My problem with this is that the EO would agree with it, they'd just be wrong about *Which* Church is the Catholic Church. Kind of like how Vatican II Catholics are wrong about which one on Sedevacantist premises, or vice versa.

I'm not trying to subjectivize the EO's error, but the EO who truly accepts ALL Of what their Church teaches seems to by this definition have the correct formal motive and simply instead be wrong on *what* is the Catholic Church.

As opposed to say a Protestant who isn't grounding his views in the teaching authority of the Catholic Church, *however* you define that, but on his own interpretation of a book.

I promise i'm not just trying to make excuses here.  I'm just trying to reason this through rationally.

But isn't that what you're doing, subjectivizing the rule of faith?  Just because they hold something else as their rule of faith, that doesn't make it the true rule of faith.  As St. Thomas says, if they substitute something else for the actual rule of faith, they do not have the habit (supernatural virtue) of faith.  Sure the EO base their beliefs on an "authority", but it's the wrong authority, a fallible authority.

But they still say the Catholic Church is the rule of faith.  They just misidentify the Catholic Church.  From your vantage point how does this differ from the Novus Ordo?

No, it's more than just a material mis-identification.  They define the Catholic Church as being without a centralized and living authority which alone can give unity and definitive determination to faith.  Novus Ordo definition of the rule of faith is still the Catholic one ... even if they wrongly think that the Conciliar Church exercises Magisterium.

Just try this mental exercise.  Pretend that you believe as the EO do that you derive your faith from the Councils and the Fathers.  Does that come anywhere near to bringing the absolute certainty that we have with the Magisterium?  Just imagine what your "faith" would be like if there were lacking the infallible rule of the living Magisterium.

They differ little from Protestantism because there's no living interpretation.  So, instead of just having the Bible and then interpreting it yourself, the EO add some Councils ... and interpret those themselves.  They just have expanded the sources of doctrine, but the paradigm is no different from Protestantism and still in the end reduces to private interpretation as far as the subject is concerned.  In essence, you could take the texts of the Councils and append them to the Bible, and that would be the Orthodox rule ... materially more extensive than the Protestant but otherwise formally (and by definition) the same in its operation.

No, it's more than just a material mis-identification.  They define the Catholic Church as being without a centralized and living authority which alone can give unity and definitive determination to faith.  Novus Ordo definition of the rule of faith is still the Catholic one ... even if they wrongly think that the Conciliar Church exercises Magisterium.

Just try this mental exercise.  Pretend that you believe as the EO do that you derive your faith from the Councils and the Fathers.  Does that come anywhere near to bringing the absolute certainty that we have with the Magisterium?  Just imagine what your "faith" would be like if there were lacking the infallible rule of the living Magisterium.

They differ little from Protestantism because there's no living interpretation.  So, instead of just having the Bible and then interpreting it yourself, the EO add some Councils ... and interpret those themselves.  They just have expanded the sources of doctrine, but the paradigm is no different from Protestantism and still in the end reduces to private interpretation as far as the subject is concerned.  In essence, you could take the texts of the Councils and append them to the Bible, and that would be the Orthodox rule ... materially more extensive than the Protestant but otherwise formally (and by definition) the same in its operation.

I think logically (and I realize Pax criticized me for being too rationalist) Sedevacantists are in the same boat then, as they effectively have no living magisterium anymore, based on their interpretation of the dead magisterium.  I don't see how the logic used here doesn't necessitate hermeneutic of continuity (which I realize isn't on the table for anyone else here besides me.  Most of you are more sure of your positions than I am).

No, the suspension of activity on the part of the living Magisterium is not the as not having one in principle.  If they're wrong, then it's a mere material error ... just as I stated earlier regarding the Novus Ordo Catholics.

EOs just think its been suspended for 1000 years instead of 61...

For those that believe that EO's are in the Church and can be saved, I ask:

Can a Catholic with one un-confessed mortal sin (say cheating on their wife once) on their soul at death be saved?

No.  Not it it’s truly a mortal sin.  Which cheating on their wife always would be.  The unspoken premise is that an EO is automatically mortally sinning.  Of this I am not persuaded 

If one can be a schismatic and not be guilty of mortal sin, then one can cheat on one's wife and not be guilty of mortal sin. Schism is a far greater sin than infidelity so I think you are being scandalous in acquitting the schismatic while condemning the adulterer as if the lesser crime is greater and the greater crime is lesser.

My thinking is not grounded in lesser vs greater, but natural law vs special revelation.

Most EOs do not really understand the debate, or have a solid understanding of the reasons why Rome is the true Church rather than EO, and that's not something that's knowable by sheer natural reason, so there could be some EOs who aren't at that level of culpability.

The same cannot be said for the cheater.

Of course it can be known by natural reason.  I think you meant to say it’s not knowable by the natural law (ie conscience)?  If so, few things are.  I mean, if you want to become a doctor, lawyer, accountant, programmer, economist - you have to spend time learning, with study and hard work.
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Same thing with religion.  If you want to know God and Truth, you have to spend TIME in STUDY, PRAYER and contemplation.  Then God will enlighten you on many things, including if you are in the wrong religion.  
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But what modern man treats religion like a duty, a vocation or an occupation?  Not many.  So they think that a few hours on Sunday and some daily prayers is “enough”.  Not hardly.

Yes I meant natural law.  And I agree, many don't.  And God will judge them.  I'm not saying ignorance is a free ticket to heaven either.

Ok, if they don’t understand the reasons why Rome is the true church, then we have to ask-
1)  Do they care at all?  If not, why not?  Laziness?  Spiritual apathy?
2)  If they do care, but they don’t know, why not?  Lack of effort in studying?  Have they done some study but not enough?
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I’m not out to condemn anyone specifically but I also get tired of the modern mindset which makes excuses for everyone generally speaking.  This is how doctrine gets watered down!  If you can’t condemn a hypothetical EO person, then you cant condemn anyone.  So doctrine vs error means nothing.  Truth is useless.
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As is usual, modern man has it backwards.  The Church condemns generally those in error, while She treats individuals and their situation with the utmost leniency.  Because life is not as clear-cut as a hypothetical case.

I think you might misunderstand me.  Though maybe I’m not being clear enough.
I’m just saying I’m not persuaded that they are automatically damned in every case.  I think some might have invincible ignorance and might be Catholic despite being intellectually wrong about what the Catholic Church is.
I’m not saying that’s a guarantee or certainly not that that’s true for all of them.
The only person I’m confident saying is certainly in hell is Judas iscariot, nevertheless, the further you get from
The truth, the more unlikely invincible ignorance is, and the more likely you won’t be saved even if you’re invincibly ignorant cause you’ll be damned for another mortal sin.
Or at least that’s how I understand it at the moment