Nuts and Bolts: ad hominem.

An ad hominem attack is one where an argument is attacked by reference to the person advancing it.

An ad hominem attack says that a person shouldn't be believed because he or she is ignorant/ugly/stupid/the wrong shape/the wrong class/has the wrong politics etc etc.

There may be some grounds for dismissing an argument in this way. If I were to claim that the Albanian word for porridge is qull, then pointing out that I speak no Albanian does make it rather more unlikely that I'm right. But it's still logically nonsense (and as it happens the Albanian word for porridge is qull).

The only intelligent way to counter an argument is by proving that the argument is false. That means proving that at least one of the facts upon which the argument is based is false, or that the claimed relationship between these facts is false.

On the positive side, the presence of an ad hominem attack does at least make it easy to identify at least one person who really isn't very intelligent, doesn't it.

Idiot To Spot Today: one using an ad hominem attack. Ad hominem is Latin for against the man.