It has been said that metaphysics is the finding of bad reasons for what we believe on instinct. -- W. Somerset Maugham, The Summing UpBrandon at Siris has written a number of good posts over the years on the taxonomy, lore, and misuse of the notion of fallacy. Having stumbled, not long ago, on his article in First Things on Reification, I was moved to the following few reflections (not as deep as his), when I encountered this cutely-illustrated Little Book of Bad Arguments recently and was struck again by how much this word "fallacy" is abused, and used to abuse. (It is not sufficient, to refute an contention, to say, "But that's a slippery slope argument!" One must say why, in any particular case, the particular slippery slope argument is not compelling.)
The book gives an example of the "fallacy of irrelevant authority": "Astrology was practiced by technologically advanced civilizations such as the Ancient Chinese. Therefore, it must be true." Put this way, of course, this is clearly fallacious. But the observation that "Astrology was practiced by technologically advanced civilizations such as the Ancient Chinese" might well feature as an exhibit in a set of arguments aiming to demonstrate the plausibility of astrology. It functions more or less as a kind of testimonial, as in a court of law or in a résumé. It is meant to establish the credentials of astrology in light of the fact that it is associated with a culture we have, presumably, other grounds for respecting. "Practiced by the ancient Chinese" here serves as an index, not (on pain of fallacy) as proof. (One possible rejoinder here, of course can be, "Yes, so was foot-binding," which presumably would press the champion of astrology to explain why the precedent matters in one case and not -- let us hope -- in the other).
One sees a variation on this from time to time in what amounts to informal "expert testimony" in various disputes, e.g. about science and religion. Someone points to Professor N., a respected professor of molecular biology or cosmology who is also a member in good standing at the local mosque or synagogue. This is frequently met with groans, and rightly so if it is supposed to demonstrate anything very far-reaching, like God's existence. But it is certainly a relevant piece of evidence for the claim that it is possible to believe in God and be a practicing scientist. The counter-interpretation that "all it proves is that scientists are not immune to wishful thinking," or "scientists can intellectually compartmentalize too," is just that -- an interpretation. If someone wanted to argue for the claim that scientists can intellectually compartmentalize and hold incompatible beliefs, and they adduced as evidence the example of Professor N., they would have (on certain premises) a decent Exhibit A, but to hold that this clinched the matter would be, well, fallacious.
Then there are the times when no fallacy has been committed at all. The most frequent occasion for this, depressingly common, is the accusation of "ad hominem" in a case like:
He thinks that's evidence that there must be a God? My God, he's an idiot!This is, strictly, different from:
Yeah, he has an "argument" for God's existence, but why even consider it? He's an idiot!Both arguments exhibit bad manners, but only one of them is, strictly, a fallacy (unless you want to quibble that the definition of "idiot" haven't been clarified sufficiently).
Very frequently, when tempted to cry "fallacy!," what one really means is that a step in the argument has been left out (or more than one). Rather than snort "ad hominem!" or "reification!" or "slippery slope!", the proper (and Socratic) response to most instances of apparent fallacy is "And why is this relevant?" When you remember your manners and press someone to explain the omitted steps, not only do they usually see where their own case is weak without your rubbing their nose in it, but both parties expand the context from which they are arguing. What is really at stake, motivating the dispute, becomes clearer, and very often, you find it is not what you thought it was at first.
Moreover, it is worth recalling that even a true claim can be argued for (badly, of course) with fallacious reasoning. (And, to be sure, rudely, as well.) To think otherwise is --