Canon Law, Religion, and Politics extends and honours the work of the distinguished historian Robert Somerville, a pre-eminent expert on medieval church councils, law, and papal history. Reflecting the focus but also the range of Somerville's studies in medieval canon law in the era before Gratian and later, the essays explore the transmission of canonical and theological texts--in particular regarding the Eucharist--as well as the significance of the texts and their complex manuscript traditions. Several essays examine texts in their practical context, highlighting the effects of canon law on religious institutions such as monasteries and the practices at law courts of medieval western Europe. Four studies dealing with the ius commune--the conjunction of canon and Roman law in daily practice, a topic of general and perennial interest--show once again how our understanding of canonistic and civilian legal developments in medieval and late medieval religious and intellectual history is evolving with greater precision when assumptions and generalities are analysed in the light of manuscript sources. The pioneering influence of Somerville and his colleagues is evident in all of the essays. They broaden current understanding of the place of law and theology in a crucial period of history, the eleventh to the thirteenth centuries. This work is written in honour of Robert Somerville, professor of history and Ada Byron Bampton Tremaine Professor of Religion at Columbia University. His scholarly honours are legion, including a fellowship in the Medieval Academy of America and the Commission Internationale de Diplomatique. He is a corresponding member of the Monumenta Germaniae Historica in Munich as well as the Bavarian Academy of Sciences. He has received numerous awards including two John Simon Guggenheim Memorial Fellowships. He is the author of numerous books and articles.