Species of Fallacious Arguments

The common fallacies are usefully divided into three categories: Fallacies of Relevance, Fallacies of Unacceptable Premises, and Formal Fallacies. Many of these fallacies have Latin names, perhaps because medieval philosophers were particularly interested in informal logic. You don’t need to know the Latin names: what’s important is being able to recognize the fallacies.

Fallacies of Relevance

Fallacies of relevance offer reasons to believe a claim or conclusion that, on examination, turn out to not in fact be reasons to do any such thing.

1. The ‘Who are you to talk?’, or ‘You Too’, or Tu Quoque Fallacy

• Rejecting an argument because the person advancing it fails to practice what he or she preaches.

Doctor: You should quit smoking. It’s a serious health risk.
Patient: Look who’s talking! I’ll quit when you quit.

2. The Red Herring Fallacy.

• An arguer tries to sidetrack his or her audience by raising an irrelevant issue and then claims that the original issue has effectively been settled by the irrelevant diversion.

There is a good deal of talk these days about the need to eliminate pesticides from our fruits and vegetables. But many of these foods are essential to our health. Carrots are an excellent source of vitamin A, broccoli is rich in iron, and oranges and grapefruits have lots of Vitamin C.

3. The Strawman Fallacy.

• Someone distorts or caricatures an opponent’s arguments or views, and then attacks the weakened version rather than the real argument.

Margaret: “We have to do something about greenhouse gases. The government should raise vehicle fuel efficiency standards to cut down the amount of CO2 we release over the next 20 years”.
Roger: “Margaret’s solution would be a disaster. It would kill the economy. How would people get to work without cars?”

4. The Ad Hominem or ‘At the Person’ Fallacy.

• Rejecting someone’s argument by attacking the person rather than evaluating their argument on its merits.

“Dear Editor, The current campaign against combining drinking with driving is terrorising law-abiding people. Many law-abiding people are cutting their alcohol consumption because they are afraid of being caught by random breath testing. But research shows that the average drink-driver in a fatal accident has an average blood alcohol level of more than twice the legal limit. The current campaign against drinking and driving is failing to achieve what should be our top priority; getting the heavy and hardened drinkers of the road.” Douglas Myers. CEO, Dominion Breweries.

“Dear Editor, I read Doug Myer’s letter yesterday but he is the CEO of a major brewing company! He has a vested interest in keeping alcohol sales up, and the anti-drink-driving campaign threatens to reduce alcohol sales. We shouldn’t take any notice of his views about drinking and driving”.

“Burton Wexler, spokesperson for the American Tobacco Growers Association, has argued that there is no credible scientific evidence that cigarette smoking causes cancer. Given Wexler’s obvious bias in the matter, his arguments should be treated with care.”

5. Fallacious Appeal to Authority.

• Relying upon the view of apparent (as opposed to genuine) authorities to settle the truth of a statement or argument.

Richard Long, a respected retired New Zealand newsreader featured in advertising campaigns for Hanover Finance. Long had no financial expertise.

1. Is the authority a genuine authority: are they experts?
2. Are they giving advice in the areas within which they are a genuine authority? (We should listen to actors about acting; not so much about investing or medicine).
3. Is there a broad consensus among authorities in the area? If not, we should not decide to believe X solely because an authority says X is true, since other genuine authorities say that X isn’t true.
4. Is the authority speaking sincerely (they might be giving an endorsement because they’re paid to do so) and are they free of obvious bias?

6. The Fallacy of Composition.

• Arguing that what is true of the parts must be true of the whole. (All of the parts of the object O have the property P. Therefore, O has the property P.)

Rugby players Ma’a Nonu, Jerome Kaino and Charles Piatau are all great players. In 2012, they all played for the Auckland Blues. Therefore, the 2012 Auckland Blues were a great team.

“Should we not assume that just as the eye, hand, the foot, and in general each part of the body clearly has its own proper function, so man too has some function over and above the function of his parts?” Aristotle, Nichomachean Ethics

7. The Fallacy of Division.

• Arguing that what is true of the whole must be true of the parts. (The opposite of the fallacy of composition: Object O has the property P. Therefore all the parts of the object O have the property P.)

Men are, on average, taller than women. Therefore, Tim is taller than Maria Sharapova.

8. Equivocation.

• A key word is used in two or more senses in the same argument and the apparent success of the argument depends on the shift in meaning.

Any law can be repealed by the proper legal authority. The law of gravity is a law. Therefore, the law of gravity can be repealed by the proper legal authority.

“The only proof capable of being given that an object is visible, is that people actually see it. The only proof that a sound is audible, is that people hear it… In like manner, I apprehend, the sole evidence it is possible to produce that anything is desirable, is that people do actually desire it… [T]his being a fact, we have not only all the proof which the case admits of, but all which it is possible to require, that happiness is a good. ” John Stuart Mill, Utilitarianism.

9. Appeal to Popularity.

• Arguing that a claim must be true because lots of people believe it.

Essential Bible Blog’s Top 10 Reason the Bible is True:

Reason 8. Leader Acceptance. A majority of the greatest leaders and thinkers in history have affirmed the truth and impact of the Bible.

Reason 9. Global Influence. The Bible has had a greater influence on the laws, art, ethics, music and literature of world civilization than any other book in history.

10. Appeal to Tradition.

• Like appeals to popularity except the appeal is to how long something has been believed, rather than to the number of people who have believed it

People have believed in astrology for a very long time, therefore, it must be true.

11. Appeal to Ignorance: Argumentum Ad Ignorantiam.

• The arguer asserts that a claim must be true because no one has proven it false, or that a claim must be false because no one has proven it to be true.

There must be intelligent life on other planets: No one has proven there isn’t.

There isn’t any intelligent life on other planets: No one has proven there is.

12. Appeals to Emotion – e.g., pity, affection.

• An arguer attempts to evoke feelings of pity or compassion, when such feelings are not logically relevant to the arguer’s conclusion.

Student to Lecturer: I know I missed most of the lectures and all of my tutorials. But my family will be really upset if I fail this course. Can’t you find a few more marks?

Daughter: Can we get a puppy?
Father: No.
Daughter: If you loved me, we’d get a puppy.

Daughter: A puppy would grow up and protect us. Can’t we get a puppy?
Father: No.
Daughter: If you wanted to keep us safe you’d get a puppy! You don’t care about us!

Fallacies of Unacceptable Premises

13. Begging the Question.

• In philosophy, unlike in many other areas, ‘begging the question’ does not mean ‘raises a question which must be answered’. In philosophy, when someone begs the question, they state or assume as a premise the very thing they are trying to prove as a conclusion.

Arthur: God exists.
Barbara: How do you know?
Arthur: Because it says so in the Bible.
Barbara: How to you know what the Bible says is true?
Arthur: Because the Bible is divinely inspired. Everything it says is true.

14. False Dilemma or False Dichotomy.

• Occurs when an argument presents two options and gives the impression that only one of them may be true, never both, and that there are no other possible options.

Either Shakespeare wrote all the plays attributed to him, or Bacon did. There’s good reason to think Shakespeare didn’t write all the plays attributed to him. Therefore, Bacon wrote all the plays attributed to Shakespeare.

15. Decision Point Fallacy or the Sorites Paradox.

• Sometimes the conditions that make the use of a term appropriate vary along a continuum and there is no sharp cut off between circumstances in which the term is correctly applied and those in which it is not.

One grain of wheat doesn’t make a heap. Suppose 1 million does. Take one away. Surely we still have a heap: if a million makes a heap, surely 999,999 does too. One grain can’t turn a heap into a non-heap. Take another away. Surely we still have a heap: if 999,999 does, surely 999,998 does too. One grain … etc. Take another away. Surely we still have a heap …. etc etc etc.
But if one grain doesn’t make a difference, then it seems that we will be forced to conclude that 1 grain does make a heap. But that means we can’t talk about heaps of wheat at all: we don’t know when we can describe a collection of grains of wheat as a heap and when we can’t.

At conception an embryo is not a person. At birth, a baby is a person. There is no non-arbitrary way of determining exactly when the embryo became a person. Therefore, there is no moral difference between the embryo and the baby at birth.

16. The Slippery Slope Fallacy.

• Arguers say that an innocent-looking first step should not be taken because once taken, it will be impossible not to take the next, and the next, and so on, until you end up in a position you don’t want to be in.

Don’t get a credit card. If you do, you’ll be tempted to spend money you don’t have. Then you’ll max out your card. Then you’ll be in real debt. You’ll have to start gambling in the hope of getting a big win. But you’ll normally lose. Then you’ll have to steal money to cover your losses. Then your partner will leave you. And you won’t be able to feed the dog, and it’ll die. And it would be bad if the dog died. So you mustn’t get a credit card.

17. Hasty Generalisations.

• Arguer draws a general conclusion from a sample that is biased or too small.

The oldest woman in the world, Jeanne Calment (122 years, 164 days) smoked until her early 110s. Therefore smoking isn’t really bad for you.

Andrew Wakefield claimed to have shown a correlation between the MMR vaccine, bowel disorders and autism, but – among other flaws – his research focused on children already thought to have the conditions he claimed were caused by the vaccine.

18. Faulty Analogies.

• The conclusion of an argument depends upon a comparison between two (or more) things that are not actually similar in relevant respects, or without pointing out how the two differ and why it does or does not matter. (See reasoning by analogy in Week 6).

I need a new car. My last three cars have all been reliable, and they were blue. So I’m going to buy a blue car.

A letter to the editor following a report someone had been turned away from an after-hours medical clinic because she couldn’t pay for treatment for her feverish, vomiting child:
“Why do people attend private clinics for medical treatment with insufficient funds to cover fees? Do these same people go to the petrol station, fill up, toss $5 out the window and say “I’ll be back with the rest later,” or perhaps after dining out one evening, pay for the meal and promise to return next week, month or year to pay for the wine? I think not. The answer is simple – don’t go to private clinics.”

19. And … the Fallacy Fallacy!

• The fallacy of inferring that merely because an argument contains a fallacy, its conclusion must be false.

Bob told me that I shouldn’t steal because everyone knows that stealing is wrong, but I recognised immediately that argument contained the popularity fallacy, so I concluded that it was ok to steal the apple.

Formal Fallacies

20. Affirming the consequent.

\(\begin{array}{ll} \text{P1} & \text{If there’s an intruder, then Brutus will bark. }\\ \text{P2} & \text{Brutus hasn’t barked. }\\ &\text{Therefore,}\\ \text{C} & \text{There’s no intruder.} \end{array}\)

\(\begin{array}{ll} \text{P1} & \text{If there’s an intruder, then Brutus will bark. }\\ \text{P2} & \text{Brutus has barked.}\\ &\text{Therefore,}\\ \text{C} & \text{There’s an intruder.} \end{array}\)

21. Denying the Antecedent.

\(\begin{array}{ll} \text{P1} & \text{If it barks, then it’s a dog.}\\ \text{P2} & \text{It’s barking.}\\ &\text{Therefore,}\\ \text{C} & \text{It’s a dog.} \end{array}\)

\(\begin{array}{ll} \text{P1} & \text{If it barks, then it’s a dog.}\\ \text{P2} & \text{It’s not barking.}\\ &\text{Therefore,}\\ \text{C} & \text{It isn’t a dog.} \end{array}\)

That’s not valid. The first premise says that if something barks then it’s a dog (i.e., that only dogs bark), but it doesn’t say that every dog barks. So we can’t be sure that the conclusion of this second argument is true even if the premises are true. It might be true that something doesn’t bark (i.e., the antecedent is false, or denied, as the second premise says), but is a dog.