The community of believers in Christ. Three approaches to the meaning of the Christian Church are distinguishable in Catholic teaching. Before the Eastern Schism in 1054 the accepted definition of the Church was the whole body of the faithful united under allegiance to the Pope. With the rise of Eastern Orthodoxy, which redefined the Church without obedience to the Pope, Catholicism began to stress the term Roman Catholic Church in order to emphasize the need for allegiance to the Bishop of Rome.
With the rise of Protestantism in the sixteenth century, the Catholic Church sensed the need to bring out the visible nature of the Church, challenged by the Reformers. Accordingly there entered the stream of Catholic theology the definition of the Church based on the words of St. Robert Bellarmine (1542-1621). "The one and true Church," he said, "is the assembly of men, bound together by the profession of the same Christian faith, and by the communion of the same sacraments, under the rule of legitimate pastors, and in particular of the one Vicar of Christ on earth, the Roman Pontiff." In modern times, Pope Pius XII defined the Church on earth as the mystical body of Christ, according to the teaching of St. Paul that the faithful followers of Christ are joined together in a mysterious union, of which Christ himself is the invisible head. The Second Vatican Council added the title "People of God" to describe the Christian world. Without abandoning the earlier definitions the Council offered this one to bring out the fact that all Christians belong by special title to God, who calls them to faith in Christ, and that they form a people, i.e., a chosen community, on whom God confers his special blessings for the benefit of mankind.