Next, the Father's utterance, This is My Son, had revealed to Peter that he must confess You are the Son of God, for in the words This is, God the Revealer points Him out, and the response, You are, is the believer's welcome to the truth. And this is the rock of confession whereon the Church is built. But the perceptive faculties of flesh and blood cannot attain to the recognition and confession of this truth. It is a mystery, Divinely revealed, that Christ must be not only named, but believed, the Son of God. Was it only the Divine name; was it not rather the Divine nature that was revealed to Peter? If it were the name, he had heard it often from the Lord, proclaiming Himself the Son of God. What honour, then, did he deserve for announcing the name? No; it was not the name; it was the nature, for the name had been repeatedly proclaimed.
This faith it is which is the foundation of the Church; through this faith the gates of hell cannot prevail against her. This is the faith which has the keys of the kingdom of heaven. Whatsoever this faith shall have loosed or bound on earth shall be loosed or bound in heaven. This faith is the Father's gift by revelation; even the knowledge that we must not imagine a false Christ, a creature made out of nothing, but must confess Him the Son of God, truly possessed of the Divine nature. - St. Hilary, *The Trinity*, VI, 36,37