Presuppositionalism is a Christian apologetic which requires that one must hold that the supernatural revelation contained in the Bible as its preeminent standard of thought. That only the existence of God provides a justification for logic.
- "You cannot use logic to argue against the existence of God, logic requires the presuppostion that God exists."
- "Without God existing as an objective source for logic, logic wouldn't work."
- "Since logic presupposes God, all arguments against the existence of God are fallacious."
Despite the ridiculous sounding nature of the apologetic, it is taken quite seriously in some circles. The argument simply consists of demanding the truth for Christianity be ceded from outside logic and without presupposing the truth of Christianity, no logical argument can exist. Due to the absurd nature of this claim, it cannot be attacked logically because presuppostionalists have rejected logic with this demand. Since one can't "defeat their arguments" (as any attempt to use logic is deemed off limits until you declare that they are right), they declare victory.
The line of apologetics is popular and often used in conjunction with the Transcendental argument either to prove or support the demanded preconditions be accepted.
What? Are you serious?
That's poisoning the middle ground. If one needs to assume that you're completely right before the debate begins there can be no debate.
Requiring false presuppositions invalidates logic. Accepting one contradictory statement allows one to successfully prove any false statement true.