Tim Keller offered this observation in his introduction to “The Reason for God”.

A faith without some doubts is like a human body without any antibodies in it. People who blithely go through life too busy or indifferent to ask hard questions about why they believe as they do will find themselves defenseless against either the experience of tragedy or the probing questions of a smart skeptic. A person’s faith can collapse almost overnight if she has failed over the years to listen patiently to her own doubts, which should only be discarded after long reflection.