Everyone knows about the “logical fallacies.” There are whole books and websites (for example: here, here, and here) written about them. People trot them out in internet debates and ‘attack’ by claiming their opponent was utilizing some logical fallacy or another. I’ve even seen people, in an internet argument, simply respond “you are using a logical fallacy” and leave a link to a website — but not even bothering to explain which fallacy was supposedly being utilized.
Something has always bothered me about the logical fallacies, namely that probably 90% of the time that they get trotted out they are used in a false way. Probably the single most commonly abused ‘logical fallacy’ is the “Ad Hominem Fallacy.” I can’t think of even a single time this one has been trotted out by someone in an internet debate that it was appropriately used.
The issue is that logical fallacies only apply to logic, but not always to rationality. Most people don’t understand the difference between the two. For example, let’s say that in a critical debate person A quotes a study (say to prove some herb really works) and person B responds, “Oh, that study came from the very company that sells the herb, so you can’t trust that study. Besides, that company is dishonest.”
When person A responds “That’s an Ad Hominem Attack! You need to learn your logical fallacies!” is person A correct?
Yes, this might technically be an Ad Hominem attack had this been a purely logical debate. That the company is dishonest doesn’t mean that they didn’t happen to do a good study. (Nor can we just assume that they are dishonest because someone said so!) One does not logically follow from another. So technically this is a logical fallacy. But so what? The reason person B brought up their doubts about the study was that they were challenging the very premise of person A’s whole argument. This is a rationally valid thing to bring up!
Pay attention to debates and you’ll quickly discover something: the vast majority of the time people are simply challenging each other about their assumptions and premises. Rarely, if ever, do debates actually challenge each other on the basis of logical deductions. Once you realize that secret, you know that the vast majority of claims to have “fallen into a logical fallacy” will turn out to be irrelevant.
Rationality isn’t the same thing as logic. Rationality is best understood via Popper’s epistemology of critical discussion. The best response from Person A would have actually been something like this: “Sure, that study came from a company that is biased. And, yes, we can’t just assume upfront that a study is correct. But this study was a double-blind study, to correct for possible bias. And the study was confirmed by another study…”
In other words, the best rational response wasn’t to call out the supposed ‘logical fallacy’ but to take the other person’s theory seriously and explain why you feel their theory still has problems to deal with.
It’s not that logical fallacies don’t sometimes become relevant. Some logical fallacies are fairly common, though not nearly as serious in a rational discussion as in a logical deduction. For example, strawman arguments are very common but in a rational discussion may well be nothing more than the fact that understanding your opponent is quite difficult. Strawman arguments at least have the advantage that the person being strawmaned now has a chance to correct the misunderstanding.
And circular arguments are common because of the vagueness of language and how hard it is to sort meanings out from words. They may still be valid problems, but the proper response might well be to not call the person out for a logical fallacy but to help them analyze their arguments better.
But for the most part, people don’t understand how a critical rational discussion differs from a logical analysis and misapply logical fallacies. Here are a few examples from this post and my analysis of why these supposed fallacies are actually possibly valid in a rational discussion:
Slippery Slope: If we ban Hummers because they are bad for the environment eventually the government will ban all cars, so we should not ban Hummers.
- Analysis: Actually, this isn’t such a bad argument if one holds certain theories about governments. So it’s probably a rationally valid point worth discussing. It can easily be strengthened by instead of saying ‘all cars’ saying ‘many more good cars’ or something like that.
Hasty Generalization: Even though it’s only the first day, I can tell this is going to be a boring course.
- Analysis: This may well be a good conjecture based on a decent heuristic. Or maybe not. But in a rational discussion, it seems unlikely that it was ever intended as a logical deduction.
Post hoc ergo propter hoc: I drank bottled water and now I am sick, so the water must have made me sick.
- Analysis: This is only a logical fallacy if you chose to read this person as meaning “absolutely proven beyond doubt the water made me sick.” But practically speaking, it would be charitable to read this speaker as meaning something closer to “The water may have made me sick,” in which case, it’s a good starting conjecture.
Genetic Fallacy: The Volkswagen Beetle is an evil car because it was originally designed by Hitler’s army.
- Analysis: This one actually is both a logical and a rational fallacy in it’s current form.
Begging the Claim: Filthy and polluting coal should be banned.
- Analysis: Coal is arguably filty and polluting under some legitimate definitions of those terms. This seems like a fair starting conjecture worth debating.
Circular Argument: George Bush is a good communicator because he speaks effectively.
- Analysis: An opinion about someone being a good communicator is always going to be difficult to show logically and there is no need to try. Explaining one’s reasons as best as you can is probably a good place to start even if the reason isn’t very deep initially. The correct next question is ‘what do you mean by speaks effectively?’ rather than claiming it is a logical fallacy.
Either/or: We can either stop using cars or destroy the earth.
- Analysis: Is this really a logical fallacy at all? Or is this a case of this person simply not having additional theories available to them yet? Rationally we can’t consider theories we don’t yet know about. It is at least a possibility that this person simply isn’t aware of better alternatives and so this is logically valid for them to say at this point. Would calling it a logical fallacy really help the person understand why we need to keep making progress?
Ad hominem: Green Peace’s strategies aren’t effective because they are all dirty, lazy hippies.
- Analysis: If this was the sole argument being made, I’d agree this is a logical fallacy. But as part of an overall discussion, the motivations and lifestyle choices of an organization do matter and are worth bringing up and debating. It may not actually be true that Green Peace is a bunch of dirty, lazy hippies, but if they are, I’d want to know about it before I supported them because it might affect their effectiveness.
Ad populum/Bandwagon Appeal: If you were a true American you would support the rights of people to choose whatever vehicle they want.
- Analysis: This one is pretty lame, I admit. But likely the overall debate included what the speaker meant by ‘true American’ and thus may or may not be rationally valid, depending on what they meant. And frankly, someone that didn’t believe I had a right to buy the vehicle I wanted probably is misunderstanding certain important Western/American values that actually do matter.
Red Herring: The level of mercury in seafood may be unsafe, but what will fishers do to support their families?
- Analysis: This actually strikes me as a fair question. Rationally speaking you can’t disentangle issues nicely such that they can cleanly be used in a logical deduction like this. And since this is really an economic question (what is the cost of making it safer than it already is compared to the cost of not doing so?) economic side effects seem to me to be spot on.
Straw Man: People who don’t support the proposed state minimum wage increase hate the poor.
- Analysis: People’s motives do matter in overall theories. This might be a true theory. Though likely not. But it is a fair point to raise if done as part of an overall argument that might include a theory as to why one group is motivated by a repeal of a law. That is definitely worth debating even if it is false. In fact, we need to debate false ideas in rational discussions.
Moral Equivalence: That parking attendant who gave me a ticket is as bad as Hitler.
- Analysis: Is this really a logical fallacy at all? Or just someone saying something colorful to express their anger?
So here was have 12 examples on a web page and only one was definitely a valid rational problem. For most of these, it’s not even clear they are true logical fallacies in the first place because they have more charitable interpretations available to them.
The logical fallacies really only apply to what you do after everyone agrees upon an initial set of assumptions. Rational debate almost never includes an agreed-upon initial set of assumptions. Pay attention to rational debates and you’ll quickly notice that so-called ‘logical fallacies’ are often rationally valid and calling them logical fallacies really just misses the point.