“Those genuine and clear [truths] which flow from the very pure fountains of the Scriptures cannot be disturbed by any arguments of misty subtlety. For this same norm of apostolic doctrine endures in the successors of him upon whom the Lord imposed the care of the whole sheepfold , whom [He promised] He would not fail even to the end of the world , against whom He promised that the gates of hell would never prevail, by whose judgment He testified that what was bound on earth could not be loosed in heaven … Let whoever, as the Apostle proclaimed, attempts to disseminate something other, than what we have received, be anathema. Let no approach to your ears be thrown open to the pernicious plans of undermining, let no pledge of revising any of the old definitions be granted, because, as it must be repeated very often, what has deserved to be cut away with the sharp edge of the evangelical pruning-hook by apostolic hands with the approval of the universal Church, cannot acquire the strength for a rebirth nor is it able to return to the fruitful shoot of the master’s vine, because it is evident that it has been destined to eternal fire. Thus, finally, the machinations of all heresies laid down by decrees of the Church are never allowed to renew the struggles of their crushed attack.”

(From the epistle “Cuperem quidem” to Basiliscus Augustus January 10, 476; Denzinger, H., & Rahner, K. (Eds.). (1954). The sources of Catholic dogma. (R. J. Deferrari, Trans.) (p. 64). St. Louis, MO: B. Herder Book Co.)