"Doubt is not the opposite of faith; it is one element of faith."-- Paul Tillich

Real faith is not blind.  Real faith takes in doubt and weaves it into the patterns of thought that define it. There is a certain harmony of design that becomes clearer when the darkness of doubt mingles with the vibrancy of faith.  Both are necessary in this tapestry of life, because both become clearer when in concert with each other--but only one feels true.  Without doubt, faith is empty indeed.