orthodoxy of the monasteries and monks of northern Mesopotamia, and to enforce discipline throughout the monasteries of northern Mesopotamia, even against occasional resistance. Babai the Great and Mar Aba administered the Nestorian Church for 17 years. Attempts were made during that time to ask the king to change his mind and allow an election, but influences in the court, such as Gabriel of Shiggar, and the king's wife Shirin, both miaphysite, blocked the requests. Gabriel was seeking to maneuver things such that the decision of Catholicos would have been in his own hands, an option completely unacceptable to the bishops. The king defended this policy until his death in 628. The situation, and vacancy, endured until Khosrau II was murdered in 628. After this, Babai was promptly, and unanimously, elected Catholicos, but he declined. Soon afterward, he died in the cell of his monastery on Mt. Izla, being 75 or 77 years old. Babai's teaching Besides bringing discipline to the monasteries and administering the church, Babai is mainly known for his orthodox teaching. Babai's writing To defend and clarify the Nestorian tradition against Henana's Origenism and the advancing Monophysites, Babai the Great produced some 83 or 84 volumes of writing. He developed a systematic Christology, the only one in Nestorian Mesopotamia. Of his extensive exegetical works on all of Scripture nothing survived. What remains are two hagiographies (of Christina and George of Izla), his principal work on the foundations of ascetic life 'On the Life of Excellency', and commentaries on mystical themes. From what has been preserved it appears that his main authority was Theodore of Mopsuestia, though in general he used few citations from the Fathers. There is no evidence that he could read Greek, and Babai must have relied on translations. He mainly fought against the ideas of the Monophysites and of the Origenist Henana. They were the inner enemies. He also wrote against Mani, Marcion, Bar Daisan, the Messalians and the general loss of discipline since Beth Lapat. The Book of Union is Babai's most systematic surviving christological treatise, divided into seven memre that cover more than 200 folios. The 'Tractatus Vaticanus' is another manuscript that deals with the "impossibility of the hypostatic union and natural union, the possibility of the parsopic union, and the significance of the expression hypostatic union among the fathers of the antiquity". An important source on the position of Babai the Great