Diodorus of Tarsus

Diodorus of Tarsus was a fourth-century Christian bishop, monastic leader, exegete, and theologian of the Antiochene school. He was born at Antioch in Syria; the year of his birth is not preserved in the ancient sources, and no reliable evidence supports a precise date. He received a thorough education in both classical learning and the Christian scriptures. Ancient ecclesiastical historians place him among the educated Christian elite of Antioch, and some later reports associate him with philosophical study, including a period at Athens, though that detail cannot be confirmed with certainty. From early adulthood he adopted an austere, celibate, and monastic manner of life rather than marriage or secular office.

Together with Flavian, later bishop of Antioch, Diodorus organized and led an ascetic community in Antioch devoted to psalmody, fasting, and intensive study of scripture. During the reign of the emperor Valens, whose policy favored Arian clergy, the Nicene churches of Antioch were often closed to the supporters of the Council of Nicaea. Diodorus and Flavian then gathered the Nicene congregation for worship in private houses and in the open air outside the city. Meletius of Antioch ordained Diodorus to the priesthood. As priest and teacher he directed a school of biblical interpretation whose most famous pupils were John Chrysostom and Theodore of Mopsuestia. His exegetical method emphasized the literal and historical sense of the biblical text and stood in deliberate contrast to the allegorical approach associated with Alexandria.

After the death of Valens in 378, Diodorus was consecrated bishop of Tarsus in Cilicia, a metropolitan see he governed until his death. In 381 he took part in the Council of Constantinople, which reaffirmed Nicene doctrine, adopted the expanded creed associated with that council, and recognized Meletius of Antioch. He also worked to heal the long-standing Meletian schism among Nicene Christians at Antioch. As a writer he produced extensive commentaries on books of the Old and New Testaments and polemical treatises against pagan philosophy, Manichaeism, and Apollinarianism. Only fragments of this large corpus survive, many of them in later citations. In Christology he insisted on the completeness of Christ's humanity and on a clear distinction between the divine and the human in the incarnate Word, while still affirming one Christ.

Diodorus died at Tarsus about the year 390, while still bishop of that city. In his own lifetime he was regarded as a leading champion of Nicene orthodoxy against Arianism. In the fifth and sixth centuries his name became entangled in the Nestorian controversy because of his influence on Theodore of Mopsuestia. Cyril of Alexandria and later imperial and conciliar authorities treated some of Diodorus's formulations as forerunners of a dual-person Christology, and much of his work was lost or preserved only in hostile excerpts connected with the Three Chapters dispute. He never held the office of patriarch or of bishop of Rome, and he is not generally assigned a feast day in the principal Byzantine or Western calendars. His lasting historical importance lies in his role as a founder of the Antiochene exegetical tradition and as the teacher of Chrysostom and Theodore.