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 judgement or that of others, that the Scriptures are from God; but, in a way superior to human judgement, 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. We ask not for proofs or probabilities on which to rest our judgement, but we subject our intellect and judgement to it as too transcendent for us to estimate. This, however, we do, not in the manner in which some are wont to fasten on an unknown object, which, as soon as known, displeases, but because we have a thorough conviction that, in holding it, we hold unassailable truth; not like miserable men, whose minds are enslaved by superstition, but because we feel a divine energy living and breathing in it—an energy by which we are drawn and animated to obey it, willingly indeed, and knowingly, but more vividly and effectually than could be done by human will or knowledge. (Institutes, 1.7.5)
While not all evangelical Christians may believe just because of some faith commitment or religious experience, I think the majority do. Once one has made this commitment then he or she will be determined to defend whatever is in the Bible. Even if they can't defend it, they will still believe, because the Spirit told them its true. One of the leading Christian apologists, William Lane Craig, admits as much.