Bishops have always played a central role in the making and enforcement of the law of the Church, and none more so than the bishop of Rome. From convening and presiding over church councils to applying canon law in church courts, popes and bishops have exercised a decisive influence on the history of that law. This book, a selection of Anne J. Duggan’s most significant studies on the history of canon law, highlights the interactive role of popes and bishops, and other prelates, in the development of ecclesiastical law and practice between 1120 and 1234. This emphasis directly challenges the pervasive influence of the concept of ‘papal monarchy’, in which popes, and not diocesan bishops and their legal advisers, have been seen as the driving force behind the legal transformation of the Latin Church in the twelfth and early thirteenth centuries. Contrary to the argument that the emergence of the papacy as the primary judicial and legislative authority in the Latin Church was the result of a deliberate programme of papal aggrandizement, the principal argument of this book is that the processes of consultation and appeal reveal a different picture: not of a relentless papal machine but of a constant dialogue between diocesan bishops and the papal Curia, in which the ‘papal machine’ evolved to meet the demand.