Isaac the Great, Armenian apostolic patriarch, has helped to develop a Greek-inspired alphabet and translate the Bible with various Christian writings into Armenian.

Through Isaac's efforts, the churches and monasteries destroyed by the Persians have been rebuilt, education is cared for in a generous way, Zoroastrianism, which Shah Yazdegerd I had tried to set up, had been cast out, and three councils have been held to reestablish ecclesiastical discipline.

Said to have been the author of liturgical hymns, Isaac dies at Ashtishat between 439 and 441.