Let it therefore be held as fixed, that those who are inwardly taught by the Holy Spirit acquiesce implicitly in Scripture; that Scripture, carrying its own evidence along with it, deigns not to submit to proofs and arguments, but owes the full conviction with which we ought to receive it to the testimony of the Spirit. Enlightened by him, we no longer believe, either on our own Judgment or that of others, that the Scriptures are from God; but, in a way superior to human Judgment, feel perfectly assured—as much so as if we beheld the divine image visibly impressed on it—that it came to us, by the instrumentality of men, from the very mouth of God.
~ ~ Institutes of the Christian Religion, Book 1, Chapter 7, Part 5, by John Calvin
The Bible cannot be held to be perfect in every manner without the indication that is provided to us by the Holy Spirit. This is why the unbeliever will continue to mock and belittle it because left to their own understanding of the text, it is only as trustworthy as is a comic book, newspaper, or their textbooks. By the empowerment of the Holy Spirit, either on their darkened minds leading them to the light of understanding, or that which is present in the mind of a believer, is what testifies to its truthfulness and leads the reader to affirm that it is true. We cannot simply start with the presuppoistion that it is the Word of God and wholly true as Muslims state the same about their holy books, and Mormons about theirs. Our defense of scripture stems from the heart of God who, through the revelation provided to us through the Holy Spirit, not only reveals to us the truth of scripture, but defends it against all the claims by other “faith books” of world religions.