In a historical introduction to each period, the authors discuss major developments in canon law, the individual prefaces, their authors and settings, and their sources and major themes. Early documents reflect the world of the monastic and cathedral school, when compilers attempted to fashion collections of laws that were both faithful to older tradition and suitable for the needs of their local churches. In prefaces to eleventh- and twelfth-century collections, the impact of ecclesiastical reform becomes apparent. Compilers sought to work out a systematic jurisprudence of canon law during the Investiture Contest, as church and secular authority clashed. Prefaces from the twelfth century and later express the professional legal culture of the high Middle Ages: trained lawyers in the environment of both university and papal curia undertook systematic commentary on canon law, employing terms and techniques from the revived study of Roman law.

"This unique book reveals much about those who collected canons in the Middle Ages -- their assumptions about law, the authority of the Church, and the nature of religion". -- John T. Noonan, Jr., United States Circuit Judge