WHETHER YOUR FAITH is that there is a God or that there is not a God, if you don't have any doubts, you are either kidding yourself or asleep. Doubts are the ants in the pants of faith. They keep it awake and moving.
There are two principal kinds of doubt, one of the head and the other of the stomach.
In my head there is almost nothing I can't doubt when the fit is upon me—the divinity of Christ, the efficacy of the sacraments, the significance of the church, the existence of God. But even when I am at my most skeptical, I go on with my life as though nothing untoward has happened.
I have never experienced stomach doubt, but I think Jesus did. When he cried out, "My God, my God, why hast thou forsaken me!" I don't think he was raising a theological issue any more than he was quoting Psalm 22. I think he had looked into the abyss itself and found there a darkness that spiritually, viscerally, totally engulfed him. I think God allows that kind of darkness to happen only to God's saints. The rest of us aren't up to doubting that way—or maybe believing that way either.
When our faith is strongest, we believe with our hearts as well as with our heads, but only at a few rare moments, I think, do we feel in our stomachs what it must be like to be engulfed by light.