The abundance of sources, the extremely broad range of subjects dealt with in late medieval canon law, and the still unsatisfactory and heterogeneous state of research suggest that a history of canon law in the late Middle Ages should be organized as a description of the surviving legal collections in chronological order. Such an approach not only provides a reliable foundation for future research, but also reflects the state of legal development that contemporaries had access to and illustrates the many contingencies that shaped the development of the legal books which constituted the official Corpus iuris canonici from 1582 to 1917.