The emperor Theodosius defined correct doctrine not only in creedal terms but also in personal terms, and Gregory’s name joined those of the bishops of Constantinople and Alexandria as standards of belief. Gregory was a speculative theologian of great originality. In addition to his clarifications of the doctrine of the Trinity, he made contributions to the doctrines of man, the soul and the resurrection, and the atonement. In his later years Gregory turned to developing a philosophical theology