Youcat commented through CCC - Question n. 51 - Part I.

YOUCAT Question n. 51 - Part I. If God is all-knowing and all-powerful, why does he not prevent evil?

(Youcat answer) “God allows evil only so as to make something better result from it” (St. Thomas Aquinas).   

A deepening through CCC

(CCC 314) We firmly believe that God is master of the world and of its history. But the ways of his providence are often unknown to us. Only at the end, when our partial knowledge ceases, when we see God "face to face" (1 Cor 13:12), will we fully know the ways by which - even through the dramas of evil and sin - God has guided his creation to that definitive sabbath rest (Cf. Gen 2:2) for which he created heaven and earth. 

Reflecting and meditating 

(Youcat comment) Evil in the world is an obscure and painful mystery. Even the Crucified asked his Father,“My God, why have you forsaken me?” (Mt 27:46). Much about it is incomprehensible. One thing, though, we know for sure: God is 100 percent good. He can never be the originator of something evil. God created the world to be good, but it is not yet complete. In violent upheavals and painful processes it is being shaped and moved toward its final perfection. That may be a better way to classify what the Church calls physical evil, for example, a birth defect, or a natural catastrophe. Moral evils, in contrast, come about through the misuse of freedom in the world. “Hell on earth”—child soldiers, suicide bombings, concentration camps—is usually man-made. The decisive question is therefore not, “How can anyone believe in a good God when there is so much evil?” but rather, “How could a person with a heart and understanding endure life in this world if God did not exist?” Christ’s death and Resurrection show us that evil did not have the first word, nor does it have the last. God made absolute good result from the worst evil. We believe that in the Last Judgment God will put an end to all injustice. In the life of the world to come, evil no longer has any place and suffering ends.

(CCC Comment)

(CCC 309) If God the Father almighty, the Creator of the ordered and good world, cares for all his creatures, why does evil exist? To this question, as pressing as it is unavoidable and as painful as it is mysterious, no quick answer will suffice. Only Christian faith as a whole constitutes the answer to this question: the goodness of creation, the drama of sin and the patient love of God who comes to meet man by his covenants, the redemptive Incarnation of his Son, his gift of the Spirit, his gathering of the Church, the power of the sacraments and his call to a blessed life to which free creatures are invited to consent in advance, but from which, by a terrible mystery, they can also turn away in advance. There is not a single aspect of the Christian message that is not in part an answer to the question of evil.

(This question: If God is all-knowing and all-powerful, why does he not prevent evil? is continued)