The key discriminator of this school is that it maintains that the Christian apologist must assume the truth of the supernatural revelation contained in the Bible (that is, the Christian worldview) because there can be no set of neutral assumptions from which to reason with a non-Christian. In other words, presuppositionalists say that a Christian cannot consistently declare his belief in the necessary existence of the God of the Bible and simultaneously argue on the basis of a different set of assumptions (presumably those of the non-Christian) in which God may or may not exist.
Presuppositionalists contrast their approach with the other schools of Christian apologetics by describing them as assuming the world is intelligible apart from belief in the existence of God and then arguing exclusively on (purportedly) neutral grounds to support trusting the Christian Scriptures. Specifically, presuppositionalists describe Thomistic (also "Traditional" or "Classical") apologetics as concentrating on the first aspect of apologetics with its logical proofs for the existence of God. Aquinas himself insists that many crucial truths can only be known through scripture, and none of his arguments are intended to show the entire Christian picture. Presuppositionalists, however, consider his arguments unglorifying to God, because they ignore even a part of revelation for the sake of argument. The goal is to argue that nonbelievers' assumptions require believing in some things about God that they don't believe (e.g. that an eternal, perfectly good, designer created the universe), but presuppositionalists consider any argument that stops short of the full biblical revelation is dishonoring to God.