is a mode of argumentation that seeks to establish a contention by deriving an absurdity from its denial, thus arguing that a thesis must be accepted because its rejection would be untenable. It is a style of reasoning that has been employed throughout the history of mathematics and philosophy from classical antiquity onwards.
1.God is Omnipotent.
2. Anything is possible for God.
3. Thus, God can will anything to exist.
4. Superman could exist.
Thesis: The attribute "omnipotence" is incompatible with the known physics of the universe.
Blogger's Note - I was in a rush when I first posted this and did not get to include the following commentary. I add it now.
I've often heard it said that positive atheism is an unjustifiable philosophical position because one can not prove with certainty that God can not (or does not) exist and that one must rest such a belief on faith alone, thus putting the atheist on equal grounds with the theist . Yet if you claim Superman can not exist no one will tell you that you are making a faith based decision regarding the existance of Superman. To admit one can not exist while claiming the other can is a form of special pleading, as there is no reason why the rules of physics should apply to one and not the other. If one maintains that it is possible for God to exist, it is of equal probability for Superman, or any other absurdity, to exist. And if you do that, the entire edifice of what we call knowledge comes crumbling down.