It slips so easily off the tongue. In fact, it’s a modern mantra. ‘Religion causes all the wars.’ Karen Armstrong claims to have heard it tossed off by American psychiatrists, London taxi-drivers and pretty much everyone else. Yet it’s an odd thing to say. For a start, which wars are we talking about? Among the many causes advanced for the Great War, ranging from the train timetables on the continent to the Kaiser’s withered left arm, I have never heard religion mentioned.