Plato, Republic, book 4 442:

καὶ οὔ τι λέγω, ὡσ, οἱών ἂν ᾖ, τοιαῦτα καὶ ἔστιν, ὡσ ἄρα καὶ τῶν ὑγιεινῶν καὶ νοσωδῶν ἡ ἐπιστήμη ὑγιεινὴ καὶ νοσώδησ καὶ τῶν κακῶν καὶ τῶν ἀγαθῶν κακὴ καὶ ἀγαθή· ἀλλ’ ἐπειδὴ οὐκ αὐτοῦ οὗπερ ἐπιστήμη ἐστὶν ἐγένετο ἐπιστήμη, ἀλλὰ ποιοῦ τινοσ, τοῦτο δ’ ἦν ὑγιεινὸν καὶ νοσῶδεσ, ποιὰ δή τισ συνέβη καὶ αὐτὴ γενέσθαι, καὶ τοῦτο αὐτὴν ἐποίησεν μηκέτι ἐπιστήμην ἁπλῶσ καλεῖσθαι, ἀλλὰ τοῦ ποιοῦ τινοσ προσγενομένου ἰατρικήν.