Letter 1089: Vice needs no teacher — it comes naturally to our fallen nature.

To Paul. On the same subject (that is, on the conduct of life). Just as it is not the robe and the staff that reveal the philosopher, but rather his frankness of speech and his way of life, so too the Christian is shown not by outward dress and discourse, but by a character and a manner of living that vie with right reason.

Περὶ τοῦ αὐτοῦ (id est, περὶ πολιτείας). Ὥσπερ τὸν φιλόσοφον οὐχ ἡ στολὴ καὶ βακτηρία δείκνυσιν, ἀλλ' ἡ παῤῥησία καὶ ἡ πολιτεία· οὕτω καὶ τὸν Χριστιανὸν οὐ σχῆμα καὶ λόγος, ἀλλὰ τρόπος καὶ βίος τῷ ὀρθῷ λόγῳ ἐφάμιλλος.