This work, written from a neo-Pyrrhonian perspective, is an examination of contemporary theories of knowledge and justification. It takes ideas primarily found in Sextus Empiricus's Outlines of Pyrrhonism, restates them in a modern idiom, and then asks whether any contemporary theory of knowledge meets the challenges they raise. The first part, entitled "Gettier and the Problem of Knowledge," attempts to rescue our ordinary concept of knowledge from those philosophers who have assigned burdens to it that it cannot bear. Properly understood, Fogelin shows that the concept of knowledge is unproblematic. The second part of this study, called "Agrippa and the Problem of Justification," examines Agrippa's contribution to Pyrrhonism, a systematic reduction of its procedures which came to be known as the "Five Modes Leading to the Suspension of Belief." These modes present a completely general procedure for refuting any claim a dogmatist might make. Though largely unnoticed, there is, according to Fogelin, an uncanny resemblance between problems posed by Agrippa's "Five Modes" and those that contemporary epistemologists address under the heading of a theory of justification. Fogelin examines the strongest contemporary theories of justification--in both foundationalist and anti-foundationalist forms. The conclusion is that recent philosophical writings on justification have made no significant progress in responding to the Pyrrhonian problems these writings have addressed.