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? In Plato's Gorgias, Socrates condemns the sophists who taught rhetoric for merely endowing their students with social power over others, power that would make them neither happy nor virtuous. Philosophy should be about getting at the truth. Aristotle acknowledges this, but still thinks that rhetoric is useful, like, say, when you have the truth about whether you've corrupted the youth of Athens and need to convince a jury of that truth so that they don't condemn you to death. That ability might come in handy.
Though the Rhetoric as a whole does talk about things you might expect from a public speaking guide (vocal tone, poise, etc.), the parts we read focused on the uses of rhetoric, the structure of its arguments, and the emotions of the audience whom the speaker needs to be cognizant of in tailoring a speech. Rhetoric as Aristotle teaches it can be used in courts of law (where it argues about whether or not specific things happened, which is different than philosophy which explores more general truths), in the legislature (we should pursue some specific course of action), and in speeches praising or blaming someone (like at a funeral, festival, or when engaging in political activity not related to some specific piece of legislation you're trying to push). In all of these cases, Aristotle thinks that people are likely to believe the truth if it's spelled out for them in ways they can understand. It's in the speaker's power to manipulate them and argue for debased things, but Aristotle of course doesn't want rhetoric used that way, and it's actually going to be harder to do so than to clearly present a valid argument.
Aristotle is well known for his works of logic (we'll get to them someday!), and this text gives us a taste of that: The main unit of Aristotelian logic is the syllogism, which if fully spelled out has three parts: two premises leading to a conclusion. But of course, when you're actually talking to someone, you don't diagram arguments, and in fact you leave lots of your premises as unstated, shared assumptions. In the Rhetoric, Aristotle calls this kind of incompletely-presented syllogism an enthymeme. You want to understand the assumptions of your audience so that you don't waste time arguing for claims that they'll already agree with, and if possible, you should even use maxims, which are cliches that resonate with the audience: claims that in that situation will require no proof even though a philosopher would likely dispute them (is it really the case that you can never "teach an old dog new tricks"?).
Syllogisms provide the forms for deductive arguments (where the proof of the premises would guarantee the truth of the conclusion); Aristotle also in this texts introduces inductive arguments, but they're not inductive in the Humean sense where we see lots of examples of something like white swans and conclude that probably all swans are white. For Aristotle, induction in rhetoric means you present one example of something (like a political leader who became corrupt after being given absolute power) and use that to argue a general point (we shouldn't give leaders absolute power). There's still an element of probability in it (would every leader be corrupted in that situation?), but the idea is that the example is exposing you to the essence of the thing (the nature of corrupting power), so you can draw the general conclusion or apply it to a new case (we shouldn't give our current president absolute power).
The beginning of book two (which we deal with in part two of this episode) deals with emotions, and our conversation focuses pretty much only on anger, following up on our conversation with Martha Nussabaum about this. The Aristotelian theory of emotions runs counter to our picture of emotions as the irrational counter to reason. No, emotions involve beliefs, and anger specifically involves a belief that someone has done you wrong, has insulted you, and a desire for revenge for that affront. Similarly, fear involves a belief that something is dangerous, and the emotion of friendship involves a belief that someone likes you and shares your interests, likes, and dislikes. Hatred is unlike anger in that it's a desire for the person not to exist; it can't be expiated by the person showing contrition or getting the revenge that anger demands. Aristotle performs this analysis of various emotions because it's useful information for a speaker; you have to understand how to navigate around an audience's anger, how to present yourself as someone who shares their concerns, how to calm them or incite them. Despite his earlier warnings about only using rhetoric to argue for the truth, his presentation here is pretty empowering, potentially even amoral.
You can read the book online or listen to it, but you'd be much better off getting a good translation with commentary. We preferred the Joe Sachs (which packages the text with Plato's Gorgias), though the preferred scholarly version seems to be the George Kennedy translation, which definitely had a helpful introduction.
Picture by Genevieve Arnold.