"I am not sure – given the virtual apartheid that existed linguistically and in day-to-day life of the Greek and Latin Churches since the 5th century A.D. – that a Greek would have recognized the same Faith in Rome or Spain even in the first millennium, let alone understand the language of the Liturgy, yet the Churches were in full communion."
I believe quite the opposite -- that they *would* have recognized the same faith. There is no way to prove either proposition, I would suppose.
Think of St. John Cassian, who moved back and forth between East and West -- he obviously recognized the same faith in Egypt and the Holy Land, and when his writings about what he experienced there returned to the West, they inspired and influenced Western monasticism. Think, even, of the fact that at Charlemagne's coronation, the Pope celebrated a Liturgy of St. John Chrysostom.
The world of the first half of the first millenium was a rather cosmopolitan one, and I would argue that the world of the second half of the first millenium was far more cosmopolitan than is commonly assumed -- both in the east and the west.
The linguistic "apartheid", as you call it, contributed to the schism in that it delayed the East's awareness of the rising strain in the West that ended up dominating Catholicism after the political takeover by the Franks.
I know that when I visit pre-schismatic church buildings, listen to pre-schismatic western chant, read pre-schismatic western patristic writings, read pre-schismatic western liturgical texts, etc..., it seems *very* familiar to me.
But that is just an opinion. It may be that all that kept the bishops in communion with each other were agreement on dogmatic declarations of faith. I think it was more than that, but again, this is difficult to prove.
"The real Great Schism that widened the gap between the two Churches occurred not in 1054 but in 1870 (Vatican I), when the ex-cathedra infallibility of the Bishop of Rome was added (and eventually dogmatized)..."
I would agree completely that it is the dogmatic declaration of infallibility that seems to be the major obstacle at this time. The filioque is still a major dogmatic theological issue, at the heart of things is are core differences in how we look at grace, original sin, etc... -- but I'm not sure to what extent the later Roman teachings are considered to be dogmatized (although they will *all* have to be dogmatized for a union to take place -- they are issues, and would need to be resolved in Council.)
But I simply do not understand how, given the fact that Orthodox Christians willfully, in full knowledge, reject that conciliarly-declared dogma of the Catholic Church, we could be invited to partake of communion in Catholic Churches. How can one be considered to be of the same faith when one specifically rejects a dogma?
Calling Vatican I a local council doesn't help -- are we to say that the Pope is infallible in the West, but not in the East? He loses his infallibility when he crosses into the territory of the Patriarch of Serbia, or any doctrinal statements he makes in writing are infallible in Rome, but not in Constantinople?
For one the "spectator" role of the laity was introduced early into the Latin Church, where only the priests received the Body and the Blood. That would have seemed mighty strange to put it mildly.
Second, the Catholics assure me that their early Mass resembles Vatican II's Novus Ordo Mass more than the Tridentine.
As for the Pope serving (liturgy means service not celebration) the Liturgy of St. John Chrysostom, I would imagine it was in Latin and as far as the external impression is concerned it could be anything but recognizable. I would imagine the Eucharist consisted of a wafer and a separate Chalice, since mixing the bread with wine is a strictly Eastern innovation in the first millennium.
Even the Eastern Catholics, with the exception of Melkites perhaps, who serve the Liturgy of St. John Chrysostom show enough external variation that one immediately senses it is not an Orthodox church.
And if they could understand Latin, they would immediately pick u on the filioque that was recited throughout Frankish lands and the Visigoth Spain.
By the time Cardinal Humbert "excommunicated" the Ecumenical Petriarch in 1054, one of things listed on his "grievance" roster was that the Orthodox clergy don;t look like the "real" Latin priests so much so that they are unrecognizable in their appearance as being of the same Church!
The Frankish pilgrims to Jerusalem noticed that the Greeks were not reciting filioque in the 9th century and reported them as saying "heresy." Likewize, Frankish missionaries in Bulgaria reported "heretical" Greeks whose clergy is married, and re "re-educating" Bulgarians not to fall for the heresy of "eliminating" the filioque.
How much the Church was unrecognizable to the Greek side is obvious from just reading St. Photios's list of "heresies" against the Latin side in the 9th century when suddenly the East and the West came to a knowledge what has been happening for several centuries in the ecclesiasticl linguistic aparthied.
Perhaps St. Cassi an had no problem go back and forth, and perhaps it was understood that some variation would exist, and his attitude was more akin to that of modern-day Catholics who say that our disagreements do not change the unity of our Faith, bot only indicate that some areas of the Faith must be coordinated.
I agree that the Filioque is a major stumbling block, but I will say that the Catholic teaching is not wrong, but merely incomplete!. They stop one step from the finish line and in that sense express the Faith incompletely.
I also agree that the "real" fires of the Purgatory are an item that will have to be addressed, and perhaps recanted, but Thad doesn't mean that the entire dogma of the afterlife's 3rd place is wrong; perhaps some aspects of the dogma of the Purgatory are, but not all.
Then we also must address if the fires of Hell will be real and gnashing of the teeth as well? After all, the sinners will be resurrected to, so that they can "fry" in eternal fire which, by all accounts, would have to be real as well.
But this leads us into absurdity of speculation: what will satan and his demons fry in? They have no teeth gnash, and no bodies to hurt. Will there be a special virtual fire for angels?
Finally, what makes Church a "valid" church? It is its inerrancy and if so, whose side is inerrant? Does our error make our sacraments invalid? We could answer that by posing a question if the moral state of decay of a priest invalidate his ability to perform sacraments? The answer is, of course, NO. East priest is also a sinner, and therefore there are no sinless priests. Yet they can administer absolutions, as vehicles (unclean as they may be) of the Holy Spirit for the benefit of the believer. Then, even if the Catholic Church were in error, their sacraments would remain valid because their priesthood received their authority from the same Apostles as ours.
The reason we cannot commune is not because one side is in error and the other one is right, but because the Eucharist is not a vehicle, a means of achieving union of Orthodox Faith, but an expression of one.
St. Cassian lived in the 4th century, hardly enough time for the complete linguistic aparthied, and certainly hardly enought time to develop "unrecognizable" praxes on both sides. In St. Cassian's time the filioque was not an isse even in Spain (it was to wait another 200 years for that to be initiated).
Yet, the West was already divided on the issue of "original sin" which the Easter managed to ignore until much later, just as the West managed to ignore the Capadoccian Fathers' clear cut assertion that we can not know God's essence, but only His uncreated enegries.
Thus, lots of theological discrapancies existed in the so-called "undivided" Church of the firts millennium, yet they intercommuned freely, consider the unresolved issues something that had to be worked out, but at the same time no one doubted that it was one and the same Church in its core.