It's a geopolitical concept, an empire united around the emperor, whose decrees and laws will be obeyed from his subjects within that territory and way of life and civilusation accepted by all, which had its impact on how christians viewed the validity of faith once it became official state religion and moreover the sole spiritual bound among those who inhabited the empire.
Therefore, this one empire, one emperor are essential for christian doctrines to be named ecumenical, since at issue was the faith of subjects of the one empire, which saw itself as the inhabited earth, or the whole world and because the same as with the state laws, the teachings of the church were to become ecumenical with the guaranty of the emperor.


Were in this sort of system no deffects from which the real ecumenicity of christians was hindered?
How far has its inefficacy affected christian society during the first millenium?
How ecumenical were the ecumenical councils?

Actually, there were always substantial Christian communities outside of the Roman oikumeme--the entire Eddesene Church, for instance, was largely under Parthian, then Persian jurisdiction.

Pockets, let us call them so, such churches as the one of eddesus, which showes the deffects of the oecumene dream. The borders of the civilised inhabited world werent always clear as the theory had it. Real life and theory are part of what ecumenity is.
And this is the question to answer. How ecumenical, as we claim them theoreticaly to be, were ecumenical councils?

I have a friend who denounces all conclusions of the ecumenical councils on the basis of a certain answer to your question. He has developed quite an alternative system of doctrines. Sort of like all of Protestantism has to in order to justify its existence. My friend is very bright, but seems to epitomize a certain answer to your question. Perhaps it is right that it is only fear of chaos that keeps us united. I do not know. But so long as I'm Catholic I shall adhere to it.

Of course, as with all things, here too, we have two extremes, which are one of absolute ideal of ecumenicity of oecumene and its ecumenical council's theory and the other one of its absolute denial.

1. "Anarchist"protestants.
2. "Parlamentary" (conciliatory) orthodox
3. "monarchial" roman catholics.

The Church of the East was hardly a pocket. By the late second century, it had established itself in India; by the fourth century, it stretched from Mesopotamia to China. From the fourth through the thirteenth centuries, it was the single largest Church in the world, greater than the Latin and Byzantine Churches combined. But for the depredations of Tamurlane, it probably would have converted China, which would have changed all human history. Chinese bishops were visiting Byzantium and Rome as late as the 1240s.

The church of east? You mean the one of eastern borders extended up tp far east. The eastern church goes alongside of eastern empire borders, which do not include Persia nither India etc within it.
That is why as extension they are pockets in and out of the empire (oecumene).

I try to avoid Wiki but here is a fascinating quote about Timur (Tamurlane): Timur's campaigns sometimes caused large and permanent demographic changes, northern Iraq remained predominantly Assyrian Christian until attacked, looted, plundered and destroyed by Timur leaving its population decimated by systematic mass slaughter..[42]

Was the Church of the East the largest in terms of adherents or geographical extent?

Both.

I agree with Stuart (and that doesn't happen every day ) - I don't have time right now to search out the reference, but the Assyrian Church at one time had more than 300 bishops in China alone.

Now, I grant you that this was in an era when the geographic scope of a bishopric was significantly smaller than what we're used to today (where some such span an entire continent). However, the fact remains, the geographic span of the Assyrians as a whole was incredible. It's harder to put numbers to the faithful, as no one was printing anything akin to the Annuario Pontificio or the census data coming out of the Hartford Studies, but it is pretty obvious that - had that growth gone uninterrupted - many of us would be celebrating according to the Anaphora of Holy Addai and Mari.

Many years,

Neil

To repeat myself, what is the church of east within the concept of roman empire oecumene? It is clear that it is the church within eastern part of that empire. It is within that empire that the schools of christian thoughts were located. Outside of its borders we find only pockets, extensions and offsprings of the oecumene christianity. That's why areas outside of empire were places of refuge for nonofficial christianity.

In east there was never a sort of independent christian oecumene, a christian God's kingdom on earth, outside of the roman empire, as there was in west with franks in 9 century.

The Franks very much considered themselves within the Roman Empire. The endeavored constantly to have that status recognized in Constantinople. The various schemes over the next two centuries to marry off the heir of the Emperor of the Romans to a daughter of the Basileus of Constantinople shows how strong the attraction was even in the West.

Despite that, as part of the roman empire, since they were playing a political game within the rules already settled, which would not allow a radical new foundation of roman oecumene, it was clear that with them there was e fresh start, the birth of an western oecumene with an emperor crowned by the bishop of west, the pope.
What the latin way of thought was lacking apart of its aspiring ideal, the universal ruling bishop, was the political support, found in the newly from pope crowned emperor.

This article is almost a year old, but I thought it was relevant to the discussion:
http://news.assyrianchurch.com/ancient-assyrian-monastery-unveiled-to-public-4/898