8. And, lastly, in these great promises Peter is specially set forth as the type and the efficient cause of visible unity in the Church. Such was the very purpose of Christ, that His disciples might be one, as He and the Father are one. For this end, in the words of S. Augustine, "He entrusted His sheep to Peter, as to another self, He willed to make him one with Himself;" and in the words of S. Leo, "He assumed him into the participation of His indivisible unity."[33] But this is seen no less plainly in the words of Christ, than in the Fathers; for He made _one_ Rock, _one_ Bearer of the keys, _one_ Confirmer of the brethren, and _one_ Shepherd. The union of millions of naturally conflicting wills in the profession and belief of one doctrine is almost the very highest work of divine power; and as grace, that is, the Holy Spirit diffused in the heart, is the inward efficient of this, so the outward, both symbol and instrument, is the Primacy, that "other self" which the Lord left in the world. And as the Church of God through every succeeding age grows and expands, the need of this power becomes greater and not less, and reverence to that "single chair in which unity was to be observed by all,"[34] a more imperative virtue, or rather an ever-deepening instinct, of the Christian mind. But antiquity itself drew no other conclusions from the concentration of these great privileges in the person of Peter. We have but to go back to a time before the present nationalities of Europe, those jealous foes of Peter's authority, had come into existence, and we find the chief men of France, and Spain, and Italy, interpreting the above texts as we have done. Take one whose testimony from the circumstances of his life ought to be above suspicion. John Cassian was by birth a Scythian, was educated in a monastery at Bethlehem, travelled through Egypt, and made himself acquainted with its most distinguished religious men, went to Constantinople, and was ordained deacon by S. Chrysostome, and afterwards at Rome priest by Pope Innocent I. On the capture of Rome by Alaric, he settled at Marseilles, about the year 410, and there founded two monasteries. In his work on the Incarnation he says,[35] "Let us ask him, who is supreme, both as disciple among disciples, and as teacher among teachers, who, steering the course of the Roman Church, held the supremacy as well of the faith as of the priesthood. Tell us, therefore, tell us, we pray, O Peter, Prince of the Apostles, tell us how the Churches ought to believe. For just it is that thou, who wast taught of the Lord, shouldst teach us, and open to us the door whose key thou hast received. Shut out all who undermine the heavenly house, and turn away those who attempt to make an entry through treacherous caverns and illicit approaches; because it is certain that no one shall be able to enter the door of the kingdom, save he to whom the key placed by thee in the Church shall open it.