"Ok. Let me try to clarify. Baptists believe they are in the correct church. They believe so because of what they determine to be orthodoxy. They have illuminated what orthodoxy is (for them) by their own interpretation of the bible. There are many other denominations and faiths which lay the same claim.
I don't think such a method works. It might if everyone agreed on what orthodoxy is, but obviously we dont. So instead, I want to look toward history. I am certain that the Orthodox and Catholic churches were once one church. That one church is the church created by Jesus and built by the Apostles. That church defined orthodoxy--they had the charge by Jesus to do so. At some point, that church split. So which one still holds the charge to protect and declare orthodoxy?
To answer that question I believe I need answers to a few more questions.
* In the areas that the two churches differ, what did the unbroken church look like? For example, if the two churches disagree on original sin, what did they unbroaken church believe about original sin?
* If the original church agreed with the Orthodox Church, then for the Catholic Church to be orthodox, it would have to at the very least be able to prove its claim for its reason for the change. What I mean by that is that Papal authority in determining such matters would have to be evident in the early unbroaken church.
* If the original church agrees with the Catholic Church, then I think I'm already in the right church."
You are right that there is only a certain number of churches that have any basis for claiming to be the historical Church. If we understand Apostolic Succession as the basis of historic continuity, then a church obviously has to be episcopal in church governance to have any ability to claim to have this Apostolic Succession. On this basis, most Protestant churches would immediately be ruled out.
However, I do not think that leaves only the RCC or the EOC. The Oriental Orthodox churches maintain the form of Apostolic Succession and also have a possibly legitimate claim to constitute the Apostolic Church. And the same goes for the Assyrian Church of the East. The Anglican Communion and the Old Catholic Union of Utrecht also potentially fits this form, but they do not even claim to exclusively be the Apostolic Church, and they do not have a terribly cohesive system of belief, so I think they can be ruled out off the bat. So, they way I see it, there really are 4 (not 2) different Communion that have to be considered at this point: the RCC, EOC, OOC, and ACE.
Given this, the period of time which can be clearly identified as the undivided church is significantly smaller. If we were to look only at the RCC and EOC, this period of time would be ~1,000 years. Now that we add in the OOC and ACE, it's really only ~400 years.
I agree with you that looking at the undivided church is the basis upon which we can judge which of these 4 current groups is the actual continuation of the undivided church.
However, the difference I am trying to point out that leads to the mentality I have, is that at this point in discerning, we have not identified a body of doctrinal authority upon which to be judging these churches teaching against those of the undivided Church. Thus, the only basis we can have at this point to judge what the teaching of the undivided Church is is our own reasoning, communication with God, and dialogue with others. There is no one yet that we know for sure who can tell us with authority what the orthodoxy of the undivided Church was. We can only determine that once we have already decided what the teachings of the undivided Church were. So yes, I do think on a certain level we do have to judge what orthodoxy is, that is judge what we find to have been the teachings of the undivided Church.
Does that make sense now?