Even to an atheist – someone who denies the existence of god – religion must have some social significance. This is because religious behaviour has shaped so much of human history. It is not really possible to understand the history of the West, for example, without knowing at least the basics of Christian belief since so many of the societies and rulers concerned adhered to that religion. The same goes for other parts of the world where other major religions are prevalent. Besides, religion matters because billions of people on the planet remain religious. At a personal level, religiosity matters because it is a big part of how many people identify themselves and organise their lives.