Arguments advanced by the Platonic Sokrates against the Protagorean doctrine. He says that it puts the wise and foolish on a par — that it contradicts the common consciousness. Not every one, but the wise man only, is a measure.
It puts every man (he says) on a par as to wisdom and intelligence: and not only every man, but every horse, dog, frog, and other animal along with him. Each man is a measure for himself: all his judgments and beliefs are true: he is therefore as wise as Protagoras and has no need to seek instruction from Protagoras.[48] Reflection, study, and dialectic discussion, are superfluous and useless to him: he is a measure to himself on the subject of geometry, and need not therefore consult a professed geometrician like Theodôrus.[49]
[48] Plato, Theætêt. p. 161. Compare Plato, Kratylus, p. 386 C, where the same argument is employed.
[49] Plato, Theætêt. p. 169 A.
The doctrine is contradicted (continues Sokrates) by the common opinions of mankind: for no man esteems himself a measure on all things. Every one believes that there are some things on which he is wiser than his neighbour — and others on which his neighbour is wiser than he. People are constantly on the look out for teachers and guides.[50] If Protagoras advances an opinion which others declare to be false, he must, since he admits their opinion to be true, admit his own opinion to be false.[51] No animal, nor any common man, is a measure; but only those men, who have gone through special study and instruction in the matter upon which they pronounce.[52]
[50] Plato, Theætêt. p. 170.
[51] Plato, Theætêt. p. 171 B. Οὐκοῦν τὴν αὑτοῦ ἂν ψευδῆ ξυγχωροῖ, εἰ τὴν τῶν ἡγουμένων αὐτὸν ψεύδεσθαι ὁμολογεῖ ἀληθῆ εἶναι;
[52] Plato, Theætêt. p. 171 C.
In matters of present sentiment every man can judge for himself. Where future consequences are involved special knowledge is required.
In matters of present and immediate sensation, hot, cold, dry, moist, sweet, bitter, &c., Sokrates acknowledges that every man must judge for himself, and that what each pronounces is true for himself. So too, about honourable or base, just or unjust, holy or unholy — whatever rules any city may lay down, are true for itself: no man, no city, — is wiser upon these matters than any other.[53] But in regard to what is good, profitable, advantageous, healthy, &c., the like cannot be conceded. Here (says Sokrates) one man, and one city, is decidedly wiser, and judges more truly, than another. We cannot say that the judgment of each is true;[54] or that what every man or every city anticipates to promise good or profit, will necessarily realise such anticipations. In such cases, not merely present sentiment, but future consequences are involved.