Informal Logic and the Ad Hominem Fallacy


There are many types of logical fallacies one discovers when talking about critical thinking. Some rely on formal logic such as the enthymeme or rhetorical syllogism, and others rely on what are called informal fallacies. These are fallacies not based directly on logic but rather often deal with emotions or what could be referred to as sleights of hand. One informal fallacy that has a lot of variation is called the Ad Hominem fallacy which mean literally “against the man.” Here are the main variations of the Ad Hominem fallacies.

 Ad Hominem Abusive

This fallacy is the best known of the Ad Hominem fallacies. This informal logical fallacy attacks the person rather than an individual’s personal position. An example of the Ad Hominem fallacy is the following: Henry cannot have any good ideas about financial planning because Henry is a drunk. The argument tells one nothing useful about whether Henry is a competent financial planner or not but rather attacks him personally to discredit him.

Ad Hominem Circumstantial.

This too is an attack on ones character but is less direct than the Ad Hominem abusive. An example of this might be “union support raising the workers` wages will most likely increase the pay of the labor union representatives.” The implication is that the union representative efforts to increase labor pay is only because the union representative wants to pad their own pockets.

Ad Hominem “Tu Quoque” or “you too” fallacy.

One might argue for example that one shouldn’t steal. Some may cheat on their taxes. A father might tell his son that it is wrong to steal. His son might say back to him that “you steal on your taxes so who are you to tell me about stealing?” The assertion by the son is that since dad does it it is ok for him to do it. Yet this ignores the fact that stealing is wrong in any circumstances.

Ad Hominem Inconsistency

An example might be when a politician claims that there should be no new taxes. Yet later in ones career that same person might vote to raise taxes. Such a person might be accused of being unreliable and even not worthy of trust. This ignores the fact that the financial circumstances of the country may have changed and therefore at this time raising taxes may have been prudent and warranted. Yet with this fallacy the implication can be that the politician is untrustworthy or ever dishonest.

Ad Hominem Poisoning the Well.

Someone might claim that such and such homosexual “in this case doesn’t have AIDS”. The insinuation here is that being homosexual (especially this homosexual) is associated with AIDS. While the claim does not directly say this person has ever been exposed to AIDS, an association is drawn between this individual and AIDS. This can be used to further attack ones character.

Positive Ad Hominem Fallacy.

Just as someone’s integrity can be attacked by the Ad Hominem, the Ad Hominem can (theoretically) also be used to establish virtue. For example one might say that so and so goes to church every Sunday and therefore it is unlikely that the person falsified accounting entries at the company where the accused is the controller. But anyone is capable of falsifying accounting entries, even those that go to church.

Sources:

  • Copi, Irving, and Cohen, Carl. Introduction to Logic. New Jersey: Prentice Hall, 1998.
  • Hurley, Patrick. A Concise introduction to Logic. Belmont: Wadsworth 2000.

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Doug Frame

I am a former professor who taught for almost 10 years. I have a BA and an MA in Philosophy. I enjoy writing about philosophy but ever more so I enjoy writing philosophy.

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