Very different indeed is the sentiment of the principal Platonic commentators. Schleiermacher will not allow the mythus of Protagoras to be counted among the Platonic mythes: he says that it is composed in the style of Protagoras, and perhaps copied from some real composition of that Sophist. He finds in it nothing but a “grobmaterialistiche Denkungsart, die über die sinnliche Erfahrung nicht hinaus philosophirt” (Einleitung zum Protagoras, vol. i. pp. 233-234).
To the like purpose Ast (Plat. Leb. p. 71) — who tells us that what is expressed in the mythus is, “the vulgar and mean sentiment and manner of thought of the Sophist: for it deduces every thing, both arts and the social union itself, from human wants and necessity”. Apparently these critics, when they treat this as a proof of meanness and vulgarity, have forgotten that the Platonic Sokrates himself does exactly the same thing in the Republic — deriving the entire social union from human necessities (Republ. ii. 369 C).
K. F. Hermann is hardly less severe upon the Protagorean discourse (Gesch. und Syst. der Plat. Phil. p. 460).
For my part, I take a view altogether opposed to these learned persons. I think the discourse one of the most striking and instructive portions of the Platonic writings: and if I could believe that it was the composition of Protagoras himself, my estimation of him would be considerably raised.
Steinhart pronounces a much more rational and equitable judgment than Ast and Schleiermacher, upon the discourse of Protagoras (Einleitung zum Prot. pp. 422-423).
One purpose of the dialogue. To contrast continuous discourse with short cross-examining question and answer.
This is the point upon which Sokrates now brings his Elenchus to bear: his method of short question and answer. We have seen what long continuous speaking can do: we have now to see what short cross-questioning can do. The antithesis between the two is at least one main purpose of Plato — if it be not even the purpose (as Schleiermacher supposes it to be) in this memorable dialogue.
Questions by Sokrates — Whether virtue is one and indivisible, or composed of different parts? Whether the parts are homogeneous or heterogeneous?
After your copious exposition, Protagoras (says Sokrates), I have only one little doubt remaining, which you will easily explain.[58] You have several times spoken of justice, moderation, holiness, &c., as if they all, taken collectively, made up virtue. Do you mean that virtue is a Whole, and that these three names denote distinct parts of it? Or are the three names all equivalent to virtue, different names for one and are the same thing? Prot. — They are names signifying distinct parts of virtue. Sokr. — Are these parts like the parts of the face, — eyes, nose, mouth, ears — each part not only distinct from the rest, but having its own peculiar properties? Or are they like the parts of gold, homogeneous with each other and with the whole, differing only in magnitude? Prot. — The former. Sokr. — Then some men may possess one part, some another. Or is it necessary that he who possesses one part, should possess all? Prot. — By no means necessary. Some men are courageous, but unjust: others are just, but not intelligent. Sokr. — Wisdom and courage then, both of them, are parts of virtue? Prot. — They are so. Wisdom is the greatest of the parts: but no one of the parts is the exact likeness of another: each of them has its own peculiar property.[59]
[58] Plato, Protag. pp. 328 E — 329 B. πλὴν σμικρόν τί μοι ἐμποδών, ὃ δῆλον ὅτι Πρωταγόρας ῥᾳδίως ἐπεκδιδάξει.… σμικροῦ τινος ἐνδεής εἰμι πάντ’ ἔχειν, &c.