Protagoras (c.481–c.420 BCE) was a pre-Socratic philosopher and teacher. One of the earliest and most famous of the Sophists, he taught the doctrine of the skeptical or relativistic view of all knowledge, perceptions, and judgments—it is summed up in the dictum usually rendered as ‘man is the measure of all things.’
Born in Abdera in northeast Greece, Protagoras spent most of his life as an itinerant Sophist, traveling throughout the Greek world. He was a frequent visitor to Athens, where he considerably influenced contemporary thought on moral and political questions. Plato named one of his dialogues after Protagoras and ascribed him with having originated the professional sophist or teacher of virtue (“arête.”) He taught for more than 40 years, claiming to teach men “virtue” in the conduct of their daily lives.
Protagoras’s taught had little to do with philosophy or the pursuit of an absolute truth; instead, it imparted its adherents the necessary skills and knowledge for success in life, especially in politics. These skills consisted mainly of rhetoric and dialectic and could be used for whatever ends a person desired.
Protagoras acquired great wealth and reputation from his teaching. He became a friend of the Athenian general Pericles. He was invited to draft a legal code for the new pan-Hellenic colony of Thurii that the Athenians established in southern Italy in 444/443 BCE. According to ancient tradition, Protagoras was accused of blasphemy, his books were publicly burned, and he was exiled from Athens.
Protagoras’s many works are lost, except for a first sentence from Concerning the Gods, which expressed his attitude toward belief in the gods. Other works include The Great Argument, Contradictory Arguments, On Mathematics, and The Art of Eristics. Greek biographer Diogenes Laërtius preserved sections of more significant works On Ambition, On Virtues, On Human Errors, and Trial Concerning a Fee.
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Man is the measure of all things: of things which are, that they are, and of things which are not, that they are not.
—Protagoras
As touching the gods, I do not know whether they exist or not, nor how they are featured; for there is much to prevent our knowing: the obscurity of the subject and the brevity of human life.
—Protagoras
When it comes to consideration of how to do well in running the city, which must proceed entirely through justice and soundness of mind.
—Protagoras
The Athenians are right to accept advice from anyone, since it is incumbent on everyone to share in that sort of excellence, or else there can be no city at all.
—Protagoras
There are two sides to every question.
—Protagoras
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