Protagoras

Protagoras, the earliest of the Greek sophists, was a native of Abdera, born about 490 B.C. Going to Athens about the middle of the century, he taught there and in other Greek cities, at home and in Sicily, a system of practical wisdom, specially fitted to train men for the duties of citizen in a Greek state, chiefly grammar, rhetoric, &c. The basis of his speculation is the proposition that 'man is the measure of all things,' a logical consequence of the teaching of Heraclitus. The Theatetus and Protagoras of Plato are devoted to a refutation of his doctrines. All Protagoras's works are lost. He himself perished at sea, probably between 421 and 415 B.C., whilst on his way to Sicily to escape a charge of atheism brought against him at Athens.