The physicist Richard Feynman used to make a joke36 about a posteriori conclusions - reasoning from known facts back to possible causes. 'You know, the most amazing thing happened to me tonight,' he would say. 'I saw a car with the licence plate ARW 357. Can you imagine? Of all the millions of licence plates in the state, what was the chance that I would see that particular one tonight? Amazing!' His point, of course, is that it is easy to make any banal situation seem extraordinary if you treat it as fateful.