38 Do you think, wretched heretic of today, that Peter would have been the more blessed now, if he had said, 'You are Christ, God's perfect creature, His handiwork, though excelling all His other works. Your beginning was from nothing, and through the goodness of God, Who alone is good, the name of Son has been given You by adoption, although in fact You were not born from God.' What answer, think you, would have been given to such words as these, when this same Peter's reply to the announcement of the Passion, Be it far from You, Lord; this shall not be, was rebuked with, Get behind Me, Satan, you are an offense unto Me ? Yet Peter could plead his human ignorance in extenuation of his guilt, for as yet the Father had not revealed all the mystery of the Passion; still, mere defect of faith was visited with this stern condemnation.
Now, why was it that the Father did not reveal to Peter your true confession, this faith in an adopted creature? I fancy that God must have grudged him the knowledge of the truth; that He wanted to postpone it to a later age, and keep it as a novelty for your modern preachers. Yes; you may have a change of faith, if the keys of heaven are changed. You may have a change of faith, if there is a change in that Church against which the gates of hell shall not prevail. You may have a change of faith, if there shall be a fresh apostolate, binding and loosing in heaven what it has bound and loosed on earth.
You may have a change of faith, if another Christ the Son of God, beside the true Christ, shall be preached. But if that faith which confesses Christ as the Son of God, and that faith only, received in Peter's person every accumulated blessing, then perforce the faith which proclaims Him a creature, made out of nothing, holds not the keys of the Church and is a stranger to the apostolic faith and power. It is neither the Church's faith, nor is it Christ's.
Source: On the Trinity (New Advent)