How to Properly Apply the Ad Hominem

A new theory parses fair from unfair uses of personal criticism in rhetoric

By Yvonne Raley / in Scientific American

A doctor tells her patient to lose weight, and the patient thinks: "If my doctor really believed that, she wouldn't be so fat." A movie aficionado pans the latest Tom Cruise flick because Cruise is a Scientologist. A home­owner ignores a neighbor's advice on lawn care because the neighbor is a ... you name it: Democrat, ­Re­publican, Christian or atheist. These examples illustrate classic uses of ad hominem attacks, in which an argument is rejected, or advanced, based on a personal characteristic of an individual rather than on reasons for or against the claim itself.

Putting the focus on the arguer or person being discussed can distract us from the issues that matter. Rather than concentrating on an individual's character, we should, in these cases, be asking ourselves questions such as, Is the doctor's advice medically sound? Is the Cruise film entertaining? Is the neighbor's lawn healthy? Meanwhile ad hominem attacks can also unfairly discredit an individual, especially because such critiques are often effective.

Although ad hominem arguments have long been considered errors in reasoning, a recent analysis suggests that this is not always the case. In his new book, Media Argumentation: Dialectic, Persuasion, and Rhetoric, University of Winnipeg philosopher Douglas Walton proposes that fallacies such as the ad hominem are better understood as perversions or corruptions of perfectly good arguments. Regarding the ad hominem, Walton contends that although such attacks are usually fallacious, they can be legitimate when a character critique is directly or indirect­ly related to the point being articulated.

If Walton is right, distinguishing clearly between these cases is important to evaluating the validity of statements people make to us about others. Good or fair uses of ad hominem critiques should, in fact, persuade us, whereas unwarranted uses should not.

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