Plato, Meno 71b

ἐγὼ οὖν καὶ αὐτός, ὦ Μένων, οὕτως ἔχω· συμπένομαι τοῖς πολίταις τούτου τοῦ πράγματος, καὶ ἐμαυτὸν καταμέμφομαι ὡς οὐκ εἰδὼς περὶ ἀρετῆς τὸ παράπαν· ὃ δὲ μὴ οἶδα τί ἐστιν, πῶς ἂν ὁποῖόν γέ τι εἰδείην; ἢ δοκεῖ σοι οἷόν τε εἶναι, ὅστις Μένωνα μὴ γιγνώσκει τὸ παράπαν ὅστις ἐστίν, τοῦτον εἰδέναι εἴτε καλὸς εἴτε πλούσιος εἴτε καὶ γενναῖός ἐστιν, εἴτε καὶ τἀναντία τούτων; δοκεῖ σοι οἷόν τʼ εἶναι; οὐκ ἔμοιγε. ἀλλὰ σύ, ὦ Σώκρατες, ἀληθῶς

And I myself, Meno, am in the same case; I share my townsmen’s poverty in this matter: I have to reproach myself with an utter ignorance about virtue; and if I do not know what a thing is, how can I know what its nature may be? Or do you imagine it possible, if one has no cognizance at all of Meno, that one could know whether he is handsome or rich or noble, or the reverse of these? Do you suppose that one could? Not I. But is it true, Socrates,