Differences in Historical Interpretation
Orthodoxy in the West before the schism was a structurally independent group of Churches whose Patriarchate was in Rome, but whom had their own independent communities throughout Metropolitan and Archepiscopal sees in Europe, some of which were Lyons, Toledo, and Milan. Concurrent with the Great Schism in 1054, a series of events took place which ruptured the continuity of the Orthodox Church in the West with the Church in the East. The interpretation of these events (if one gets their most basic facts straight) can fall into three categories:
1) A developmental interpretation of the great schism, or the "Gradual Estrangement" theory common among Roman Catholics and Protestants, as well as a number of Orthodox convert writers, which predisposes that there were no significant changes in the 11th century that marked schism, and that those who were abandoning Orthodoxy were unaware of such, but that the nature of the divergence of belief from Orthodoxy did not become clear until much later (this view is most clearly expressed in popular literature about the history of Orthodoxy from writers such as Fr John Meyerndorff and Francis Dvornik).
2) A catastrophic interpretation of the events surrounding the great schism, or the "Ethnic Cleansing" theory proposed by a number of Orthodox writers on the West, including Fr. John Romanides and Vladimir Moss, which predisposes that heretics physically overtook the Orthodox and wiped them off the map in their native lands, or subjugated them to slavery, while replacing their liturgical forms, or that there were definitive events that ended Orthodoxy's presence in an area.
3) A domino-effect interpretation, or a "downward spiral" theory which incorporates elements of both of the above.
Suitability of Definitions
It has been argued that the above descriptions are too broad and therefore unsatisfactory, falling within the realm of personal opinions. Interpretations of events are usually colored by opinions. Yet every history of Orthodoxy and the great schism in the 11th century employs either one or the other:
Bp Kallistos Ware points out that "Even after 1054 friendly relations between East and West continued. The two parts of Christendom were not yet conscious of a great gulf of separation between them. … The dispute remained something of which ordinary Christians in East and West were largely unaware" ("The Orthodox Church", p.67) By contrast, Fr John Romanides writes, regarding the Balamand agreement, that "...the Orthodox at Balamand accommodated the Latins by joining them in using the context of medieval Franco-Latin propaganda about the schism with a more or less Orthodox content, a combination which had been dominating Orthodox schools for a long time; This agreement thus avoids the implications of the fact that since the 7th century the Franco-Latins usually received their apostolic succession by exterminating their West Roman, Celtic and Saxon predecessors having reduced the West Romans to serfs and villeins of Frankish Feudalism. This happened not only in Gaul, but also in North Italy, Germany, England, South Italy, Spain and Portugal." ("Orthodox and Vatican Agreement", Balamand, 1993) That these two sets of beliefs can have been argued historically over centuries forces us to admit that these mindsets exist, regardless of whatever we call them in this article for convenience.
While neither of the two opinions or their combination in any way affects Eastern Orthodoxy's self-interpretation, both color very strongly how Western-rite Orthodox perceive themselves. For the purposes of this argument, we shall refer to those who adhere to the first theory, even if there is some variation with the overarching premise defined here as "developmentalists", as opposed to those of the second as "catastrophists", regardless of whether this view is universally present in a person's worldview, as we are dealing with the general thrust of mindsets.
"Catastrophist" Thought and Orthodox Traditionalism
Western-Rite "catastrophist" thought makes certain implicit assumptions which are not made by Western-Rite "developmentalists". These assumptions are on liturgical and ideological grounds.
On liturgical grounds, the "catastrophist" argues that there is an extant body of Orthodox liturgical material for use available for Western-rite Christians from before or around the time of the Great Schism of 1054, that was either ignored or altered heavily over centuries. This difference is the most marked separation between the schools of thought, and makes for the bulk of the argument for the separate existence of these communities. Because the charge is warranted (some pre-schism Western liturgies survive in hundreds of manuscripts, available to the public in copied forms) it is a direct attack on the legitimacy of liturgies in use by "developmentalists" such as the Liturgy of St. Tikhon of Moscow or the Liturgy of St. Gregory the Great.
Ideologically, the "catastrophist" argues that the Western-rite Orthodox churches are substantially separate bodies from the ecclesial communities they came from; in this, they find support in the writings of virtually every leader in the Western-rite Orthodox movement. The "developmentalists" tend to defend the ecclesial communities they came from as having "diverged somewhat" from Orthodoxy, without ever clearly defining the difference.
These differences, which have been repeatedly stated within parts of the Orthodox world, tend to define the separations within Western-rite Orthodox Christians, and also reinforce the old Latin dictum, Lex orandi, lex credendi ("the law of prayer is the law of faith"). The hostility between the different mindsets of Western-rite Orthodox is one precisely of how Orthodox Christians view themselves; and is a problem which continues to require resolution in Orthodoxy, whether of Eastern or Western rite.