How is it possible to know of one's own mental states for the most part effortlessly and authoritatively? How can we know substantive facts of logic and mathematics, applicable to the natural world, just by thinking? These basic questions concern kinds of knowledge--psychological self-knowledge and knowledge a priori--that, however different in their subject matters, both seem to exemplify a species of immediate, non-sensuous apprehension which resists assimilation to perception and, to that extent, integration within naturalistic accounts of knowledge at large. Self-Knowledge and Knowledge A Priori shows how the philosophical challenges we face in accounting for these two kinds of (presumptive) knowledge are strikingly similar. In each case, there is an initial problem of providing a satisfactory characterization of the target phenomenon; each has provoked a sweep of sceptical reactions, as well as a variety of (unsuccessful) attempts at constructive explanatory models; in each case there is argument that knowledge (or, at least, epistemically respectable judgement) of the kind in question is indispensable to rational inquiry, deliberation, and action.Written by seventeen leading researchers in contemporary analytic epistemology, this book builds on the Knowledge Beyond Natural Science project at the University of Stirling and fosters the dialogue between the philosophical problems of the priori and self-knowledge, while advancing novel contributions to each of the ongoing debates.