Vicar of Christ
(Latin Vicarius Christi).
A title of the pope implying his supreme and universal primacy, both of honour and of jurisdiction, over the Church of Christ. It is founded on the words of the Divine Shepherd to St. Peter: “Feed my lambs. . . . Feed my sheep” (John 21:16-17), by which He constituted the Prince of the Apostles guardian of His entire flock in His own place, thus making him His Vicar and fulfilling the promise made in Matthew 16:18-19.
In the course of the ages other vicarial designations have been used for the pope, as Vicar of St. Peter and even Vicar of the Apostolic See (Pope Gelasius, I, Ep. vi), but the title Vicar of Christ is more expressive of his supreme headship of the Church on earth, which he bears in virtue of the commission of Christ and with vicarial power derived from Him. Thus, Innocent III appeals for his power to remove bishops to the fact that he is Vicar of Christ (cap. “Inter corporalia”, 2, “De trans. ep.”). He also declares that Christ has given such power only to His Vicar Peter and his successors (cap. “Quanto”, 3, ibid.), and states that it is the Roman Pontiff who is “the successor of Peter and the Vicar of Jesus Christ” (cap. “Licet”, 4, ibid.). The title Vicar of God used for the pope by Nicholas III (c. “Fundamenta ejus”, 17, “De elect.”, in 6) is employed as an equivalent for Vicar of Christ.
newadvent.org/cathen/15403b.htm
882 The Pope, Bishop of Rome and Peter’s successor, “is the perpetual and visible source and foundation of the unity both of the bishops and of the whole company of the faithful.”(LG 23.) “For the Roman Pontiff, by reason of his office as Vicar of Christ, and as pastor of the entire Church has full, supreme, and universal power over the whole Church, a power which he can always exercise unhindered.”(LG 22; cf. CD 2,9.)
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We can also look to the Code of Canon Law:
SECTION I.
THE SUPREME AUTHORITY OF THE CHURCH (Cann. 330 - 367)
CHAPTER I.
THE ROMAN PONTIFF AND THE COLLEGE OF BISHOPS
Can. 330 Just as by the Lord’s decision Saint Peter and the other Apostles constitute one college, so in a like manner the Roman Pontiff, the successor of Peter, and the bishops, the successors of the Apostles, are united among themselves.
Art. 1.
THE ROMAN PONTIFF
Can. 331 The bishop of the Roman Church, in whom continues the office given by the Lord uniquely to Peter, the first of the Apostles, and to be transmitted to his successors, is the head of the college of bishops, the Vicar of Christ, and the pastor of the universal Church on earth. By virtue of his office he possesses supreme, full, immediate, and universal ordinary power in the Church, which he is always able to exercise freely.
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