God is infinitely good and all his works are good. Yet no one can escape the experience of suffering or the evils in nature which seem to be linked to the limitations proper to creatures: and above all to the question of moral evil. Where does evil come from? “I sought whence evil comes and there was no solution”, said St. Augustine, and his own painful quest would only be resolved by his conversion to the living God. For “the mystery of lawlessness” is clarified only in the light of the “mystery of our religion”.The revelation of divine love in Christ manifested at the same time the extent of evil and the superabundance of grace. We must therefore approach the question of the origin of evil by fixing the eyes of our faith on him who alone is its conqueror.
From the Catechism of the Catholic Church 385