Dont really know where this would fit in for a discussion about the East and West?
But here goes anyway.
Is not in the words of Luther "the aticulus stantis et cadentis ecclessia" not Romans 3:28 but rather Matthew 16:18 or in an Eastern fashion 2 Thes 2:15?

The Church does not stand or fall on the article of justification as Luther taught but on its very make up and nature of the Church (Ecclesiology). For the Latin the Papacy as the Proto Thronos of the Pentarchy.
Or for the East on the Paradosis ie, the Traditon of the Church.

Stephanos I