T. Parent

Some Informal Argument Fallacies

Fallacies are frequent mistakes people make in argumentation. Each fallacy listed here, specifically, makes the argument deductively invalid (except petitio principii; see below). Yet in every case, the premises never rationally compel you to accept the conclusion. 

But note: If an argument is fallacious, it does not follow that its conclusion is false.* After all, I can give a bad argument for a conclusion that happens to be true. (e.g. “The moon is made of ranch dressing. So, Mexico is in North America.”) Thus, when you identify a fallacy in an argument, that doesn’t mean the conclusion is false; rather, it means that the argument does not effectively prove its conclusion.

1. Red Herring Fallacies

The Appeal to Emotion: Argument Ad Populum

Instead of giving reasons, this kind of argument just uses expressive language for provoking sympathy or antagonism toward a particular claim.

You should not oppose President Bush. It is Unamerican

This isn’t a good argument; it’s just rhetoric. If we were to try to construct some sort of valid argument out of this, it would be patently absurd. The argument would rest on the premise that you cannot be a patriot if you do not agree with everything Bush believes.

Some types of argument ad populum have their own name that indicates the kind of emotion they attempt to exploit. (Ad misericordiam evokes pity; ad in terrorem inspires fear; ad odium provokes spite, and so on.)

The Appeal to the Majority: Ad Majoritatum

Instead of giving reasons, this kind of argument just cites popular opinion in order to compel your acceptance of a conclusion.

You should love High School Musical. Everyone else does.

This is trying to intimidate you into accepting an opinion, by identifying it as the majority opinion. But of course, the majority can be wrong.

Yet sometimes appealing to majority opinion is legitimate, as when the opinion of the majority bears directly on the truth of the conclusion. Consider:

Most voters preferred Obama over McCain. Therefore, Obama won the presidency.

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*Otherwise, you would commit (what some call) the “fallacy fallacy.”

The Appeal to Force: Argument Ad Baculum:

This fallacy occurs when there is a threat of some kind (e.g. brutality) if one does not accept the conclusion.

Communism is wrong. If you disagree, I’ll prosecute you as a traitor.

This is just trying to scare you into accepting the conclusion. The threat here does not show that communism is wrong.

Character Assassination: Argument Ad Hominem

This is the fallacy of attacking a view by attacking the person who holds it.

Clinton’s views on conducting domestic affairs can’t be right. After all, he can’t even conduct himself.

It is quite possible for someone to be a brilliant at domestic policy, yet be a lousy person. (There have in fact been some U.S. presidents like this.) Thus, the details of the person’s character, in this case, are irrelevant.

Of course, sometimes character traits are relevant. For example, the fact that Clinton cheats on his wife would support the claim that he is not a great moral leader (though it may not necessarily imply this). So again, not all arguments ad hominem are completely wrong-headed.

The Appeal to Authority: Argument Ad Verecundiam

When an argument appeals to something said by an authority.

You should vote for Obama. Brett Favre endorsed him, after all.

No matter whom you cite, the truth of a conclusion never follows from someone’s saying so.

BUT: If you cite a legitimate authority, you then have some reason for believing the conclusion. Yet often the trick is deciding when you have such an authority. The rule of thumb is that someone is a legitimate authority to the extent that she is in a better position than “the person on the street” to discern the truth of the matter.

The Argument from Ignorance: Argument Ad Ignorantiam

When a proposition is argued to be true because it has not been proven false OR when a proposition is argued to be false because it has not been proven true

There are no alien life forms because no one has proven that there are.

The fact that we have not proven anything about aliens does not show either way whether there are aliens. Our ignorance just shows that our ignorance about the existence of aliens.

BUT: An argument from ignorance is not always inappropriate. Consider:

We should not say that the accused committed the murder because no one has proven it.

This sort of argument relies on the suppressed yet plausible premise that it is better to let the guilty go free than to punish the innocent.

Red Herring

An argument is a “red herring” when it introduces an irrelevant or secondary subject, and thereby diverts attention from the main issue. Usually, the red herring is an issue about which people have strong opinions, so that people are less likely to notice how their attention is being diverted.

Look officer, I wasn’t speeding—after all, I’m on my way to volunteer at the homeless shelter. 

In this case, where I am going is clearly irrelevant to how fast I was going there.

It is plausible to see all of the preceding fallacies as special cases of the “red herring” fallacy. (So for example, an argument ad hominem introduces an irrelevant matter, viz., the character of the opponent, and thereby diverts attention from the main issue.) However, the speeding example would be an example of a “red herring” which is not classifiable as an ad hominem, nor an ad ignorantium, nor an ad majoritatum, [etc].

2. Fallacies of Causation

Cum hoc; ergo, propter hoc “With the thing; therefore, because of the thing”

This is the fallacy of inferring that x caused y, from the premise that x and y are correlated. Thus, the fallacy assumes falsely that “Correlation implies causation”

Our study finds that people with clinical depression are more likely to be vegetarian. Therefore, depression influences someone’s decision to be a vegetarian.

The conclusion does not follow from the premise, since it is possible that the correlation here is accidental. Alternatively, it may be that being a vegetarian causes you to be depressed (instead of the other way around).

Note, however, that some cases of Cum hoc; ergo, propter hoc are legitimate as abductive arguments. Depression and suicide are correlated, for example, and it is plausible to infer abductively that this is because depression causes suicide.

Genetic Fallacy
To commit the genetic fallacy is to argue that an idea is misguided, because of its suspicious origins (i.e. its genesis).

Taxation by the government is wrong. After all, in the Middle Ages, the practice was used by the ruling class to exploit working peasants.

Taxation may have a shady history, but it is still possible that it is the best policy, all things considered. Its dubious history in some cases may serve as defeasible evidence of its wrongness—but its wrongness does not strictly follow from its history. (After all, even bad circumstances can cause good things.)

3. Part-Whole Fallacies

The Fallacy of Division

This is the fallacy of inferring that the parts of x must have a certain feature, from the premise that x as a whole has that feature.

Big Corporation lost a lot of money this year. That means each financial advisor in the corporation is responsible for losing the company’s money..

Just because the Corporation lost money doesn’t mean that each financial advisor in the company lost the company some of its money. It is even possible that some financial advisors might have made quite a bit of money for the company, if the losses generated by other advisors were greater.

The Fallacy of Composition

This is the fallacy of inferring that x as a whole must have a certain feature, from the premise that its parts individually have that feature.

Each individual in Big Corporation has a right to free speech. Therefore, Big Corporation itself has a right to free speech.

The argument here is invalid. Although the premise may be true, corporations generally do not have a civil or human right to say whatever they want in selling their products.

4. Other Informal Fallacies

Nirvana Fallacy

This is the fallacy of inferring that x is bad, from the premise that x is imperfect.

Affirmative Action should be abolished, since it causes animosity between the races and the sexes.

Just because affirmative action has a downside does not prove that it is better to forego it. After all, the downside of abolishing affirmative action may be much worse. Though again, a downside to affirmative action can possibly serve as evidence that it should be discontinued. (But of course, one would need to weigh the evidence on the other side of the issue as well, before making up your mind.)

Equivocation

To equivocate is to switch between at least two meanings of a single word or phrase—accidentally or deliberately—so that the argument appears sound.

I see that there is no greatest prime number. Since seeing is done with the eyes, it is with my eyes that I see there is no greatest prime number.

Here the argument is invalid due to the equivocation on “seeing.” One can see with the eyes, but also we sometimes use ‘see’ to mean (roughly) “understand” or “recognize.”

“Straw-Man” Argument

To give a “straw man” argument is to argue against a mere caricature of your opponent’s view. In such an argument, you build your opponent out of “straw” so that she or he is easily knocked down.

It is silly to oppose cloning technology. Anyone who does so is telling us to “go back to the caves” and live in ignorance.

Straw man arguments are fallacious, since if you only discredit a simplified version of a view, it of course doesn’t follow that the more sophisticated version is absurd.

Circular Argument, or “Begging the Question”: Petitio Principii

To beg the question is to assume the truth of what one seeks to prove, in the effort to prove it.

God exists, since the Bible says so. After all, every word of the Bible is true, since the Bible was revealed to us by God.

This argument assumes there is a God who has revealed the Bible to us. But that is what the argument is trying to prove, i.e. that God exists. So the argument won't convince anyone who doesn't already believe in God. The argument goes in a circle: It starts from the very claim it wants as a conclusion.

[Note: The mass media has developed a bastardized use of the phrase “to beg the question” where it means roughly “to raise the question.” This is not how the phrase is used in academic philosophy.]

N.B. Begging the question is a unique fallacy in that, technically speaking, question-begging arguments are valid. (In a circular argument, if all the premises are true, then trivially, the conclusion is true since the conclusion is assumed in the premises.) Nevertheless, circular arguments are still fallacious because they are ineffective in proving their conclusions. A “proof” that appeals to its conclusion as a premise does not really function to prove that conclusion.