The effects which follow too constant and intense a concentration upon evil are always disastrous. Those who crusade, not for God in themselves, but against the devil in others, never succeed in making the world better, but leave it either as it was, or sometimes even perceptibly worse than it was, before the crusade began. By thinking primarily of evil we tend, however excellent our intentions, to create occasions for evil to manifest itself.

The devils of Loudon (ed. 1971)