Presuppositional Exclusivism

There cannot be two books that both claim to be God's Word and that both provide sufficient presuppositions to "make sense of life," unless of course they both provide the same presuppositions. Why is this so?

To accept the Bible as a mere hypothesis, even the most likely hypothesis, is to say that there were other hypotheses out there, however unlikely, that might eventually prove to be true. This, among other reasons, is why Bahnsen had problems with an evidentialist approach to apologetics. To pile up "facts" divorced from revelation to make God's existence likely or even "probable" was also to admit to the possibility that God might not exist.

It was Van Til's (and Bahnsen's) contention not only that the Bible contains the starting point to "make sense of life," but also that it is the only conceivable starting point for doing so. Hence, any other book claiming to be the Word of God would ultimately be based on an incoherency, a "brute fact" without context. The Bible, for example, starts with God, assumes God's self awareness, and declares that humanity is incapable of determining truth by means of its own, limited, fallen, autonomous mind. One reason for this is that human reasoning, logic, etc., is recursive in the sense that one has to assume the truth of it in order to "prove" it. Logic isn't "provable," it simply "is." One can start either with an entity that contains his own cause (God) or something that doesn't (reason). The first is coherent, the second, incoherent.

Having more than one "holy book" with conflicting accounts would require mankind to determine the truth through independent reason, something that Van Til (and the Bible) declare to be impossible.

On page 508 of his Van Til's Apologetic: Readings & Analysis, Bahnsen wrote:

Likewise, the presuppositional argument does not first debate the formal possibility of a book from God, but rather begins the argument from the outset with the actuality of the Bible - whose worldview is offered for internal comparison with any other contrary viewpoint [Emphasis mine: L.G.]

.As it's impossible for me to do justice to Van Til's apologetic (and Bahnsen's exposition of it) in this short space, I think you would be best advised to secure a copy of the book from which I just quoted, as well as John Frame's Cornelius Van Til: An Analysis of His Thought. Both are available through Presbyterian and Reformed Publishing. In my opinion these are the best volumes available in presenting what presuppositional apologetics is about. But they do not agree on all the details, and you will doubtless find them challenged by other presuppositionalists!