Epistemology explores the possibilities and limits of knowledge as applied to different cognitive domains (knowledge of the external worlds, knowing one’s own mind, understanding language, etc.). The classic definition of knowledge is that a person knows that p iff s/he has the justified, true belief of that p (see Dancy 1985 and Dancy & Sosa 1992 for details). A central issue is the correct characterization of the justification required for knowledge. Inaugurated by Descartes, classical foundationalism is perhaps the most influencial position in epistemology. Foundationalism divides our beliefs into two groups: those which need support from others, and those which need no support themselves (truths we know without relying on perceptual evidence). The latter constitute our epistemological foundations. Foundationalism need not be associated with cartesian rationalism, however. Empiricism identified states which do not need justification with sensory states, our own immediate experiences of the external world. They are infallibly true and stand on their own feet. Other beliefs are supported by them. A central objection to both positions is that no belief is infallible — there is no region in our thoughts which is entirely immune from the possibility of error. Recent epistemology has therefore drawn a distinction between the possibility that all beliefs could be false (the sceptical option) and the global claim that each particular belief could be false without the global system of cognitive attitudes being false. The latter claim is weaker and leads to the well-known fallibilist position in epistemology and the philosophy of science.