Papacy & Christian Unity
The Pope
As Vicar of Jesus Christ, the Pope governs the Catholic Church as its supreme head. The Pope, as Bishop of Rome, is the chief pastor and shepherd of the whole Church. We believe that the Pope is the successor of Peter, and his bishops are successors of the Twelve Apostles.
It is clear throughout that it is a question of the bishops acting in conjunction with their head, never of the bishops acting independently of the Pope. In the latter instance, without the action of the head, the bishops are not able to act as a College: this is clear from the concept of "College." This hierarchical communion of all the bishops with the Supreme Pontiff is certainly firmly established in Tradition. (Lumen Gentium, Note of Explanation)
In the Acts of the Apostles, we come to know Peter is the head of the early church. When Peter is given the “keys to the kingdom,” Christ is establishing the divine office of leadership over the church. The permanence of the office of the Pope is essential to the everlasting nature of the church.
"The Roman Pontiff, head of the college of bishops, enjoys this infallibility in virtue of his office, when, as supreme pastor and teacher of all the faithful – who confirms his brethren in the faith – he proclaims by a definitive act a doctrine pertaining to faith or morals…The infallibility promised to the Church is also present in the body of bishops when, together with Peter's successor, they exercise the supreme Magisterium," above all in an Ecumenical Council. When the Church through its supreme Magisterium proposes a doctrine "for belief as being divinely revealed," and as the teaching of Christ, the definitions "must be adhered to with the obedience of faith." This infallibility extends as far as the deposit of divine Revelation itself. (CCC 891)
Divine assistance is also given to the successors of the apostles, teaching in communion with the successor of Peter, and, in a particular way, to the bishop of Rome, pastor of the whole Church, when, without arriving at an infallible definition and without pronouncing in a "definitive manner," they propose in the exercise of the ordinary Magisterium a teaching that leads to better understanding of Revelation in matters of faith and morals. To this ordinary teaching the faithful "are to adhere to it with religious assent" which, though distinct from the assent of faith, is nonetheless an extension of it. (CCC 892)
Christian Unity
Unity is essential for the followers of Jesus. John’s gospel reminds us, “The glory which You have given Me I have given to them, that they may be one, just as We are one; I in them and You in Me, that they may be perfected in unity, so that the world may know that You sent Me, and loved them, even as You have loved Me.” (John 17:22-23)
The Catholic Church is united under the leadership of the Bishop of Rome, the Pope. Historical breaks and schisms have left us fractured, with the Eastern Orthodox churches no longer in full unity with Roman Catholicism. Beginning with John XXIII and continuing through the papacy of John Paul II and our current pope, the movement to come together in full Christian unity has been underway.
And Jesus came and said to them, "All authority in heaven and on earth has been given to me. Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you; and lo, I am with you always, to the close of the age."
Matthew 28: 18-20 (RSV-CE)