>>546695
>Why does He say "upon this rock" instead of "you the rock"?
For he said "You are Rock and upon this Rock I will build my Church"
> Why do the pronouns shift?
You mean gender shift. For Greek, like all normal languages, have genders.
> Did He start speaking to someone else?
Nope.
> It is "upon this rock" because it is referring to Peter's confession, "Thou art the Christ, the Son of the living God".
And you know that as Catholic we can also say this but it does not make Peter=Rock any less valid, on contrary, it reaffirms this.
>When Christ says "And I say also unto thee, That thou art Peter", He does not give Peter this name, He already did (John 1:42)
On contrary.
And he brought him to Jesus. And Jesus looking upon him, said: Thou art Simon the son of Jona: thou shalt be called Cephas, which is interpreted Peter.
It's future tense
>So when He says "thou art Peter, and upon this rock I will build my Church", He explains Peter's name, as meaning that he the first rock built on the Rock that he has confessed, as being the twelve he is the first of many living stones.
And upon this Rock, Cepha or Petra, upon Peter, he will bulit his Church. For as Church Fathers said:
"[Christ] made answer: ‘You are Peter, and upon this rock will I build my Church. . . . ’ Could he not, then, strengthen the faith of the man to whom, acting on his own authority, he gave the kingdom, whom he called the rock, thereby declaring him to be the foundation of the Church [Matt. 16:18]?" (The Faith 4:5 [A.D. 379]).
"It is to Peter that he says: ‘You are Peter, and upon this rock I will build my Church’ [Matt. 16:18]. Where Peter is, there is the Church. And where the Church is, no death is there, but life eternal" (Commentary on Twelve Psalms of David 40:30 [A.D. 389]).