This dissertation begins with a general discussion of the role of epistemic principles in arguments for and against Cartesian skepticism . The skeptic may be viewed as trying to establish that, according to non-arbitrary epistemic principles we ordinarily accept, we have no knowledge of the external world. So construed, the skeptic's challenge cannot be dismissed. It can, however, be refuted, particularly if the epistemic principles invoked by the skeptic prove to be invalid. ;One epistemic principle is that of the closure (...) of knowledge under known logical implication: that if a person knows A, and knows that A entails B, then that person knows, or can know, B. ;The validity of the closure principle has been challenged recently by Fred Dretske and Robert Nozick. Dretske's case against the principle rests on some apparent counterexamples. I maintain that these examples don't have the force Dretske thinks, and that other, even stronger examples fail to undermine the closure principle. Nozick bases his criticism of the closure principle on a plausible assumption about the conditions for knowledge. I argue that this assumption is deeply flawed, especially in light of certain facts about inductive knowledge. ;I next consider and defend the claim that justification is closed under known logical implication. On the assumption that knowledge does require justification, this result supports two further conclusions: that knowledge itself is likely to obey closure, and that, even if it doesn't, the skeptic could still proceed with his argument unimpeded. In connection with these issues, I discuss some relevant views of Peter Klein, and argue that his attempted refutation of skepticism isn't fully successful. ;A principal result is that rejection of the closure principle doesn't provide a legitimate way to avoid Cartesian skepticism. The discussion also indicates that a convincing refutation of the skeptic may be found in an appeal to principles of inference to the best explanation. I distinguish various skeptical hypotheses and show that they may be rejected on grounds of explanatory inadequacy. When faced with this sort of response, Cartesian skepticism either becomes untenable or collapses into skepticism about induction. (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.

A central problem facing a probabilistic approach to the problem of induction is the difficulty of sufficiently constraining prior probabilities so as to yield the conclusion that induction is cogent. The Principle of Indifference, according to which alternatives are equiprobable when one has no grounds for preferring one over another, represents one way of addressing this problem; however, the Principle faces the well-known problem that multiple interpretations of it are possible, leading to incompatible conclusions. I propose a partial solution to (...) the latter problem, drawing on the notion of explanatory priority. The resulting synthesis of Bayesian and inference-to-best-explanation approaches affords a principled defense of prior probability distributions that support induction. (shrink)

1 Knowledge and Justification This book is an investigation of one central problem which arises in the attempt to give a philosophical account of empirical ...

A certain skeptical strategy involves a skeptical hypothesis that closely mirrors the structure of our standard theory of the world; this strategy insulates the skeptical argument from attacks based on standard criteria of theory choice. A standard reply to this strategy is to claim that proffered alternative is just the standard theory expressed in a different notation. But this reply does not succeed, given plausible assumptions about semantics. However, there is an alternative strategy--also semantical--which can deal with the problem, at (...) least in those cases where, intuitively, the skeptic's challenge should fail. (shrink)

Laurence BonJour has recently proposed a novel and interesting approach to the problem of induction. He grants that it is contingent, and so not a priori, that our patterns of inductive inference are reliable. Nevertheless, he claims, it is necessary and a priori that those patterns are highly likely to be reliable, and that is enough to ground an a priori justification induction. This paper examines an important defect in BonJour's proposal. Once we make sense of the claim that inductive (...) inference is "necessarily highly likely" to be reliable, we find that it is not knowable a priori after all. (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)

the symmetry of our evidential situation. If our confidence is best modeled by a standard probability function this means that we are to distribute our subjective probability or credence sharply and evenly over possibilities among which our evidence does not discriminate. Once thought to be the central principle of probabilistic reasoning by great..

Outlines a tenable version of a traditional foundationalist account\nof empirical justification and its implications for the justification\nof beliefs about physical or material objects. Presupposing the acceptability\nof other beliefs about physical objects; Concept of a basic belief;\nMetabeliefs about one's own occurrent beliefs; Beliefs about sensory\nexperience.

The goal of this paper is to challenge the rather insouciant attitude that many investigators seem to adopt when they go about describing the items and events in their " visual fields". There are at least three distinct categories of interpretation of what these reports might mean, and only under one of those categories do those reports have anything resembling an observational character. The others demand substantive revisions in one's beliefs about what one sees. The ur-concept of a " visual (...) field" is that of the "sum of things seen", but one can interpret the latter in very different ways. The first is the "field of view", or the sum of physical things seen. The second is an array of visual impressions, whose spatial relations are distinct from those of physical phenomena in front of the eyes. The third is an intentional object: the world as it is represented visually. These three categories are described, and various locutions of vision science--such as "optic array", "retinocentric space", " visual geometry", "virtual object" and others--are analyzed and variously located within them. Finally, a recent argument purporting to necessitate the existence of a version two visual field is examined and shown wanting. (shrink)

Visual space can be distinguished from physical space. The first is found in visual experience, while the second is defined independently of perception. Theorists have wondered about the relation between the two. Some investigators have concluded that visual space is non-Euclidean, and that it does not have a single metric structure. Here it is argued that visual space exhibits contraction in all three dimensions with increasing distance from the observer, that experienced features of this contraction are not the same as (...) would be the experience of a perspective projection onto a fronto-parallel plane, and that such contraction is consistent with size constancy. These properties of visual space are different from those that would be predicted if spatial perception resulted from the successful solution of the inverse problem. They are consistent with the notion that optical constraints have been internalized. More generally, they are also consistent with the notion that visual spatial structures bear a resemblance relation to physical spatial structures. This notion supports a type of representational relation that is distinct from mere causal correspondence. The reticence of some philosophers and psychologists to discuss the structure of phenomenal space is diagnosed in terms of the simple materialism and the functionalism of the 1970s and 1980s. (shrink)

the symmetry of our evidential situation. If our confidence is best modeled by a standard probability function this means that we are to distribute our subjective probability or credence sharply and evenly over possibilities among which our evidence does not discriminate. Once thought to be the central principle of probabilistic reasoning by great..