Note 19 — Chapter XXVII · PARMENIDES.

Plato, Parmenid. p. 134 A. Οὐκοῦν καὶ ἐπιστήμη, αὐτὴ μὲν ὃ ἔστιν ἐπιστήμη, τῆς ὃ ἔστιν ἀλήθεια, αὐτῆς ἂν ἐκείνης εἴη ἐπιστήμη; … Ἡ δὲ παρ’ ἡμῖν ἐπιστήμη οὐ τῆς παρ’ ἡμῖν ἂν ἀληθείας εἴη; καὶ αὖ ἑκάστη ἡ παρ’ ἡμῖν ἐπιστήμη τῶν παρ’ ἡμῖν ὄντων ἑκάστου ἂν ἐπιστήμη σύμβαινοι εἶναι;

Aristotle (Topica, vi. p. 147, a. 6) adverts to this as an argument against the theory of Ideas, but without alluding to the Parmenides; indeed he puts the argument in a different way — τὸ δ’ εἶδος πρὸς τὸ εἶδος δοκεῖ λέγεσθαι, οἷον αὐτὴ ἐπιθυμία αὐτοῦ ἡδέος, καὶ αὐτὴ βούλησις αὐτοῦ ἀγαθοῦ. Aristotle argues that there is no place in this doctrine for the φαινόμενον ἀγαθόν, which nevertheless men often wish for, and he remarks, in the Nikom. Ethica, i. 4, 1096 b. 33 — that the αὐτὸ-ἀγαθὸν is neither πρακτὸν nor κτητὸν ἀνθρώπῳ.