Van Til’s followers often speak of the “transcendental argument” for the existence of God. Greg Bahnsen applied this in a famous (in our circles) debate with atheist Gordon Stein. In short, the transcendental argument for the existence of God (or TAG) states that the Christian God must be presupposed for any fact to be rendered intelligible. That is to say, all facts are what and as they are because of the Christian God. Take away the Christian God (in all His particulars) and you have an unintelligible world and no basis by which to judge any proposition true or false. The preconditions for all intelligibility are to be found in the triune God’s special revelation to us. Van Til and his followers often start with the ontological Trinity (communicated in special revelation) and then apply this premise in terms of a solution to the “problem of the one and the many,” moving on to other philosophical or ethical problems from there. Some of Van Til’s followers (especially John Frame) have made the case that this argument cannot work unless it is elaborated in terms of more classical arguments. To say that the Christian God underlies the intelligibility of any facts requires more spelling out– and that inevitably involves considerable overlap with classical apologetics. Others disagree with Frame and argue that the transcendental argument is unique and in its emphasis on the preconditions for our beliefs, does not rely on the supplementation of any other arguments.
What does one make of this debate? The classical position is that reality is communicated commonly in reason and experience and specially in Scripture– and that these cannot (even in principle) contradict one another precisely because reality is one and their Author is one. Neither natural nor special revelation is more authoritative than the other, but one’s understanding of the content of and relationship between natural and special revelation is different. To a large extent, much of the content of reason and experience is immediately intuited by human beings. Unlike the Bible, which we can imaginably doubt, the unique quality of reason is that our persuasion of (at least many of) its conclusions is coercive. Indeed, if the Bible said in Proverbs 12:4 (thankfully, it does not) that “two and two is five,” not even Cornelius Van Til (despite his declared positions) would have believed the Bible on this matter. No amount of appeal to the transcendental argument or Scriptural authority could have made him believe it. Why? Because he was a reasonable man. Because he believed, despite some of his formulations, certain propositions with a sort of coerced certainty. This does not mean that Scripture must be demonstrated by reason, but it may never contradict reason as such. In most of the moments wherein Van Tilians appeal to realities beyond reason, it is clear that they finally settle on a position that goes something more like “Certain aspects of biblical teaching are beyond our ability to comprehend” (Something more like James Anderson’s “unarticulated equivocation” than any tension within reason itself). They do not contradict reason, but rather point to realities or a mode of being which human reason is incompetent to analyze. But of course, this is the conclusion of reason itself, and has plenty of analogues in non-Christian thought. The limitations of reason are precisely where we’d expect them to be, in the principled place of the boundary between the finite and the infinite. Reason can find its own boundary, but not its contrary. Call this, then, the transcendental argument against the transcendental argument. The preconditions for the intelligibility of the transcendental argument are the very tools of reason and experience that it is supposed to explain. Many presuppositionalists live on the “borrowed capital” of commonsense realism, but claims it for their Van Til’ian transcendentalism. For all the rhetoric, the authority of the Bible is not absolutely “over” the authority of reason or experience. It is not “made” authoritative by those things. It is authoritative by virtue of what it is, the speech of God. But it would not be the speech of God, or authoritative, if it contradicted the other modes in which reality authoritatively confronts us, including the modes of reason and experience. Granted the conversation between these is subtle, complex, and there are plenty of conundrums, but the reality is that no-one consistently applies a “trump card” approach in which Scriptural revelation “trumps” the legitimate inferences of reason and experience. Cut an “orthodox” Van Tilian with reality, and watch a Thomist bleed. The real “precondition of intelligibility” is just that, an intelligibile singular Reality in which both reason and Scripture participate.
The Bible itself assumes this, of course. Paul allows that if the resurrection did not occur (entertaining the possibility for the sake of argument) that his faith would be in vain. In the Hebrew prophets, God Himself is willing to enter into confrontation with His people around the authority of “reason.” The Hebrew prophets mock idolatry as “obviously” stupid. This is ultimately by God’s own authority, of course, but it is by reason itself also nevertheless. And while the larger argument might include the “reasonableness” of special revelation, it is still just that: reasonable. Any negation of special revelation can, then, be reduced to precisely a failure to reason properly or to an illegitimate philosophical move such as, say, the skepticism of Descartes or the dualism of Kant. It is within this latter framework and history that we find the tradition of skeptical rationalism to which Van Til’s philosophy is ultimately an early 20’th century Neo-Kantian response. He would have done much better to abandon the modern project altogether. Despite his best efforts, Van Til still stands on the shoulders of Descartes and Kant. But each of these stand on the shoulders of the common reality which falsifies them both – an objective order which God is pleased to reveal to children but which He sometimes hides from the critical philosopher.
Here's a Thought 
[…] 10. See my own brief remarks on Van Til’s famous “transcendental argument.” […]
Thank-you, Joseph. You wrote, “But it would not be the speech of God, or authoritative, if it contracted the other modes . . .” I assume you mean “contradicted.” Correct?
Ha! Indeed. Thanks for this. I will fix it.
Hello! According to what standard do you judge something to be reasonable or not?
Hello, it looks my previous comment was deleted.
So, what’s your absolute standard to determine whether some claim is reasonable or not?
It was not deleted. I just rarely check this blog, and so it was a few days before I got to it. As for your question, I don’t think I could answer that in the singular. If we take absolute standard to mean something like, “That by which I think I ought to check all my judgments,” then there are a number of them. There is Scripture. There is reason (understood not as my competency in reason-ing, but as the “being” of reason / the Logos). There are probably a few other things that “function” in an absolute way (i.e. no matter which voice tells me that I’m not experiencing the sensation of typing right now, I won’t believe them because I am immediately experiencing the sensation of typing right now). I guess, then, my immediate self-awareness is that which I don’t try to question. Bavinck started there as well. Like the philosopher Stephen RL Clark, I’m inclined to believe that there are certain lines of inquiry that just aren’t worth all that much. So anything that tries to make one skeptical about the veracity of these things strikes me as immediately philosophically suicidal (since the argument will always depend upon a tacit prior assent to these things).