Protagoras

Protagoras of Abdera was a Greek thinker of the fifth century BCE and the most famous of the sophists, the travelling teachers who charged fees to train young men in argument, speaking and the conduct of public life. He is remembered for two bold statements: that a human being is the measure of all things, and that he could not know whether the gods exist. His writings are lost, and the picture of him comes mainly from Plato, who admired his ability but opposed his ideas.

Protagoras was born around 490 BCE in Abdera, a Greek city on the coast of Thrace, in what is now north-eastern Greece. The same city later produced the atomist Democritus, and a late anecdote, of little historical value, claims that Democritus discovered the young Protagoras working as a porter and, impressed by the clever way he tied a bundle of wood, took him on as a pupil. Since Protagoras was probably the older of the two, the story is almost certainly invented.

He spent his career travelling among Greek cities, and visited Athens several times. In Plato's dialogue Protagoras, set around 433 BCE in the house of the wealthy Athenian Callias, he appears as an eminent and self-assured celebrity, surrounded by admirers. He was on good terms with Pericles: Plutarch reports that the two once spent a whole day debating who was to blame when an athlete accidentally killed a spectator with a javelin, the thrower, the javelin or the organisers of the games. In 444 BCE, according to a report from Heraclides of Pontus, Pericles chose him to draft the laws of Thurii, a new colony founded with Athenian backing in the south of Italy, a sign of the high regard in which he was held.

Plato's Meno says that Protagoras died at around seventy, after some forty years of teaching, with his reputation intact, which places his death around 420 BCE. A different tradition, found in later writers such as Diogenes Laertius, says that he was prosecuted at Athens for impiety because of his book on the gods, that copies of it were burned in the marketplace, and that he drowned in a shipwreck while leaving the city. Many historians doubt this story, which conflicts with Plato's account and may have grown from later worries about free-thinking intellectuals.

Protagoras was, by Plato's account, the first to call himself a sophist openly and to charge fees for teaching, which made him rich. What he offered, in his own words as Plato presents them, was good judgment, both in managing one's household and in speaking and acting effectively in the affairs of the city. In democratic Athens, where citizens spoke in the assembly and pleaded their own cases in court, such training was in great demand.

He was credited with the principle that there are two opposing arguments on every matter, and Aristotle reports that he promised to make the weaker argument the stronger, a claim that critics, including the comic playwright Aristophanes, turned into a charge of teaching people to make wrong look right. He also took an interest in language, distinguishing the grammatical genders of nouns and different kinds of sentence, such as questions, answers, commands and prayers. Ancient lists give titles of his works, including Truth, On the Gods and Antilogiai, or Opposing Arguments, but only a handful of short fragments survive.

The most famous surviving fragment, apparently the opening of his book Truth, states that of all things the measure is man: of the things that are, that they are, and of the things that are not, that they are not. Its meaning has been debated since antiquity. In the Theaetetus, Plato interprets it as a theory of relativism about perception and belief: if the wind feels cold to one person and warm to another, it is cold for the first and warm for the second, and there is no further fact about the wind in itself. On this reading, whatever seems true to someone is true for them.

Plato then raises what became a classic objection: if every belief is true for whoever holds it, then the belief of Protagoras' critics, that his doctrine is false, is also true for them, so the theory seems to undermine itself. Plato also has Protagoras reply that, although no belief is truer than another, some are better, and that the wise person, like a doctor, changes people's states so that better things seem true to them. Some modern scholars think Protagoras meant something narrower, perhaps that human experience is the only standard available to us, and whether Plato's version is fair is still discussed.

The opening of his book On the Gods declared that he was unable to know whether the gods exist or what they are like, because many things prevent such knowledge, including the obscurity of the subject and the shortness of human life. This is one of the earliest clear statements of agnosticism in Western thought. It does not deny the gods, but it treats the question as beyond human knowledge.

In Plato's Protagoras, he tells a myth about the origins of society. The Titans Prometheus and Epimetheus hand out abilities to living creatures, leaving humans without natural defences; Prometheus steals fire and technical skill for them, but they still cannot live together in cities until Zeus grants all people a share of justice and a sense of shame. The myth supports Protagoras' claim that political virtue can be taught and that every citizen has some share in it, an argument that fits well with Athenian democracy. Whether Plato is reporting Protagoras' own ideas or inventing on his behalf is uncertain, though many scholars think the speech reflects genuine Protagorean views.

Protagoras helped make the sophists a central force in the intellectual life of fifth-century Greece, and his questions about truth, belief and convention shaped the debates of Socrates, Plato and Aristotle, who discussed and rejected the measure doctrine in his Metaphysics. Because his critics defined him, he was long remembered as a clever relativist who sold rhetorical tricks. Modern historians of ancient Greek philosophy generally give him more credit, seeing him as a serious thinker about knowledge, language and politics, and his "man the measure" has often been read, more loosely than he may have intended, as a motto of humanism.