5. In the fourth and fifth centuries the Petrine theory was generally accepted by the Church Fathers East and West.[169:1] The theory had become a dogmatic principle of law founded upon historical facts. Optatus, the African Bishop of Mileve (c. 384), strongly asserted the visible unity of the Church and the immovable _Cathedra Petri_, with the Roman Bishop as Peter's successor.[170:1] Ambrose of Milan (d. 397) gave the Bishop of Rome the same position in the Church that the Emperor had in the Empire,[170:2] and recognised him as the great champion of orthodoxy, but at the same time called Peter's primacy one of confession and faith, not of rank. He put Paul on an equality with Peter. Jerome (d. 419) recognised the Pope as the successor of Peter and said, "Following none but Christ, I am associated in communion with . . . the chair of Peter. On that rock I know the Church to be built."[170:3] Innocent I. (414) made a magnificent defence of the theory. Augustine (d. 430), the greatest of the Latin Fathers, admitted the primacy of Peter and recognised the Roman Bishop as his successor.[170:4] In his remarkable book, the _City of God_, he did more than all the Fathers to idealise Rome as the Christian Zion. Maximus of Turin (d. 450) and Orosius (d. 5th century) bore similar testimony. The Greek Fathers uniformly spoke of Peter in lofty terms as the "Prince of Apostles," the "Tongue of the Apostles," the "bearer of the keys," the "keeper of the kingdom of Heaven," the "Pillar," the "Rock," _et cetera_, but they held generally that Peter's primacy was honorary, and that he transferred his power to both the Bishop of Antioch and the Bishop of Rome.[170:5] But these modifications of the Petrine theory did not arrest the evolution of the papal power. The important historical fact to be taken into account is, that the _belief_ in the supremacy of St. Peter's successor was quite generally recognised and accepted.