This volume deals with Epistemology. The period from the sixth century BC to the second and third centuries AD was one of the most fertile for the theory of knowledge, and the range of 'epistemic states' explored in the ancient texts is much wider than those to be found in contemporary discussions of epistemology or cognition. Greek philosophers approached these problems in a great variety of ways, from the extreme relativism of Protagoras to the scepticism of the Pyrrhonists, and the contributors demonstrate both the familiarity and novelty of this range of views in their critical essays.