II. The proposal to reconsider the question proceeds from Antichrist or the Devil himself.
Since, therefore, the universal Church has become a rock (petra) through the building up of that original Rock, and the first of the Apostles, the most blessed Peter, heard the voice of the Lord saying, “You are Peter, and upon this rock (petra) I will build My Church,” who is there who dare assail such impregnable strength, unless he be either antichrist or the devil, who, abiding unconverted in his wickedness, is anxious to sow lies by the vessels of wrath which are suited to his treachery, while under the false name of diligence he pretends to be in search of the Truth.
And his unrestrained madness and blind wickedness has deservedly brought contempt and disrepute on himself, so that while he rages against the holy church of Alexandria with diabolical purpose, men may learn the character of those who desire to reconsider the Synod of Chalcedon. For it cannot possibly have been that an opinion was there expressed contrary to the holy Synod of Nicæa, as the heretics falsely maintain, who pretend that they hold the faith of the Nicene Council, in which our holy and venerable fathers, being assembled against Arius, affirmed not that the Lord's Flesh, but that the Son's Godhead was homoousion with the Father, whereas in the Council of Chalcedon against the blasphemy of Eutyches, it was defined that the Lord Jesus Christ took the reality of our body from the substance of the Virgin-mother.
Source: Letters (New Advent)