1. What general principles underlie this chapter's categories of pseudoreasoning?

2. Is there a simple way of telling one type of ad hominem attack from another?

3. Does the label "ad hominem" really imply that we can't discount anyone's character flaws when deciding on moral issues?

1. What general principles underlie this chapter's categories of pseudoreasoning?

If you divide this chapter into two sections, the types of the ad hominem and everything else, you can see the ways in which fallacies begin with some sort of legitimate reasoning.

Ad hominem fallacies bear a certain resemblance to the concern over a source's credibility discussed in Chapter 3. Very often, considering the source of information provides us with a good reason not to give it much weight.

In the fable of the boy who cried "Wolf!" the townspeople who finally stopped rushing to help him were justified in ignoring his shouts, because he had repeatedly demonstrated his unreliability.

The ad hominem goes inappropriately beyond this habit of weighing a speaker's credibility in its habit of denying the claim instead of not accepting it. When I refuse to accept a claim, I am keeping my mind open; when I deny it, I commit myself to the contrary claim. Even the fable of the hoax-happy boy shows this fact, because in the end a real wolf did chase him. If the townspeople had inferred from his shouts that no wolf was present they would have been reasoning fallaciously, despite their sound reasons for not inferring that a wolf was present. Anyone may stumble upon the truth, even if for the wrong reasons. (For the more complicated case of moral assertions, see the last question in this section.)

The remaining fallacies lie even closer to good methods of argumentation; for this reason, many of them are fallacies that people fall into inadvertently, with no desire to mislead or change the subject. (Ad hominem criticisms have a way of arising out of ill will, with a bias toward defamation of character.)

In just about every dispute, for example, one side faces a greater burden of proof than the other. One ought to require one's opponents to substantiate what they say, if any burden of proof lies with them; the fallacious application of this principle crosses a line that is often hard to see.

Likewise, straw man fallacies may arise unintentionally when you try to apply the excellent practice of stating and rebutting someone else's view. Complex, difficult, or obscurely presented positions find themselves mistreated in this process.

The slippery slope and false dilemma get much of their power from their own similarity to sound reasoning. A slippery slope scenario condemns an action or position because of its consequences; thus it begins with an unimpeachable pattern of argument. "Don't run into the street because a car might hit you" argues against a kind of action because of what can or probably will follow. Even reasoning closer to the slippery slope may make good sense (see "Tips on Applications" below). The slippery slope turns fallacious not because of its inherent structure, but because it rests on false or unsubstantiated predictions about likely consequences.

Finally, a false dilemma works as well as it does by resembling a true dilemma. In cases of a pair of alternatives that exhaust all possibilities, failing to agree with one binds you to agreeing with the other. Again, the structure of the argument commits no fallacy--for this reason, you should take care not to call just any appeal to a pair of alternatives a false dilemma. When you can show that a further alternative exists, however, you have a false dilemma.

2. Is there a simple way of telling one type of ad hominem attack from another?

Excessive fussing over classification is not the purpose of studying fallacies. Very seldom does anything hinge on whether you have spotted the precise name for a fallacy. Still, the different subcategories of the ad hominem do possess distinguishing marks.

In practical terms, it helps to eliminate obviously inapplicable possibilities. For instance, when a person is being talked about without reference to a larger group that person belongs to, you may rule out the circumstantial ad hominem. The two other specialized versions of this fallacy are the inconsistency ad hominem and poisoning the well. The former requires some allegation of inconsistency, whereas the latter characteristically looks ahead to what you are likely to hear from a person.

When none of the above holds, the ad hominem in question probably counts as a personal attack. If pressed, you can fit most ad hominems under the broad construal of the genetic fallacy as any appeal to the origins of a claim. However, the genetic fallacy more precisely invokes a culture's first development of an idea--for example, "You can't trust the concept of equality, since it was invented by white male slaveholders."

Finally, more than one category might apply to a case. This is true for two reasons. First, the categories themselves are not always logically independent of one another; nor do they need to be independent to help us understand fallacies. Second, spurious attacks on a position have a way of firing like shotguns, leveling a number of different criticisms in the hopes that one will hit the target. If you can, look for the category that fits best; when there is no such category, the fault may lie in the nature of things.

3. Does the label "ad hominem" really imply that we can't discount anyone's character flaws when deciding on moral issues?

Ad hominem attacks call for the greatest delicacy in cases of moral assertion. Certainly we feel entitled to ignore self-righteous posturing from a degenerate. But it is important to keep in mind what does follow from someone else's failings and what does not.

When a man you know to be habitually adulterous loudly condemns someone else's infidelity, you may well call him a hypocrite. You also have good reason to think that his hypocrisy makes him worse than if he committed his adultery in shame and embarrassment. It may be time for him to stop talking. But these are all judgments about him, not about the truth of what he is saying.

Take a more difficult case: An embezzler criticizes you for eating in an expensive restaurant, when the world is full of hungry children. You are likely to reply that such moral judgments require credibility, that weighing personal gratification against the needs of others is a task for one with a more finely honed ethical sensibility than the embezzler possesses. After all, morality is not theory alone.

Even so, the embezzler's lack of credibility does not demonstrate that the claim in question is false. It gives you a reason to discount or dismiss the criticism, but not to believe the opposite. That is, you may stop worrying about eating in expensive restaurants, but you haven't shown that it is right.

If the ethical ad hominem ever really works, it works when an unreliable person advises you that something you worried about is actually all right. Suppose someone who habitually lies to get out of work tells you, "A little white lie this time won't hurt." You think, maybe correctly, that it was probably a few little lies that got this person into the habit of dishonesty, and that if you follow this one piece of well-meant advice you might find yourself in the same bad habit. Now you have a reason to believe that what the person said is false. Such reasoning is sometimes sound. It is no excuse for indulging in wanton personal attacks, but it does illustrate the subtlety of ad hominem reasoning in moral contexts.