The idea of holding a church council, which can be attributed to Pius XI and Pius XII, four hundred years after the Council of Trent and one hundred years after the First Vatican Council, as well as the realization of this idea, must be seen in historical perspective. The principal formative influence on the life of the Roman Catholic church until the Second Vatican Council, besides the impact of the institutional and doctrinal differentiation of Christian churches resulting from the Reformation, was the Council of Trent (1545–1563), especially through its decisions on faith and morals. Although the First Vatican Council, through its definition of the universal jurisdictional primacy and infallibility of the pope, had expanded to some extent the decisions made at Trent, it did so without addressing the question of the relationship of primacy and episcopacy. The problem of conformity between proclamation...