Ever since Plato, philosophers have faced one central question: what is the scope and nature of human knowledge? In this volume the distinguished philosopher Ernest Sosa collects essays on this subject written over a period of twenty-five years. All the major topics of contemporary epistemology are covered: the nature of propositional knowledge; externalism versus internalism; foundationalism versus coherentism; and the problem of the criterion. 'Sosa is one of the most prominent and most important epistemologists on the current American scene.' William P. Alston, Syracuse University