> To complicate matters, many of these dogmas were only formalized by the Catholic church in the past 200 years. Quite a hard sell for the "sola scriptura" contingent.

There are only four things on that list, and only two of them are dogmas (and there are a whole two more Marian dogmas that aren’t on your list), so I am not sure where the “many of these dogmas” comes from; also, the various Protestant positions on the role of scripture (prima scriptura, sola scriptura, and nuda scriptura, in ascending order of how far they differ from the Catholic [or, for that matter, Eastern Orthodox] position) were themselves formalized not much less recently.

> Many Catholics believe that Mary was born without sin (immaculate conception), never died (assumption into heaven), can advocate to Jesus for believers (intercession) and has been crowned the Queen of Heaven.

So do the Orthodox churches. And both have roots going back way longer that 'just' two hundred years:

> Mary as Queen of Heaven is praised in the Salve Regina ("Hail Queen"), which is sung in the time from Trinity Sunday until the Saturday before the first Sunday of Advent. It is attributed to a German Benedictine monk, Hermann of Reichenau (1013–1054). Traditionally it has been sung in Latin, though many translations exist. In the Middle Ages, Salve Regina offices were held every Saturday.[21]

* https://en.wikipedia.org/wiki/Queen_of_Heaven#Salve_Regina

> "Majestic and Heavenly Maid, Lady, Queen, protect and keep me under your wing lest Satan the sower of destruction glory over me, lest my wicked foe be victorious against me." St. Ephrem the Syrian (4th Century)

* http://theorthodoxfaith.com/article/mary-as-the-queen-of-hea...

* https://en.wikipedia.org/wiki/Ephrem_the_Syrian

And if we're going to with potentially troublesome dogmas, I would think the Real Presence would be much higher on the list:

* https://en.wikipedia.org/wiki/Real_presence_of_Christ_in_the...

Lay members of these various churches certainly seem to believe there are huge theological differences, which they infer from the differences in day-to-day practices. But if you read the views of most of the high-level clergy and theologians in all these churches (and not the fringe, e.g. not the monks on Mt. Athos, or bishops trying to score political points), the differences are incredibly thin and not at all significant when comparing Catholic, Orthodox, Oriental, and Syrian churches to other Christian denominations. The patriarchs of all these churches in particular have been remarkably careful across the centuries, and especially today, to avoid formally committing their churches to views that necessarily prevent union. To be sure there have been many exceptions, but invariably succeeding patriarchs walk them back, it just takes centuries. I get the sense that at any particular time most patriarchs have been amenable to union and willing to make the necessary compromises demanded of the day, but fear conservative factions splitting away, which would be particularly painful for Orthodox and Syrian churches already beset by fragmentation nominally justified by much more minor issues (e.g. Julian calendar).

The biggest sticking points theologically today, from what I gather, arise primarily from 19th century Catholic pronouncements regarding papal infallibility and Mary, specifically the Immaculate Conception and how it relates to Original Sin. Most of the historical disputes (e.g. re miaphysitism, theotokos, unleavened bread, purgatory) have largely fallen away as misunderstandings.

In the case of papal infallibility, all ancient churches admit that the Rome pontiff held supremacy, but there was never agreement on precisely what that meant. The Catholic articulation of papal infallibility offends the synodal view of how doctrine is established, and while many Catholic theologians, including several popes throughout the 20th and 21st century, have publicly explained that popes can only legitimately pronounce what the church, synodally, has already accepted, the precise language used in the formal dogmatic pronouncement is too strictly worded. And it doesn't help that many fringe conservative Catholic theologians are more pro-pope than any pope since the the 19th century and promote this more extreme interpretation.

In the case of the Immaculate Conception, it's not so much that the Catholic view is unacceptable to Orthodox or Orientals, but that the Catholic doctrine is too specific (similar to infallibility) and excludes their alternative framing that beforehand had been understood not to be incompatible with union. Some (all?) the Syrians (Churches of the East), though, seem to accept it, despite not having a tradition rooted in the Augustinian articulation of original sin. And views of the Immaculate Conception among Orthodox and Oriental churches nominally in union with each other differ. (But to be clear, the differences are extremely technical; to most people, including Protestants and especially non-Christians, the varying views of all these churches would be indistinguishable, and theologians themselves often seem to articulate them wrongly, at least compared to how their patriarchs do.)

The Filioque also isn't a theological barrier. The way it's formally understood in Catholicism is not in conflict with accepted Orthodox or Oriental theology, but for various reasons Orthodox see it as an offense to synodality and respect for previous councils' compromises about how far to go in textually articulating the Trinity. I would think most Orthodox theologians see themselves closer theologically to the Oriental churches, but Oriental churches have changed the creed in much more significant ways--IIRC, the Armenian Church added whole new paragraphs. Not that Orthodox theologians are any more willing to overlook these changes, but they certainly don't make much hay about them.

Note that one of the ancient Syrian churches (I always get their names confused) is poised to reunite with the Catholic church. All the doctrinal stuff has long been ironed out, which took about a century, IIRC, from the beginning of earnest dialogue. The sticking point relates to the Catholic church demanding the Syrian church replace their organically evolved clerical disciplines and practices with comprehensive written canonical rules similar to the Catholic church (Latin and Eastern). In truth, the division between the Catholic, Orthodox, Oriental, and Syrian churches have always been primarily cultural (lay) and political (clerical), not theological. The theological differences have tended to be exaggerated on all sides in service of political (clerical, state, and social) machinations. The 19th century Catholic dogmatic pronouncements were largely triggered by political and social revolutions in Europe which caused turmoil among Catholics, with subsequent political and cultural backlashes that resulted in the peculiar theological focus that unfolded and overwhelmed the typical ecumenical circumspection of church leaders.)

Theological differences among churches nominally in union with each other are often arguably no less significant than between churches where union is supposedly not possible. And there has often been de facto union. For example, for several periods throughout the centuries the Orthodox and Oriental churches in Egypt de facto placed their churches under the authority of the rival patriarch while they weathered political winds and suppressions, without the feared theological contamination divisive theologians claimed were inevitable, and despite the claimed differences being deemed much greater and more incompatible than they're believed to be today.

Of course. My comment was just describing a very common view in the southern United States. Not all Protestants believe that (especially Anglicans which are basically Catholic without the Pope), but it's something I heard a lot growing up.

I didn't say I agreed with it, but I think it's important to mention when some comments on here are suggesting a unification can happen. As someone extremely familiar with both groups, they may share most of the Bible in common as well as some core beliefs, but there other core beliefs that are hugely important and different between the groups that can never be reconciled. One important aspect is that Catholics (and I think Greek Orthodox) believe that the bread and wine literally become the body and blood of Jesus Christ during mass.

Good idea! I haven't and won't. Now read me the original text of Anselm's ontological argument and explain it in modern English without falling back to ancient philosophical gibberish like "substance" and "potentiality".