Plato, Laws 659a

δὲ ἥτις ἕνα τὸν ἀρετῇ τε καὶ παιδείᾳ διαφέροντα· διὰ ταῦτα δὲ ἀρετῆς φαμεν δεῖσθαι τοὺς τούτων κριτάς, ὅτι τῆς τε ἄλλης μετόχους αὐτοὺς εἶναι δεῖ φρονήσεως καὶ δὴ καὶ τῆς ἀνδρείας. οὔτε γὰρ παρὰ θεάτρου δεῖ τόν γε ἀληθῆ κριτὴν κρίνειν μανθάνοντα, καὶ ἐκπληττόμενον ὑπὸ θορύβου τῶν πολλῶν καὶ τῆς αὑτοῦ ἀπαιδευσίας, οὔτʼ αὖ γιγνώσκοντα διʼ ἀνανδρίαν καὶ δειλίαν ἐκ ταὐτοῦ στόματος οὗπερ τοὺς θεοὺς

and the highly educated as about the best, and as quite the best if it pleases the one man who excels all others in virtue and education. And we say that the judges of these matters need virtue for the reason that they need to possess not only wisdom in general, but especially courage. For the true judge should not take his verdicts from the dictation of the audience, nor yield weakly to the uproar of the crowd or his own lack of education; nor again, when he knows the truth, should he give his verdict carelessly through cowardice and lack of spirit, thus swearing falsely out of the same mouth with which he invoked Heaven when he first took his seat as judge.