Let us imagine that, in the midst of a heated discussion on faith and reason, you've exposed an apparent contradiction in the Christian Scriptures for which I simply cannot account. I will then experience a phenomenon psychologists call "disruption." Rational beings are compelled to make rational sense of their world and will restlessly seek to reconcile contrary concepts until they are settled. A disruption is an opportunity for a man to either subject his life to reason until the discrepancy is resolved, or to delude himself into thinking that there is no discrepancy in his foundational tenets at all, or to weigh the gravity of the discrepancy to determine what action should be taken in light of it.
So now, back to the scenario. I am faced with a disruption, and a choice must be made. You, the anti-scripturist, likely have an irrational expectation that I will now reject entirely the basis of my life reasoning, (which is my faith in the reliability of scriptures), to accept the basis of your life reasoning, (which is your faith in the unreliability of scriptures). I say this is an irrational expectation because what you fail to take into account is that this is a deeply invested lifestyle I have, and it would be irrational to move from it toward anything short of what I could rationally accept as a superior lifestyle. Imagine I'm climbing a cliff and I realize that my foothold is not as secure as I believed it was when I took it. If I have no where better to go, then it must suffice until I can get further up the mountain, or else I fall to my death. Any lifestyle will have points of discrepancy for which faith must account until total truth is discovered (or revealed). My choice then is based not on those truths to which I can hold firmly, but those truths to which I must hold by necessity.
Truth be told, my cliff-face still looks better than yours, even with my loose foothold. The rational system through which I make sense of the world gives me basis to believe that men are created equal; that life is sacred; that integrity is honorable; that authority should be respected; that property should be protected; that marriage is for life; that people ought to be free. As I see it, without these Scriptures, I have nothing to convince me that these truths are evident at all, which would make it impossible for me to teach others to hold them with any rational integrity. Society will have taken a severe downgrade as will have my private life. You may point to the utility of these beliefs as basis to hold them, but utility is meaningless without an aim, and nihilism is aimless. Advancement of the species, you say? Without Scripture, I have no vested interest in anything beyond my personal experience.
The choice then to delude myself into thinking there is no discrepancy would be a relatively rational one, since, practically speaking, it would keep me functioning in a positive sphere. However, self-delusion as a whole is a non-rational lifestyle and I believe (because the Scriptures teach me so), that I am created to live in the light of sober-minded truth; not make-believe happy-land.
Since I cannot simply sit around until I resolve every rational discrepancy in the world, and since I cannot reject my lifestyle because I have no better position to which to retreat, and since I cannot in good conscience ignore the problem, the only rational action I can take is to say, "Good move, old chum. Can't argue with that one." And be on my merry way.