Internet Catholic and Protestant pugilists have had plenty of “fun” for a long time quarreling about Matthew 16:18:
And I tell you, you are Peter, and on this rock I will build my Church, and the gates of Hades shall not prevail against it. (RSV2CE)
I am not going to sit here and tell you that anything that I have to say here will settle the arguments. That would be silly of me. What I am going to present, though, is something that I cannot recall having seen discussed elsewhere before. I do not pretend to any innovation in what I am offering here; I am pretty sure that someone must have made this observation before. After all, New Testament has been studied for two millennia or so. :-) The most I will say is that I have not seen it before, which surely says more about me than what the history of biblical studies actually holds.
Let us compare part of Mt. 16:18 with the following from the Gospel of St. John:
I am the living bread which came down from heaven; if any one eats of this bread, he will live for ever; and the bread which I shall give for the life of the world is my flesh. (John 6:51, RSV2CE)
This verse is a subject of controversy as well, but I do not think that the disputes about it dwell much on what I shall say here. The thing that I find interesting is the use of the demonstrative this in the two passages: this rock and this bread. What I would like to observe is that the usage of this construction in the two verses is basically identical, and that this fact ought to tell us something about how to interpret it. This is a case, as it were, of letting Scripture interpret Scripture. Let me explain.
In John 6:51 it is very obvious what this bread is referring to: it is referring back to the “living bread” mentioned earlier in the sentence. My suggestion is that the usage in Matthew 16:18 is the same: “this rock” refers back to the “rock” mentioned earlier in the sentence. The semantic significance of this in Matthew seems obvious: Peter really is the rock Jesus identifies as the one on which He will build His Church.
Obviously it cannot be as simple as that. There is a tiny bit of complication in the Greek gender endings of the two usages of rock: Petros vs. Petra. I have three replies to that. First off, given the comparable construction in John 6:51 (where the meaning is pretty obvious), it seems unnecessary to suppose that the Lord is injecting a new and previously undisclosed secret referent into the sentence in Matthew. More than unnecessary: it seems like special pleading to avoid something the interpreter does not wish to see. Secondly, as many have said, the gender difference between the two nouns seems like a non-starter given the fact that Petra is feminine and consequently cannot serve as Simon’s new name. So it only makes sense that the genders do not match. But that opens up the old can of worms that I am unable to resolve better than others, so I will not belabor the point here. Lastly, I think we have good reason for believing that Petros and Petra are Greek translations of something that was actually said in Aramaic (where, if memory serves, the gender issue does not exist). Why? Because that is what he is called by St. Paul repeatedly, and it is also said of him in John 1:42. So we have two external witnesses to the name having been given in Aramaic. Given these facts, I do not think that there is a genuine gender difference intended in Matthew 16:18 but rather one necessitated by translation.
My notion about the this (noun) construction in John 6:51 and Mt. 16:18 may not satisfy everyone, but it seems to me to support the Catholic belief that Peter is the Rock of the latter passage.