Council of Seleucia-Ctesiphon

The Council of Seleucia-Ctesiphon, also called the Council of Mar Isaac, met in AD 410 in Seleucia-Ctesiphon, the capital of the Persian Sassanid Empire. Convoked by King Yazdegerd I (399–421), it organized the Christians of his empire into a single structured Church, which became known as the Church of the East. It is often compared to Constantine's Edict of Milan, approximately a century earlier.^[1] The events of this council are documented in the Synodicon Orientale.

Previously, the Persian state persecuted those Christians, fearing that their loyalty lay with the Roman Empire, which under Constantine the Great had legalized Christianity and with which the Sassanid Empire was repeatedly at war. Persecution had been most severe under Shapur II (309–379).^[2] Shapur I (241–272), the second shahinshah (king of kings) of the Sasanian dynasty had advanced as far as Antioch in 260, and both he and Shapur II deported eastward much of the population of the invaded territories to strengthen the Persian economy.

Yazdegerd I adopted a policy of engagement with the Roman Emperor in Constantinople and with the Christian minority in his own empire. In 409, he allowed the Christians to worship openly and to have churches. Zoroastrianism continued to be the official religion, and apostasy from it was punishable by death.^[3]

At the suggestion of a bishop from the Roman side of the frontier, a council of bishops was called to organize the Persian Christians as a single Church, with a single bishop in each diocese and with one bishop to act as their head collectively throughout his empire (See Maruthas of Martyropolis).