Reasoning / Logic: Reason is a word we used in everyday conversation to mean thinking or arguing carefully. When we say something “is reasonable,” or, “stands to reason,” we mean it is rationale and makes sense. Whenever we think consciously about our reasons for doing things, we use logic. In rhetorical practice, we use what is often called "informal logic," distinct from "formal logic," which is an abstract exercise of reasoning akin to mathematics. Real-world thinking, reasoning rhetorically, is much messier. It engages issues about which people don't agree. What seems "reasonable" to me may not seem reasonable to you. There is no mathematical precision within rhetorical situations!
Often referred to by the Greek term logos, logic or informal reasoning is at the core of much communication. In this sense, reasoning refers to the linking of statements that lead to a conclusion. What assertions or “premises” will particular audiences most likely accept as valid? How much and what kind of support will assertions need?
Consider this "line of reasoning" (or, chain of premises) commonly used by writing teachers when talking to their students:
Premise: Completing the first draft of an assigned essay early leaves time for careful revision.
Premise: Students learn the most and do their best writing when they revise carefully.
Premise: Learning and doing the best possible work increase students’ chances of academic success and of gaining knowledge and skills that will benefit them in the future.
Premise: Academic success and future benefit are worthy goals.
Conclusion: Completing an early first draft is worth the effort.
The hypothetical teacher might not actually explicitly state each of these premises. The assertion, for example, that doing well in school and learning a lot are good for students hardly needs to be emphasized. Spelling each out clearly as we have above lets us see how when we reason with an audience, we try to get our readers or listeners to accept a premise that leads to another, which in turn leads to another until eventually we reach an acceptable conclusion. Audiences must consciously or unconsciously accept each premise to follow in agreement with the writer or speaker’s reasoning.
Reasoning charted out in this way may seem like a backwards version of how you have been taught to construct an academic argument. Students typically learn to write papers that “support a thesis.” A thesis, however, even if you position it at the beginning of an essay, is actually a conclusion, a point at which audiences can only truly arrive through a well-reasoned path of statements. Simply put, the thesis statement at the beginning of a traditional academic essay can be thought of as a signpost announcing the place to which you’d like to bring your readers. The reasoning you build in your argument—sentence by sentence and statement by statement—is the road that can actually take an audience to the place you want them to be.