“If the Divine call does not make us better, it will make us very much worse. Of all bad men religious bad men are the worst. Of all created beings the wickedest is one who originally stood in the immediate presence of God. There seems no way out of this. It gives a new application to our lord’s words about ‘counting the cost.’” (Lewis, C. S. Reflections on the Psalms. London: Fontana, 1961, p. 32.)
The worst evils are a twisting and distortion of the greatest goods. Sexual sins are so destructive and grievous because human sexuality is one of God’s wonderful masterpieces.
But Lewis isn’t talking about sexuality. He’s talking about spirituality and faith. The reason that so many horrific sins have been committed “in the name of God” is that there is no greater capacity that we as humans have than our spiritual nature. When that nature is distorted or misdirected, terrible evil can result.
There can’t be much evil in the world of invertebrates (except perhaps in the movies—“Attack of the Killer Slugs”!). It is we who are made in God’s image. We are meant to display His character. And it is we who can fall furthest.