Note 59 — Chapter XXVIII · THEÆTETUS.

Plato, Theætêt. p. 152 A. Οὐκοῦν οὕτω πως λέγει (Protagoras) ὡς οἷα μὲν ἕκαστα ἐμοὶ φαίνεται, τοιαῦτα μέν ἐστιν ἐμοί — οἷα δὲ σοί, τοιαῦτα δὲ αὖ σοί. 158 A. τὰ φαινόμενα ἑκάστῳ ταῦτα καὶ εἶναι τούτῳ ᾧ φαίνεται. 160 C. Ἀληθὴς ἄρα ἐμοὶ ἡ ἐμὴ αἴσθησις· τῆς γὰρ ἐμῆς οὐσίας ἀεί ἐστι· καὶ ἐγὼ κριτὴς κατὰ τὸν Πρωταγόραν τῶν τε ὄντων ἐμοί, ὡς ἔστι, καὶ τῶν μὴ ὄντων, ὡς οὐκ ἔστιν.

Comp. also pp. 166 D, 170 A, 177 C.

Instead of saying αἴσθησις (in the passage just cited, p. 160 D), we might with quite equal truth put Ἀληθὴς ἄρα ἐμοὶ ἡ ἐμὴ νόησις· τῆς γὰρ ἐμῆς οὐσίας ἀεί ἔστιν. In this respect αἴσθησις and νόησις are on a par. Νόησις is just as much relative to ὁ νοῶν as αἴσθησις to ὁ αἰσθανόμενος.

Sextus Empiricus adverts to the doctrines of Protagoras (mainly to point out how they are distinguished from those of the Sceptical school, to which he himself belongs) in Pyrrhon. Hypot. i. sects. 215-219; adv. Mathematicos, vii. s. 60-64-388-400. He too imputes to Protagoras both the two doctrines. 1. That man is the measure of all things: that what appears to each person is, to him: that all truth is thus relative. 2. That all phantasms, appearances, opinions, are true. Sextus reasons at some length (390 seq.) against this doctrine No. 2, and reasons very much as Protagoras himself would have reasoned, since he appeals to individual sentiment and movement of the individual mind (οὐκ ὡσαύτως γὰρ κινούμεθα, 391-400). It appears to me perfectly certain that Protagoras advanced the general thesis of Relativity: we see this as well from Plato as from Sextus — καὶ οὕτως εἰσάγει τὸ πρός τι — τῶν πρός τι εἶναι τὴν ἀληθείαν (Steinhart is of opinion that these words τῶν πρός τι εἶναι τὴν ἀληθείαν are an addition of Sextus himself, and do not describe the doctrine of Protagoras; an opinion from which I dissent, and which is contradicted by Plato himself: Steinhart, Einleitung, note 8). If Protagoras also advanced the doctrine — all opinions are true — this was not consistent with his cardinal principle of relativity. Either he himself did not take care always to enunciate the qualifications and limitations which his theory requires, and which in common parlance are omitted — Or his opponents left out the limitations which he annexed, and impugned the opinion as if it stood without any. This last supposition I think the most probable.

The doctrine of Protagoras is correctly given by Sextus in the Pyrrhon. Hypot.