The argument from fallacy
, also known as argumentum ad logicam
or fallacy fallacy
, is a logical fallacy
which assumes that if an argument
is fallacious, its conclusion must be false.
It has the general argument form:
- If P, then Q.
- P is a fallacious argument.
- Therefore, Q is false.
- Tom: "All cats are animals. Ginger is an animal. This means Ginger is a cat.".
- Bill: "Ah you just committed the affirming the consequent logical fallacy. Sorry, you are wrong, which means that Ginger is not a cat".
- Tom: "OK — I'll prove I'm English — I speak English so that proves it".
- Bill: "But Americans and Canadians, among others, speak English too. You have committed the package-deal fallacy, assuming that speaking English and being English always go together. That means you are not English".
Of course, the mere fact that the argument from fallacy can be invoked against a position does not automatically "prove" the position either, as this would itself be yet another argument from fallacy. An example of this false reasoning follows:
- Joe: Bill's assumption that Ginger is not a cat uses the argument from fallacy. Therefore, Ginger absolutely must be a cat.
The argumentum ad logicam can be seen as a variant of the ad hominem fallacy, because it relies on the opposing speaker's seeming lack of credibility, a factor which is usually irrelevant to the actual correctness of a given theory (although it can help bolster the evidence in an inductive argument).