Clare Carlisle in The Guardian:
“Evil” is a strong word, and a provocative one. Nowadays it tends to be reserved for acts of exceptional cruelty: the Moors murders, organised child abuse, genocide. It is not just the extreme nastiness of such acts – and their perpetrators – that makes people describe them as evil. There is something unfathomable about evil: it appears to be a deep, impenetrable darkness that resists the light of reason. To say that a murderer has killed because she or he is evil is really to point to an absence of motive. Far from the usual muddle of human motivation, evil has a cold, horrifying purity. Phrases like “unthinkable evil” or “unspeakable evil” highlight the way the word is used to say the unsayable, to explain the inexplicable.
So how can we think about evil? Perhaps we can't, or shouldn't. Ludwig Wittgenstein famously wrote that we should remain silent about “that whereof we cannot speak” – a quotation beloved of lesser philosophers seeking a convenient way to end an academic paper. On a more practical level, most victims of evil will find that simply coping takes all their energy – and in the midst of their suffering, it may be difficult to disentangle the questions “why?” and “why me?” But the very familiarity of these questions suggests that there is something about evil that calls for thinking. And Wittgenstein's remark about remaining silent can be countered by Martin Heidegger's suggestion that the proper subject matter for philosophical thinking is precisely what is “unthought” and even unthinkable.
The Christian tradition offers huge resources for our thinking about the nature, origin and meaning of evil. This is partly because the history of western philosophy is intimately bound up with Christianity, so that supposedly secular debates on morality and human nature usually involve theological ideas even if these remain implicit. But more specifically, the Christian doctrine of creation makes the question of evil particularly pressing. If the world was designed and brought into being by a perfectly good, just and all-powerful creator, why does it contain evil at all? If God did not create evil, where did it come from? And why would God make human beings capable of extreme cruelty?