Ever since the Enlightenment, deep thinkers have claimed that modernity would drive out religion, probably by the end of the 20th Century. But since the 1970's, that trend has gone into reverse. Newsweek magazine's current cover announces “The Decline and Fall of Christian America,” while a recent book is entitled God Is Back. The contrast illustrates the worldwide tension between secularism in modern political life and the growing prevalence of religious belief. Free-market thinking has some people shopping between denominations. Some traditionalists threatened by the secular world go to extremes. Do religions compete for believers? Which one is likely to win? Why is Osama bin Laden's al Qaeda such a “Modern” phenomenon?