Tuesday, August 28, 2012

Fallacy Fallacy (Formal Fallacies Part 2)

Formal fallacies are arguments that are always wrong, regardless whether the argument's premises (statements claimed as fact) are true or false. In the previous installment, the appeal to probability, a claim that because something could happen, therefore it will happen is false even if it's true that the something in question could indeed happen.

Argument from Fallacy

If an argument contains a fallacy, what does that say about the conclusion? Actually, it doesn’t say very much. Excessively pointing to fallacies can itself trigger a fallacy of its own: the argument from fallacy, or the fallacy fallacy.

The argument from fallacy is the error of concluding that if an argument can be shown to be fallacious, that means its conclusion necessarily must be false. The form of the argument is:
If P, then Q
P is a fallacious argument.
Therefore, Q is false.
Take, for example, the following claim: “I speak English, therefore I am an American citizen.” That’s a fallacious argument, because many people who speak English are not American citizens. To conclude, however, that because the argument is fallacious, you must not be an American citizen, is taking the claim a step too far. A conclusion can be right even if the argument supporting it happens to be wrong.

If you can show that a particular argument is fallacious, the only thing that means is that the particular argument can’t be used to prove the proposition. The opposite argument, that the fallacious argument itself disproves the proposition, is also a fallacy.

The argument from fallacy is also known as the argument to logic (argumentum ad logicam) and the fallacist’s fallacy. It’s part of a group of fallacies known as fallacies of relevance.

Base Rate Fallacy
Conjunction Fallacy

The base rate fallacy and the conjunction fallacy also fall into the category of cognitive bias, and were both treated earlier in this blog and in my compilation of cognitive biases, published separately.

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