A major problem which occupied thinkers in the later Middle Ages was the question of the internal structure of the Church and the proper interrelationship of its members. Dr Tierney's 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). It is concerned particularly with the juristic development of the fundamental conciliar doctrine, the assertion that the universal Church was superior to the Church of Rome, with a consequent denial of the Pope's supreme authority.