Unbelievers: theory about Big Bang, still fuzzy. Many theories. Not sure. Still trying to work out what life is.
Believers: have the bible, also fuzzy. believe in God because (1) touched/experienced God (to varying degrees) (2) believe and are convicted to believe because of 'faith' (are attracted to the bible's message of love)
If God wanted us to make the bible alot clearer with logical explanations for everything, he could have I'm sure. But then everyone would have no reason not to believe and there wouldn't be the right motive to want to know God anymore. The bible states that if we came to him even though we didn't see him or touch him, our motives are greater and better than those who had to touch him to believe.