Thank You for Arguing (Revised and Updated)

by Jay Heinrichs

  All logical fallacies come down to…bad logic. In the logic of deliberative argument, you have the proof and a choice. We saw in Chapter 13 how deductive logic works; it starts with what the audience knows or believes—the commonplace—and applies it to a particular situation to prove your conclusion. In deduction, the commonplace serves as your proof. The proof in induction is a set of examples.

  So, to see whether a fallacy lies hidden in an argument, ask yourself three questions:

  Does the proof hold up?

  Am I given the right number of choices?

  Does the proof lead to the conclusion?

  I suppose I should add a fourth question:

  Who cares?

  Honestly, there’s no need to care, provided you never fall for fallacies yourself. In fact, one big difference between formal logic and the art of persuasion is their attitudes toward the rules. Logical fallacies are verboten in logic, period. Commit one, and logic sounds the gong and you’re booted off the stage. (Never mind that there is no stage for formal logic, which exists only in theory.)

  Rhetoric, on the other hand, has virtually no rules. You can commit fallacies to your heart’s content, as long as you get away with them. Your audience bears the responsibility to spot them; if it does, there goes your ethos. Your audience will consider you either a crook or a fool. So before you commit a fallacy, you will want to know your fallacies.

  Besides, assuming that you have fallen for logical tricks like the rest of us, this chapter will come in handy as a defensive tool. (In Chapter 16 we’ll look at a more advanced version of logical defense.) An ability to detect a fallacy helps you protect yourself—against politicians, salespeople, diet books, doctors, and your own children. All you have to do is look for a bad proof, the wrong number of choices, or a disconnect between the proof and the conclusion.

  Bad proof includes three sins: false comparison (lumping examples into the wrong categories), bad example, and ignorance as proof (asserting that the lack of examples proves something).

  Wrong number of choices covers one essential sin, the false choice: offering just two choices when more are actually available, or merging two or three issues into one.

  Disconnect between proof and conclusion results in the tautology (in which the proof and the conclusion are identical), the red herring (a sneaky distraction), or the wrong ending (in which the proof fails to lead to the conclusion).

  I’ll throw in some fallacies along the way, if only to show you I know what I’m talking about. The seven sins show the beautiful variety of ways that people cheat, lie, and steal. Just keep in mind that they all boil down to bad proofs, wrong number of choices, or a disconnect between the proof and the conclusion.

  First Deadly Sin: The False Comparison

  Plums and grapes are purple, but their color doesn’t make purple a fruit. You need not be an Aristotle to figure that one out. But how many consumers have fallen for the same kind of fallacy?

  Made with all natural ingredients.

  What Makes This a Sin

  The examples don’t hold up. Why? Because they were slotted into the wrong category. Imagine those Venn circles. Purple is a big circle. Fruit is another big circle. Grapes fall in the overlap. But purple still won’t fit entirely within the fruit circle. All the fallacies I listed under this sin have the same wrong-circle problem.

  It may not seem like it, but the “all natural” pitch commits the “purple is a fruit” error: because an ingredient belongs to the same group as things that are good for you (natural substances, purple fruit), the ingredient also must be good for you. But botulism is natural, too, and not at all good for you. (Not to mention the sneaky syntax that implies a hyphen between “all” and “natural.” Add a gram of grape pulp and a gram of wheat germ to a doughnut’s chemical blend and voilà! All-natural ingredients. Two all-natural ingredients, to be exact.)

  You can spot the all natural fallacy by breaking it in half. “This doughnut has purple, and purple is a fruit, so you should eat this doughnut.” Purple’s fruitiness constitutes the “reason.”

  But purple isn’t a fruit, which means the proof doesn’t hold up, and the argument is spoiled. If I said, “This doughnut has a grape jelly filling, grapes are fruit, so this doughnut is a fruit,” the proof (grape jelly, grapes) would have been legit. But the argument would still be a fallacy. The proof, even a correct one, has to lead to the conclusion. Just because the doughnut has fruit doesn’t make the doughnut fruit. It’s a false comparison.

  Small children seem to have a passion for proofs, judging by their love of “why.”

  Meanings

  One category of fallacy that I don’t deal with is ambiguity, logic’s version of “Eats shoots and leaves.” The hyphen in “all-natural ingredients” commits this fallacy.

  Common Fallacy

  THE ALL NATURAL FALLACY: It assumes that members of the same family share all the same traits.

  TRY THIS IN ACADEMIA

  College administrators like to say each school is unique, but then they do all they can to imitate one another. In the 1980s, Ivy League schools began favoring candidates interested in one thing rather than the well-rounded students of tradition, and the fad spread. An alumnus who objects to the policy could ask officials what other schools use that policy, and if the administrator offers his list with a smug tone, retort, “When my kids said, ‘Everyone else does it,’ I’d tell them, ‘Don’t you want to rise above the crowd?’ ”

  PARENT: Don’t go into the living room.

  KID: Why?

  PARENT: Because the dog was sick.

  KID: Why?

  PARENT: Because your father fed it hot dogs from the table.

  KID: Why?

  PARENT: Go ask him.

  That may explain their equal love of fallacious reasoning.

  KID: Why won’t you drive me to school? All the other parents drive their kids to school.

  Other parents drive their children; therefore you should drive your child. The kid falsely compares her parents with all the others. What makes it false? For one thing, not all parents are chauffeurs; surely some make their kids take the bus. For another, her parents happen not to be the parents of the kid’s schoolmates; what is good for those others may not be good for her. How does one respond? First, you might raise the child’s self-esteem.

  PARENT: That was an Aristotelian enthymeme, dear!

  Now squash her.

  PARENT: But I see Wen Ho at the bus stop every morning. And even if all the other parents drove their kids, your proof doesn’t support your choice.

  Common Fallacy

  THE APPEAL TO POPULARITY: “Because all the other kids get to, I should, too.” The premise fails to prove the conclusion.

  Persuasion Alert

  What about persuasion by character? Isn’t any appeal to ethos an appeal to popularity? Indeed it is. This is one of the logical fallacies actually encouraged in rhetoric, as you’ll see in the next chapter.

  The kid may not understand a word you say, but she will eventually, and when she does, look out. You may never win another argument. Meantime, if you feel especially obnoxious, name the fallacy: the appeal to popularity, which legitimizes your choice by claiming that others have chosen it. My children would rather suffer an old-fashioned caning than hear me label their fallacies.

  If you simply used a parental cliché instead of logic, you yourself would be guilty of a similar fallacy.

  PARENT: What if all the other children’s parents told them to jump off a cliff? Would you follow?

  Common Fallacy

  REDUCTIO AD ABSURDUM: Reducing an argument to absurdity. The premise is unbelievable.

  John Locke, the philosopher (and rhetoric professor!) who describe
d many logical fallacies in the early 1700s, would call this shot a foul. The collective parents of an entire school are extremely unlikely to propose mass suicide, which makes your fallacy a reductio ad absurdum, reducing an argument to absurdity. You falsely compared being driven to school with jumping off a cliff. The proof crumbles and the conclusion collapses.

  Logic can do more than save you from driving your kid to school. It can also save your life.

  DRIVER: I don’t need to slow down. I haven’t had an accident yet.

  Since there are no examples here—just one adrenaline-challenged driver—you know to look for a reason. He thinks he can speed safely because he has a good driving record. Does his proof lead to his conclusion? Does the man’s perfect record keep you safe? It may increase the likelihood of an accident-free trip, but weigh that against the guy’s lead foot and, personally, I would take the bus. His claim is a form of false comparison: because what he did in the past is perfect, what he does in the future must be perfect, too. The official name for this logical error is fallacy of antecedent, but you probably won’t have the presence of mind to trot it out at eighty miles an hour. Instead, try conceding.

  Common Fallacy

  THE FALLACY OF ANTECEDENT: It never happened before, so it never will. Or it happened once, so it will happen again. Another reply to the antecedent fallacy: “That’s a long time to tease fate.” Or for a certain audience: “Your karma must be terrible.”

  YOU: I’m sure you’re a great driver, but going this fast scares me. So I’m irrational. Humor me.

  Or if you don’t mind risking road rage on top of unsafe driving, give a snappy answer.

  PROPER RHETORICAL REPLY: No one is DOA a second time!

  Another sham comparison, the false analogy, bollixes up government across this great land of ours.

  CANDIDATE: I’m a successful businessman. Elect me mayor and I’ll run a successful city.

  So the guy made a lot of money in business. The problem is that city hall is not a business. Many entrepreneurs have successful political careers, but at least as many do not. Entrepreneurs have learned the hard way that in public service, political skills count for more than business skills.

  PROPER RHETORICAL REPLY: I’ll vote for you if you give me dividends and let me sell off my shares of the city.

  False comparisons also cause very bad math.

  What’s Wrong with This Argument?

  “My dog doesn’t bite.” That’s a classic fallacy of antecedent.

  YOU: Our profits rose by 20 percent this fiscal year.

  PAL: What was your margin at the beginning of the year?

  YOU: Twelve percent before taxes.

  PAL: Wow, so your profit’s 32 percent!

  The proof is that your profits started at 12 percent and grew by 20 percent. So what’s the problem? Twelve plus 20 equals 32, right?

  Common Fallacy

  THE FALSE ANALOGY: I can do this well, so I can do that unrelated thing just as well.

  What’s Wrong with This Argument?

  When told I cut my own trees for firewood, a New Yorker gasped, “How can you make yourself do it? Someone told me they shriek when they fall.” They do sometimes, but sounding human doesn’t make them human. She committed a type of false analogy called “anthropomorphism,” also known as the pathetic fallacy. You see this fallacy in reverse when people refer to sex offenders as “predators” and other criminals as “animals.” It’s a false analogy: because they act inhumanely, they must be another species.

  The problem is called a unit fallacy, mistaking one kind of unit for another. People commit this error all the time in business. To avoid it, try to keep track of the difference between a piece of the pie and the whole pie. I give you a piece that amounts to one-eighth of a pie. Not big enough, you say. So I give you an additional tiny sliver that measures just one-fifth the size of the first piece I gave you. I’m not giving you a fifth of the pie, am I? A percentage is a piece of the pie. A percentage of a percentage (20 percent of 12 percent profit) is not a fraction of the whole. If this still confuses you, just stick to this rule: never add up percentages without a calculator.

  PROPER RHETORICAL REPLY: That 20 percent was on top of 100 percent of our profit. So we actually made 120 percent!

  A simpler version of the unit fallacy helps pad the profits on consumer goods. This box of laundry detergent sells for less than the same-sized box next to it; the cheaper box mysteriously weighs less than the costlier one. The unit cost—the amount you pay per ounce of detergent—is actually more on the “cheaper” box. The manufacturer hopes you don’t notice, and that you fail to pay attention to the unit prices on the store shelves. My wife figured she was on to that trick. One day she asked me to lug a huge box of detergent out of the car trunk. The box was so large, you had to decant some of the stuff into a smaller container so you could lift it up to the washing machine.

  Common Fallacy

  THE UNIT FALLACY: One apple plus one orange equals two apples.

  ME: Why did you buy this?

  DOROTHY SR.: It’s the super economy size. It’s cheaper.

  ME: Than what?

  DOROTHY SR.: Than the smaller sizes. If you did more of the shopping, you’d know about these things.

  That stung. I found a receipt from the previous month with a smaller box of detergent on it. I went to the basement and read the box to see how much it held. And then I found a calculator, which produced a very satisfying result.

  ME: Unless prices jumped dramatically this month, the super economy size costs 7 percent more per ounce than the regular size.

  DOROTHY SR.: Yes, but it’s a larger box, so it works out as less expensive.

  ME: No, dear, a larger box doesn’t make something cheaper. You would save money buying the smaller box.

  DOROTHY SR.: Oh.

  ME: So do you think maybe you’re sorry for saying I don’t know these things?

  DOROTHY SR.: Yes, I’m sorry. I’m very, very sorry. It’s clear that I don’t have the math skills to do the shopping. From now on, you’d probably better do it.

  Oh.

  Second Deadly Sin: The Bad Example

  Not all proofs depend on a reason or a commonplace. Many use examples—facts, comparisons, or anecdotes. You find numerous fallacies among bad examples, or examples that fail to prove the conclusion. For instance, fallacies that misuse examples keep security companies in business.

  What Makes This a Sin

  There’s a disconnect between the examples and the choice. While the examples themselves might be true and relevant, they don’t actually support the choice.

  PARENT: Seeing all those crimes on TV makes me want to lock up my kids and never let them out.

  Common Fallacy

  MISINTERPRETING THE EVIDENCE: The examples don’t support the conclusion.

  The examples don’t support the conclusion, because local television news—which depends on crime for ratings—misrepresents the crime rate. The actual rates of most crimes have been dropping for years, but perceptions of crime continue to rise. In other words, the parent uses unrepresentative examples to reach her paranoid conclusion. This is a fallacy called misinterpreting the evidence.

  PROPER RHETORICAL REPLY: Good! That’ll keep a couple more potential criminals off the streets.

  Common Fallacy

  HASTY GENERALIZATION: The argument offers too few examples to prove the point.

  An offspring of misinterpreting the evidence is the hasty generalization, which reaches vast conclusions with scanty data.

  COWORKER: That intern from Yale was great. Let’s get another Yalie.

  The proof won’t hold up. One example won’t suffice to prove that the next kid from Yale will make a good intern. There
are fifty-three hundred undergraduates at Yale, which makes the sample size of the company’s intern experiment 0.019 percent of the study population.

  PROPER RHETORICAL REPLY: Didn’t that jerk in Legal go to Yale?

  Third Deadly Sin: Ignorance as Proof

  Defense Secretary Donald Rumsfeld made this fallacy famous before the Iraq War, when he said of Saddam Hussein’s unfound weapons of mass destruction, “The absence of evidence is not evidence of absence.” Logically, at least, he was correct.

  Scientists and doctors often commit the same sin by assuming that their examples cover all possible examples—a mistake appropriately called the fallacy of ignorance: what we cannot prove, cannot exist.

  DOCTOR: There’s nothing wrong with you. The lab tests came back negative.

  Proof: The lab tests are all negative. So…