Tuesday, May 5, 2009

Fallacy of the Week #3

First, perfunctory apologies for the recent hiatus. Now.

The fallacy I'd like to begin with today is called argumentum ad hominem. It is a type of non sequitur, which is an exceedingly broad category of error and which, therefore, comprises many subtypes. You're committing a non sequitur fallacy whenever you make irrelevant or unsubstantiated claims, or when you make excessively large leaps of inference. A few examples of non sequitur errors:
(1) Jack: I think we should nationalize the banks.
     Jim:  The moon may or may not be made of cheese.

(2) If you like yams, you'll probably hate Beethoven.
Note that even if the claim you're making is true (it is tautologically true to claim that "Object X has or does not have Trait Y"), it can still be irrelevant.

So, back to the ad hominem. Over time, two different kinds of bad arguments have been called ad hominems:
(1) In the past, an ad hominem argument was one that appealed to the audience's emotions -- their sympathy, pride, compassion, greed, etc. These days, this fallacy is unimaginitively called appeal to emotion.
(2) More recently, an ad hominem argument is one that challenges a source's character and uses that as justification for rejecting that source's claims (i.e., "Jill likes yams, so we shouldn't listen to heropinions on politics").
As is usually the case with such common "errors," they're so common because they're not always errors. It is sometimes quite reasonable to argue in a way very similar to this. Consider the following:
(1) Jill likes yams, so we shouldn't listen to her opinions on politics.
(2) Jill likes yams, so we shouldn't listen to her opinions on what to have for dinner.
Now, (1) is clearly an example of a non sequitur -- there's no reasonable connection between having terrible taste and being qualified to make political decisions. But (2) is not a non sequitur -- there is a reasonable connection between having terrible taste and being qualified to make culinary decisions. Generally speaking, if you attempt either (1) or (2), you will probably be called out for using an ad hominem. If what you tried was (1), then you should probably just hang your head in shame and fall upon your sword. But if what you tried was (2), then you have a defense.

You see, there's a substantive difference between impeaching someone's character and impeaching their qualifications. Suppose, for example, that I had written and published a treatise on quantum mechanics, or Sumerian cuneiform, or whatever. You would be wrong to respond,
Peter's an asshole, so this is all bunk. (I'll even bet he likes yams.)
This is because whether or not I'm an asshole (and whether or not I have terrible taste) has no bearing on my hypothetical explanation of quantum mechanics or cuneiform. However, you would be perfectly justified in responding,
Peter doesn't know anything about quantum mechanics or Sumerian cuneiform, so this is all bunk.
This is because my knowledge of a subject does have bearing on my attempts to hold discourse on that subject.

All of this is pretty straightforward. The amiguity really arises because we so rarely bother to pay attention to what we're actually talking about, and even when we are paying attention, it's not always easy to know. In academic discourse, we usually know whether we're talking about literary analysis or class struggle or the potential effects of nanotechnology on medicine, because we usually enter that discourse with intent and awareness. But in "real life," in a world where political and religious ideologies mingle with social norms, economic conditions, Hollywood, the manufacture of needs, and so on... well, it really is legitimately difficult to figure out where and why your opponent stands on the issues, and what the issues are in the first place.

It gets a little more complicated because there are definitely times when we want to feel justified in impeaching someone's character -- as a rule, we're not even going to bother listening to someone's positions on education reform if we know (or believe) him to be a murderer, a rapist, a child molestor, etc. Formally, we are wrong in doing so, unless the topic of discourse is relevant to the prior offense. But we don't really care -- in extreme cases, we generally reserve the freedom to reject someone's arguments on the basis of their character.

It gets a little more complicated still because it's unclear what constitutes an extreme case. Schoolteachers? Probably not. Cannibals? Probably. Drug traffickers? Probably. Politicians? Probably not. Gays? Apparently so, for a lot of people.

And for an extra dose of complexity: sometimes, the very things we use to impeach someone's credibility/qualification on a subject -- to exclude them from a given discourse -- are the things that make them participate in that discourse. For example, a claim like
Jill is gay, so we should ignore her opinions on legalizing gay marriage [on the grounds of her obvious bias]
is admissible given the guidelines we've established so far. Her gayness does have bearing on her position on gay marriage. But is this really grounds to dismiss those opinions?

So the moral of the story is this: pay attention. Pay attention to who says what and why. Pay attention to the accusation -- both to its veracity ("Does Tim like yams?") and its defensibility ("Is liking yams really such a failing?" [... yes, yes it is]). Pay attention to whether or not you're dealing with an extreme case, as well as to the potential differences with regard to what constitutes such an extreme case.

And just remember... if after all this, someone continues to disagree with you, it's probably because they're stupid.

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