Many of us have endless questions about faith, spirituality, and the place of religious thinking in the world. But one central question - perhaps the central question - about religion has remained strangely inaccessible: Why do we have it at all? Until recently, if you'd asked this of most anthropologists, they'd have told you that the question was ill-formulated and too vague to be of scientific interest. In fact, the intellectual tools for thinking about the problem simply didn't exist. Now, says Pascal Boyer, they do, provided by theories and research in evolutionary biology and cognitive psychology.