Monday, January 2, 2012

ad hominem

The ad hominem fallacy occurs when one mentions things about a person in an attempt to show that the person’s argument is flawed.  An argument stands or falls depending on whether its premises adequately support its conclusion. (The premises are the reasons given as evidence; the conclusion is the claim the arguer is defending.) Characteristics, associations, past history, motives, etc. of the person making the argument are irrelevant to whether premises support a conclusion.

Fallacies are errors in reasoning. The error in the argumentum ad hominem is in attacking the person making an argument in an attempt to undermine that person’s argument. Arguments are refuted only by showing that the premises do not provide adequate evidence for the conclusion. No argument is refuted by showing that the arguer is flawed or biased. Good people with good intentions can argue fallaciously and bad people with evil motives can argue cogently.

The ad hominem fallacy has nothing to do with trying to undermine the credibility of a witness by providing evidence of his untrustworthiness. Testifying is not arguing. It is reasonable and relevant to question the motives or character of someone who is testifying. Testimony stands or falls on whether the claims made are believable. Jurors may draw conclusions based on testimony, but the one testifying is making claims not arguments. The ad hominem fallacy occurs only when one attempts to refute another person’s argument by focusing on the arguer rather than the argument.

Perhaps the most common ad hominem fallacy is to attack the motives of the person making the argument. Critics of judicial decisions often cite suspected motives of a judge that might bias his or her decision, as if the judge’s motives were relevant to the cogency of the judge’s argument for making the decision. Even a biased judge can make a cogent argument in defense of a ruling. In any case, you can’t refute an argument by accusing the arguer of being biased. The bias of the arguer is irrelevant to whether the premises support the conclusion. People with good motives sometimes make fallacious arguments, and people with bad motives sometimes make good arguments.

Another common ad hominem is to try to refute an argument by claiming that the arguer stands to profit from others accepting the argument. For example, pointing out that physicians are paid for giving vaccinations or that pharmaceutical firms profit from the sale of vaccines is irrelevant to refuting the argument that children should get vaccinated according to a standard recommended vaccination schedule because of the health benefits to both the children and others.

A favorite ad hominem of those who do not like the arguments of defenders of scientific medicine against the use of such practices as distant healing, homeopathy, or acupuncture is to claim that those who practice scientific medicine oppose alternative medicine because it cuts into their profits. The same fallacious appeal is often made by opponents of  so-called alternative health practices. Presumably, anyone who makes a living from providing health care expects to profit from it. So what?

There are times when it is relevant to refer to a person’s character, associations, occupation, hobbies, motives, mental health, likes or dislikes, but refuting an argument isn’t one of them. If I make an argument defending the claim that 9/11 was not an inside job by the Bush administration but the work of a conspiracy by a group of Islamic jihadists associated with the international terrorist group al-Qaeda, you do not refute my argument by making claims about me. It doesn’t matter whether your claims are true. I may be a supporter of Bush’s foreign policy, I may be an old man who wants to believe his pension is secure, I may not be an engineer or an explosives experts. But none of that matters when trying to refute my argument. To refute my argument, you must show that my evidence is insufficient, that it is based on false or questionable assumptions, that the evidence I present is irrelevant, that I’ve omitted important evidence, or that I’ve given improper weight to various pieces of evidence. An argument’s cogency depends on the evidence presented for the claims defended, not on the character, associations, interests, motives, beliefs, or anything else about the person making the argument.

It may be true that I’m a skeptic, an atheist, and a liberal, but none of those facts are relevant to whether any argument I make is a good one. Pointing out what one considers negative personal matters poisons the well; it suggests the argument is defective because the arguer is flawed. But even the most evil or stupid person in the world can make a good argument: it all depends on the premises presented and the conclusion defended. No argument ever became a good argument simply by putting it in the mouth of a good person. When attacking arguments, personal matters should be ignored.

A favorite form of poisoning the well is to sprinkle value judgments throughout one's rebuttal. For example: "I can't believe they let you teach critical thinking. Your standards are so low that you are a danger to your students."


I once publicly criticized a scientist’s published paper that claimed his experiments had provided good evidence that a parrot he tested has psychic abilities. The scientist in question did not respond to a single criticism I made of his methodology or reasoning. Instead, he reverted to several ad hominem comments. Here is a sampling of those comments:

“Carroll is a committed skeptic who is strongly motivated to try and discredit the positively and statistically significant results of these tests, which imply some form of unexplained communication between Aimee and N’kisi.”
Carroll is “a committed ideologist who wants to censor what the public gets to know.”
“Of course he is free to dismiss with contempt any research he doesn’t like, but he is wrong to mislead his readers by pretending to be scientific.”
“Carroll’s comment is deliberately misleading.”
“Carroll has no scientific credentials, and he gets carried away by his strong beliefs and dogmatic zeal. His style of analysis is amateur and pretentious; his intentions are polemical.”
All of the above claims may be true—I don’t think they are; that is a separate issue—but they are irrelevant to whether my criticisms of the scientist’s work are cogent.

One of the more deceptive ad hominem attacks is to accuse another arguer unjustly of the ad hominem while making an ad hominem attack oneself.  In response to criticisms I made of Steven F. Hayward’s analysis of the emails stolen from the University of East Anglia’s Climatic Research Unit (Keeping a cool head about global warming), an anonymous critic wrote: “Your defense of 'Climategate' (I HATE THAT TERM) wandered off into ad hominem attacks on conservatives. Science is in trouble when your political beliefs determine your scientific opinion…. A skeptic goes into denial when we need honesty.” I had accused Hayward of being politically motivated, but I was not trying to refute his claims. Rather I was trying to explain why he seemed not to care about the science at all and why he might distort and exaggerate the material in the emails to fit his preconceived ideas about climate change and the scientists whose data support anthropogenic global warming. Hayward titled his piece to include reference to “a corrupt cabal of global warming alarmists.” That bit of poison in the well was a reference to the scientists who hold the consensus view regarding anthropogenic climate change. Hayward refers to the hacking and theft of the East Anglia emails as a “document leak” and recklessly speculates that the documents may have been “leaked” by a “whistleblower from the inside.” My real concern, though, was with Hayward’s argument against the consensus view on climate change and his characterization of the stolen emails as revealing a conspiracy by corrupt scientists. I offered reasons for my criticisms. I didn’t rely on my charge of his being politically motivated to make my case.

A common rhetorical ploy is the false charge of ad hominem to divert attention away from criticism. Dr. Francine Shapiro responded to criticism of her eye movement desensitization processing therapy (EMDR) by claiming that the criticisms were ad hominem and without merit. One of the criticisms she considered an ad hominem was that the therapy worked with blind people, and so there must be something going on besides the trick of having the patient move her eyes back and forth while following a light or pencil held by the therapist. The criticism is substantive and about her therapy; it is not about her.

I have an entry in The Skeptic’s Dictionary that is critical of EMDR. I don’t claim the therapy doesn’t help anyone. I claim that the packaging of the therapy is deceptive. It is actually a form of cognitive behavioral therapy, which has a track record of empirical validation. EMDR makes claims about some sort of magical transformation of the brain by having a person follow with her eyes the movements of the therapist’s hand. A patient who found EMDR helpful responded to my article, but said nothing of substance about my criticisms. She asked the rhetorical question: “Are all of your books critical about things you know nothing about?” She also wrote: “There are also exercises to do with your mind between the sessions. But, hey, you never took the training to learn that, did you? You never had PTSD so bad that every waking moment was agony, did you?” True enough, but irrelevant to my argument that Shapiro is offering cognitive behavioral therapy, which is not new with her. In fact, the patient/critic supports my point by noting that the therapy includes exercises “with your mind” between sessions. My critic continued with more ad hominem claims: “I should have known you’d be a philosophy PhD, a breed of smarty that typically enjoys criticizing more than learning.” For good measure, she got in one more jab: “Good grief, man. Your logic skills are atrocious. How on earth did you ever get a professorship in philosophy?” In addition to her ad hominem cascade, this critic also committed the straw man fallacy, which I will cover in this blog somewhere down the line. She wrote: “You don’t benefit anyone by trying to convince people that EMDR doesn’t work.” As noted, I never claimed that EMDR doesn’t work. She’s attacking a position I do not hold.

When Dr. Mary Lefkowitz, who argues against Afrocentrism in her book Not Out of Africa, tried to debate the issue with some college students, the African-American moderator asked her: “How many times have you been to Africa, Professor Lefkowitz?” Whether Lefkowitz has been to Africa is irrelevant to the cogency of her arguments against the idea that African-Americans should trace their roots back to ancient Egypt because it was dominated by a race of black Africans.

Another favorite rhetorical ploy of those who use the ad hominem fallacy is to completely ignore the arguments made against something they believe in and simply call the one criticizing their belief “closed-minded.” Whether I’m closed-minded or open-minded, my arguments stand or fall by the reasons I give for my conclusions. Even a closed-minded person can make a cogent argument. He may even make money from it and he may be making the argument only because he thinks the homeopath he is refuting is the ugliest person he has ever met. So what? Do the reasons he gives provide adequate support for the conclusion of his argument? That's all that should matter in evaluating arguments.


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