Protagoras of Abdera

(c. 490– c. 420 BC)

The most successful of the Sophists, whose independent importance is attested by Plato, Aristotle, and Sextus Empiricus . He taught virtue (aretē ) in Athens, was a friend of Pericles, and was employed to draw up the code of laws for the Athenian colony at Thurii. He is famous for the assertion that ‘man is the measure of all things’: a relativistic slogan whose precise meaning is debatable, for unless it leads to subjective idealism, as in Berkeley, it seems to leave the one object possessing contradictory properties, if one person takes it one way and another takes it in a contradictory way (see peritrope, but see also perspectivism ). It seems clear that while Protagoras believed that each person's sense perceptions are true (for their owner), he also believed that moral and political doctrines, to which his relativism might seem especially well-adapted, are capable of improvement and can be taught. It is quite possible that Protagoras established in Athens the dialectical method, later made famous through Plato's Socratic dialogues.