ISAAC, Bishop of Seleucia-Ctesiphon and Catholicos of the Church of the East (399-410; see CHRISTIANITY i, ii, iii). Isaac is said to have come from Kashgar and to have been a relative of an earlier bishop of Seleucia-Ctesiphon, Tomarsa (363-71). He was elected to office (after an interregnum caused by earlier persecution) in 399 at the time when Marutha, bishop of Maipharqat, had been sent by the Roman emperor Arcadius on embassy to Yazdegerd I at his winter residence in Seleucia-Ctesiphon. On this visit Marutha won the shah’s favor as a result of his medical skill; thanks to this, Marutha’s second embassy to Yazdegerd I in 410 provided the opportunity to get royal permission to summon a synod of 40 bishops, to strengthen Isaac’s position against some bishops who were causing him trouble, and to regularize church affairs in general. At this synod Marutha read out a letter from the “western bishops” (that is, from the Eastern Roman Empire) and the doctrinal creed of the Council of Nicaea (325) was formally accepted by the Church of the East, along with the decrees of various provincial church synods of the Eastern Roman Empire. Internal church affairs were also regulated in a series of 21 canons.

The texts of the Creed and of the canons survive in both an East and a West Syriac recension, and it is the latter which has preserved the original text of the form of the Nicaean Creed accepted at the synod.

The most detailed (but clearly, edited) account of this important synod of 410 is found in the East Syriac collection of synods known as the Synodicon Orientale. Shorter, but sometimes also embroidered, accounts are to be found notably in the Chronicle of Seert (sec. 66), Barhebraeus’ Ecclesiastical History (II.16), and the East Syriac writers Mari and Sliba. It should be noted that, although the embassies of Marutha are mentioned both in Socrates, Ecclesiastical History (VII.8) and in the Armenian and Greek Lives of Marutha, no reference is made in any of these sources either to the synod of 410 or to Isaac.



Jean Baptiste Chabot, Synodicon Orientale, ou receuil des synodes nestoriens, Paris, 1902, pp. 253-75, 292-93 (Figure 1).

Jean Dauvillier, “Droit (chaldéen),” in Dictionnaire de droit canonique 3, 1942, cols. 292-388, esp. 301-4.

André de Halleux, “Le symbole des évêques perses au synode de Séleucie-Ctesiphon (410),” in Gernot Wiessner, ed., Erkenntnisse und Meinungen, II = Göttinger Orientforschungen, Reihe Syriaca 17, 1978, pp. 161-90.

Jean Maurice Fiey, “Isaac (catholicos),” in Dictionnaire d’histoire et de géographie ecclésiastique 26, 1997, pp. 90-92.

Jean Gribomont, “Le symbole de la foi de Séleucie-Ctesiphon (410),” in Robert H. Fischer, ed., A Tribute to Arthur Vööbus: Studies in Early Christian Literature and its Environment, Chicago, 1977, pp. 283-94.

Jérome Labourt, Christianisme dans l’empire perse sous la dynastie sassanide (224-632), Paris, 1904, pp. 87-99.

Thomas Joseph Lamy, Concilium Seleuciae et Ctesiphonti habitum anno 410, Leuven, 1868.

Ralph Marcus, “The Armenian Life of Marutha of Maipharkat,” Harvard The-ological Review 25, 1932, pp. 47-71.

Jacques Noret, “La vie grecque ancienne de s. Maruta de Mayferqat,” Analecta Bollandiana 91, 1973, pp. 77-103.

Arthur Vööbus, “New Sources for the symbol in early Syrian Christianity,” Vigiliae Christianae 26, 1972, pp. 291-96 (West Syriac recension of Creed of 410).

(Sebastian Brock)

Originally Published: December 15, 2006

Last Updated: March 30, 2012

This article is available in print.
Vol. XIII, Fasc. 6, pp. 610-611