Protagoras was the first philosopher to charge fees to his pupils and – together with Anaxagoras – the first to attach himself to a political protector, in both cases the hopelessly corrupt Pericles.

Plutarch wrote that Pericles and Protagoras, attorneys as they were, spent a whole day discussing an interesting point of legal responsibility, later reworked by modern philosophers as one of causation: "In an athletic contest a man had been accidentally hit and killed with a javelin. Was his death to be attributed to the javelin, to the man who threw it, or to the authorities responsible for the conduct of the games?"

At the center of Protagoras’ thought was the question of whether “arete” (excellence or virtue) could be taught, particularly taught for money, a commonplace issue of Fifth Century BC Greece, that has been related to modern readers through Plato's dialogue of that name.

He tried to sell arete, all right: a man of an entrepreneurial bent, Protagoras wrote practical self-help books, was one of the first philosophers to take part in rhetorical contests in the Olympic games, and appears to have operated as a sort of life coach for whoever met his financial expectations.

It’s no wonder that, from a philosophical perspective, Protagoras is most famous for having created something like agnosticism (the word itself didn’t exist in ancient Greece), a veiled form of Atheism popular since among adolescents and people too busy to study theology.

Despite his animus towards the sophists, Plato depicts Protagoras as quite a sympathetic and dignified figure, hinting at Protagoras' well-hidden scorn for the mass. He took their money but didn't let himself be fooled by their silliness, Plato seems to be telling us.