Plato, Laws 751c

συμβαίνοι, σχεδὸν δὲ βλάβαι καὶ λῶβαι πολὺ μέγισται ταῖς πόλεσι γίγνοιντʼ ἂν ἐξ αὐτῶν. πῶς γὰρ οὔ; τοῦτο τοίνυν νοήσωμέν σοι περὶ τῆς νῦν, ὦ φίλε, πολιτείας τε καὶ πόλεως συμβαῖνον. ὁρᾷς γὰρ ὅτι πρῶτον μὲν δεῖ τοὺς ὀρθῶς ἰόντας ἐπὶ τὰς τῶν ἀρχῶν δυνάμεις βάσανον ἱκανὴν αὐτούς τε καὶ γένος ἑκάστων ἐκ παίδων μέχρι τῆς αἱρέσεως εἶναι δεδωκότας, ἔπειτα αὖ τοὺς μέλλοντας αἱρήσεσθαι τεθράφθαι ἐν ἤθεσι νόμων εὖ πεπαιδευμένους

but is likely also to prove the most fertile source of damage and danger in such States. Undoubtedly. Let us then, my friend, mark this result in dealing now with your polity and State. You see that it is necessary, in the first place, that those who rightly undertake official functions should in every case have been fully tested— both themselves and their families— from their earliest years up to the time of their selection; and, secondly, that those who are to be the selectors should have been reared in law-abiding habits,