I find this topic and conversation quite interesting...
He saith unto them, But whom say ye that I am?
Mat 16:16 And Simon Peter answered and said, Thou art the Christ, the Son of the living God.
Mat 16:17 And Jesus answered and said unto him, Blessed art thou, Simon Bar-jona: for flesh and blood hath not revealed it unto thee, but my Father which is in heaven.
Mat 16:18 And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.
As I see it looking at this in context, Jesus asked the entire group who they thought He was...Simon Bar-Jona spoke up first and echoed what was obviously the perception of the entire group...
And Jesus says to Simon, You are Peter (which means what??? Stone, or little rock, or something to that effect?)...
One could suppose that Jesus then walks up to Peter and puts His arm around him to signify to the rest of the group when he then says, and upon 'this' (little) rock, I will build my church...But then maybe not...
Jesus was the big rock, the rock of offense...He knew it...They knew it...They were all familiar with the Old Testament...
But I suspect Jesus was pointing at Himself when he said, and upon 'this' (exceedingly large) rock, I will but my church, contrasting Himself with Peter ...He didn't say 'upon you, or upon Peter'...They knew who THE rock was...
And immediately after, Peter was severely rebuked as a doubting Thomas and even called Satan...
And as we see, Jesus is talking about a future church...And Peter preached...And people were saved under his ministry, and filled with the Holy Spirit...And he baptised them after they were filled with the Spirit...
And then Paul shows up...And God shows Paul the mystery of the church...