How doth it appear that the Scriptures are the Word of God?

Q. 4. How doth it appear that the Scriptures are of the Word of God?

A. The Scriptures manifest themselves to be the Word of God, by their majesty and purity; by the consent of all the parts, and the scope of the whole, which is to give all glory to God; by their light and power to convince and convert sinners, to comfort and build up believers unto salvation: but the Spirit of God bearing witness by and with the Scriptures in the heart of man, is alone able fully to persuade it that they are the very word of God. – Westminster Larger Catechism

I’m reading through Johannes G. Vos’ commentary on the Westminster Larger Catechism. His thoughts on this aspect of question four seem especially relevant. I know many believe the Bible to be errant, or at least fallible when it comes to some things, but that it contains truth when it comes to things regarding salvation. I agree with Doctor Vos, if we can’t trust all of the Bible then we can’t trust any of it.

We believe that the Scriptures are entirely free from errors, not because we find no apparent errors in the Bible, for it cannot be denied that a few apparent errors have been pointed out in the Bible, but because the Bible itself claims to be free from errors. Our belief about the Scriptures must not be an inference from facts of our own experience, but a formulation of the teachings of the Scriptures themselves about themselves. If we find some apparent errors in the Bible, that is a matter of our own experience as finders. But if we observe that the Bible represents itself as being free from errors, that is an observation concerning the teaching of the Bible. We must accept the Bible’s teaching about hell and other matters. The fact is that the Bible teaches that the Bible is inerrant. Even though we may have some unsolved problems concerning apparent errors in the Bible, still these problems do not justify setting aside the Bible’s teaching about itself, unless it can be proved that the Bible really contains errors, and that they exist in the genuine text of the Hebrew or Greek original. If that could be proved, the trustworthiness of the Bible as a teach of truth on all subjects would thereby be destroyed. If we are to trust the Bible in what it says about God and man, sin and salvation, we must also trust the Bible in what it says about its own infallibility. –  The Westminster Larger Catechism: A Commentary by Johannes G. Vos, edited by G.I. Williamson. pg 13 commentary on Westminster Larger Catechism Question 4