Because beliefs are so well matched with their opposites, they not only focus on the resistance of others, they are dependent on it. When that opposition fades so does the passion with which one’s own belief is held. To be an atheist you will need to find just the right theist to face off against. How could one deny the existence of God unless someone supplies a God that can be denied? The odd consequence of this is that one cannot be a believer without simultaneously being an unbeliever. Believing is an inherently self-contradictory act.