Here is a quote taken from an eastern orthodox website:
"But how can we know that the Church has preserved the Apostolic Tradition in its purity? The short answer is that God has preserved it in the Church because He has promised to do so. Christ said that He would build His Church and that the gates of Hell would not prevail against it (Matthew 16:18). Christ Himself is the head of the Church (Ephesians 4:16), and the Church is His Body (Ephesians 1:22-23). If the Church lost the pure Apostolic Tradition, then the Truth would have to cease being the Truth — for the Church is the pillar and foundation of the Truth (I Timothy 3:15)."
Same argument the Roman Catholic church makes. So how can both be right? Each one believes the other departed from apostolic tradition, however they both claim to uphold the apostolic traditions and make as their arguement the idea that God will keep the church on the right path. So obviously God couldn’t the above couldn’t be true of both.
From my own studies I would tend to agree with the Eastern Orthodox on several issues, in which I believe they stayed true to apolostic doctrine and where the RC departed paths. However I can say I also see where the EO have added at least one tradition which is not apostolic such as iconography. If both can make the same claims about God leading them, but each exclude the other, then why couldn’t both be misguided? It appears that in light of the two ancient streams tracing their roots back to Christ that it is moot to even make your appeals to ancient history.
Now something that is disturbing to me is partially the fact that Catholics are so condemning of protestants for example. I mean in light of the RC’s own history of blood shed, corruption and the fact that outside observers see all this and are also faced with the split between east and west, I would think you folks could be a little more humble in your dealings with non-catholics. Let me put it another way, after looking into some of what RC is and what EO is it makes one wonder why they even should be one or the other.