Plato, Meno 99a

ὀρθῶς δέ γε ἡγεῖσθαι δύο ὄντα ταῦτα μόνα, δόξαν τε ἀληθῆ καὶ ἐπιστήμην, ἃ ἔχων ἄνθρωπος ὀρθῶς ἡγεῖται— τὰ γὰρ ἀπὸ τύχης τινὸς ὀρθῶς γιγνόμενα οὐκ ἀνθρωπίνῃ ἡγεμονίᾳ γίγνεται—ὧν δὲ ἄνθρωπος ἡγεμών ἐστιν ἐπὶ τὸ ὀρθόν, δύο ταῦτα, δόξα ἀληθὴς καὶ ἐπιστήμη. δοκεῖ μοι οὕτω. οὐκοῦν ἐπειδὴ οὐ διδακτόν ἐστιν, οὐδʼ ἐπιστήμη δὴ ἔτι γίγνεται ἡ ἀρετή; οὐ φαίνεται.

true opinion and knowledge—that guide rightly and a man guides rightly if he have these; for things that come about by chance do not occur through human guidance; but where a man is a guide to what is right we find these two things—true opinion and knowledge. I agree. Well now, since virtue is not taught, we no longer take it to be knowledge? Apparently not.