Self-Knowledge and Knowledge A Priori

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 ...