Albert Camus or Isaac Asimov, religiously
I believe the answer is:
atheist
(Other definitions for atheist that I've seen before include "One who does not believe in the existence of a god" , "Someone who denies the existence fo God" , "One who has no belief in a god" , "Person who does not believe in existence of a god" , "One who disbelieves the existence of gods" .)