358–381

The Cappadocian Fathers and the Formula "One Ousia, Three Hypostases"

Basil of Caesarea was converted under the influence of his sister Macrina. Around 358 he founded a monastery in Pontus and later became bishop of Caesarea in Cappadocia. There he contended with Arianism under Emperor Valens and with the Pneumatomachians.

Together with his brother Gregory of Nyssa and his friend Gregory of Nazianzus (the Theologian), he upheld the formula "one ousia, three hypostases" (a dispute about the Trinity). Answering charges of tritheism, Gregory of Nyssa wrote the treatise "That There Are Not Three Gods", while against Apollinaris the Fathers defended the full humanity of Christ. Their theology formed the basis for the decisions of the Council of Constantinople in 381.