I was taught in my youth that faith and doubt were incompatible.  Now, I find they go hand-in-hand.  I feel that faith without doubt is largely dishonest, or as Sartre described it, “Bad faith.”

And note what Unamuno had to say on the subject:

Those who believe that they believe in God, but without passion in their hearts, without anguish in mind, without uncertainty, without doubt, without an element of despair even in their consolation, believe in the God idea, not God himself. ~Miguel de Unamuno

And William Butler Yeats puts this truth so pithily:

Oh God, guard me from those thoughts

Men think in the mind alone.

He who sings a lasting song

Must think in the marrow bone.