Relativism, the position that things are for each as they seem to each, was first formulated in Western philosophy by Protagoras, the 5th century BC Greek orator and teacher. This book focuses on 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. In his book Truth, Protagoras made vivid use of two provocative but imperfectly spelled out ideas. First, that everyone is (...) a ‘measure’ of the truth, and that everyone is already capable of determining how things are, since the senses are the best and most credible guides to the truth. Second, given that things appear differently to different people, there is no basis on which to decide that one appearance is true rather than the other. Plato developed these ideas into a more fully worked-out theory, which he then subjected to refutation in the Theaetetus. Aristotle argued that Protagoras’ ideas lead to skepticism in Metaphysics Book G, a chapter which reflects awareness of Plato’s reaction in the Theaetetus. Finally, Democritus incorporated modified Protagorean ideas and arguments into his theory of knowledge and perception. 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. This book offers a new account of this important chapter in the development of Greek epistemology. (shrink)

Plato argues, at Theaetetus 170e-171c, that Protagoras’ relativism is self-refuting. This argument, known as the ‘exquisite argument’, and its merits have been the subject of much controversy over the past few decades. Burnyeat (1976b) has argued in defense of Plato’s argument, but his reconstruction of the argument has been criticized as question-begging. After offering an interpretation of Protagoras’ relativism, I argue that the exquisite argument is successful, for reasons that Burnyeat hints at but fails to develop sufficiently. I consider Protagorean (...) relativism under both of the two possible readings with respect to its scope: global relativism, according to which all truths are only relatively true, and qualified relativism, according to which the relativistic thesis itself is excepted. Taking into consideration some contemporary work on relativism and self-refutation, I show that Plato’s argument succeeds on both of these readings. Given that Protagoras could avoid self-contradiction simply by denying that an enduring subject exists, I argue that the exquisite argument is best understood as confronting Protagoras with a dilemma between self-contradiction and self-defeat of various sorts, all of which lead to the same result, that Protagoras violates the requirements of rational discourse in such a way that he becomes an absurd figure who has nothing to say to us. (shrink)

Book Gamma of Aristotle’s Metaphysics contains a vigorous defense of the principle of non-contradiction (PNC). A chief part of Aristotle’s strategy is to attack those, such as Heraclitus and Protagoras, who are said to deny the principle. Commentators have found a number of logical and historical problems with Aristotle’s arguments, but none are more troubling than those he deploys against Protagoras. Midway through Gamma 4, and throughout Gamma 5, he represents Protagoras not as simply denying PNC but rather as asserting (...) the contrary of the principle. The latter, the proposition that every thing has every property and its negation, I call the strong denial of PNC. In particular, Aristotle argues that Protagoras is committed to strong denial because of ‘Protagorean’ relativism – the doctrine that if something appears to be the case, then it is the case. This paper provides a reconstruction of Aristotle’s arguments in Gamma 4 and 5, and suggests that the second argument may infact hold against the Protagorean. (shrink)