Plato, Laws 735c

καὶ πονηρὰ τροφὴ διεφθαρκυῖα προσαπόλλυσιν τὸ τῶν ὑγιῶν καὶ ἀκηράτων ἠθῶν τε καὶ σωμάτων γένος ἐν ἑκάστοις τῶν κτημάτων, ἄν τις τὰ ὑπάρχοντα μὴ διακαθαίρηται. τὰ μὲν δὴ τῶν ἄλλων ζῴων ἐλάττων τε σπουδὴ καὶ παραδείγματος ἕνεκα μόνον ἄξια παραθέσθαι τῷ λόγῳ, τὰ δὲ τῶν ἀνθρώπων σπουδῆς τῆς μεγίστης τῷ τε νομοθέτῃ διερευνᾶσθαι καὶ φράζειν τὸ προσῆκον ἑκάστοις καθαρμοῦ τε πέρι καὶ συμπασῶν

ill-nurture have combined to ruin, and which themselves bring ruin on a stock that is sound and clean both in habit and in body,—whatever the class of beast,—unless a thorough purge be made in the existing herd. This is a matter of minor importance in the case of other animals, and deserves mention only by way of illustration; but in the case of man it is of the highest importance for the lawgiver to search out and to declare what is proper for each class both as regards purging out and all other modes of treatment. For instance, in respect of civic purgings,