God is infinitely more powerful than the Devil and his hosts. So why doesn’t God prevent them from their evildoing on planet earth? We could ask a similar question about why God doesn’t stop human beings from committing wicked deeds. Evil’s continuing presence among us is a mystery we can’t fully figure out in this life.
Nevertheless, we can say this much: God allows evil because He’s powerful enough to bring out of even the greatest evil a much greater good.
The crucifixion of Jesus Christ provides a vivid illustration of this reality. According to the Gospel, when “Satan entered Judas,” one of the twelve Apostles, he went out to betray Jesus (see Luke 22:3-14). So the worst evil we can imagine — the torture and murder of God’s innocent Son — occurred through the Devil’s influence.
Yet the triumph of the empty tomb transformed the horror of the Cross. Satan was thwarted. When Jesus rose from the dead, He displayed God’s power to bring out of the greatest of evils an even greater good: the world’s redemption.
Meanwhile, our days in this life provide a season for God to test, purify, strengthen, and perfect us, making us fit to live with Him forever in heaven. To that end, demons serve as useful tools for Him as they constantly test us by tempting us, so that we become purer and stronger and closer to perfection every time we resist temptation.
In this sense, we might say, quoting St Augustine: “As an artist, God makes use even of the Devil.”
– Paul Thigpen-
Manual for Spiritual Warfare, TAN books, 2014.