GREGORY OF NYSSA (c. 335–c. 395), also known as Gregory Nyssen, was a Christian theologian. With his elder brother, Basil of Caesarea (c. 329–379), and Basil's lifelong friend, Gregory of Nazianzus (c. 329–c. 391), Gregory of Nyssa was a principal architect and interpreter both of the trinitarian settlement canonized by the ecumenical Council of Constantinople (381) and, in his later years, of the ascetic and mystical tradition of Eastern monasticism.

Little is known of the details of Gregory's life. The child of an aristocratic Christian family of Cappadocia, he had two bishops among his brothers, while his elder sister, Macrina, whose biography is numbered among his works, was a noted and saintly ascetic. Destined for an ecclesiastical career, Gregory was early made a lector in the church and was educated in the local schools at Caesarea, thus missing the opportunity to study, as Basil had, at one or...