I discovered later, and I'm still discovering right up to this moment, that is it only by living completely in this world that one learns to have faith. By this-worldliness I mean living unreservedly in life's duties, problems, successes and failures. In so doing we throw ourselves completely into the arms of God, taking seriously, not our own sufferings, but those of God in the world. That, I think, is faith.

The martyred Christian: 160 readings from Dietrich Bonhoeffer (ed. Scribner, 1983)