argues that the situation is not quite so hopeless, and that an a posteriori resolution of the debate becomes possible (...) once it is recognized that the skeptic holds overly defensive and ill-motivated positions vis-à-vis both evidence and inference, and that more reasonable ones are available. In stating these more reasonable positions, as well as in showing how they make possible an a posteriori resolution of the skepticism debate, the paper draws on the machinery of Bayesian epistemology. (shrink)

Skeptics try to persuade us of our ignorance with arguments like the following: 1. I don’t know that I am not a handless brain-in-a-vat [BIV]. 2. If I don’t know that I am not a handless BIV, then I don’t know that I have hands. Therefore, 3. I don’t know that I have hands. The BIV argument is valid, its premises are intuitively compelling, and yet, its conclusion strikes us as absurd. Something has to go, but what? Contextualists contend that (...) an adequate solution to the skeptical problem must: (i) retain epistemic closure, (ii) explain the intuitive force of skeptical arguments by explaining why their premises initially seem so compelling, and (iii) account for the truth of our commonsense judgment that we do possess lots of ordinary knowledge. Contextualists maintain that the key to such a solution is recognizing that the semantic standards for ‘knows’ vary from context to context such that in skeptical contexts the skeptic’s premises are true and so is her conclusion; but in ordinary contexts, her conclusion is false and so is her first premise. Despite its initial attractiveness, the contextualist solution comes at a significant cost, for contextualism has many counterintuitive results. After presenting the contextualist solution, I identify a number of these costs. I then offer a noncontextualist solution that meets the adequacy constraint identified above, while avoiding the costs associated with contextualism. Hence, one of the principal reasons offered for adopting a contextualist theory of knowledge–its supposedly unique ability to adequately resolve the skeptical problem – is undermined. (shrink)