No they don't. They say, "I may not know absolutely, but I believe and have faith." There is a huge difference. If I see a sign on the door of a business that makes the claim that there is beer inside, I may not know absolutely, but I am pretty sure it's in there. Having faith is making the conscious decision to believe in something beyond ourselves, greater than ourselves. Believing in a creator without "proof" other than the miracles we see every day is something that goes beyond science and the physical realm to let us know that the way we live our lives matters. The Bible is more than just a collection of stories, it is a map that shows us the way to conduct our lives for the maximum return in joy and satisfaction.