An argument against the person (ad hominem) is a type of informal fallacy that arises when the arguer ignores the real claims or issues in the argument so that what is emphasized is the character, personality, or belief of the opponent. In other words, in the argument against the man, the arguer attacks the person rather than the person’s ideas in order to drive his point.
Let us consider the example below.
Example 1
You honor, it is impossible for us not to believe that the accused of this murder case is not guilty because his father and grandfather had been convicted of murder several years ago. And besides, the accused is of bad moral reputation.
As we can see, the arguer in the example above attacks the personality of the accused instead of providing the proofs or evidence that indeed it is the accused has committed the crime. For sure, we cannot say that the accused is guilty of the crime of murder simply because he is of bad moral reputation or his father and grandfather had been convicted of murder several years ago. Again, the arguer needs to show the proofs in order to say that the accused is guilty of the crime of murder.
The following examples may help further illustrate the fallacy of argument against the person (ad hominem):
Example 2
Well now, you have heard Professor Smith tell us about the theory of evolution. But I am not surprised that he neglected to tell you that he is an atheist. How can this man speak the truth, I ask you?
Example 3
I’m not surprised that your mechanic recommends a complete engine overhaul. Do you know how much money he gets from that?
Example 4
It was his fault, officer. You can tell me by the kind of car I am driving and the kind of clothing I am wearing that I am a good citizen and would not lie. Look at the rattletrap that he is driving, and look at how he dressed. You can’t believe anything that a dirty, long-haired hippie like that man might tell you. Search his car; he probably has a pot in it.
Example 5
Franklin Putnam says he would make a good president. But he is no man for the White House; not only has he been divorced, but he is a Catholic and divorced.