Argument from Fallacy

Christian Cotton

The Sun is made out of gas, and stars are made out of gas, so the Sun is a star.

A fallacious piece of reasoning with all true claims

Also known as argumentum ad logicam, argument to logic, fallacy fallacy, and fallacist’s fallacy, the argument from fallacy occurs when one reasons that because the argument for some conclusion is fallacious, the conclusion of that argument is false.

(1) If Atlanta is the capital of Georgia, then it is in the United States.

(2) Atlanta is in the United States.

(3) Therefore, Atlanta is the capital of Georgia.

This argument illustrates the fallacy of affirming the consequent. As a deductive argument, it is invalid - one cannot draw/infer the conclusion from the premises - and yet the conclusion is true. As such, it should be clear that poor reasoning (committing a fallacy) does not entail a false conclusion. One would not, in the above example, respond reasonably if she were to suggest that, because a fallacy has been committed, it is false that Atlanta is the capital of Georgia. Nevertheless, the conclusion of the fallacious argu­ment may well be false. The reason is that it’s one thing to commit an error in reasoning and quite another to get the facts wrong. The one does not follow from the other. Therefore, because the truth or falsity of a claim cannot be inferred solely from the quality of the reasoning, concluding that a claim is false because an error in reasoning (a fallacy) has occurred is itself an error in reasoning. Hence, the name fallacy fallacy.

To take another example, suppose someone commits the slippery slope fallacy (see Chapter 94), and you respond that because he has used a fallacy, the conclusion of his argument is false.

Brad: Dammit, Janet! We simply cannot allow same-sex marriage. If we allow same-sex couples to marry, then the next thing you know we’ll have to allow people to marry their parents, their pets, even monkeys. I mean, where do we draw the line?

Janet: Oh, Brad! That’s the slippery slope fallacy, and you can’t use falla­cious reasoning to support an argument. So, see, you’re wrong that we shouldn’t allow same-sex marriage.

Does such an error in argumentation really need an explanation? Sadly, it does. This kind of fallacy occurs all the time in casual conversation, espe­cially online. No doubt the thought process is something like this: “If I can show my interlocutor has committed some kind of fallacy, that means I don’t have to accept his argument, so I can dismiss his position.” Notice that our imagined fallacist has just made an argument to justify dismissing her interlocutor’s position. While it’s an example of good reasoning to claim that if there is a fallacy, then one need not accept the argument, the further inference that one is justified in dismissing the position, that is, the conclu­sion of that argument, isn’t good reasoning. It is, in fact, bad reasoning because it conflates the quality of an argument (i.e., the logical connection between the premises and the conclusion) with the truth-value of the posi­tion (i.e., the conclusion of the argument). In other words, while we needn’t accept a fallacious argument, it doesn’t follow that we can reject the conclu­sion of the argument as false. So, while Janet is perfectly correct to call out Brad on his fallacious reasoning, Brad’s sloppy thinking doesn’t justify asserting that his conclusion is false. In other words, while the conclusion may not follow from the premises, it doesn’t follow that his conclusion is false.

Suppose someone commits the post hoc fallacy, and you respond that because she has used fallacious reasoning, the conclusion of her argument must be false.

Jon: Look, man, I’m telling you: I prayed for this gig to open up for

us - every night for a week - and when I checked my messages last night, there was one that said we got the gig! It worked, man!

Richie: Dude, saying that you prayed for something and it then happened, so it must have happened because you prayed for it, is a fallacy called the post hoc fallacy. That means prayer doesn’t work.

Maybe this is a bit less clear than the previous example because many of us believe in the efficacy of prayer. So, we have to be clear about what is being said here and why it’s problematic. Jon believes that his praying for the gig worked. But, whether the prayer actually worked is not clear; it may just be a coincidence that one night he prays for a gig and the next day there’s a message to confirm the gig. So, Richie is correct to point out the fallacy (the post hoc fallacy, very briefly, is the fallacy that assumes that because one thing occurs after another, it must have been caused by that thing). But, it remains an open question whether the prayer actually worked. Because it is an open question, Richie is not justified in then concluding that prayer doesn’t work. To be sure, the question of whether prayer works is closely related to another fallacy of explanation called untestability: Is there any way to test whether or not prayer really works? If not, the claim that prayer works is an untestable claim and thus fails to be informative about the efficacy of prayer.

This fallacy is truly one of the easiest fallacies to avoid. As long as you understand that no matter how poor the reasoning of an argument, nothing follows from that about the truth or falsity of the conclusion, you won’t fall prey to this one. Also, it helps when entering into spirited debate not to think of your interlocutor as an opponent whom you are attempting to defeat in some kind of intellectual battle. Very often this is a cause of falla­cious reasoning of all sorts. Instead, think of yourselves as companions in search of the truth or, failing that, something that more closely approxi­mates the truth. In this way, when a fallacy is committed, you can point it out, and then go about the business of clarifying the position in a way that avoids the initial fallacy without thereby committing a second fallacy.