Protagoras

Protagoras of Abdera (circa 490–c. 420 BCE) was an ancient Greek philosopher and one of the early Sophists. A native of Abdera in Thrace, he traveled widely offering instruction in rhetoric, virtue, and public affairs, and he is often regarded as a foundational figure in the Sophist movement. Much of what is known about his thought comes from fragments and later reports, since his own writings survive only in part.

His best-known claim is the relativist maxim that “Man is the measure of all things,” interpreted to mean that truth and value are relative to each perceiver or to cultural convention. Related strands of his thought emphasize skepticism about absolute knowledge and a pragmatic approach to argument, law, and civic life. He is also associated with a form of religious agnosticism, as recordings suggest he might have said that regarding the gods, he had no means of knowing whether they exist or not.

Protagoras reportedly taught that persuasive skill in speech is essential for success in public life, and he offered instruction in rhetoric, ethics, and politics. His writings—often cited as Truth and other treatises—are largely lost; what remains is known through later authors and through Plato’s dialogue Protagoras, which presents a major account of his views and their reception.

Legacy: Protagoras helped shape the role of the sophist as a professional teacher of rhetoric and argument, and his relativistic positions stimulated ongoing debates about knowledge, morality, and religion in ancient Greece. His thought influenced later skeptical and relativist currents and remains a central reference point in discussions of early Greek philosophy.