Both the Believer and the Unbeliever Share Doubt and Belief

Just as the believer is choked by the salt water of doubt constantly washed into his mouth by the ocean of uncertainty, so the non-believer is troubled by doubts about his unbelief, about the real totality of the world which he has made up his mind to explain as a self-contained whole… Both the believer and the unbeliever share, each in his own way, doubt and belief.

— Josef Cardinal Ratzinger  <link>