Plato, Laws 820b

παντάπασι μὲν οὖν. εἰ δʼ ἔστιν αὖ μηδαμῶς μηδαμῇ δυνατά, πάντες δʼ, ὅπερ εἶπον, Ἕλληνες διανοούμεθα ὡς δυνατά, μῶν οὐκ ἄξιον ὑπὲρ πάντων αἰσχυνθέντα εἰπεῖν πρὸς αὐτούς· ὦ βέλτιστοι τῶν Ἑλλήνων, ἓν ἐκείνων τοῦτʼ ἐστὶν ὧν ἔφαμεν αἰσχρὸν μὲν γεγονέναι τὸ μὴ ἐπίστασθαι, τὸ δʼ ἐπίστασθαι τἀναγκαῖα οὐδὲν πάνυ καλόν; πῶς δʼ οὔ; καὶ πρὸς τούτοις γε ἄλλα ἔστιν τούτων συγγενῆ,

Most certainly. But if they cannot be thus measured by any way or means, while, as I said, all we Greeks imagine that they can, are we not right in being ashamed for them all, and saying to them, O most noble Greeks, this is one of those necessary things which we said it is disgraceful not to know, although there is nothing very grand in knowing such things. Of course. In addition to these there are other matters, closely related to them,