“The fallacy of ad hominem (Latin: against the man”) is the assertion that someone’s argument or viewpoint should be discounted because of character flaws that have nothing to do with the issues at hand. It is a fallacy because it ties the outcome of an argument to a question or set of questions that are not at issue. Arguments, not arguers, are the proper subject of a debate.”—Reading the World: Ideas that Matter

I am very familiar with this textbook definition of the ad hominem argument. I wrote it. It is part of my rhetoric textbook used in several hundred colleges and universities in the United States and Canada to teach students about (among other things) the right and wrong ways to frame arguments. Arguments must stand or fall on their own merits; the character of the arguer does not matter.

Except when it does.

I don’t usually muddy these waters in freshman composition, but the fact is that ad hominem arguments are very often the best and most logical responses to another person’s claims. This is true because most arguers place their own character, expertise, or credibility at issue when they make a claim. If somebody supports an argument with a pro hominem argument (which we normally call an “appeal to authority”) then the ad hominem argument becomes both a necessary and a proper response.

And this brings us to Dick Cheney and the Iraq War.

In a recent article in New York Magazine, Johnathan Chait, who I consider one of the most intelligent pundits around, falls into a logical trap that I call the Ad Hominem Fallacy Fallacy. This happens when somebody overcorrects for the ad hominem bias by labeling a legitimate challenge to authority as an ad hominem attack:

"When you’re trying to set the terms for a debate, you have to do it in a fair way. Demanding accountability for failed predictions is fair. Insisting that only your ideological opponents be held accountable is not fair. Nor is it easy to see what purpose is served by insisting certain people ought to be ignored. The way arguments are supposed to work is that the argument itself, not the identity of the arguer, makes the case. We shouldn’t disregard Dick Cheney’s arguments about Iraq because he’s Dick Cheney. We should disregard them because they’re stupid."

This is exactly how it works out in theory. Dick Cheney has a right to make arguments about the current situation in Iraq, and it simply does not matter whether he was wrong before, or whether he made serious mistakes in office, or that he may have committed war crimes, or whatever. All that matters is what he is saying now, and we must judge his arguments on their own merits. If Adolph Hitler said the world was round, that would not make it flat. And so on.

His Dick Cheneyness is an inherent part of his current argument — which relies almost entirely on his claims of experience, expertise, and moral character. And it is precisely because he is making these claims that his experience, expertise, and moral character must be part of the debate.

It is not a fallacy to directly rebut claims that have actually been made. If somebody makes an abstract statistical argument about the effectiveness of a certain medical procedure, then their evidence must stand by itself. However, when somebody says, “trust me, I’m a doctor,” then both their integrity and their medical school history become completely relevant to the question at hand.

We are in a rhetorical position where it would be very difficult to commit the ad hominem fallacy even if we tried. The architect of one of the worst foreign policy disasters in America’s history is standing before us once again and saying, “trust me, I’m Dick Cheney.” It seems to me that the only rational response to such a request is, “because you are Dick Cheney, we will never trust you again.”