Plato, Letters 329b

ὡς οἷόν τε ἀνθρώπῳ μάλιστα, διά τε τὰ τοιαῦτα καταλιπὼν τὰς ἐμαυτοῦ διατριβάς, οὔσας οὐκ ἀσχήμονας, ὑπὸ τυραννίδα δοκοῦσαν οὐ πρέπειν τοῖς ἐμοῖς λόγοις οὐδὲ ἐμοί· ἐλθών τε ἐμαυτὸν ἠλευθέρωσα Διὸς ξενίου καὶ τῆς φιλοσόφου ἀνέγκλητον μοίρας παρέσχον, ἐπονειδίστου γενομένης ἄν, εἴ τι καταμαλθακισθεὶς καὶ ἀποδειλιῶν αἰσχύνης μετέσχον κακῆς. ἐλθὼν δέ—οὐ γὰρ δεῖ μηκύνειν—ηὗρον στάσεως τὰ περὶ Διονύσιον μεστὰ σύμπαντα καὶ διαβολῶν

and it was because of such motives that I left my own occupations, which were anything but ignoble, to go under a tyranny which ill became, as it seemed, both my teaching and myself. And by my coming I freed myself from guilt in the eyes of Zeus Xenios and cleared myself from reproach on the part of Philosophy, seeing that she would have been calumniated if I, through poorness of spirit and timidity, had incurred the shame of cowardice. On my arrival—I must not be tedious—I found Dionysius’s kingdom all full of civil strife and of slanderous stories