Nestorian Church. This is the name given in modern times to those whom
5th-cent. writers called simply "Easterns"; by which they meant the church that
existed to the east of them, outside the boundary of the Roman empire, in the kingdom that was at first Parthian, and later Sassanid Persian. The body is also called "east Syrian" (the term Syrian implying use of the Syriac language rather than residence in "Syria"), and sometimes also "Chaldean" or "Assyrian."
Foundation of the Church.—During the course of the 1st cent. Christianity
spread from Antioch, not only to the west but also eastwards, and in particular
it extended to Edessa, then the capital of the little "buffer state" of Osrhoene, situated between the Roman and Parthian empires. The political independence of the state ended in 216, but it had lasted long enough to give a definite character to the local church, which was marked off by its Syriac vernacular and Oriental ways of thought from the Greek Christianity to the west of it. Missionaries went out from Edessa to the east again, and founded two daughter-churches, one in Armenia and one in what was then Parthia, the latter of which is the subject of this article.
The first two "apostles" and founders of this church were Adai (=Thaddeus) and
Mari. Tradition identified the former with either the disciple of Christ—a statement hard to reconcile with the recorded fact that he was still able to travel in the year 100—or with one of "the Seventy." He is known to have preached in Assyria and Adiabene before the close of the 1st cent., and to have consecrated his disciple Paqida as first bishop of the latter province, in 104 (Hist. of Mshikha-zca); while the statement of the "doctrine of Adai" that the apostle died in peace at Edessa has the ring of truth in it. The later history of the church in that place is outside our subject.
Of Mari, his companion, little is known certainly (his life is a mere piece of
hagiography), but he appears to have penetrated into the southern provinces of the Parthian kingdom, to have preached without much success at the capital, Seleucia-Ctesiphon, and to have died in peace at Dor-Koni. There seems no reason to doubt the historic character of both these teachers; and later tradition added that St. Thomas the Apostle, passing through this country on his way to India, was co-founder of the church with them.
The Church under the Arsacids and Sassanids.—Under Parthian rule, which
was tolerant, and where the state religion was an outworn and eclectic paganism, the new faith spread rapidly and easily. There was no persecution by the government, though converts from one special religion, Zoroastrianism, had sometimes to face it, from the powerful hierarchy of that faith, the Magians. Thus the church had more than 20 bishops, and these were distributed over the whole country when, in 225, the 2nd Persian replaced the Parthian kingdom, and the Arsacid dynasty gave way to the Sassanid. This revolution was to its authors a revival of the old kingdom destroyed by Alexander, and the Persian nation rose again with a national religion, that of Zoroaster. It made no effort to destroy the Christianity that it found existing, but, like Islam later, tolerated it as the religion of a subject race, and so put it into the position that it still occupies in those lands, though the dominant religion has changed. Christians became a melet (a subject race organized in a church), recognized by the government, but despised by it. For them to proselytize from the state faith was a crime, punishable with death, though they were allowed to convert pagans. Apostasy from Christianity to the established faith meant worldly prosperity, but there was no persecution, though there was often oppression, by the government, until the adoption of Christianity by the Roman emperor (the standing enemy of the shah-in-shah) made every Christian politically suspect. Thus Persia continued to be a refuge for many Christians from Roman territory during the "general" persecutions of the 3rd cent., and the church grew, both by conversions and by the advent of "captivities," largely Christian in faith, brought by conquerors like Sapor I. from Roman territory.