Isho’yabh IV was a schoolmaster of very high repute and later became the Catholicos of the Church of the East. He wrote tracts on liturgical matters in the first two decades of the eleventh century in order to restore the traditions of his church. In Nestorian Questions of the Administration of the Eucharist, Willem Cornelis van Unnik offers a comprehensive study of the liturgical writings of Isho’yabh IV in the context of the "Nestorian" liturgical tradition based on the manuscript tradition. After an analysis of the text, the author gives an annotated English translation of the text and a reproduction of the original Syriac text with a critical apparatus.

Willem Cornelis van Unnik (1910-1978) studied Theology at the Universitiy of Leiden and Birmingham where he specialized in Syriac with A. Mingana. The latter gave him the liturgical manuscript that became the subject of his dissertation, with which he wrote Nestorian Questions. In 1946 he received the Mallinckrodt Award for this dissertation, a prize that is awarded once every ten years for the best theological dissertation in the Netherlands. In 1946 he was appointed Professor of New Testament and Old Christian literature at the University of Utrecht. The main focus of his research was on the cultural context of the New Testament, especially gnosticism and the Hellenistic world.