His Patrimoniality, the estimable Fr Hunwicke has begun a series on councils. I commend it to you. I am looking forward very much to seeing what he has to say.
This is a subject which has exercised my mind for quite a number of years. There is a general assumption that councils teach infallibly and certainly with great authority. However:
1) I am not convinced that, say, Nicæa I saw itself that way. Several of those who agreed to homoousios there didn't feel particularly bound to teach consubstantiality afterwards. Its prohibitions against bishops changing sees didn't prevent Eusebius, a signatory, changing from the see of Nicomedia to Constantinople. To my view, the fathers at Nicæa saw the council as being not a lot different from a local council, just on a bigger scale. It was an agreement, not a mouthpiece for the Holy Ghost.
2) How is one to regard a council, such as at Ephesus, where the business gets under way before an important party even has time to arrive and discuss the matter? Old Cyril of Alexandria (who presided) must be one of the several examples of people who became saints despite the magnitude of their, shall we say, darker side.
The Syrians, who at that time had a problem with the dual nature in one person of our Lord, were the party concerned. They went off into schism as a result, labelled as Nestorians. A later great figure of the Syrian (or, better, Assyrian) schism, Babai the Great, with his work on qnome and parsopa came up with, basically, what Ephesus taught, but in different language. Are they to be held to the verbal formulation of Ephesus (which they don't like for reasons as much historical as anything else) if what they believe adds up to the same thing in any case?
3) The same thing can probably be said of Chalcedon and the Copts, Armenians and Jacobite Syrians.
4) Athanasius' little councilettes at Alexandria (21 bishops in 362) and Antioch (25 bishops) managed to overturn the Arian council(s) of Ariminum/Seleucia (500 (!) bishops in 359), confirmed at Constantinople in 360 (when the world groaned to find itself Arian) which certainly saw itself as an Ecumenical Council. No doubt he swung it because he had the support of the new Emperor (successor to Julian the Apostate), Jovian.
5) By the middle ages, it seems to have been established that a Canon (with an anathema) in a Council document was highly authoritative, perhaps infallible, whereas the preamble and any notes were illuminative (if I can put it like that). So when Trent teaches whoever denies that the Sacrament of Order consists of both major and minor orders, anathema sit, that's gotta be taken really really seriously, but when in a note it lists the orders as porter, lector, exorcist, acolyte, subdeacon, deacon, priest; that can be taken as seriously illuminative, but not infallible in any way (which it can't be, since the East does it differently, and Trent knew that—Council of Florence, and all that).
6) Vatican II has no canons at all. Some people, therefore, treat the whole thing as infallible. Is it all to be considered 'preamble' and therefore illuminative, or infallible?
Others consider infallible the bits they like (Gaudium et Spes, for instance) and pretend the bits they don't like (the use of Latin must continue in the Western rites) don't exist. Traddies can be as guilty of this as trendies.
Paul VI and Bd John XXIII seem to have thought that the council was to proclaim no new dogmas. What, then, does that make of the occasions when it does seem to vary from what has been held before? (e.g. Holy Orders as being Bishop, Priest, Deacon, see Trent above). Pope Benedict's idea of the Hermeneutic of Continuity is probably the best approach to this, but there are wrinkles that have to ironed out.
The East (when it stops trying to long for the days of the Emperor) seems to think that 'reception' is what makes the difference between a dodgy Council (like Ariminum/Seleucia, or the Robber Council of Ephesus) and a pukka one. I think that this is rather like our notion of the Sensus Fidelium. In other words, it all depends on whom you speak to. When Gregory the Great went to Constantinople as Papal Legate, he found almost every single church there still basically Subordinationist (kind of Arian). It was really only after centuries that Nicene orthodoxy really rooted itself in the East.
It has often been said that the Church thinks in centuries. Perhaps here we have an indication to Reception/Sensus Fidelium. It isn't an instant thing, but can take a very long time. Like the psychohistory of Hari Seldon, it only operates on a vast scale. A priest once commented to me that we are, sub specie æternitatis, still living in the Early Church; this is, of course, right. The bigger picture is something we will only see when we have all gone to our reward.
What I think is harder to prove is that the Holy Spirit whispers in the ears of every Father in an Ecumenical Council in such a way that, in effect, every Ecumenical Council takes verbal dictation from God. In some ways, a Council opens up more questions than it hopes to solve; the present dialogue taking place between the Society of St Pius X and what it calls 'Conciliar Rome' is a good example of this. That the Society is still trying to settle this matter, and hasn't simply separated itself from the Church, as so many have before, is a very good sign, and may perhaps help us to settle this issue of what a Council actually is.
If in any way I have gone over the line in this, I apologize, and submit my judgment to that of the Church. I am just trying to feel my way through an interesting set of ideas.