Ad hominem

An ad hominem argument, also known as argumentum ad hominem (Latin, literally "argument to the man") or attacking the messenger, is a logical fallacy that involves replying to an argument or assertion by attacking the person presenting the argument or assertion rather than the argument itself.

The derived neologism ad feminam is more specifically used to refer to sexist prejudice directed towards women. (For example, "Their recourse ... to ad feminam attacks evidences the chilly climate for women's leadership on campus.") Ad hominem does not pertain to the male sex, as homo in Latin refers to all humans; thus certain usage of "ad feminam" may be considered redundant, or even erroneous:

• "... in which both or multiple parties ... avoid ad hominem and ad feminam judgements ..." (Barbara Levy Simon)
• "Almost any ad hominem (or, in this case, ad feminam) response ..." (Marsha M Linehan)

Ad hominem as logical fallacy

A (fallacious) ad hominem argument has the basic form:

1. A makes claim B;
2. there is something objectionable about A,
3. therefore claim B is false.

The first statement is called a 'factual claim' and is the pivot point of much debate. The last statement is referred to as an 'inferential claim' and represents the reasoning process. There are two types of inferential claim, explicit and implicit. Arguments that (fallaciously) rely on the positive aspects of the person for the truth of the conclusion are discussed under appeal to authority.

Ad hominem is one of the best-known of the logical fallacies usually enumerated in introductory logic and critical thinking textbooks. Both the fallacy itself, and accusations of having committed it, are often brandished in actual discourse (see also Argument from fallacy). As a technique of rhetoric, it is powerful and used often, despite its lack of subtlety.

Usage

An ad hominem fallacy consists of asserting that someone's argument is wrong and/or they are wrong to argue at all purely because of something discreditable/not-authoritative about the person or those persons cited by them rather than addressing the soundness of the argument itself. The implication is that the person's argument and/or ability to argue correctly lacks authority. Merely insulting another person in the middle of otherwise rational discourse does not necessarily constitute an ad hominem fallacy. It must be clear that the purpose of the characterization is to discredit the person offering the argument, and, specifically, to invite others to discount his arguments. In the past, the term ad hominem was sometimes used more literally, to describe an argument that was based on an individual, or to describe any personal attack. But this is not how the meaning of the term is typically introduced in modern logic and rhetoric textbooks, and logicians and rhetoricians are widely agreed that this use is incorrect.

Examples:

"You claim that this man is innocent, but you cannot be trusted since you are a criminal as well."

"You feel that abortion should be legal, but I disagree because you are uneducated and poor."

Not all ad hominem attacks are insulting:

Example:

"Paula says the umpire made the correct call, but this is false because Paula is too important to pay attention to the game."

This is an ad hominem fallacy, even though it is saying something positive about the person, because it is addressing the person and not the topic in dispute.

Ironically, accusing an opponent of ad hominem can itself be an example of ad hominem if it is worded as an insult: "I'm not going to stand here and let him insult me!" or "My opponent is resorting to logical fallacy to win." or "Since he is out of good argument, he's attacking me." (partial Argument from silence)

Validity

Ad hominem is fallacious when applied to deduction, and not the evidence (or premise) of an argument. Evidence may be doubted or rejected based on the source for reasons of credibility, but to doubt or reject a deduction based on the source is the ad hominem fallacy.

Premises discrediting the person can exist in valid arguments, when the person being criticized is the sole source for a piece of evidence used in one of his arguments.

1. A committed perjury when he said Q
2. We should not accept testimony for which perjury was committed
3. therefore, A 's testimony for Q should be rejected

Subtypes

Three traditionally identified varieties are ad hominem abusive, ad hominem circumstantial, and ad hominem tu quoque.

Ad hominem abusive

Ad hominem abusive (also called argumentum ad personam) usually and most notoriously involves insulting one's opponent, but can also involve pointing out factual but damning character flaws or actions. The reason that this is fallacious is that — usually, anyway — insults and even damaging facts simply do not undermine what logical support there might be for one's opponent's arguments or assertions; argumentum ad personam short-circuits these potential arguments from logic in favor of a direct attack on the opponent's authority.

Example:

"You can't believe Jack when he says there is no god because he doesn't even have a job."

Example 2: This can be called the internet example, or the childish example. Somebody disproves a troll, or a bully's argument, and they respond with: "Yeah, but you're gay!." The logical fallacy is that because the person is accused of being homosexual, their argument is invalid.

Ad hominem circumstantial

Ad hominem circumstantial involves pointing out that someone is in circumstances such that he is disposed to take a particular position. Essentially, circumstantial ad hominem constitutes an attack on the bias of a person. The reason that this is fallacious is that it simply does not make one's opponent's arguments, from a logical point of view, any less credible to point out that one's opponent is disposed to argue that way. Such arguments are not necessarily irrational, but are not correct in strict logic. This illustrates one of the differences between rationality and logic.

Examples:

"Tobacco company representatives are wrong when they say smoking doesn't seriously affect your health, because they're just defending their own multi-million-dollar financial interests."

"He's physically addicted to nicotine. Of course he defends smoking!”

The Mandy Rice-Davies ploy, "Well, he would [say that], wouldn't he?" is a superb use of this fallacy.

This form of the fallacy needs to be distinguished from criticisms directed at testimony, which are not fallacious, since pointing out that someone stands to gain from testifying a certain way would tend to cast doubt upon that testimony.

For instance, when a celebrity endorses a product, it is usually in return for money, which lowers the evidentiary value of such an endorsement. In contrast, the fact that an arguer may gain in some way from an argument's acceptance does not affect the evidentiary value of the argument, for arguments can and do stand or fall on their own merits.

Ad hominem tu quoque

Ad hominem tu quoque (literally, "at the person, you too") could be called the "hypocrisy" argument. It occurs when a person's claim is dismissed or concluded as false either because the claim is about actions the claimant or another individual has engaged in too, or because the claim is inconsistent with other claims that the person has made. The tu quoque fallacy mimics the legitimate use of the principle of ethical symmetry. The error is that while expressing "fair play" sentiments, what the argument is actually advocating is "equal rights for foul play." In "fair play", if one reasoner is not entitled to use a particular appeal, then no other reasoner may use it either. It does not entitle reasoners to use illegitimate appeals because other reasoners have used, possibly without challenge, similar illegitimate appeals. That the illegitimate appeal has been used before does not make it legitimate.

You-too version

This form of the argument is as follows:

A makes criticism P.

A is also guilty of P.

Therefore, P is dismissed.

This is an instance of the two wrongs make a right fallacy.

Example:

"You cannot accuse me of libel because you yourself have also been convicted of libel."

"You cannot complain about my smoking because you smoke too."

United States: the Soviet Union's human rights record is questionable.

Soviet Union: And you are lynching Negroes.

Inconsistency version

This form of the argument is as follows:

A makes claim P.

A has also made claims which are inconsistent with P.

Therefore, P is false (or is dismissed).

If the conclusion is that "P is false", then this is a logical fallacy because the conclusion that P is false does not follow from the premises; even if A has made past claims which are inconsistent with P, it does not necessarily prove that P is either true or false.

Example:

"You say airplanes are able to fly because of the laws of physics, but this is false because twenty years ago you also said airplanes fly because of magic."

"US Democrats say that we shouldn't participate in war in Iraq, but they supported it after 9/11."

"US Republicans say that CIA intelligence is faulty, but they relied on it when we sent troops to Iraq."

Taxonomy

This form of the argumentum ad hominem is a genetic fallacy and red herring, and is often but not necessarily an appeal to emotion. Argumentum ad hominem includes poisoning the well.

See also

• "And you are lynching Negroes"
• fundamental attribution error
• validity