Abstract
Skepticism has been (and remains) a central concern of the theory of knowledge. Indeed, some philosophers think that, without the problem of skepticism, we would not know what to make of the idea of distinctively philosophical theories of knowledge. However, a philosopher who thinks along these lines is likely to have in mind a rather special form of skepticism. Let us call it philosophical skepticism. Philosophical skepticism has a long history. Indeed, it is almost coeval with systematic philosophy itself.