Book excerpt: This book is an account of those canonistic theories of Church government which contributed to the growth of the conciliar theory, and which were formulated between Gratian's "Decretum" (c. 1140) and the Great Schism (1378). "Foundations of the Conciliar Theory" is considered by many to be one of those rare books that significantly influenced twentieth century medieval historical studies. Now again available in a new enlarged edition, it will continue to be an indispensable work for all those interested in Church history and the Middle Ages.