[The presence of evil] in his life provokes him into either overcoming it or yielding to it. If the first, it has led him to work for his own improvement; if the second, it has led him to acknowledge his own weakness. Sooner or later, the unpleasant consequences of such weakness will lead him to grapple with it and develop his power of will. That is part of the mission of evil, to stimulate him into its own destruction and to force him into his own betterment. Immediately and directly, it may either strengthen him or weaken him. Ultimately, it can only strengthen him.

~ Paul Brunton