(31) “Simon, Simon, behold, Satan demanded to have you, that he might sift you like wheat, (32) but I have prayed for you that your faith may not fail; and when you have turned again, strengthen your brethren.” (33) And he said to him, “Lord, I am ready to go with you to prison and to death.” (34) He said, “I tell you, Peter, the cock will not crow this day, until you three times deny that you know me.”
-Luke 22:31-34
What beauty! The Lord Jesus powerfully exhorted Peter in this passage. Yes, he prophesied the three-fold denial. We must also remember the seriousness of Peter’s role among the apostles. Satan demanded to have him. Satan knew there was something special about Peter and wanted to strike him down, to take him away from the mission of Jesus. In verse 31, “you” is plural. In verse 32, “you” is singular. Take that into consideration. Jesus spoke to Peter while referencing and addressing the apostles. However, in the following verse, it is the faith of Peter himself that will strengthen his brethren.
Peter is a symbol of unity of the Church. Why? Because Jesus entrusted this role to him. The faith and strength of the universal pastor, the visible head of the Catholic Church, is part of what makes the church visible. Yes, we Christians have an invisible unity; we call it the mystical body of Christ spread throughout the world. In addition, we also have a visible unity. God became incarnate, became visible. Think about evangelism. Is the fruit of evangelism only a mere agreement to believe the same things the evangelizer believes? It can’t be!
Yes, we need belief, we need faith. But, to say the unity of the Christian people is only invisible is wrong. To say the church is the entire Christian people spread throughout the world with no visible unity offends the action of God. God became incarnate. He did not make himself less visible but more visible in the person of Jesus Christ. The Incarnate Word is the very reason redemption is possible for us today. Did Jesus say you must agree with what he taught? No, he said “follow me,” “take up your cross,” “love one another as I have loved you.” These are action words, not hide-inside-and-be-only-intellectual words.
Think about it. How else will anyone come to believe that Jesus Christ was sent by the Father but by visible Christian unity? Have you not read the prayer of Jesus himself in regard to this matter?
“I do not pray for these [apostles] only, but also for those who believe in me through their word, that they may all be one; even as thou, Father, art in me, and I in thee, that they also may be in us, so that the world may believe that thou hast sent me. The glory which thou hast given me I have given to them, that they may be one even as we are one, I in them and thou in me, that they may become perfectly one, so that the world may know that thou hast sent me and hast loved them even as thou hast loved me.”
-John 17:20-23
What beauty! Can you begin to see the significance of Jesus’ exhortation to Peter? Peter was the visible sign of unity among the apostles. For proof, read the Acts of the Apostles and notice how frequently Peter speaks for the apostles or in representation of the community. Did this unity dissolve when Peter died? No, it continued! Catholics call that apostolic succession. I’m not sure what other denominations call it.
Acts 1:12-26 has the first story of apostolic succession. The apostles discern and choose someone to replace Judas Iscariot. They enroll Matthias as an apostle. This doesn’t mean the apostleship of ministry of Jesus is limited to twelve people. Rather, it demonstrates the continuity and necessity of people to take responsibility for the mission of Jesus. This action shows that the visible unity (apostolic) and universal mission (catholic) of the one Church of Christ is meant to be carried on through the ages, and is not meant to die off as the apostles died off.
The Chair of Peter testifies to that continued unity of the Christian people. Is there one Lord? Then there is one Church. How many New Jerusalems appear in the vision John has in Revelation? One! There was one holy city of Jerusalem, one covenant between God and His people. There is one Bride of Christ to whom he weds himself. Yes, we are different members and parts, but of the same body. That body is visible. It was visible 2,000 years ago and it is visible today.
St. Paul affirms this when he writes that he is eager to maintain the unity of the Spirit in the bond of peace. He says there is one body and one Spirit, one hope, one Lord, one faith, one baptism, one God and Father of all (Ephesians 4:1-6). He is clear. What else does he say about the Church? He says it is built upon the foundation of the apostles and prophets, Christ Jesus himself being the cornerstone (2:20). This echoes the language of Acts 1:12-26. Yes, the Lord Jesus is the cornerstone, is the Head of the Church. The Church is also built upon the apostles and their faithfulness to Christ. Remember again what Jesus said to Peter (Luke 22:32).
This “foundation of apostles” is echoed in Revelation. Remember it is a vision of the Church finally triumphing and meeting the Lord face to face. It is envisioned as a holy city, “The New Jerusalem.” John says that this city had twelve foundations, and on them the twelve names of the twelve apostles of the Lamb (21:14). Hello? John said twelve three times. This reminds the reader of the (desired) unity of the twelve tribes of Israel. They were scattered through a certain land area but all united in the one holy city.
So too, the Christian people are scattered throughout the world but all (meant to be) united in the Chair of Peter, to be united in the Catholic (universal) Church. The Christian people have their earthly-holy city in Vatican City. Let us rejoice in this great gift! May the faith of Peter and his successors strengthen us to follow Jesus to the Cross.

The Chair of St. Peter
This article writes about the same topic but in a different light.