Here are 7 reasons why Peter is the Rock:
1) Change of Name in Scripture Signifies Change of Mission.
Think Abram (father), and His new name Abraham (Father of many). Abraham's wife, Sarai (my princess), had her name changed by God to Sarah (Mother of Nations) - See Genesis. How about Jacob (supplanter) having his name changed to Israel (having power with God); or one of my favorite's, Saul (great one), had his name changed to Paul (little one; humility), and God raised him up to be the Great Apostle to the Gentiles!
Jesus changed Simon's name (God has heard) to Peter (ROCK) and this name change, like the others, represents what it means.
2) Historical Context.
At the time of Christ, Keys were a symbol of authority. If a King were to travel outside of their Kingdom, they would literally give their Prime Minister (or Royal Steward) the "Keys to the Kingdom" so the Kingdom can have a visible authority until the King returns. Jesus is King and He has the ability to elect a Prime Minister to govern His Kingdom until He returns as was understood.
"I will place on his shoulder the KEY to the house of David; what he opens no one can shut, and what he shuts no one can open." - Isaiah 22:22
While considering history it is important to know that all Christians for the first 1,000 years of Christianity accepted the authority of Peter and his successors. It wasn't until a political dispute arose when the Church had her first schism in 1054 (East/West).
3) Jesus Tells us and Commands us!
Jesus says what He means and means what He says. He directs His statements to the confessor, not to the confession:
“But what about YOU?” he asked. “Who do YOU say that I am?”
Simon Peter answered, “You are the Messiah, the Son of the living God.” Jesus replied, “Blessed are YOU, Simon son of Jonah, for this was not revealed to YOU by flesh and blood, but by my Father in heaven. And I tell YOU that YOU are Peter, and on this rock I will build my church, and the gates of Hades will not overcome it. I will give YOU the keys of the kingdom of heaven; whatever YOU bind on earth will be bound in heaven, and whatever YOU loose on earth will be loosed in heaven.”
Jesus is talking to Simon Peter (not his confession of faith) and we know from the context that no other interpretation would make literary sense.
4) Unity Requires Authority.
As we read through the Acts of the Apostles we see an actual Church with authority. When Paul has a revelation from God he doesn't start a new denomination, and when other disciples want to create a new denomination they are set straight by the magisterium of the Church (see "gnosticism" and this list of Early Church Heresies - without an authority guiding the Church there would have been the splintering we see today in Protestantism right from the beginning. All Christians accept what the authoritative Church passed down and taught; such as the cannon of Scripture, the Divinity of Christ (Fully Human/Fully Divine), the Apostles Creed, the Trinity, Baptism, etc.; but some reject that it is the Holy Spirit guiding this authoritative Church.)
While the Bible shows that Peter is a sinner who makes mistakes (the Pope is clearly NOT infallible!), he is also referenced as the leader of the Apostles (Matt 10:2). Paul goes to Peter and the Apostles to straighten them out and have them make the official pronouncement regarding Baptism taking the place of circumcision (Acts 15). We also see Church hierarchy (holy order) and Apostolic Succession in the book of Acts with the offices of Apostles, Priests, Elders (Acts 14:23), Bishops, Pastors (Acts 20:17-30) and Deacons (Acts 1,2 & 6) as well as the laying on of hands (Acts 8:17), receiving of the Holy Spirit (John 20:21-22) and anointing to certain roles within the Church (1 Corinthians 12:28-29). These practices continue today in the Catholic Church and you can also find an unbroken line of succession from Peter and the Apostles and ALL of the Catholic Bishops of the Church.
We can trust the Pope's authority and official teachings (on faith and morals) since it is the Holy Spirit that guides the teaching of His Church. Just as the Holy Spirit guided the writing of the Sacred Scriptures, He also guides his Church: "Stand firm and cling to the traditions we taught you, whether by speech or by letter." - 2 Thessalonians 2:16. The Holy Spirit will not leave us orphans (John 14:18) or left hopelessly to define all revelation on our own ("no prophecy of the scripture is of any private interpretation."- 2 Peter 1:20).
Without a visible authority there is unorganized religion, relativity and division ("a house divided will not stand" - Matt 12:22 "That they may be one ... perfectly united" - John 17 "They were one in heart and mind." - Acts 4:32). Business leaders believe this, countries understand it and Jesus knows this truth. Jesus only has one bride and She does not contradict Herself nor suffer from multiple personality disorder (Ephesians 5:27). His Church is "one, holy, catholic and apostolic" (Apostles' Creed). The Church is the salt of the earth, a city on a hill and Jesus doesn't hide Her under a bushel, but lets Her shine as a light to the nations (Matt 5:13-16). The Church is not invisible, a simple idea or any vague interpretation of revelation; "The Church is the pillar and foundation of truth." (1 Tim 3:15) Jesus instructs us to confront the sinner, and if they don't listen, "take it to the Church." (Matt 18:16-17) If we don't follow the Church (governing body; teaching authority), we end up following a man made authority (Mark 7:8) or ourselves and forming God into our own image and likeness.
"We need men who love Jesus Christ and His Church more than their own opinions!" - Bishop Chaput
Following authority (the pastoral care of Peter and the Apostles) is not submitting to a man, but obeying the plan that Jesus gave us. There is no contradiction between following Peter and Jesus since this is what Jesus commanded us to do!
5) Jesus is the Rock too!
But isn't Jesus the Rock, Foundation and Chief Cornerstone? ... YES! When you compare/contrast analogies, both can be correct depending on the context. For example, I can be the "shepherd" to my family (or a pastor can be the shepherd to their congregation) without taking away from Christ as The Shepherd! The vine, gate, bridegroom, priest, father, doctor, etc. can all effectively be used to describe people other than Jesus without taking away from His primacy and supremacy. The rock is a symbol of authority, foundation and stability. Jesus is THE primary rock that the Church is built on and He has elected to give us a visible authority to sit in His seat of authority to look after His Kingdom while He is away. Jesus is The Rock and "only foundation" (1 Cor 3:11) that He has built upon. Any authority that isn't built upon Christ is weak, insufficient and will crumble!
6) Jesus spoke Aramaic (not Greek).
The Greek (and English) break down in translation since we can't use the same word for rock to be a male's name (since the Greek word for rock is "petras" which is feminine), but Jesus didn't speak Greek. French would be a better translation where you can embrace the wit of Christ when He says, "You are 'Pier' and on this 'Pier' I will build My Church." (you are "Rock" and on this "Rock" I will build ...)
7) The Bible Confirms that Peter has a Unique Authority!
Jesus preaches from Peter's Boat (Luke 5:3)
Jesus tells Peter to feed His Sheep and tend His Flock (John 21:15-17)
Jesus establishes His Church with Peter as the Leader (Matt 16:18) giving him the Keys, the Seat and a new Name.
The Bible lists Peter first (throughout) and more frequently than the Apostles (Peter mentioned by name 191 times; the rest of the disciples listed 130 times combined)
Peter is FIRST: Sermon (Acts 2:14); Miracle (Acts 9:38); Commissioned to Proclaim the Gospel to Gentiles (Acts 15:7); Rebuker (Acts 5:15); Healer (5:15) The doctrine of the circumcision was committed to Peter (Galatians 2:7); After His resurrection, Jesus went to see Peter before any of the other apostles (1 Corinthians 15:5-7).
Peter's first epistle is from Rome (1 Peter 5:13) and Tradition tell us He also died in Rome.
The Bible describes a Church with authority (Binding and Losing ability; "Whoever hears you, hears me" - Luke 10:16, "Practice and Observe everything they tell you" - Matt 23-2)
JESUS IS WISE and the Bible tells us that a wise man doesn't start building something without first calculating the cost (Luke 14:29); Jesus is Strong, He won't let the gates of Hades prevail (Matt 16:19) and won't let His House be overthrown (Luke 11:22); He will not divorce His Bride (Matthew 19:4-6); The wise man builds His house on ROCK (Matt 7:29)!
There is only one Church that we can trace back to the Church that Jesus established on St. Peter nearly 2000 years ago (there can only be one original). While we are all sinners (including the Pope), we have been blessed with numerous holy, heroic leaders of the Church (29 or the first 30 Popes were martyred for the faith)! Seek this Church, find this Church and follow this Church that Christ so awesomely established, built and has given to us!
Please Note: The Pope has only exercised his ability to speak "ex cathedra" - from the chair - 2 times in the history of the Church. The Church has authority along with the ability to speak on behalf of the Holy Spirit (like Scripture does - through flawed vessels) as we can see in it's first Council (there has been 20 Church Councils in its 2000 year history) in Jerusalem in 48AD (Acts 15:6-31):
"The apostles and elders met to consider this question (of circumcision). After much discussion, Peter got up and addressed them: 'Brothers ... We believe it is through the grace of our Lord Jesus that we are saved, just as they are.' The whole assembly became silent as they listened to Barnabas and Paul telling about the signs and wonders God had done among the Gentiles through them. When they finished, James spoke up. 'Brothers,' he said, 'listen to me. Simon, has described to us how God first intervened to choose a people for his name from the Gentiles. The words of the prophets are in agreement with this, as it is written:
‘After this I will return and rebuild David’s fallen tent. Its ruins I will rebuild, and I will restore it, that the rest of mankind may seek the Lord ...
Then the apostles and elders, with the whole church, decided to choose some of their own men and send them to Antioch with Paul and Barnabas...So we all agreed to choose some men and send them to you with our dear friends Barnabas and Paul to confirm by word of mouth what we are writing. It is the decision of the Holy Spirit and of us not to burden you with anything beyond the following requirements ... So the men were sent off and went down to Antioch, where they gathered the church together and delivered the letter. (Acts 15:6-30)
"Be it known to you, my lord, that Simon [Peter], who, for the sake of the true faith, and the most sure foundation of his doctrine, was set apart to be the foundation of the Church, and for this end was by Jesus himself, with his truthful mouth, named Peter, the first fruits of our Lord, the first of the apostles; to whom first the Father revealed the Son; whom the Christ, with good reason, blessed; the called, and elect" (Letter of Clement to James 2 [A.D. 221]).