On the Rhetoric (ca. 335 BCE) book 1, ch. 1-6 and book 2, ch. 1-5, 18-24.
What role does persuasion play in philosophy? Aristotle (contra Plato) argues it can and should be used for good: in law courts, political debates, public speeches. He describes the arguments forms used in rhetoric ("enthymemes") and analyzes the emotions that an audience might have so that speakers know what points are worth dwelling on and how to best argue them.