Back by popular demand, we continue the Fallacy Friday series with the often misunderstood ad hominem.
Simply put, it's attacking the person rather than the argument. It's saying that the person's claim is wrong
because of the person, and not because of reason or facts. It might seem obvious to avoid attacking the character of a person rather than their ideas, but it happens all too often in the heat of an argument. Sometimes a person might refuse to accept another person's statement and justify that refusal by criticizing the person. This fallacy serves as a Red Herring because it drives the attention away from the actual argument at hand.
"You claim that atheists can be moral, yet I happen to know that you beat your wife and children!"
I said that this fallacy is often misunderstood. What I mean is that calling someone names or otherwise being generally abusive toward them doesn't make your statements fallacious. It's not an ad hominem to malign your opposition -- as long as the maligning is not the basis of your argument. It can sometimes be subtle. Just pay attention to what is being objected to. Essentially the difference is "you're wrong and you're an idiot" versus "you're wrong because you're an idiot". The latter is fallacious.
Don't be abusive to try to win arguments. Remember, the truth of a statement isn't dependent upon the virtues, character, actions, or motives of the person making the claim. All too often, it seems, people justify their stance on issues based solely on what they think about the character of their opposition. That's another type of Argumentum ad Hominem: circumstantial. It's usually phrased as "Of course, that's what you'd expect him to say." We need to be careful with this kind, however. If someone is a known perjurer or liar, that fact will reduce their credibility. It won't, however, prove that their testimony is false in this case. It also won't alter the soundness of any logical arguments they may make. It's not always invalid to refer to the circumstances of an individual who is making a claim, but there are some cases in which it may throw extra skepticism onto their position.