Plato, Meno 78b

ἀληθῆ λέγειν, ὦ Σώκρατες· καὶ οὐδεὶς βούλεσθαι τὰ κακά. οὐκοῦν νυνδὴ ἔλεγες ὅτι ἔστιν ἡ ἀρετὴ βούλεσθαί τε τἀγαθὰ καὶ δύνασθαι; εἶπον γάρ. οὐκοῦν τοῦ λεχθέντος τὸ μὲν βούλεσθαι πᾶσιν ὑπάρχει, καὶ ταύτῃ γε οὐδὲν ὁ ἕτερος τοῦ ἑτέρου βελτίων; φαίνεται. ἀλλὰ δῆλον ὅτι εἴπερ ἐστὶ βελτίων ἄλλος ἄλλου, κατὰ τὸ δύνασθαι ἂν εἴη ἀμείνων. πάνυ γε. τοῦτʼ ἔστιν ἄρα, ὡς ἔοικε, κατὰ τὸν σὸν λόγον ἀρετή,

It seems that what you say is true, Socrates, and that nobody desires evil. Well now, you were saying a moment ago that virtue is the desire and ability for good? Yes, I was. One part of the statement—the desire—belongs to our common nature, and in this respect one man is no better than another? Apparently. But it is plain that if one man is not better than another in this, he must be superior in the ability. Certainly. Then virtue, it seems by your account,