P.S. Other than the Christological controversy, the Oriental Orthodox and the Eastern Orthodox are in complete agreement regarding beliefs and practices (and I think that is almost the case with the Assyrians as well). None of these Churches has developed the innovations that the Roman Church has since 1054 A.D. No purgatory, no satisfaction/reparations theology, indulgences, immaculate conception, no priestly celibacy, no Marian doctrines such as "mediatrix of all graces," etc. This is just my personal view, but I think so much of the problem is trying to explain in precise technical language divine mysteries. For instance, the RCC holds to transubstantiation to explain the eucharist. Orthodox are free (as far as I know) to accept such a view, but the Orthodox Church ultimately considers it a mystery. We are only required to confess that we truly receive the body and blood of the Lord in the eucharist, and not any precise view of how the change happens. All the ancient Churches accept the Nicene Creed, and that was sufficient to deal with the Arian heresy. All the trouble started when different parties attempted to explain in detail how Christ relates to the Father, rather than accepting simply that he is truly God, and truly man, undivided and unconfused. Thank God no one tried to exactly define how the Trinity operates, or their would have been even more schisms.