“Your post raises a technical question that i want to ask, as a way of understanding how a church claims a path back to the original church.”
The process is through Apostolic Succession. What this means is that Priest A was ordained by Bishop X, who was ordained in turn by Bishop Y all the way back to St. Peter.
As far as I’m aware, only two retain this succession, the Catholics and Orthodox.
The reason the Protestant orders are invalid is because somewhere along the line a priest (not a bishop), left the church and started ordaining other people, and elevated himself to a bishop. This is true for Anglicanism, for Lutheranism, and for Calvinism.
Or, as in the case of the anabaptists, that they avoided the issue altogether by arguing there was no need for a heirarchy. So after the death of Menno Simons, their apostolicity was broken.
“Suppose a significant part of the Church had decided at that time to reject that teaching, and had made their own church but otherwise held to every tenet of the Catholic faith and tradition.”
They would need to have bishops go along. As far as I’m aware the last time that occurred was at the schism. Prior to that you have the anti-nicenes and the anti-chalcedonians, both of whom have orders that still exist today, but they aren’t considered to have the succession (mostly because of the Arab conquest) and other such niceties.
“Or the one which is exactly the same except that they don’t accept the doctrine of the Immaculate Conception, which means they still practice the faith just as it was for 1822 years after the foundation of the church?”
Well the problem with the Orthodox is that they don’t practice the faith as it was back prior to the schism. For one, they reject the primacy of the Pope. Two, who’s the head, Patriarch of Moscow or Patriarch of Constantinople? What about the Alexandrines and the Antiochines? The old system was the Pope as one of the five (Constantinople, Alexandria, Antioch, Constantinople and Jerusalem), but the chief among them is Rome.
You are correct that the Catholic church has proclaimed the authority of the Immaculate conception, but that is a teaching that was affirmed by the church fathers prior to the schism. It isn’t an issue of division between Catholics and the Orthodox.
“In my opinion, no church seems to have a pure bloodline of doctrinal teaching that mirrors the original church — but that is an opinion based partly out of ignorance of the details of doctrine of every church in the world.”
There are two, and I have examined this question closely. The Catholics and the Orthodox. Yes, there have been changes over the last while, but the doctrine remains the same in both as before. I encourage you to go back and examine things, and raise the questions that you think the Catholic church has broken from the early church. You will find that they preach what was preached before.
“Never said it wasn’t. The point that doesn’t get made enough is there was a basis for fearing the RC’s and the RCC. If RC posters want to start with the “everybody is picking on me” nonsense then we should look at why there was a fear.”
Well it starts with Napoleon. Is that liberty? He tried to destroy the church altogether in France. Everywhere we have seen the French Revolution and their ideals, we have seen anti-catholicism hand in hand.
You should read Edmund Burke on his response to the revolution in France. Liberty and the Catholic church are not by any means opposed. Liberty in the form of Revolution as in the French Revolution, and the Catholic church are diametrically opposed, and have slugged it out for at least 200 years already.
Liberty does not equate with Modernity, although Modernity claims such. Liberty, can be acheived in harmony with the teachings of the Church.