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Critical Thinking By Example

 Chapter 6: Fallacies of Relevance
  Quiz 6.1 Quiz 6.2 Quiz 6.3 Quiz 6.4 Quiz 6.5


Material covered in this chapter

  • 6.1 Twelve fallacies of relevance.

 With a good argument, it is possible to answer “yes” to each of these questions:

1. Assuming that the premise set is acceptable, is the premise set relevant to the conclusion?

2. Assuming that the premise set is acceptable, does the premise set provide sufficient support for the conclusion?

3. Is the premise set acceptable?

A bad argument is one which answers “no” to one or more of these questions. In this chapter we will examine arguments where the answer to question 1 is “no” by examining twelve fallacies of relevancy:

6.1 Twelve Fallacies of Relevance


Fallacy of Irrelevant Reason

An argument contains this fallacy if the premise set is irrelevant to the question of whether we should accept the conclusion.

Note: the remaining eleven fallacies are specific forms of this fallacy. On quiz material, if you detect an argument that involves irrelevant reasons you should choose this fallacy only if none of the other eleven fallacies are appropriate.


Example 6.1

"Mark's shoes are black. Therefore, all polar bears are white.”

Red Herring Fallacy

This fallacy is committed when an unrelated issue is introduced into an argumentative exchange, as if it were relevant, in such a way as to shift the focus away from the original issue. 

Notice in example 6.2 how the topic quickly changes. Andy is arguing about the issue of whether the war was justified; Carlos is arguing about whether the US has done the morally right thing subsequently. The question of what the US did subsequently is irrelevant to whether the US was justified in the first instance.


 Example 6.2

Andy: "The war in Iraq is not justified, since the US only went there for oil."
Carol: "Wars are started for all sorts of reasons. The important point here is that the US has tried hard to help the Iraqi people after the war. The US did not just up and leave, but has invested billions of dollars rebuilding the nation of Iraq."

Strawperson Fallacy

This fallacy is committed when an opponent’s position is substituted for a position that is weaker and easier to criticize than the opponent’s actual position.

In example 6.3, Juanita misrepresents Juan's position: universal health care is normally understood as a theory about access to health care; in particular, a government funded scheme for making available health care services. Juanita makes it sound as if universal health care means that not only would the services be provided, but that they would be forced upon those who would refuse such services. The question of whether we have a right to refuse medical treatment is irrelevant to the question of how access to medical services ought to be distributed.

Notice too that the Strawperson fallacy diverts attention from the issue at hand, just as the Red Herring fallacy does. But it does so in a particular way: it does so by attributing a position not held by the argumentative opponent. So, the Strawperson fallacy is a specific type of the Red Herring fallacy. In other words, all Strawperson fallacies are Red Herring fallacies, but not vice versa.


Example 6.3

Juan: "We should have universal health care."
Juanita: "I don't know how you can say that Juan. Universal health care violates individual liberty. We have every right to refuse medical treatment: we don't want the state telling us what medical treatments we must receive—as if we are children."

Ad Hominem Fallacy

This fallacy occurs when (i) an opponent’s person, character or circumstance is attacked rather than the opponent’s argument, and (ii) the attack has not been shown to be relevant to the acceptability of the opponent’s argument.

In example 6.4 the author attacks both Fox’s circumstances—Fox had his license suspended—and his character—he has trouble getting along with others. The author says nothing about what reasons Fox offers for anarchism, nor why Fox’s circumstances or character are relevant to the viability of anarchism as a political doctrine.


Example 6.4

“Bob Fox's rant in favor of anarchism is just the sort of thing you would expect from someone who has had his driver's license taken away by the court and who can’t seem to get along with anyone.”


Tu Quoque Fallacy

This fallacy is committed when (i) an opponent is accused of an inconsistency between position and actions, and (ii) the inconsistency has not been shown to be relevant to the assessment of the opponent’s position.

In example 6.5 the Beastie Boys do not address Pop’s reasons for not smoking, but simply point out the inconsistency of his recommendation (don’t smoke) and his actions (he’s a smoker). Suppose Pop’s reason for the conclusion, “don’t smoke”, is that smoking causes cancer. The fact that Pop smokes does not show that this reasoning is wrong.


Example 6.5

“You gotta fight for your right to party

Your Pop caught you smoking, and he said, “No Way!”

That hypocrite smokes two packs a day.”

(The Beastie Boys)

Fallacy of Appeal to Ignorance

This fallacy is committed when (i) a position P is asserted to be true (or false) based on the fact that there is no evidence for not-P, and (ii) the fact that there is no evidence for not-P is irrelevant to the truth (or falsity) of P.

Example 6.6

Big Foot, a completely different species of hominid, exists, since no researcher has been able to show conclusively that Big Foot does not exist.

Fallacy of Guilt by Association

This fallacy occurs when a position P (or person) is attacked on the basis of an association to Q, where the association to Q is not relevant to the acceptability of P.

In example 6.7 the author tries to impugn vegetarianism by associating it with Hitler. The fact that Hitler did or believed X is not in itself relevant to whether we ought to believe or do X. After all, Hitler breathed oxygen, and presumably this is not something we ought to renounce. 

Example 6.7

“I can’t believe you support vegetarianism. Did you know that Hitler was a vegetarian?”

Fallacy of Appeal to the Majority

This fallacy occurs when a position P is said to be true because the majority believes that P, and the fact that the majority believes P is irrelevant to whether we should believe P.

Example 6.8

“You should believe in God, the vast majority of people in this great country do.”

Fallacy of Appeal to the Select Few 

This fallacy occurs when a position P is said to be true because not everyone believes P, and the fact that not everyone believes P is irrelevant to the acceptability of P.


Example 6.9

“Most people simply believe in the religion of their parents. It is a rare, stronger type, who is capable of seeing the truth of atheism.”

The Gambler’s Fallacy

This fallacy is committed when it is argued that the past has an influence on a random event

Example 6.10

“I can’t possibly leave my slot machine now! I’ve been losing for two hours straight—it has to get hot soon.”

Fallacy of Appeal to Tradition

This fallacy occurs when it is asserted that a position P is true because it has always been believed, and the tradition is not relevant to the acceptability of P.


Example 6.11

“Of course it is right to spank your children when they misbehave. My parents spanked me; their parents spanked them, and so on.”

Fallacy of Improper Appeal to an Epistemic Authority

This fallacy occurs when one or more of the following conditions are not met.

1. The authority must be identified.

2. The authority must be respected in her field.

3. The authority must be speaking about a matter in her field of expertise.

4. The matter must be one in which there is a reasonable consensus amongst the relevant experts.

In example 6.12 the first condition is not met: the authority is not identified sufficiently to identify him or her (there is more than one famous British physicist). Without knowing the identity of the physicist, it is impossible to ascertain whether he or she is respected in the field. The third condition is not met, since the question of whether we ought to genetically engineer humans is an ethical question, and there is no indication that the physicist is an expert in the realm of ethics. Finally, the fourth condition is not met, since there is no consensus amongst ethicists as to whether we ought to genetically engineer humans.

Example 6.12

“We need to genetically engineer humans to be much smarter. Don’t take my word for it, I saw a famous British physicist make this claim on television last night.”