Secularization traces the decline of religion and the rise of secular belief systems. But it also touches on the transition from traditional to modern systems of organization, the replacement of metaphysical beliefs with science, the transition from community to association and much more besides. The debate about secularism and secularization has become a central issue in politics, public policy and international affairs. There is a long history of thinking about the religious and the secular, but the modern debate has special features and a great urgency mainly as a result of fears about religious fundamentalism, religious revival, political Islam and religious nationalism. Volume One explores the history and meaning of key terms: secular, secularism, secularity, secularization and laicity. It is primarily concerned with the philosophy and theology of the secular and examines the evolution of the debate from St Augustine's two cities to contemporary writings and is not confined to Christian debate. Volume Two deals with the sociology of secularization and contains the classic statements by sociologists such as Max Weber, Georg Simmel, Bryan Wilson, David Martin, and Thomas Luckmann. Volume Three considers American exceptionalism. Much the debate in sociology has centred on the question of America's differences from secular Europe. Religion and politics have been significantly interconnected in American history. America is a very special but influential case of secularization and merits a separate volume. Volume Four involves the comparative sociology of modern religious revivalism and the notion that we are in a post-secular society. The manifestations of religious revival in post-secular societies are truly global. This volume looks at the revival of world religions and popular religions such as spirit possession in the post-communist societies.