Saint Diodorus of Tarsus

Diodore of Tarsus (Greek Διόδωρος ὁ Ταρσεύς; died c. 390) was a Christian bishop, monastic reformer, and theologian. A strong supporter of the orthodoxy of Nicaea, Diodore played a pivotal role in the Council of Constantinople and opposed the anti-Christian policies of Julian the Apostate. Diodore founded one of the most influential centers of Christian thought in the early church, and many of his students became notable theologians in their own right. Diodore was born into a noble family in the area of Antioch. He received a classic philosophical education at the school of Athens, and very quickly after his education he entered into the monastic life. During this period, Diodore's work focused on philosophical treatises and opposing Emperor Julian's attempts to restore paganism in the empire. When an Arian named Leontius was made bishop of Antioch, Diodore and his friend Flavian (who later was appointed as bishop of Antioch) organized those who followed the Nicene orthodoxy outside the walls of the city for worship. Those services are seen as the beginning of antiphonal singing in the church, a practice that became widespread among Christians. During his time at the monastery in Antioch, Diodore came under the tutelage of Meletius of Antioch. Meletius was elected bishop in 360 and ordained Diodore as a priest. When the Antioch split into factions, Diodore was a strong supporter of Meletius and of his move towards Nicene orthodoxy. Diodore was noted for living with few possessions, being dependent on alms for food, frequently being imprisoned on account of his beliefs. His physical appearance was rough, but John Chrysostom describes his expression as angelic. During his priesthood, Diodore founded a monastery and catechetical school near the city of Antioch. It was through this school that Diodore became the mentor of the controversial theologian and liturgist Theodore of Mopsuestia as well as Chrysostom.