Keywords: Theory of Rhetoric; Plato; Aristotle and the Capacity of Persuasion.
After the second World War a new philosophical interest in logic and rhetoric entailed also a renewed study of Plato’s and Aristotle’s rhetoric. This field was explored in Italy by Carlo Augusto Viano above all. In this context I emphasized as well the relevance of the Platonic reference to medicine as an important tool for construing key aspects of a philosophical rhetoric. However, I missed that this philosophical transformation of rhetoric had the consequence of limiting the very persuasive power of rhetoric. In this paper I try to show that the way in which the “Phaedrusµ describes philosophical rhetoric, that is by its capacity to address the discourses fitting to each soul in its peculiarities, entails its incapacity to persuade large audiences, namely audiences constituted by a great variety of types of soul. Socrates’ failure to persuade the members of the jury in his trial provides evidence for this incapacity.