Sophists

Are justice and truth natural, or human conventions?

Democratic Athens in the 5th century BCE rewarded anyone who could speak well in the assembly and the law courts. Travelling teachers such as Protagoras and Gorgias charged fees to teach rhetoric and “virtue” for public life, and their experience of many cities’ customs made them doubt that any one code was natural.

Customs differ from city to city, so they rest on agreement (nomos) rather than nature (physis). If “man is the measure of all things”, as Protagoras said, there is no neutral standpoint to settle disputes, and persuasion takes the place of proof. Gorgias went further, arguing that nothing exists, that if it did it could not be known, and that if known it could not be communicated.

1. “Man is the measure of all things.”
2. Law and morality are conventions (nomos), not nature (physis).
3. Rhetoric is a teachable power over belief.

They put relativism, the nature–convention debate and the ethics of persuasion on the agenda; Plato’s hostility made “sophist” an insult, but modern scholars read them more sympathetically.