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

—Paul Tillich, Dynamics of Faith

Self-will often wants certainty before it will commit. It waits for proof, for resolution, for clarity that seems reliable. In the absence of those things, it may interpret uncertainty as failure—evidence that whatever is being sought is not really there. Doubt becomes a reason to stop rather than a sign that something real is being engaged.

Tillich suggests that doubt and faith may not be enemies. Faith that has never been tested by doubt may be closer to certainty—which requires no trust at all. The willingness to keep moving toward what cannot be fully seen or proven may be closer to the heart of faith than any confident declaration. Doubt, in this reading, may be less a threat to the inner life than a sign that it is actually alive.