"Argument against the man" The Fallacy of Persona

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Argumentum ad Hominem
Translation: "Argument against the man" (Latin)
Alias: The Fallacy of Personal Attack

Type: Genetic Fallacy

Exposition:
A debater commits the Ad Hominem Fallacy when he introduces irrelevant personal premisses about his opponent. Such red herrings may successfully distract the opponent or the audience from the topic of the debate.

Exposure:
Ad Hominem is the most familiar of informal fallacies, and—with the possible exception of Undistributed Middle—the most familiar logical fallacy of them all. It is also one of the most used and abused of fallacies, and both justified and unjustified accusations of Ad Hominem abound in any debate.

The phrase "ad hominem argument" is sometimes used to refer to a very different type of argument, namely, one that uses premisses accepted by the opposition to argue for a position. In other words, if you are trying to convince someone of something, using premisses that the person accepts—whether or not you believe them yourself. This is not necessarily a fallacious argument, and is often rhetorically effective.

Subfallacies:
Abusive: An Abusive Ad Hominem occurs when an attack on the character or other irrelevant personal qualities of the opposition—such as appearance—is offered as evidence against her position. Such attacks are often effective distractions ("red herrings"), because the opponent feels it necessary to defend herself, thus being distracted from the topic of the debate.
Circumstantial: A Circumstantial Ad Hominem is one in which some irrelevant personal circumstance surrounding the opponent is offered as evidence against the opponent's position. This fallacy is often introduced by phrases such as: "Of course, that's what you'd expect him to say." The fallacy claims that the only reason why he argues as he does is because of personal circumstances, such as standing to gain from the argument's acceptance.
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—often to nothing! 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.

Poisoning the Well

Poisoning the Well


Description
Discredit the other person before they speak. Or discredit the topic or argument that they may support.

There are many ways of discrediting the person. Call them names. Talk about their lies. Show them to be unworthy. Tell how they are unintelligent, crazy or otherwise undesirable, inferior and not worth listening to, let alone believing.

To discredit the topic or argument, indicate how it is patently absurd, proven to be false or that only fools would support it.


Tu Quoque
Source:
S. Morris Engel, With Good Reason: An Introduction to Informal Fallacies (Fifth Edition) (St. Martin's, 1994), pp. 198-206.

Resources:
Alan Brinton, "The Ad Hominem" in Fallacies: Classical and Contemporary Readings, edited by Hans V. Hanson and Robert C. Pinto (Penn State Press, 1995), pp. 213-222.
Frans H. Van Eemeren & Rob Grootendoorst, "Argumentum Ad Hominem: A Pragma-Dialectical Case in Point" in Fallacies: Classical and Contemporary Readings, edited by Hans V. Hanson & Robert C. Pinto (Penn State Press, 1995), pp. 223-228.
Douglas N. Walton, Arguer's Position: A Pragmatic Study of Ad Hominem Attack, Criticism, Refutation, and Fallacy (Greenwood, 1985).
Acknowledgement:
The Da Vinci sketch art print is available from AllPosters.com.

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Genetic Fallacy
Type: Red Herring
Exposition:
The Genetic Fallacy is the most general fallacy of irrelevancy involving the origins or history of an idea. It is fallacious to either endorse or condemn an idea based on its past—rather than on its present—merits or demerits, unless its past in some way affects its present value. For instance, the origin of evidence can be quite relevant to its evaluation, especially in historical investigations. The origin of testimony—whether first hand, hearsay, or rumor—carries weight in evaluating it.

In contrast, the value of many scientific ideas can be objectively evaluated by established techniques, so that the origin or history of the idea is irrelevant to its value. For example, the chemist Kekulé claimed to have discovered the ring structure of the benzene molecule during a dream of a snake biting its own tail. While this fact is psychologically interesting, it is neither evidence for nor against the hypothesis that benzene has a ring structure, which had to be tested for correctness.

So, the Genetic Fallacy is committed whenever an idea is evaluated based upon irrelevant history. To offer Kekulé's dream as evidence either for or against the benzene ring hypothesis would be to commit the Genetic Fallacy.

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Appeal to Misleading Authority
Alias:
Appeal to Authority
Argument from Authority
Argumentum ad Verecundiam
("Argument from respect/modesty", Latin)
Ipse Dixit ("He, himself, said it", Latin)
Type: Genetic Fallacy
Form:
Authority A believes that P is true.
Therefore, P is true.

Example:
Cheating by the Soviets

"Barry Schweid of the Associated Press, in his efforts to criticize President Reagan's space-based defense against Soviet missiles, came up with a report from some Stanford University group that claimed to find little evidence of cheating by the Soviet Union on arms-control treaties.

"Where were they when Secretary of Defense Caspar Weinberger and George Shultz, secretary of state, and several members of our military forces went on TV and described and enumerated the different times and ways that the Soviet Union has cheated on the 1972 Anti-Ballistic Missile Treaty?

"Does Schweid really believe that the group at Stanford is more knowledgeable about U.S. arms-control policy than all our military experts, with Congress thrown in for good measure? If I thought that was true, I wouldn't sleep much tonight. And I doubt if he would either."
(Middleton B. Freeman, Louisville, "Letters From Readers", The Courier-Journal, April 1, 1987.)

Analysis

Exposition:
We must often rely upon expert opinion when drawing conclusions about technical matters where we lack the time or expertise to form an informed opinion. For instance, those of us who are not physicians usually rely upon those who are when making medical decisions, and we are not wrong to do so. There are, however, four major ways in which such arguments can go wrong:

An appeal to authority may be inappropriate in a couple of ways:
It is unnecessary. If a question can be answered by observation or calculation, an argument from authority is not needed. Since arguments from authority are weaker than more direct evidence, go look or figure it out for yourself.
The renaissance rebellion against the authority of Aristotle and the Bible played an important role in the scientific revolution. Aristotle was so respected in the Middle Ages that his word was taken on empirical issues which were easily decidable by observation. The scientific revolution moved away from this over-reliance on authority towards the use of observation and experiment.

Similarly, the Bible has been invoked as an authority on empirical or mathematical questions. A particularly amusing example is the claim that the value of pi can be determined to be 3 based on certain passages in the Old Testament. The value of pi, however, is a mathematical question which can be answered by calculation, and appeal to authority is irrelevant.

It is impossible. About some issues there simply is no expert opinion, and an appeal to authority is bound to commit the next type of mistake. For example, many self-help books are written every year by self-proclaimed "experts" on matters for which there is no expertise.
The "authority" cited is not an expert on the issue, that is, the person who supplies the opinion is not an expert at all, or is one, but in an unrelated area. The now-classic example is the old television commercial which began: "I'm not a doctor, but I play one on TV...." The actor then proceeded to recommend a brand of medicine.
The authority is an expert, but is not disinterested. That is, the expert is biased towards one side of the issue, and his opinion is thereby untrustworthy.
For example, suppose that a medical scientist testifies that ambient cigarette smoke does not pose a hazard to the health of non-smokers exposed to it. Suppose, further, that it turns out that the scientist is an employee of a cigarette company. Clearly, the scientist has a powerful bias in favor of the position that he is taking which calls into question his objectivity.

There is an old saying: "A doctor who treats himself has a fool for a patient," and a similar version for attorneys: "A lawyer who defends himself has a fool for a client." Why should these be true if the doctor or lawyer is an expert on medicine or the law? The answer is that we are all biased in our own causes. A physician who tries to diagnose his own illness is more likely to make a mistake out of wishful thinking, or out of fear, than another physician would be.

While the authority is an expert, his opinion is unrepresentative of expert opinion on the subject. The fact is that if one looks hard enough, it is possible to find an expert who supports virtually any position that one wishes to take. "Such is human perversity", to quote Lewis Carroll. This is a great boon for debaters, who can easily find expert opinion on their side of a question, whatever that side is, but it is confusing for those of us listening to debates and trying to form an opinion.
Experts are human beings, after all, and human beings err, even in their area of expertise. This is one reason why it is a good idea to get a second opinion about major medical matters, and even a third if the first two disagree. While most people understand the sense behind seeking a second opinion when their life or health is at stake, they are frequently willing to accept a single, unrepresentative opinion on other matters, especially when that opinion agrees with their own bias.

Bias (problem 3) is one source of unrepresentativeness. For instance, the opinions of cigarette company scientists tend to be unrepresentative of expert opinion on the health consequences of smoking because they are biased to minimize such consequences. For the general problem of judging the opinion of a population based upon a sample, see the Fallacy of Unrepresentative Sample.

To sum up these points in a positive manner, before relying upon expert opinion, go through the following checklist:

Is this a matter which I can decide without appeal to expert opinion? If the answer is "yes", then do so. If "no", go to the next question:
Is this a matter upon which expert opinion is available? If not, then your opinion will be as good as anyone else's. If so, proceed to the next question:
Is the authority an expert on the matter? If not, then why listen? If so, go on:
Is the authority biased towards one side? If so, the authority may be untrustworthy. At the very least, before accepting the authority's word seek a second, unbiased opinion. That is, go to the last question:
Is the authority's opinion representative of expert opinion? If not, then find out what the expert consensus is and rely on that. If so, then you may rationally rely upon the authority's opinion.
If an argument to authority cannot pass these five tests, then it commits the fallacy of appeal to misleading authority.

Exposure:
Since not all arguments from expert opinion are fallacious, some authorities on logic have taken to labelling this fallacy as "appeal to inappropriate or irrelevant or questionable authority", rather than the traditional name "appeal to authority". For the same reason, I use the name "appeal to misleading authority" to distinguish fallacious from non-fallacious arguments from authority.
Sources:
Irving M. Copi & Carl Cohen, Introduction to Logic (Tenth Edition) (Prentice Hall, 1998), pp. 165-166.
T. Edward Damer, Attacking Faulty Reasoning: A Practical Guide to Fallacy-Free Arguments (Third Edition) (Wadsworth, 1995), pp. 31-34.
Resources:
James Bachman, "Appeal to Authority", in Fallacies: Classical and Contemporary Readings, edited by Hans V. Hanson and Robert C. Pinto (Penn State Press, 1995), pp. 274-286.
Robert Todd Carroll, "Appeal to Authority", The Skeptic's Dictionary.
Case Study: The Hollow Man: The Strange Case of David Manning

Reader Response:
"A thought about the 'Appeal to Misleading Authority' fallacy. In your section on this fallacy, you propose a five-point checklist for determining if an appeal to authority is appropriate. I would suggest a sixth: 'Is there opinion available from this expert on this subject?'. In other words, does the authority actually support the appeal, or are the authority's words being taken out of context or otherwise misunderstood?"―John Congdon
I have seen similar checklists for evaluating arguments from authority which include such a point. However, there are two reasons why there is no such point on my list:

Certainly, when evaluating an appeal to authority for cogency, the first step one should take is to verify that the authority is cited correctly. If the authority's position is either misquoted, misrepresented, or misunderstood, then the argument will be uncogent due to a false premiss. However, having a false premiss is not, in my view, a logical fault, but is a factual fault. Factual errors can be just as important as logical errors, but they are distinct types of error.
Quoting out of context is a fallacy in its own right. It is uncommon to treat quoting out of context as a separate fallacy, but I do so because it is a more common error than a number of traditional fallacies. Because I treat it separately, I don't include it in the checklist for appeal to misleading authority. However, it is true that quoting out of context often occurs in appeals to authority, so it is something to watch out for.
Acknowledgements:
My thanks to Dr. Gary Foulk for critiquing this entry, though I did not take all of his advice. Also, thanks to readers Stephen Beecroft, Brandon Milam, and Sarah Natividad for criticizing the Analysis of the Example, which led me to revise it.


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Analysis of the Example:
The example commits the fallacy of Ad Verecundiam because most of the authorities cited are not disinterested (problem 3). Weinberger and Shultz were members of Reagan's cabinet, and could be counted on to support his proposals. Similarly, members of the armed forces are not encouraged to disagree with the Commander-In-Chief, especially when the services stand to benefit from the proposal. The one exception in this letter is Congress, which was controlled by the opposition party, but this evidence is added as an afterthought and is difficult to assess. In contrast, the Stanford University group cited by Schweid was disinterested, so far as we can tell from the letter.

Some readers have suggested that the Stanford University group might be ideologically biased against a space-based missile defense. However, even if true—and there is no evidence from the letter that it is—members of the administration were likely to be ideologically biased in favor of such a system. So, ideological bias is a tie between the two sources. The problem with the administration authorities is not ideological bias, but institutional bias in favor of an employer. The Stanford University group lacks that kind of bias.