There are understandable reasons why you might doubt science and believe in fairies instead - indeed, science tells us so. That is the theme of developmental psychologist Hood's perky book. What he rather effortfully dubs our "supersense" is not a sense, but a "mind design" or innate tendency to interpret the world in terms of causation and intention, and thus to ascribe supernatural causes to random or otherwise explicable phenomena. Children think supernaturally from the start, and grown-up secular atheists often have supernatural beliefs, too - defined not just as belief in ghosts or telepathy, say, but as any kind of essentialist thinking. (My favourite way of determining whether an apparently ice-cold paragon of rationality was prey to supernatural beliefs was to measure whether he or she was more or less "able to throw darts at pictures of babies".) The book ends with a strange, woolly plea for the preservation of supernatural beliefs in the form of "sacred values" on which social cohesion apparently depends. Well, it worked for the Nazis.