Plato, Meno 94d

δαπανώμενον διδάσκειν, ταῦτα μὲν ἐδίδαξε τοὺς παῖδας τοὺς αὑτοῦ, οὗ δὲ οὐδὲν ἔδει ἀναλώσαντα ἀγαθοὺς ἄνδρας ποιῆσαι, ταῦτα δὲ οὐκ ἐδίδαξεν, εἰ διδακτὸν ἦν; ἀλλὰ γὰρ ἴσως ὁ Θουκυδίδης φαῦλος ἦν, καὶ οὐκ ἦσαν αὐτῷ πλεῖστοι φίλοι Ἀθηναίων καὶ τῶν συμμάχων; καὶ οἰκίας μεγάλης ἦν καὶ ἐδύνατο μέγα ἐν τῇ πόλει καὶ ἐν τοῖς ἄλλοις Ἕλλησιν, ὥστε εἴπερ ἦν τοῦτο διδακτόν, ἐξευρεῖν ἂν ὅστις ἔμελλεν αὐτοῦ τοὺς ὑεῖς ἀγαθοὺς ποιήσειν, ἢ τῶν ἐπιχωρίων τις ἢ τῶν

and then have omitted to teach them at no expense the others that would have made them good men, if virtue was to be taught? Will you say that perhaps Thucydides was one of the meaner sort, and had no great number of friends among the Athenians and allies? He, who was of a great house and had much influence in our city and all over Greece, so that if virtue were to be taught he would have found out the man who was likely to make his sons good, whether one of our own people