Invention is the process of coming up with things to say. Today we tend to think of scholarly research and empirical observation as the only viable methods of invention. Ancient rhetorical lore suggests that invention is all about asking the right questions in the right order (stasis theory and dialectic), and searching the collective wisdom of the community (history, literature) for useful quotations, illustrations, and advice. During those historical moments when invention has been identified as belonging primarily to other disciplines, to scientific method or to philosophy, rhetoric has been primarily focused on style and delivery. Contemporary teachers of rhetoric, taking social constructivism as their epistemological foundation, have foregrounded invention among the divisions, arguing that much of what people believe as they go about their daily lives results from persuasion rather than science or philosophy. Aristotle lead the way to this position by arguing that we should only use rhetoric in decision making situations where the truth is unknowable because the evidence doesn't exist or won't arrive in time or when the truth is known but the audience is incapable of understanding it. Rhetorical thinking, invention, is relevant only in these settings. For all other decisions we should use what he called dialectic and what, were he alive today, he would call scientific reasoning.
Probably the most direct way into thinking about invention is to ask, as Plato did, does rhetoric have a subject matter and if so what is it?
Each inventional concept is linked below. If you want to read the sections in order, click the Next button at the bottom of each screen. Use the links below if you want to jump straight to one or jump around. The section on dialectic is quite long and a bit complicated and will reward multiple readings, I think. You will want to revisit when we read Plato's Gorgias, perhaps before and after but definitely after.