Occasional Logic - Ad Hominem

I'm going to be posting tidbits of logic now and then under the title of Occasional Logic. I was going to call it Daily Logic, but then I'd have to commit to doing it every day, which I don't know if I'll be able to do. Plus, I'd probably run out of logic if I did it every day. (Pun intended.)

I'll be focusing on the common fallacies, at least for now. I'll be getting most of my info from wikipedia and adding some things here and there. Here's today's bit:

Ad Hominem

An ad hominem argument, also known as argumentum ad hominem (Latin, literally "argument to the man") or attacking the messenger, is a logical fallacy that involves replying to an argument or assertion by attacking the person presenting the argument or assertion rather than the argument itself.

A (fallacious) ad hominem argument has the basic form:

A makes claim B;
there is something objectionable about A,
therefore claim B is false.


Here's my own example:

Joe: "...and therefore I believe the tires on your car are faulty."
Bill: "Well of course you'd think that, you work for a different tire company!"
Joe: "What does that matter? What about the reasons I gave you?"
Bill: "Your reasons don't count, you work for the competitor so you have to say my tires are faulty."

The fact that Joe works for another tire company shouldn't really come into play. If his arguments are sound then they should be able to stand on their own. In this case, Bill is automatically disregarding any possible argument made by Joe simply because of his employment. Argumentum Ad Hominem.