Diodorus of Tarsus

Saint Diodorus, bishop of Tarsus, was a theologian, a reformer of monastic life and a defender of the faith of Nicaea, who died around the year 394. He played a leading part in the Second Ecumenical Council at Constantinople and founded one of the most influential centres of Christian thought in the early Church, the school of Antioch.

Early life and monastic years

He was born into a noble family in the region of Antioch. He received a fine philosophical education at Athens, where, according to one source, he studied together with Basil the Great. Soon after his studies he entered the monastic life. In the time of the emperor Julian the Apostate he wrote philosophical treatises against the attempt to revive paganism in the empire.

When an Arian named Leontius was made bishop of Antioch, Diodorus and his friend Flavian (later bishop of Antioch himself) gathered the faithful who held to the faith of Nicaea outside the city walls for worship. In those gatherings, Theodoret says, antiphonal singing was introduced, which then spread throughout the Church. He was a disciple of Meletius of Antioch, who ordained him priest after being elected bishop, about 360. He lived in poverty, depending on alms for food, and was often imprisoned for his faith. His appearance was rough, but John Chrysostom described his face as angelic.

The school and exile

As a priest he founded a monastery and a catechetical school near Antioch, through which he became the teacher of John Chrysostom and of Theodore of Mopsuestia. From this school grew the Antiochene way of interpreting Scripture, by the letter and history of the text, and of understanding the teaching about Christ. For his leading role in the school he was exiled in 372 by the emperor Valens to Armenia, where he met Basil the Great. After Valens died he returned from exile in 378 and was made bishop of Tarsus, the city of the Apostle Paul.

Bishop and theologian

As bishop Diodorus stood against Arianism and Apollinarianism, teaching that Christ is fully God and fully man. He had a leading part in the local Council of Antioch in 379 and in the Second Ecumenical Council in 381, where his name was entered among the fathers of the council. The emperor Theodosius the Great called him a “champion of the faith.” When Meletius died in 381, Diodorus proposed Flavian as his successor, which prolonged the division in the Church of Antioch. He passed away about 394.

He wrote commentaries on almost all the books of the Bible, but only fragments of his works survive, so his teaching is known mainly through his disciples. After his death, when the debate on the two natures of Christ grew sharper, many, among them Cyril of Alexandria, saw in his teaching a forerunner of Nestorianism, and a local synod at Constantinople condemned it in 499. In his own lifetime, however, he was regarded as a supporter of the orthodoxy of Nicaea. He is venerated as a saint in the Assyrian Church of the East.