

No matter how absurd the title sounds this is the fundamental claim of Van Tillian Christian presuppositional apologetics. Presuppositionalists first presume the existence of God and the truth of scripture as their epistemology. Then they claim that Christianity, by necessity of its god, is the only possible standard for truth as man does not possess ‘autonomous intellectual authority’ because God is the ultimate and objective origin of truth. Obviously saying this doesn’t make it true but they claim assuming humans have the ability to determine truth would deny a neutral starting ground as god is defined as filling that role.
Presuppositionalism commits the informal fallacy of begging the question, for it advocates presupposing the truth of Christian theism in order to prove Christian theism. It is difficult to imagine how anyone could with a straight face think to show theism to be true by reasoning, ‘God exists, therefore God exists.’ - William Lane Craig in Five Views on Apologetics p 232-233