The Nestorian heresy left a permanent Nestorian Church, the Monophysite and Monothelite quarrels made several more, the reunion with Rome of fractions of every Rite further increased the number, and quite lately the Bulgarian schism has created yet another; indeed it seems as if two more, in Cyprus and Syria, are being formed at the present moment (1908).We have now a general criterion by which to answer the question: What is an Eastern Church?To these we must add those formed by missionaries (especially Russians) from one of these Churches.Later Latin and Protestant missions have further complicated the tangled state of the ecclesiastical East.
All are covered by a division into the great , those formed by the Nestorian and Monophysite heresies (the original Monothelites are now all Eastern-Rite Catholics), and lastly the Catholic Eastern Rites corresponding in each case to a schismatical body.
But it must not be imaged that either half is in any sense one Church.
The Latin half was so (in spite of a few unimportant schisms) till the Reformation.
To find a time when there was one Eastern Church we must go back to the centuries before the Council of Ephesus (431).
Since that council there have been separate schismatical Eastern Churches whose number has grown steadily down to our own time.