“Presuppositions are necessary to reasoning. Every system of thought has some starting point, some standard of authority by which truth and error are evaluated, the real and the unreal are recognized, and the possible and impossible are determined. You must challenge a person’s basic assumptions supporting his worldview to uncover his ultimate commitment. You must press the unbeliever to provide you with his standard of evaluation from his outlook. When he offers it, you must challenge it by pressing him: “How do you know that is the right standard?” The respondent has one of four options available:
(1) He can admit that his standard of evaluation in his worldview has no justification (thus rendering his position arbitrary and irrational);
(2) he can argue that his standard is established by some standard outside of itself (thus admitting that a new standard becomes more ultimate, thereby destroying his previously determined “ultimate” standard;
(3) he can then keep seeking a more ultimate standard, becoming trapped in an infinite regress argument, thereby rendering his standard unknown and unknowable; or
(4) he can point to a truly ultimate, self-verifying standard that explains all else, in that it is the ultimate standard beyond which no appeal can be made, as in the Christian worldview which points to God (Heb. 6:13).
Unbelieving systems should be pressed to show that they must have an ultimate authority upon which to rest if they are to objectively and intelligibly evaluate anything. Evaluation requires a standard. When any system gets around to verifying its ultimate authority, it will have to presuppose that ultimate authority.”
(Bahnsen, Pushing the Antithesis, 122)