Gorgias, Defense of Helen 13-14
“The persuasion intrinsic to speech also shapes the mind as it pleases. We must first consider the narratives of astronomers who, by undermining one idea and developing another one, alter beliefs and make the incredible and invisible manifest to the eyes of belief. In turn, consider the necessary struggles in which one argument delights and persuades a great crowd when it has been written skillfully, even if it is spoken falsely. Finally, consider the rivalrous claims of philosophers which feature as well the speed of opinion that engenders volatility in the fidelity of a belief.”
(13) ὅτι δ’ ἡ πειθὼ προσιοῦσα τῶι λόγωι καὶ τὴν ψυχὴν ἐτυπώσατο ὅπως ἐβούλετο, χρὴ μαθεῖν πρῶτον μὲν τοὺς τῶν μετεωρολόγων λόγους, οἵτινες δόξαν ἀντὶ δόξης τὴν μὲν ἀφελόμενοι τὴν δ’ ἐνεργασάμενοι τὰ ἄπιστα καὶ ἄδηλα φαίνεσθαι τοῖς τῆς δόξης ὄμμασιν ἐποίησαν· δεύτερον δὲ τοὺς ἀναγκαίους διὰ λόγων ἀγῶνας, ἐν οἷς εἷς λόγος πολὺν ὄχλον ἔτερψε καὶ ἔπεισε τέχνηι γραφείς, οὐκ ἀληθείαι λεχθείς· τρίτον <δὲ> φιλοσόφων λόγων ἁμίλλας, ἐν αἷς δείκνυται καὶ γνώμης τάχος ὡς εὐμετάβολον ποιοῦν τὴν τῆς δόξης πίστιν.
“The power of speech has the same logic regarding the disposition of the soul as that of the application of drugs to the natural function of bodies. For, just as certain drugs dispel certain afflictions from the body, and some end disease while others end life, so too are there stories that create grief and others that cause pleasure; some send us running, others make their audiences bold. Others still intoxicate and deceive the soul though some evil persuasion.”
(14) τὸν αὐτὸν δὲ λόγον ἔχει ἥ τε τοῦ λόγου δύναμις πρὸς τὴν τῆς ψυχῆς τάξιν ἥ τε τῶν φαρμάκων τάξις πρὸς τὴν τῶν σωμάτων φύσιν. ὥσπερ γὰρ τῶν φαρμάκων ἄλλους ἄλλα χυμοὺς ἐκ τοῦ σώματος ἐξάγει, καὶ τὰ μὲν νόσου τὰ δὲ βίου παύει, οὕτω καὶ τῶν λόγων οἱ μὲν ἐλύπησαν, οἱ δὲ ἔτερψαν, οἱ δὲ ἐφόβησαν, οἱ δὲ εἰς θάρσος κατέστησαν τοὺς ἀκούοντας, οἱ δὲ πειθοῖ τινι κακῆι τὴν ψυχὴν ἐφαρμάκευσαν καὶ ἐξεγοήτευσαν.