Ad hominem is a term that is used to describe a personal attack made against a person. It is most widely used in law, usually in the context of an argument, where somebody attacks or challenges their opponent’s character rather than their case.
Ad hominem translates literally as ‘to the man.’ It is the shortened and more widely used version of the phrase argumentum ad hominem. The feminine form is ad feminam. It is believed to have come into English use around 1600.
It could be argued that the shortened phrase itself, meaning only ‘to the man,’ is incorrect as its literal translation is very vague. It is clearer when written as argumentum ad hominem, which translates as ‘appeal/argument to the man.’
Ad hominem should only be used as a term given to a situation when one is making an argument about the character or past deeds of their opponent which is irrelevant to the case at hand, often in an attempt to disprove their viewpoint on the basis that they are not to be trusted. Examples are as follows:
Bob: Gerbils would be great to keep as pets.
Joe: How would you know? Your goldfish died because you didn’t feed it.
Everyone around: How awful. Bob should never be allowed to keep a gerbil!
Joe: Two plus two equals four.
Bob: You must be wrong. You’ve failed every maths test you’ve ever taken.
Everyone around: Well, clearly two plus two doesn’t equal four!