The power of modernity to secularise has been a foundational idea of the western world. Both social science and church history understood that the Christian religion from 1750 was deeply vulnerable to industrial urbanisation and the Enlightenment. But as evidence mounts that countries of the European world experienced secularising forces in different ways at different periods, the timing and causes of de-Christianisation are now widely seen as far from straightforward. Secularisation in the Christian World brings together leading scholars in the social history of religion and the sociology of religion to explore what we know about the decline of organised Christianity in Britain, Europe, the United States, Canada and Australia. The chapters tackle different strands, themes, comparisons and territories to demonstrate the diversity of approach, thinking and evidence that has emerged in the last 30 years of scholarship into the religious past and present. The volume includes both new research and essays of theoretical reflection by the most eminent academics. It highlights historians and sociologists in both agreement and dispute. With contributors from eight countries, the volume also brings together many nations for the first consolidated international consideration of recent themes in de-Christianisation. With church historians and cultural historians, and religious sociologists and sociologists of the godless society, this book provides a state-of-the-art guide to secularisation studies.