Plato, Laws 638b

νικῶσιν μαχόμεναι καὶ καταδουλοῦνται, Συρακόσιοι μὲν Λοκρούς, οἳ δὴ δοκοῦσιν εὐνομώτατοι τῶν περὶ ἐκεῖνον τὸν τόπον γεγονέναι, Κείους δὲ Ἀθηναῖοι· μυρία δὲ ἄλλα τοιαῦτʼ ἂν εὕροιμεν. ἀλλὰ περὶ αὐτοῦ ἑκάστου ἐπιτηδεύματος πειρώμεθα λέγοντες πείθειν ἡμᾶς αὐτούς, νίκας δὲ καὶ ἥττας ἐκτὸς λόγου τὰ νῦν θῶμεν, λέγωμεν δʼ ὡς τὸ μὲν τοιόνδʼ ἐστὶν καλόν, τὸ δὲ τοιόνδε οὐ καλόν. πρῶτον δʼ ἀκούσατέ τί μου, περὶ αὐτῶν τούτων ὡς δεῖ τό τε χρηστὸν καὶ τὸ μὴ σκοπεῖν.

and we find the Syracusans subjugating the Locrians, who are reputed to have been the best-governed of the peoples in that part of the world: and the Athenians the Ceians,—and we could find countless other instances of the same kind. So let us leave victories and defeats out of account for the present, and discuss each several institution on its own merits in the endeavor to convince ourselves, and explain in what way one kind is good and another had. And to begin with, listen to my account of the right method of inquiring into the merits and demerits of institutions.