Argument from fallacy is theformal fallacy ofanalyzing anargument and inferring that, since it contains a fallacy, itsconclusion must be false.[1] It is also calledargument to logic (argumentum ad logicam), thefallacy fallacy,[2] thefallacist's fallacy,[3] and thebad reasons fallacy.[4]
An argument from fallacy has the following generalargument form:
If P, then Q.
P is a fallacious argument.
Therefore, Q is false.[5]
Thus, it is a special case ofdenying the antecedent where the antecedent, rather than being a proposition that is false, is an entire argument that is fallacious. A fallacious argument, just as with a false antecedent, can still have a consequent that happens to be true. The fallacy is in concluding the consequent of a fallacious argument has to be false.
That the argument is fallacious only means that the argument cannot succeed in proving its consequent.[6] But showing how one argument in a complex thesis is fallaciously reasoned does not necessarily invalidate its conclusion if that conclusion is not dependent on the fallacy.
Alice: All cats are animals. Ginger is an animal. Therefore, Ginger is a cat.
Bob: You have just fallaciouslyaffirmed the consequent. You are incorrect. Therefore, Ginger is not a cat.
Alice: I speak English. Therefore, I am English.
Bob: Americans and Canadians, among others, speak English too. By assuming that speaking English and being English always go together, you have just committed thepackage-deal fallacy. You are incorrect. Therefore, you are not English.
Both of Bob's rebuttals are arguments from fallacy. Ginger may or may not be a cat, and Alice may or may not be English. The fact that Alice's argument was fallacious is not, in itself, proof that her conclusion is false.
Charlie: Bob's argument that Ginger is not a cat is fallacious. Therefore, Ginger absolutely must be a cat.
That one can invoke the argument from fallacy against a position does not prove one's own position either, as this would also be an argument from fallacy, as is the case in Charlie's argument.
Argumentum ad logicam can be used as anad hominem appeal: by impugning the opponent'scredibility orgood faith, it can be used to sway the audience by undermining the speaker rather than byaddressing the speaker's argument.[3]
William Lycan identifies the fallacy fallacy as the fallacy "of imputing fallaciousness to a view with which one disagrees but without doing anything to show that the view rests on any error of reasoning". Unlike ordinary fallacy fallacies, which reason from an argument's fallaciousness to its conclusion's falsehood, the kind of argument Lycan has in mind treats another argument's fallaciousness as obvious without first demonstrating that any fallacy at all is present. Thus in some contexts it may be a form ofbegging the question,[7] and it is also a special case ofad lapidem.
Thefallacist's fallacy consists in any of the following false propositions... 3. The appearance of a fallacy in an argument is an external sign of its author's depravity.
c since A
A is fallacious
¬c
