Is religion in decline? What is its relationship to secularization? One argument is that modernisation differentiates society, leading to the shrinking and relativization of religion. Another view is that a diversity of religious worldviews strengthens religion: religion only declines when suppliers become complacent and monopolistic. Finally, others draw attention to the importance of demography and nationalism in spurring religious revival. I also consider how modernity may be boosting fundamentalist variants of religion.