I believe in divine revelation, but I do not accept every sacred book that claims to be such, mainly because they are rationally exclusive.  But I don’t just dismiss them out-of-hand, blindly, I reject them for specific reasons.  Even though they claim to be divine revelation, I put them all through the same grid of reason which is necessary to identify something as revelation.  I remember my first two in-depth conversations with Heba about this very subject; in both cases she approached me at an evangelistic booktable we were conducting.  We talked about many things related to the Bible and the Qur’an and how we can test a book that claims to be divine revelation, which both do.  At the end of our talk she gave me the challenge to find anything wrong with the Qur’an.  She asserted that if I could not find anything wrong with the Qur’an then it must be the word of God and therefore Jesus could not be the Son of God.  She assured me with confidence that I could not find anything wrong with the Qur’an.  Before she left I politely made one particular charge that the Qur'an does not offer the problem of sin which is unnecessary to state here.  Although she did not deny the charge she readily dismissed it as not the category she was getting at.  It seemed she had some other category in mind, which was unclear to me.  We continued to dialogue by email but I never could get a good grasp of the category of criteria she was driving at.  (Here again a law of logic is touched upon again, that of category.  Heba and I were each stuck in different categories of criteria which neither of us could wrap our minds around, so we could not successfully compare “apples with apples” at the time.  

But more specifically, there is a very clear logical problem concerning the Bible and the Qur’an, namely the law of non-contradiction.  This states that two opposite things cannot both be true in the same sense at the same time.  The Bible claims that Jesus was executed, but the Qur’an claims that he was not.  Logically, either he was or he was not.  Only one can be true, not both, so it is an irreconcilable contradiction. Therefore, only one book or the other can be true on this point, a major one in both religions.  So logically one must choose one and reject the other as true revelation.  (But actually, this claim is a matter of historical inquiry.  From the Christian perspective at least, whether or not Jesus was executed can be known without divine revelation per se.  And indeed, that is one of the rational criteria that is applied to the Bible, if not also to the Qur’an.  Any book that makes historical references can be examined by those references.  If they are true then that book passes the test of history, at least.  If they are not, it does not.  This is no less true for a book that claims to be divine revelation such as the Bible and the Qur’an.  Both make historical references.  Assuming that a book of revelation contains only true historical references, the presence of false references would disqualify it as divine revelation.  That is, if a purportedly divine book states that something happened in history that did not actually happen, or if it states something did not happen that actually did, it is disqualified as revelation—especially if that one historical event is essential to the whole.  For the Bible the execution of Jesus is exactly that.  If it were not historically true it would fail the test of historicity and of coherent theology.  The whole Christian message would be invalid as it is meant to be understood. It would be nonsense. It may still be valuable for some of its other information, but not its core doctrine, and therefore it could not qualify as divine revelation in the Christian understanding in which historical events are a primary vehicle for revelation.  This is a simple reasoning.  Moreover, on this particular criterion the Bible and the Qur’an differ sharply, for while the Bible claims to reveal truth because of an event that is historically verifiable, the Qur’an claims to reveal truth in spite of that event’s verifiability, in rejection of it.  The former’s claim is based on the premise of historical fact, the latter’s claim is one that is above historical fact.  So for Muslims, that there is strong historical evidence for Jesus’s execution is irrelevant.  This violates good reason.

Whether you agree or disagree with my reasoning above, you can plainly see it.  And, again, that is the real point.  Reason is applied even to revelation, and it must be.  In our conversation Heba and I both were using our best powers of reason to define and clarify the notion of divine revelation with respect to the Bible and the Qur’an.  We were not praying or meditating; we were not talking to angels or expecting a heavenly light to shine down from heaven on the true sacred book.  No, we were trying our level best to apply the principles of good reason, first to agree on the acceptable criteria for analyzing and comparing the two books, and second to determine if one or both of them qualify.   In actual fact, some of the criteria are the same and some are different, which is why we were straining to understand each other.  Sure there are people who accept a holy book on the authority of their faith community alone, and although that is not the best form of reason, appeal to authority is a form of reason.  We use it all the time, even in combination with other forms.  Some caliber of reason, valid or invalid, is always applied even to revelation.  Otherwise nobody would believe in it.