Obsessions occur in two forms: questions and assertions. For instance, a contamination obsession might take the form, “what if my hands are still dirty?” Or it might pop up as, “your hands are dirty!” Uncertainty in present in both. In assertions, it becomes prominent as the OCD sufferer begins begin to question why the thought of dirty hands has become so distressing. Therefore, uncertainty in one form or another plays a central place in the great majority of obsessions. That’s why OCD is called “the doubting disease.”
Why does God allow tormenting uncertainty? The reason is, according to Luther, the deep-seated, almost ineradicable pride we have in our wisdom. We think we can figure everything out, including how to overcome all our fears and feel good. This pride must be destroyed. How does God destroy it? By allowing us to suffer tormenting uncertainty. God has to teach us that in the last analysis we cannot rely on ourselves for anything, including certainty about our well being. Rather we must learn to rely on Him. Luther writes,
God does not want us to glory in our physical birth, in our strength, in the freedom of our will, or in our wisdom and righteousness. All this must be mortified…God mortifies His own in various ways to the point of despair, and then He lifts us up again, so that by experience we are compelled to say, “I did not do this, though I expended all my strength, but the hand of the Lord did it.” Therefore He thoroughly afflicts us, He purifies us well so that we may learn to rely on Him completely. But this will not happen unless our presumption has been destroyed.
This is all part of God’s plan for shaping us into the sort of people he wants us to be—namely, people who trust in him fully and not in themselves. We have a choice: We can willingly go along with his plan for shaping us or not. In one sense it doesn’t matter; because God loves us and his plan for our salvation will move forward no matter what. Yet it is pleasing to God when he sees us cooperating with him and following his commands—and we are commanded to have faith and trust in him. For the OCD sufferer, therefore, it is wise to set the goal of willingly tolerating painful uncertainty as much as we can in order to obtain the gift of trusting in him.