I think it's pretty normal to have doubts about God, the Bible, and Christianity.  Certain people just seem to be better at ignoring those doubts, much to their credit.  And when a person has doubts, the standard procedure is to ask questions and do research and keep poking and prodding until at least some of those questions are answered.  But I think a skeptic will reach a point where, regardless of how many of their questions are answered and how good the answers are, even if all the questions are answered and they're answered well and the person becomes the smartest, most answer-filled person on earth, it still won't be enough to fully understand God and be completely sure of everything.  And when that point is reached, as much as this is a crappy "Christianese" response, that person will need to take an illogical, irrational leap of faith in believing in a God that's beyond our understanding.  If we're on the edge of a cliff and God is on the other side of the valley, I personally don't think anyone will ever have enough building material to make a bridge to God.  At some point, a leap is required. #religion