The heart of man is revealed in temptation. Man knows his sin, which without temptation he could never have known; for in temptation man knows on what he has set his heart. The coming to light of sin is the work of the accuser, who thereby thinks to have won the victory. But it is sin which is become manifest which can be known, and therefore forgiven. Thus the manifestation of sin belongs to the salvation plan of God with man, and Satan must serve this plan.
– Dietrich Bonhoeffer –