Sunday, August 14, 2011

Logical Fallacy of the Week - Argument from fallacy: Week 4

By Rich Kozlovich

I find this to be a fallacy used constantly by greenies....and a host of others. As an example:
Many pesticides are neurotoxins. Children are born with brain damage, therefore pesticides caused it.
This is a fallacious conclusion because this conclusion was drawn from inadequate evidence. So, does this prove that nerutoxic pesticides don’t cause brain damage? No, it just means that the conclusion was drawn without sufficient evidence to show this conclusion is correct.

I have to note at this point that not all logical fallacies are wrong. As time goes by you will see that the issue regarding logical fallacies is how one uses logic to arrive at conclusions. Both correct and incorrect conclusions can be drawn from the use of logical fallacies, ergo, an argument from fallacy. Confusing? Please follow the link provided which will lead to further links; seemingly designed to confuse. RK

Argument from fallacy

Argument from fallacy is the formal fallacy of analyzing an argument and inferring that, since it contains a fallacy, its conclusion must be false. It is also called argument to logic (argumentum ad logicam), fallacy fallacy, or fallacist's fallacy.

It has the general argument form:

If P, then Q.
P is a fallacious argument.
Therefore, Q is false.

Thus, it is a special case of denying 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. But showing how one argument in a complex thesis is fallaciously reasoned does not necessarily invalidate the proof; the complete proof could still logically imply its conclusion if that conclusion is not dependent on the fallacy:


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.
Both Bill's rebuttals are arguments from fallacy, because Ginger may or may not be a cat, and Tom may or may not be English. Of course, the mere fact that one can invoke the argument from fallacy against a position does not automatically "prove" one's own 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.

An argument using fallacious reasoning is capable of being consequentially correct.

Logical Fallacy of the Week: Week 1
Logical Fallacy of the Week, Argument from authority: Week 2
Logical Fallacy of the Week, Appeal to Probability: Week 3


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