Thank You for Arguing: Chapter 13 Summary & Analysis

So far, Heinrichs has been talking about how to get the audience to think of the speaker in a favorable light. Now, it’s time to discuss how to use logos to persuade an audience. Perhaps the most challenging aspect of arguing is not knowing enough about an issue to win. But as important as a command of the facts is, it’s not the be-all, end-all. Logos allows the skilled persuader to skip the facts and focus on rational strategy and definition. Logos is also invaluable for refuting an opponent’s argument when you lack a command of the facts: even if you don’t know everything, you’ll be able to recognize your opponent’s logical fallacies.

As it’s taught in universities, formal logic is probably too rigorous and mathematical to be of much help in day-to-day conversation, and in fact, some arguments that would be considered fallacious in a university classroom are rhetorically acceptable. Indeed, there’s an important difference between logic and logos (which simply means, “word” in Greek). Logos allows the persuader to use facts as well as values and attitudes to make a convincing case.

To understand rhetorical logic, Heinrichs looks at the syllogism, a logical technique that’s more or less useless in daily conversation. An example: “All men are mortal; Socrates is a man; therefore, Socrates is mortal.” Sometimes, businesses and marketers use more complicated syllogisms to determine the total available market for a product. For example, if a company determines that lots of people aged twenty-five to forty read a magazine, and if the magazine’s ads sell cars, then a car company might want to advertise in the magazine. Ads sometimes use fallacious syllogisms; for example, the implicit message of many car commercials is, “Babes go for people who drive our car; therefore, if you go for babes, you should buy our car.”

Logical formulations that use the structure of the syllogism fall into the category of deductive logic, beginning with a premise, applied to a specific case, in order to reach a conclusion. Another kind of logic is inductive logic, which begins with specific cases and then uses those cases to prove a premise or conclusion. For example, an inductive logician might observe that all humans born more than 150 years ago are dead, and conclude that all humans are mortal. The fictional character Sherlock Holmes was a master of deductive logic: he used his vast knowledge of premises to draw surprising, unexpected conclusions about specific people.

In a deliberative argument, the conclusion is a choice about how to behave. Many deliberative arguments use inductive logic. For example, a toothpaste ad that says, “nine out of ten doctors recommend” it is encouraging the viewer to make an induction about the product’s quality. Deliberate arguments might also use deductive logic, offering a premise in support of a specific conclusion.

Sometimes, it can be difficult to tell the difference between an argument’s conclusion and its proof. A persuader’s conclusion doesn’t always follow from their proof and premises. Once, Heinrichs had an exchange with someone who followed his blog about teaching intelligent design in schools. Heinrichs claimed that schools shouldn’t be required to teach both creationism and biology in science classes, while the follower argued that teachers should teach both theories as scientific hypotheses. Heinrichs responded by pointing out that intelligent design advocates refuse to name the designer of the universe. Therefore, there are two possibilities: 1) intelligent design advocates believe that some events have no cause, or 2) intelligent design advocates believe that a supernatural being created the universe. If 1), then intelligent design isn’t logical, and if 2), it’s not scientific; in either case, it shouldn’t be taught in science courses.

Heinrichs returns to Annie, who was trying to convince Kathy to consider voting Democratic (Kathy insisted that the Democrats would raise taxes). Annie could use induction, arguing that, since she lives in a Republican state where the taxes are high, and since Congress continues borrowing money, it’s likely that Congress will continue raising taxes. Therefore, she could say, both Democrats and Republicans will raise taxes—and it makes more sense to vote for the party that’s honest than the one that lies about taxes.

Often, the strongest arguments combine induction and deduction. A persuader can make use of the facts, but can also strengthen their point with comparisons, or even tell a story. When trying to convince a friend to play poker instead of going to a concert, you could employ all three approaches. You could remind him that he likes cigars and home cooking (facts). You could also tell him that the opera won’t allow him to drink beer, while playing poker will (comparison), or you could tell him about another friend who died at the opera (story). All three approaches could work. Heinrichs concludes by encouraging readers to scope out their significant others’ commonplaces, and try to persuade their significant others with facts, comparisons, and stories.