Plato, Meno 87c

ὁποτέρῳ ἂν τῷ ὀνόματι χρώμεθα—ἀλλʼ ἆρα διδακτόν; ἢ τοῦτό γε παντὶ δῆλον, ὅτι οὐδὲν ἄλλο διδάσκεται ἄνθρωπος ἢ ἐπιστήμην; ἔμοιγε δοκεῖ. εἰ δέ γʼ ἐστὶν ἐπιστήμη τις ἡ ἀρετή, δῆλον ὅτι διδακτὸν ἂν εἴη. πῶς γὰρ οὔ; τούτου μὲν ἄρα ταχὺ ἀπηλλάγμεθα, ὅτι τοιοῦδε μὲν ὄντος διδακτόν, τοιοῦδε δʼ οὔ. πάνυ γε. τὸ δὴ μετὰ τοῦτο, ὡς ἔοικε, δεῖ σκέψασθαι πότερόν ἐστιν ἐπιστήμη ἡ ἀρετὴ ἢ ἀλλοῖον ἐπιστήμης.

is it taught? Or is not this fact plain to everyone—that the one and only thing taught to men is knowledge? I agree to that. Then if virtue is a kind of knowledge, clearly it must be taught? Certainly. So you see we have made short work of this question—if virtue belongs to one class of things it is teachable, and if to another, it is not. To be sure. The next question, it would seem, that we have to consider is whether virtue is knowledge, or of another kind than knowledge.