"Relativism, the position that things are for each as they seem to each, was first formulated in Western philosophy by Protagoras, the fifth-century BC Greek orator and teacher. Mi-Kyoung Lee examines the challenge to the possibility of expert knowledge posed by Protagoras, together with responses by the three most important philosophers of the next generation, Plato, Aristotle, and Democritus." There have been many important recent studies of these thinkers in isolation. However, there has been no attempt to tell a single, coherent story about how Democritus, Plato, and Aristotle responded to Protagoras' striking claim, and to its perceived implications about knowledge, perception, and truth. By studying these four figures in relation to each other, we arrive at a better understanding of an important chapter in the development of Greek epistemology.