Paul is clear in 1 Corinthians 3:11
“For no other foundation can anyone lay than that which is laid, which is Jesus Christ.” We can’t look to a mere human being as the foundation of the Christian church! “It is better to trust in the Lord than to put confidence in man.”
(Psalm 118:8). Like David said, “The
Lord is my rock”
(Psalm 18:2) “And who is a rock, except our God?”
(Psalm 18:31).
Jesus Christ obviously knew we needed a human leader for His Church, If it’s important for a country to have a president to perserve unity, it’s even more important for a worldwide church to have a leader. *We *didn’t invent this system, Jesus gave it to us through the Apostles, later written down into the Scriptures. Sure it would be nice if we could see Jesus physically leading the Church, but instead he chose to work through mere men,(following Scripture and Sacred Tradition, guided by the Holy Spirit) until he comes again. I trust Him to appoint His Popes through Apostolic succession. The Holy Spirit worked though “mere men” to write Scripture, who are you to change Scripture because in it Jesus appoints a “mere man” on whom to build his Church? He appointed a “mere man” named Moses to lead his people and give them the 10 commandments.
“Stand firm and hold fast to the traditions you were taught, either by oral statement or by a letter of ours.” 2 Thessalonians 2:15 The Catholic Church has held these Sacred Traditions intact for over 2000 yrs. Of course, the core of Christianity is Jesus Christ, the Pope is simply carrying out his part in that design as a vicar of Christ.
“But if I should be delayed, you should know how to behave in the household of God, which is the church of the living God, the pillar and foundation of truth.” Will you accept teachings in *some *scripture and not
others? The Bible isn’t a salad bar, you can’t take the peas and leave the carrots!
Peter was not “rock solid” at this point in time. If we read on in Matthew 16
, just a few verses after Jesus spoke of the rock, we find Christ rebuking Peter for trying to hinder His ministry: “But He turned and said to Peter, Get behind Me, Satan! You are an offense to Me, for you are not mindful of the things of God, but the things of men.”
(Matthew 16:23) Later, it was Peter who denied three times that he even knew Jesus
(Matthew 26:69-75). So he obviously had some growing to do in his relationship with the Lord, and Jesus knew that
(Luke 22:31-32).
Yes, we are all well aware of when Jesus rebuked Peter, and that he denied Jesus 3 times. You are right, Peter wasn’t rock solid, yet. He did not believe that he could be capable of denying Jesus. What you may be forgettng is that after the resurrection, Jesus confirmed Peter as the head of the Church.
“Jesus said to Simon Peter ‘feed my lambs’… tend my sheep’…‘feed my sheep.’” John 21:15-17
I see a connection between Peter denying Jesus 3 times and Jesus asking him to feed and tend the lambs of his Church 3 times. I think this tells us something about forgiveness, mercy and that whatever God has chosen us to do(,even if it’s for a mere man to be the rock on which he would build his Church, )with His Grace, we can become a new creation, to do His will. Peter would later be crucified for being a Christian… only he was crucified upside down because he did not consider himself worthy to be crucified like Christ. That sounds rock solid to me. By the way,This also explains the upside down cross you may see in religious art, it’s a symbol for St. Peter.
). The Bible is but one of the Tradition! 
