Sokrat. Οὐκοῦν οὕτω πως λέγει, ὠς οἷα μὲν ἕκαστα ἐμοὶ φαίνεται, τοιαῦτα μέν ἐστιν ἐμοὶ — οἷα δὲ σοί, τοιαῦτα δὲ αὖ σοί· ἀνθρωπος δὲ σύ τε κἀγώ.
Theætêt. Λέγει γὰρ οὖν οὕτως.
Here Plato appears to transcribe the words of Protagoras (compare p. 161 B, and the Kratylus, p. 386 A) which distinctly affirm the doctrine of Homo Mensura — Man is the measure of all things, — but do not affirm the doctrine, that knowledge is sensible perception. The identification between the two doctrines is asserted by Plato himself. It is Plato who asserts “that Protagoras affirmed the same doctrine in another manner,” citing afterwards the manner in which he supposed Protagoras to affirm it. If there had been in the treatise of Protagoras any more express or peremptory affirmation of the doctrine “that knowledge is sensible perception,” Plato would probably have given it here.
[11] Plato, Theætêt. p. 152 E. καὶ περὶ τούτου πάντες ἑξῆς οἱ σοφοὶ πλὴν Παρμενίδου ξυμφερέσθων, Πρωταγόρας τε καὶ Ἡράκλειτος καὶ Ἐμπεδοκλῆς, καὶ τῶν ποιητῶν οἱ ἄκροι τῆς ποιήσεως ἑκατέρας, κωμῳδίας μὲν Ἐπίχαρμος, τραγῳδίας δὲ Ὅμηρος.
Plato here blends together three distinct theories for the purpose of confuting them; yet he also professes to urge what can be said in favour of them. Difficulty of following his exposition.
The one main theme intended for examination here (as Sokrates[12] expressly declares) is the doctrine — That Cognition is sensible perception. Nevertheless upon all the three opinions, thus represented as cognate or identical,[13] Sokrates bestows a lengthened comment (occupying a half of the dialogue) in conversation, principally with Theætêtus, but partly also with Theodôrus. His strictures are not always easy to follow with assurance, because he often passes with little notice from one to the other of the three doctrines which he is examining: because he himself, though really opposed to them, affects in part to take them up and to suggest arguments in their favour: and further because, disclaiming all positive opinion of his own, he sometimes leaves us in doubt what is his real purpose — whether to expound, or to deride, the opinions of others — whether to enlighten Theætêtus, or to test his power of detecting fallacies.[14] We cannot always distinguish between the ironical and the serious. Lastly, it is a still greater difficulty, that we have not before us either of the three opinions as set forth by their proper supporters. There remains no work either of Protagoras or of Herakleitus: so that we do not clearly know the subject matter upon which Plato is commenting — nor whether these authors would have admitted as just the view which he takes of their opinions.[15]
[12] Plato, Theætêt. p. 163 A.
[13] Plato, Theætêt. p. 160 D. Sokrat. Παγκάλως ἄρα σοι εἴρηται ὅτι ἐπιστήμη οὐκ ἄλλο τί ἐστιν ἢ αἴσθησις· καὶ εἰς ταὐτὸν συμπέπτωκε, κατὰ μὲν Ὅμηρον καὶ Ἡράκλειτον καὶ πᾶν τὸ τοιοῦτον φῦλον, οἷον ῥεύματα κινεῖσθαι τὰ πάντα — κατὰ δὲ Πρωταγόραν τὸν σοφώτατον, πάντων χρημάτων ἄνθρωπον μέτρον εἶναι — κατὰ δὲ Θεαίτητον, τούτων οὗτως ἐχόντων, αἴσθησιν ἐπιστήμην γίγνεσθαι.
[14] See the answer of Theætêtus and the words of Sokrates following, p. 157 C.
[15] It would be hardly necessary to remark, that when Plato professes to put a pleading into the mouth of Protagoras (pp. 165-166) we have no other real speaker than Plato himself, if commentators did not often forget this. Steinhart indeed tells us (Einleit. zum Theætêt. pp. 36-47) positively — that Plato in this pleading keeps in the most accurate manner (auf das genaueste) to the thoughts of Protagoras, perhaps even to his words. How Steinhart can know this I am at a loss to understand. To me it seems very improbable. The mere circumstance that Plato forces into partnership three distinct theories, makes it probable that he did not adhere to the thoughts or language of any one of them.