Sample from Chapter Five of A Becoming Critical Thinker
4.3.1 Ad hominem
One of the most common ways of trying to cast doubt on a claim or position which has been argued for by another is to criticize the person making the argument rather than the argument itself. An ad hominem is an irrelevant assertion about a person who has taken a position or made an argument with which one disagrees. The assertion about the arguer is made in the belief or hope that it will be taken as relevant evidence against the position one opposes. Rather than criticize a person's premises or reasoning, an ad hominem asserts something about the person's character, associations, occupation, hobbies, motives, mental health, likes or dislikes, etc.
The fallacy in the ad hominem is on the irrelevant nature of the appeal made, not its falsity. If what is said about the person is false, in addition to being irrelevant, two fallacies are committed, false premise and irrelevant premise. Not only do many people make ad hominem attacks, many more are seduced by them. The appeal of the ad hominem is that it puts bad doctrines (i.e., those you disagree with) into the mouths of bad people. So, one can feel that one's opponents are evil as well as stupid. Attacking a person, rather than the person's position or argument, is usually easier as well as more psychologically satisfying to the simple-minded who divide the world into two classes of people--those who agree with them and are therefore good and right, and those who disagree with them and are therefore evil and wrong.
The ad hominem is also attractive to the lazy who would rather ridicule or belittle a person than seriously examine an opposing viewpoint. The ad hominem is also a tactic of the clever manipulator of crowds, the experienced demagogue who knows how to play on the emotions of people and seduce them into transferring their attitude of disapproval for a person to a belief in disagreement with that person's position.
Examples of ad hominem appeals
--"Nietzsche's criticisms of Christianity are completely false; after all, he was insane!"
--"You shouldn't believe a word my opponent says about me since he is just bitter because I'm ahead in the polls."
--"Of course the American Dental Association advises us to have our teeth checked twice a year. Their members stand to profit quite a bit from this bit of advice. Don't listen to them."
--"Reagan's economic policies are absurd; but what should we expect from an actor."
--"We know communism is an erroneous doctrine, since the only people who adhere to it are wicked and evil."
--"Samson's views on strategic air command are wrong; what would a former employee of Disneyworld know about such matters?"
--"Why should we listen to an ignorant fool like you?"