Plato, Letters 330d

μοχθηρὰν πρὸς ὑγίειαν ἄλλο τι χρὴ πρῶτον μὲν μεταβάλλειν τὸν βίον, καὶ ἐθέλοντι μὲν πείθεσθαι καὶ τἆλλα ἤδη παραινεῖν· μὴ ἐθέλοντι δέ, φεύγοντα ἀπὸ τῆς τοῦ τοιούτου συμβουλῆς ἄνδρα τε ἡγοίμην ἂν καὶ ἰατρικόν, τὸν δὲ ὑπομένοντα τοὐναντίον ἄνανδρόν τε καὶ ἄτεχνον. ταὐτὸν δὴ καὶ πόλει, εἴτε αὐτῆς εἷς εἴη κύριος εἴτε καὶ πλείους, εἰ μὲν κατὰ τρόπον ὀρθῇ πορευομένης ὁδῷ τῆς πολιτείας συμβουλεύοιτό

a mode of life that is bad for his health to try first of all to change his life, and only proceed with the rest of his advice if the patient is willing to obey? But should he prove unwilling, then I would esteem him both manly and a true doctor if he withdraws from advising a patient of that description, and contrariwise unmanly and unskilled if he continues to advise. So too with a State, whether it has one ruler or many, if so be that it asks for some salutary advice when its government is duly proceeding by the right road,