[NRx]

“The Holy Spirit did not depart from the Church. Rome did. "The Holy Spirit was not the personal property of the Roman See.” This statement encapsulates the crux of it all and flies in the face of the scriptural primacy of Peter and his successors that last until the end of time. The Catholic Church is the only Church that has an unbroken line of successors from Peter to this day. Surely, Petrine authority that provided the infallibility in the selection of God’s Word, does not have an expiration date or a termination date based on breakaway branches.

The whole Petrine Infallibility is a Roman invention. See again the 28th canon from Chalcedon. It was never accepted by the entire Church or even most of it. Nor was the Roman Canon of Scripture accepted in the East. To the extent that synod you cite carries weight, it is not by virtue of Papal decree, but rather acceptance and reception by the rest of the Church, which in this case did not happen. Not all synods or councils receive universal acceptance.

[Steelfish]

A “Roman invention”
I hadn’t heard that before. And yet the Orthodox Churches until 1054 accepted this “Roman invention” and agreed to the decrees issued under Petrine authority in the first seven councils including the Catholic Nicene Creed. Those decrees were mandates, not suggestions, and were infallible on issues of dogma BECAUSE of Petrine authority.