LONDON – War, the systematic and organised use of violence with all its bestial destructiveness, is peculiar to the most advanced of animals, man. Writing in the early sixteenth century, Erasmus considered war “unnatural”. “Animals do not make war on one another. Whoever heard of 100,000 animals rushing together to butcher each other, as men do everywhere?” It was the European thinkers of the eighteenth century Enlightenment who saw the issue of war in perhaps more realistic terms. “Want of a common judge with authority puts all men in a state of nature,” wrote John Locke. Or as Michael Howard, the distinguished war historian, has written more recently, “War is an inherent element in a system of sovereign states which lack any supreme and acknowledged arbiter.” There is probably something in this. After all, the few societies which have never practised war appear to have a common ingredient, a homogeneous culture...