Protagoras

Life

Protagoras was born around 490 BCE in Abdera, the same Thracian city that produced Democritus. He reportedly spent much of his career traveling throughout the Greek world, teaching in major cities and gaining enormous fame and wealth. He visited Athens on several occasions and became closely associated with Pericles, who commissioned him to draft the laws for the new Athenian colony of Thurii in southern Italy (around 444 BCE) — a remarkable sign of political trust.

Protagoras was reportedly the first person to charge fees for teaching, and ancient sources say he accumulated vast wealth through his profession. He was the most prominent representative of the Sophistic movement — a group of traveling intellectuals who taught rhetoric, argumentation, grammar, and civic virtue during the golden age of Athens.

The Man-Measure Doctrine

Protagoras' most famous pronouncement opens his work 'Truth' (Alētheia): "Of all things the measure is man (anthrōpos metron), of things that are that they are, and of things that are not that they are not." The interpretation of this statement has been debated for over two millennia.

Plato, in the Theaetetus, interprets it as a radical perceptual relativism: for each individual, things are as they appear to that individual. If the wind feels cold to you and warm to me, then it IS cold for you and warm for me, and neither judgment is more 'true' than the other. There is no wind-in-itself apart from how it appears to particular perceivers.

Broader interpretations extend this to cultural relativism: what is just, noble, or good varies between communities, and no external standard exists by which one community's norms can be judged superior to another's. However, Protagoras may have been more moderate than Plato's portrayal suggests. In the 'Great Speech' attributed to him in Plato's Protagoras, he argues that while no opinion is more 'true' than another, some are more beneficial or useful — and the Sophist's skill lies in helping people and cities move from less beneficial to more beneficial beliefs.

On the Gods

Protagoras' treatise 'On the Gods' reportedly opened with: "About the gods I am unable to know whether they exist or do not exist, or what they are like in form; for there are many things that hinder knowledge — the obscurity of the subject and the shortness of human life." This agnostic declaration was reportedly the cause of his prosecution for impiety (asebeia) in Athens, though the details and chronology are uncertain. Some sources say his books were publicly burned in the agora — the earliest recorded book-burning in Western history.

Teaching Virtue

In Plato's dialogue Protagoras, the Sophist makes a bold claim: he teaches political virtue (politikē aretē) — the capacity to be an effective citizen, to deliberate well about public and private affairs, and to manage one's household and city. This claim was controversial because Socrates and others questioned whether virtue could be taught at all. Protagoras defends his claim with a famous myth about Prometheus and Epimetheus, arguing that Zeus gave all humans a share of justice (dikē) and shame (aidōs), so that political virtue is universal in potential but requires cultivation through education.

Antilogies

Protagoras taught the method of antilogies (antilogiai) — the technique of arguing both sides of any question. He reportedly claimed that "on every matter there are two arguments opposed to each other" (duo logoi). This skill was of enormous practical value in Athenian democratic life, where success in the assembly and the courts depended on rhetorical ability. Critics saw this as teaching people to make the weaker argument stronger (ton hēttō logon kreittō poiein), essentially training in manipulation. But Protagoras may have intended something more philosophical: the recognition that every question has multiple defensible perspectives.

Legacy

Protagoras died around 420 BCE, reportedly in a shipwreck while leaving Athens after his prosecution. His influence was enormous. He stands at the fountainhead of the Western tradition of relativism, pragmatism, and rhetorical theory. Plato devoted two major dialogues to him (Protagoras and Theaetetus), and his Man-Measure doctrine has been taken up in various forms by thinkers from Sextus Empiricus to Nietzsche to contemporary pragmatists.