As Christians (actually, as humans), we do not have a rationalistic approach to our worldview. We don't reason towards the truthfulness of Scripture. Scripture is truthful from the outset, and we know that it is not because we've figured it out in some other manner, but because the Holy Spirit Himself has opened our eyes to accept it as a pre-rational authority. Scripture is the ground of all reasoning and not merely the conclusion of metalogical reasoning. In fact, the methodology of trying to find out which authority is correct is a flaw which Van Til pointed out in Francis Schaeffer's (I think) apologetic, for doing so presupposes that there is some authority external to the one for which we are searching, and from which we can reason in the first place. If we try to say the Bible is not necessarily true and "neutrally" attempt to find out what is a necessary precondition of intelligibility, then we are assuming that a separate framework is possible from which we can neutrally reason, and that the Bible is not completely necessary. So, in other words, because of the Holy Spirit's witness, we do in a sense obtain the presupposition of Scripture out of thin air. We start with it before even reasoning in the first place. We still have a rational account for holding this presupposition, but not for arriving at it, because by definition we must start with it. And if we don't start with our presupposition, then we are trying to lay the groundwork for rationality is a purportedly neutral fashion, which is in fact evidentialism, albeit an uncommon variance of it. But, again, this does not establish the Bible's authority, even if all other revelations (e.g. the Qur'an) are disproven. This is true because, in such a case, we are still saying that the Bible is God's Word iff it passes a test for us humans (viz. that we find it to be consistent), and iff it remains rationally appropriate for us humans. If there is some methodology which does not necessarily have Scripture's veracity as its basis, then Scripture cannot be as authoritative as it ought to be -- for in that case whatever methodology was used to arrive at the conclusion "Scripture is true" is in fact more authoritative than Scripture itself. Moreover, a nonbeliever could legitimately claim, after being confronted with this argument, that whatever appropriate revelation there was is now gone. Why not the revelation of the Mayans or the Incans? Why not some Eastern religion whose text we have lost in the annals of history? If we establish the necessity of revelation, and even if we establish the Bible as consistent, this still leaves plenty of (rational) safety valves for unbelief. I'm not saying it's wrong to argue for the fact that revelation is needed. That is still an awesome argument to use. However, once we establish the necessity of revelation, we should not view this as some "neutral" fact from which we can move to Scripture. Rather, we show how the starting point of Scripture accords with this fact (of the necessity of revelation), and how the unbeliever's starting point adamantly does not. In other words, the argument for the necessity of revelation is a "primary interpretation" as I espouse in this thread. I have, however, changed my current terminology to "immutable fact" rather than "primary interpretation," because the former term fits the concept much better than the latter does. The last post in that thread makes note of this modification.