InsideCatholic recently did an interesting survey of the reasons Catholics (and, for that matter, Christians in general) leave the Church by asking several prominent Catholics (bishops, professors, lay authors, etc.) for their opinion on the reasons and solutions. I think the bishop of Baker, Oregon, Robert Vasa, gives us the most acute explanation:
“We, as Americans, tend to look for rational reasons for action or for failure to act. There is inherent in the question a search for ‘reason,’ but perhaps it is reason itself, cut off from faith, that is precisely the cause of the abdication of the Catholic Faith. Have we not, after all, made the concept of assent to the truths and teachings of the Catholic Faith much more a matter of reason than faith? Phrases like ‘I just cannot believe that’ manifest a great confusion between reason and faith. What we believe as Catholics is certainly reasonable, but raw reason, without any input from Faith, would of necessity reject a vast majority of what the Church believes and teaches. Modern man finds faith unreasonable and therefore unbelievable.
In America there is a very strong notion that what we believe must make perfect sense to us, and that we are somehow automatically absolved from believing that which does not seem to be rational.”