An ad hominem argument or attack is where the arguer advances an irrelevant criticism of the source of the opposing argument as evidence or proof that the arguer is correct:
- "You must be an idiot if you think that."
- "Of course you would say that, being a high-school dropout."
- "What lying commie-traitor blog did you get that from?"
"Name-calling" is an ad hominem technique.
Ad hominem is a form of reasoning by reputation, in that it presumes destruction of an opposing arguer's reputation also destroys the opposing argument.