Plato, Meno 87b

εἰπεῖν σοι τὸ συμβαῖνον περὶ τῆς ἐντάσεως αὐτοῦ εἰς τὸν κύκλον, εἴτε ἀδύνατον εἴτε μή. οὕτω δὴ καὶ περὶ ἀρετῆς ἡμεῖς, ἐπειδὴ οὐκ ἴσμεν οὔθʼ ὅτι ἐστὶν οὔθʼ ὁποῖόν τι, ὑποθέμενοι αὐτὸ σκοπῶμεν εἴτε διδακτὸν εἴτε οὐ διδακτόν ἐστιν, ὧδε λέγοντες· εἰ ποῖόν τί ἐστιν τῶν περὶ τὴν ψυχὴν ὄντων ἀρετή, διδακτὸν ἂν εἴη ἢ οὐ διδακτόν; πρῶτον μὲν δὴ εἰ ἔστιν ἀλλοῖον ἢ οἷον ἐπιστήμη, ἆρα διδακτὸν ἢ οὔ, ἢ ὃ νυνδὴ ἐλέγομεν, ἀναμνηστόν—διαφερέτω δὲ μηδὲν ἡμῖν

in the circle by saying whether it is impossible or not. In the same way with regard to our question about virtue, since we do not know either what it is or what kind of thing it may be, we had best make use of a hypothesis in considering whether it can be taught or not, as thus: what kind of thing must virtue be in the class of mental properties, so as to be teachable or not? In the first place, if it is something dissimilar or similar to knowledge, is it taught or not—or, as we were saying just now, remembered? Let us have no disputing about the choice of a name: