One spring morning in Tucson, Arizona, in 1994, an unknown philosopher named David Chalmers got up to give a talk on consciousness, by which he meant the feeling of being inside your head, looking out ?" or, to use the kind of language that might give a neuroscientist an aneurysm, of having a soul. Though he didn't realise it at the time, the young Australian academic was about to ignite a war between philosophers and scientists, by drawing attention to a central mystery of human life ?" perhaps the central mystery of human life ?" and revealing how embarrassingly far they were from solving it.