If the Apostles by virtue of the commission of Jesus Christ were the perpetual pastors of the Church, and enjoy the perpetual presence of Jesus Christ to the end of time, the Apostolic office is by its own nature perpetual in the Church, and the original Apostles have been succeeded by others. For the same reason, the office of Prince of Apostles must be perpetual. The plenitude of the Apostleship was given to St. Peter alone, under the similitude of the keys, and afterwards the same power was given to the others by participation and in subordination to him. The supremacy of the chief enters, then, into the primary constitution of the Apostolate or Catholic Episcopate, as one of its essential and component parts, and is therefore perpetual. Jesus Christ committed the government of His Church to one supreme Ruler, whose authority was signified by the symbol of the keys. He committed His flock to one chief Pastor, when He said to St. Peter: "Feed my lambs--feed my sheep." {220} If, therefore, the authority of St. Peter expired with his person, then a total and fundamental change took place after his death in the constitution and government of the Church, a supposition not to be admitted for one moment without clear evidence. But there is none such. On the contrary, our Lord declares without distinction or limitation that "there shall be one fold and one shepherd." [Footnote 83] [Footnote 83: John x. 16.] The metaphor of a foundation which He uses to express the supremacy of St. Peter, of itself shows the perpetuity of his office. This supremacy is the Rock on which the Church is built. But a foundation must last as long as the building itself; it can neither be removed nor changed; therefore the supremacy of Peter must endure with the Church itself. Again, the reason for which Christ instituted the Primacy exists always, and, indeed, demands much more imperatively its continuance than it did require at first its foundation. The reason is thus expressed by St. Jerome: "__Ut capite constituto, schismatis tolleretur occasio__"--"That a head being constituted, the occasion of schism might be removed." [Footnote 84] [Footnote 84: Lib. i. adv. Jov. 26.] {221}