Protagoras

Protagoras of Abdera (c. 490–420 BCE), the first and most famous of the Greek sophists — itinerant professional teachers of aretē (excellence/virtue) — and the figure after whom Plato's Protagoras is named. He appears in the wiki in two distinct registers, which must be kept apart: as the teacher of civic virtue who delivers the Great Speech in the Protagoras, and as the relativist whose "man is the measure" doctrine is stated and examined in the Theaetetus (not in the Protagoras).

Key Points

• The first sophist. Protagoras "admit[s] that I am a sophist" (Protagoras 317b) and presents himself as a teacher of "sound deliberation… the art of citizenship" — i.e. human virtue — for a fee. He is "the wisest man alive" in the dialogue's framing (310d).
• The Great Speech (Protagoras 320c–328d): his set-piece defense of the teachability of virtue, via the Prometheus myth — Zeus distributes aidōs (shame) and dikē (justice) "to all" humans, grounding why everyone partakes of civic virtue and why it can be taught, blamed, and punished. He defends the separability of the virtues (especially courage), resisting Socrates' reduction of all virtue to knowledge.
• "Man is the measure of all things" (Theaetetus 152a): his signature relativist thesis — "of the things that are, that they are; of the things that are not, that they are not" — examined and refuted in the Theaetetus, not in the Protagoras. Reading the Great Speech as a statement of this relativism is an error.
• Head of the "Counter-tradition" (per Madison): on one reading "man is the measure" names a humanism (the human as the universal measure), not subjectivism — the wiki homes that placement on counter-tradition.
• A skeptic about the gods: famously "Concerning the gods, I am unable to know whether they exist or not" — his agnosticism is part of his historical reputation (reported, not from the dialogues ingested here).

What's Not Obvious

• The dialogue named for him is not where his famous doctrine appears. The Protagoras gives the Great Speech (virtue is teachable, universally distributed); the relativist "man is the measure" is a Theaetetus doctrine. The wiki sources each to the right dialogue to avoid the standard conflation.
• He wins a round against Socrates. When Socrates argues "the courageous are confident, therefore the confident are courageous," Protagoras cleanly exposes the illicit conversion (Protagoras 350c–351b) — Plato lets the sophist score a fair logical point.

Connections

• is the speaker of the Great Speech in plato-protagoras — the Prometheus myth grounding universal, teachable civic virtue.
• is the relativist examined in plato-theaetetus — "man is the measure" (152a), refuted there; not stated in the Protagoras.
• is the head of counter-tradition — the "man is universal measure" humanist reading.
• defends the separability of the virtues against socratic-intellectualism — resisting the reduction of virtue (esp. courage) to knowledge.
• is the relativist of "man is the measure" — examined and refuted in the Theaetetus, not stated in the Protagoras.

Open Questions

• Is "man is the measure" subjectivism (each perception true for the perceiver) or a humanism (the human as the measure of intelligibility)? The Theaetetus and the counter-tradition reading pull in different directions.
• How far is the Great Speech's "conventional but universal and teachable" virtue compatible with the relativism — or are the Protagoras and Theaetetus Protagorases two different constructions by Plato?
• The historical Protagoras' own works (Truth, On the Gods) survive only in fragments and report; the wiki has no Protagorean primary source (a source gap).

Sources

• plato-protagoras — Protagoras as teacher of virtue; the Great Speech (316a–328d); the defense of separable virtues.
• plato-theaetetus — "man is the measure" and its refutation (152a, 160d–183c).