THE POPE: SIGN AND PRINCIPLE OF UNITY
The pope is the bishop of Rome, the Church headed by the Apostle Peter before his martyrdom at the command of the Emperor Nero. It is clear in Scripture that Jesus chose Peter to lead the Apostles and that his leadership would have a unique role in the foundation of His Church and in preserving the Gospel He handed on to them.
[Jesus] said to them, “But who do you say that I am?” Simon Peter said in reply, “You are the Messiah, the Son of the living God.” Jesus said to him in reply, “Blessed are you, Simon son of Jonah. For flesh and blood has not revealed this to you but my heavenly Father. And so I say to you, you are Peter, and upon this rock I will build my church, and the gates of the netherworld shall not prevail against it. I will give you the keys to the kingdom of heaven. Whatever you bind on earth shall be bound in heaven; and whatever you loose on earth shall be loosed in heaven.”Matthew 16:15-19
Simon’s confession of faith was inspired by God, and Jesus declares that this divine aid to take hold of the truth makes Simon (and not just his faith) the rock foundation of the Church, so much so that Jesus changes Simon’s name to the Rock (Kephas in Aramaic (see John 1:42) or Petros (Peter) in Greek). Jesus further gives to Peter the role of leadership among the Apostles by telling him “you must strengthen your brothers.” (Luke 22:32) and “feed my sheep” (John 21:15-19). Peter continued to exercise this leadership in the life of the early Church at the Council of Jerusalem (Acts 15), declaring what “we believe” (v. 11), even to the extent that the Church under his leadership can speak in the name of the Holy Spirit (v. 28).
The men who have succeeded Peter as the bishop of the Church in Rome continue to exercise the same leadership over the universal (i.e., Catholic) Church, even from the earliest times. For example, St. Clement (pope around the year 80 AD) exercised authority over the Church at Corinth, even though St. John the Apostle was still alive (cf. his Letter to the Corinthians).
The ministry of the pope guarantees the fidelity of the Church to Gospel that Jesus entrusted to the care of Peter and the Apostles. It is how Jesus fulfills the promise to preserve the Church in His truth.
I have much more to tell you, but you cannot bear it now. But when he comes, the Spirit of truth, he will guide you to all truth. He will not speak on his own, but he will speak what he hears, and will declare to you the things that are coming.John 16:12-13
The guarantee of divine protection for the Church to profess and teach the truth is expressed in the doctrine of Papal Infallibility. The pope cannot err when formally declaring matters of faith and morals, not because of his personal holiness or wisdom, but because of God’s special guidance.