The ad hominem fallacy occurs when an arguer attacks a person of the opposing view by attributing negative characteristics or motives to that person, and from this concludes that the person's opinion on the topic must be wrong. It is thereby an attempt to move away from the original topic, to make the conversation be about that person's alleged faults or shortcomings.

Here is an example:

"You should ignore this news article because the writer is a brand new journalist right out of school who has no experience in this subject matter."

The problem here is that these criticisms of the writer do not address the actual claims in the article at all.

There are many variations of ad hominem, and it is especially common in political (or any ideologically charged) debates. The attack may depict the opponent as stupid, evil, silly, naive, selfish or otherwise debased, in an effort to get the audience to dismiss that person's statement(s).

A general template of this fallacy is:

1. Person A who holds opinion B has negative trait C.

2. Therefore, opinion B is false.