Ad Hominem
From SkepticWiki
Contents |
[edit] Definition
The ad hominem fallacy is an informal logical fallacy, formally known as argumentum ad hominem (Latin: "argument at the person"), where a participant argues that a belief is incorrect because of some failure or flaw in the person making the argument. The most general structure of this argument runs something like the following:
- Person A claims that P
- Person B claims that there is something objectionable about person A
- Therefore, P is false.
This is a fallacy because the truth or falsity of the claim is not necessarily related to the personal qualities of the claimant.
[edit] Example
Example 1:
- Protagonist: There's nothing necessarily immoral about atheism.
- Antagonist: How can you say that when you've been married and divorced four times?
Example 2:
- Protagonist: I think that Isaac Newton is the greatest scientist that ever lived.
- Antagonist: You studied music in school! You don't know anything about science!
Example 3:
- Protagonist: California makes a much better burgundy than France.
- Antagonist: Well, of course you say that. You own a California winery.
[edit] Types of ad hominem fallacies
There are two traditional types of ad hominem fallacies:
- ad hominem (abusive)
- ad hominem circumstantial
Ad hominem (abusive) is also known as argumentum ad personam and occurs (notoriously) when one abuses one's opponent instead of arguing with them ("if you weren't such an idiot, you would realize I was correct"), but is more generally applied whenever one focuses on irrelevant but negative information about the circumstances of one's opponent. Since usually the facts do not in any way influence the standing of the person's claims, this is fallacious. This is, however, a very commonly committed fallacy.
Example:
- Protagonist: I think we should raise the minimum wage.
- Antagonist: So? You're a convicted felon!
A more subtle form of ad hominem occurs when the speaker points out that his opponent shares a belief with an obviously "evil" (or otherwise rejectable) person.
Example:
- Protagonist: Vegetarianism can be a healthy diet.
- Antagonist: That's what Hitler thought, too!
Ad hominem circumstantial is also known as poisoning the well. It occurs when someone points out that someone else is in a special position where they may be expected to believe (or to say) certain things, typically out of reasons of personal interest or advancement.
Example:
- Protagonist: I think we should raise the minimum wage.
- Antagonist: Well, of course you say that. Your job only pays minimum wage, so you would be seeing a raise in your paycheck.
Please note that although this argument is formally a logical fallacy, it is not necessarily an irrational or inappropriate response.
[edit] Exceptions to the Rule
It can sometimes be very difficult to evaluate the impact and appropriateness of an ad hominem argument, in part because the argument, although formally fallacious, is often appropriate and relevant. For example, the testimony of a convicted perjurer should probably be given little weight in a subsequent trial, simply because the perjurer has shown himself to be untrustworthy. Similarly, since people can and do act out of personal self-interest without regard to the truth, poisoning the well can be a very powerful technique for evaluating whether or not someone has an external incentive to shade the truth.
A related problem with ad hominem arguments is that frequently the people in the best position to evaluate the truth or falsity of a statement are exactly the people with experience and a vested interest. For example, a person who has lived on minimum wage jobs would know from personal experience whether or not it needed to be raised, in a way that the more affluent might not. Similarly, a person with no knowledge or experience in a particular area may not have command of enough facts to make correct statements. Argumentam ad hominem thus shades into appeal to authority in giving allowing personal characteristics to affect our assessment of the truth or falsity of a statement.
[edit] Historical Usage
Ad hominem seems to have had a quite different meaning as recently as the nineteenth century. In those days, an ad hominem argument meant an appeal to beliefs of the audience that are not, or not necessarily, shared by the arguer. For example, if an atheist was to argue with an anti-Semitic Christian by referring him to the passages in the Bible calling the Jews God's chosen people, that would be an ad hominem argument in the nineteenth century sense, since this is a consideration that should have weight with the Christian but would have no weight with the atheist making the argument. This, then, is an argument literally "to the man" (ad hominem). An example of the phrase used in such a sense may be found here.
