Plato, Laws 738e

καὶ γνωρίζωσιν, οὗ μεῖζον οὐδὲν πόλει ἀγαθὸν ἢ γνωρίμους αὐτοὺς αὑτοῖς εἶναι. ὅπου γὰρ μὴ φῶς ἀλλήλοις ἐστὶν ἀλλήλων ἐν τοῖς τρόποις ἀλλὰ σκότος, οὔτʼ ἂν τιμῆς τῆς ἀξίας οὔτʼ ἀρχῶν οὔτε δίκης ποτέ τις ἂν τῆς προσηκούσης ὀρθῶς τυγχάνοι· δεῖ δὴ πάντα ἄνδρα ἓν πρὸς ἓν τοῦτο σπεύδειν ἐν πάσαις πόλεσιν, ὅπως μήτε αὐτὸς κίβδηλός ποτε φανεῖται ὁτῳοῦν, ἁπλοῦς δὲ καὶ ἀληθὴς ἀεί, μήτε ἄλλος τοιοῦτος ὢν αὐτὸν διαπατήσει.

since nothing is of more benefit to the State than this mutual acquaintance; for where men conceal their ways one from another in darkness rather than light, there no man will ever rightly gain either his due honor or office, or the justice that is befitting. Wherefore every man in every State must above all things endeavor to show himself always true and sincere towards everyone, and no humbug, and also to allow himself to be imposed upon by no such person.