It is widely recognized that the sixteenth-century Reformation remains one of the most fascinating and exciting areas of scholarship. A central and important question, raised by intensive modern research on the Renaissance and late medieval scholasticism, concerns the intellectual origins of the Reformation. This updated and expanded version of the original, highly-acclaimed edition of 1987 explores the complex intellectual roots of the Reformation, offering a sustained engagement with the ideas of humanism and scholasticism. McGrath demonstrates how the intellectual origins of the Reformation were heterogeneous, and draws out the implications of this finding for our understanding of the Reformation as a whole. McGrath’s reading of the Reformation against its complex intellectual background opens up new insights into this highly significant historical phenomenon. Yet this is more than a fascinating exploration in the history of ideas: it is also a defence of the entire enterprise of intellectual history in the face of social historical approaches, and a reaffirmation of the importance of ideas to the development of history.