There are, then, these three means of effecting persuasion. The man who is to be in command of them must, it is clear, be able (1) to reason logically, (2) to understand human character and goodness in their various forms, and (3) to understand the emotions--that is, to name them and describe them, to know their causes and the way in which they are excited.
The Works of Aristotle: Rhetorica, by W. R. Roberts. De rhetorica ad Alexandrum, by E. S. Forster. De poetica, by I. Bywater (ed. 1924)