The historian and socialist R.H. Tawney’s Religion and the Rise of Capitalism (1926) was one of the most influential works of non-fiction to be written in Britain during the first half of the twentieth century. Fusing historical, religious and social thought, it is the central work of Tawney’s oeuvre, but commentary upon it has focused narrowly on its historiographical significance. When attention is paid to the text and its context, it becomes clear that it arose from Tawney’s project of renewing Christian teaching on economic and social conduct. Crucial to the recovery of Tawney’s purposes here is his contribution to a Church of England report on Christianity and Industrial Problems (1918), a key text in the growth of socialism in the established church in the inter-war years. This article draws on the hitherto unused papers of the committee behind this report to demonstrate for the first time that Tawney was its main author; and it reveals that this was the first place in which he set out the ideas which would become Religion and the Rise of Capitalism. These discoveries force us to reassess Tawney’s early political thought, especially The Acquisitive Society (1921), and to conclude that Tawney as a thinker was not merely an ‘ethical socialist’, but a thinker profoundly indebted to a tradition of austere, Anglo-Catholic socialism associated especially with the theologian Charles Gore. This also revises our view of Tawney’s conception of capitalism, showing that he saw ‘usury’ as pivotal to its historical ascent.