For the sake of argument denial:

Definition Example
When there is an attempt to disallow an assumption introduced for the sake of argument because the assumption is not actually believed by the one making the argument. Your argument that Santa is not real because he would need to fly his sleigh at impossible speeds on Christmas Eve is not valid since you don’t even believe in Santa.
Also known as: denying a hypothetical / denying a reductio ad absurdum
This fallacy is often used in response to an “reductio ad absurdum” in which assumptions are granted for the sake of argument to demonstrate that they lead to an incoherency. To plug an assumption into an argument to show the failure of that argument does not require an epistemic commitment to the assumption.

Case Study One

Some atheists argue that “any god that is both omnipotent and omniscient would not allow evil into the world.” When theists dismiss this or a similar argument by saying “you don’t believe in god, so you can’t use the notion of god in your assumptions”, they are denying a hypothetical that is quite permissable for reductio ad absurdum arguments.

Case Study Two

To argue “If Bigfoot were real, physical evidence would have turned up by now” carries no epistemic commitment to the existence of Bigfoot.

Case Study Three

To argue that a man 100 meters tall would not be able to support his own weight does not require the existence of such a man.

Case Study Four

Some Christians called “presuppositionalists” claim that their theistic position is unassailable since those attacking their position must first believe in a creator of logic to ground the use of logic in their logical attack. However, the assumption of the reliability of logic by the non-theist is not necessary since, as long as the presuppositionalists themselves believe in the reliability of logic, the reductio ad absurdum remains legitimate.

Keep in mind that a fallacious argument does not entail an erroneous position.

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