What is an ad-hominum attack?

Answer 1

An ad hominem is a type of logical fallacy that refers to a personal attack directed at the character of another person rather than the specifics of their argument.

An ad hominem is used in an attempt to discredit the premise of an opponent's argument by insulting or belittling them. The fallacy being that the merits of an opponent's argument are not necessarily connected to their personal character.

e.g.

John says, "Smoking is harmful to your health."

Sue says, "What do you know John? You're an idiot and you smoke too, so keep your opinion to yourself!"

Regardless if John is a smoker or an "idiot", neither criticism invalidates his argument. A thoughtful rebuttal to John would have to address what he said without attacking him.

e.g.

Provide evidence or reasoning that smoking is not harmful to ones' health.

Note: The above example also contains the logical fallacy: "Tu quoque."

Tu quoque is an attempt to invalidate an opponent's argument by pointing out that they engage in the same behaviour that they are criticizing (hypocrisy).