I trust that readers will recall the emphasis laid by Blessed John Henry Newman on the essentially negative function of the Papal Ministry. " ... the Church of Rome ... has originated nothing, and has only served as a sort of remora, or break in the development of doctrine ... such I conceive to be the main purpose of its extraordinary gift."
This, of course, was also affirmed by Vatican I in its lapidary assertion that the Holy Spirit was not promised to the Successors of S Peter so that they could promote new doctrines, but to help them to defend and teach what had been handed down through the Apostles, the Deposit of Faith.
In the first millennium, a pope might associate with himself a Synod of those bishops who happened to be in Rome. We should expect this to be in discharge of the Ministry of resisting error which is the Pope's essential function.
So it was that in 679-680, an Anglo-Saxon bishop called Wilfrid who found himself in Rome on hs own business, was included in a synod of 125 bishops, gathered to act collegially with Pope Agatho in condemnation of the Monothelite heresy. (S Agatho, by the way, was one of those popes who, in the period after the heretic-pope Honorius I, had to try clear up the mess bequeathed by that disastrous pontificate. This sanitary job, incidentally, took some ten pontificates to complete. Nasty business. Smelly work.)
S Wilfrid was invited to state his own faith on the controverted points, not as an individual, but on behalf of the "provincia sive insula de qua venerat". This he did, and the Gesta of the Synod duly recorded that "placed with the other 125 fellow-bishops in Synod in the Seat of Judgement, and on behalf of the whole Northern part of Brittain and Ireland, and the islands which are inhabited by the nations of the Angles, the Brittons, the Scots and the Picts, he confessed the true and Catholic Faith and conferred upon it the authority of his signature (cum subscriptione sua corroboravit)."
The Ecclesiology of this is very plain, and is identical with the anti-heretical teaching of S Irenaeus in the second century: the Catholic Faith is 'corroborated' by the agreement of a significant body of bishops, acting in union with the Successor of S Peter, and witnessing to the faith handed down in all their own orthodox particular Churches.
To quote Newman again, "the Church of Rome possessed no great mind in the whole period of persecution. Afterwards, for a long while it has not a single doctor to show; St Leo, its first, is the teacher of one point of doctrine; St Gregory, who stands at the very extremity of the first age of the Church, has no place in dogma or philosophy."
Exactly. Synods ... and popes ... do not have the munus of brilliantly 'developing' Faith or Morals so that what this decade desires to teach will (to the eyes of poor ordinary Christians) look like the diametrical opposite of what was taught a decade previously.