Gregory of Nyssa in Wikipedia
St. Gregory of Nyssa (Greek: Ἅγιος Γρηγόριος Νύσσης; Latin: Gregorius Nyssenus; Armenian: Գրիգոր Նիւսացի; Arabic: غريغوريوس النيصي) (c 335 – after 394) was a Christian bishop and saint. He was a younger brother of Basil the Great and a good friend of Gregory Nazianzus. His significance has long been recognized in the Eastern Orthodox, Oriental Orthodox, and Roman Catholic branches of Christianity. Some historians identify Theosebia the deaconess as his wife, others hold that she, like Macrina the Younger, was actually a sister of Gregory and Basil.
Gregory along with his brother Basil of Caesarea and Gregory of Nazianzus are known as the Cappadocian Fathers. They attempted to establish Christian philosophy as superior to Greek philosophy.
Despite reservations, he consented to become bishop of Nyssa in 372. Nyssa is in a region then called Cappadocia, in modern-day Turkey. His brother Basil appointed him bishop in Nyssa because he wanted an episcopal ally near to his metropolitan see of Caesarea. He was present at the Council of Antioch, and later at the Second Ecumenical Council (381) which took place in Constantinople. There he defended the Nicene Creed against the Arians.
Gregory made two major contributions to Christian theology. The first is his doctrine of the Trinity, a development of the theology of Basil and their mutual friend Gregory Nazianzus. The second is his spiritual theology, which posited God as infinite and salvation as potentially universal (see Apokatastasis). The Western interpretation that Gregory of Nyssa taught or endorsed Apokatastasis is disputed by Eastern Theologians as incorrect. Eastern theologians also dispute the Western interpretation of Gregory as a philosopher, and specifically of the Neoplatonic variety.
Following Basil's lead, Gregory argues that the three Persons of the Trinity can be understood along the model of three members of a single class: thus, the Father, Son, and Holy Spirit are three in the same way that Peter, Paul, and Timothy are three men. So why do we not say there are three Gods? Gregory answers that, normally, we can distinguish between different members of the same class by the fact that they have different shapes, sizes, and colors. Even if they are identical, they still occupy different points in space. But none of this is true of incorporeal beings like God. Even lesser spiritual beings can still be distinguished by their varying degrees of goodness, but this does not apply to God either. In fact, the only way to tell the three Persons apart is by their mutual relations - thus, the only difference between the Father and the Son is that the former is the Father of the latter, and the latter is the Son of the former. As Gregory puts it, it is impossible to think of one member of the Trinity without thinking of the others too: they are like a chain of three links, pulling each other along.
Gregory is the first Christian theologian to argue for the infinity of God, and one of the earliest Church Fathers to reveal some universalist tendencies. However, it isn't entirely clear what Gregory's actual position on universalism was since he displays marked non-universalist tendencies also. For instance, in Chapter 7 of Gregory's "Great Catechism" he says:
"Man, like some earthen potsherd, is resolved again into the dust of the ground, in order to secure that he may part with the soil he has now contracted, and that he may, through the resurrection, be reformed anew after the original pattern; at least if in this life that now is he has preserved what belongs to that image."
Origen of Alexandria, a major influence on Gregory, had explicitly argued that God is limited, since to be limited is to be clearly defined and knowable. Gregory, however, argues that if God is limited he must be limited by something greater than himself. As there is nothing greater than God, He is therefore without boundaries, and thus infinite. The idea had already been developed by Neoplatonic philosophers, especially Plotinus. But he is the first Christian to defend it, apart from some hints in the work of Irenaeus of Lyons.
Accordingly, Gregory argues that since God is infinite he cannot be comprehended. Origen had spoken of the spiritual journey as a progression of increasing illumination, as the mystic studies Scripture and comes to learn more about God. Nyssa taught on the other hand that God was knowable in his manifestations but that ultimately one must transcend knowledge or gnosis (since knowledge is based on reflection). Gnosis is limited and can become a barrier between man and God. If one wishes to commune with God one must enter into the Divine filial relation with God the Father through Jesus Christ, one in ousia with the Father which results in pure faith without any preconceived notions of God. Once one reaches this point one can commune with God just as Moses did in Nyssa's mystical classic, The Life of Moses.
Gregory speaks of three stages of spiritual growth: initial darkness of ignorance, then spiritual illumination, and finally a darkness of the mind in contemplation of the God who in being or essence (ousia) cannot be comprehended.
Like earlier authors, including Philo, he uses the story of Moses as an allegory for the spiritual life. Moses first meets God in the burning bush, a theophany of light and illumination, but then he meets him again in the cloud, where he realizes that God cannot be seen by the eyes. Ascending Mount Sinai, he finally comes to the "divine darkness", and realizes that God cannot be known by the mind either.
It is only through not-knowing and not-seeing that God can, paradoxically, be known and seen, knowledge that can only be gained through an "ascending life of holiness." This notion would be extremely influential in both Western and Eastern spirituality, via the mystical writings of Pseudo-Dionysius the Areopagite, and later in the anonymous 14th century work, The Cloud of Unknowing. Thus he is a major figure in the history of apophatic theology and spirituality.
Epektasis (constant progress)
Related to this is Gregory's idea of epektasis (ἐπέκτασις) or constant progress. Platonic metaphysics holds that stability is perfection and change is for the worse. In contrast, Gregory described the ideal of human perfection as constant progress in virtue and godliness. In his theology, God himself has always been perfect and has never changed, and never will. Humanity fell from grace in the Garden of Eden, but rather than return to an unchanging state, humanity's goal is to become more and more perfect, more like God, even though humanity will never understand, much less attain, God's transcendence. This idea has had a profound influence on the Eastern Orthodox teaching regarding theosis or "divinization". While the question of salvation or damnation is settled at the moment of death, nobody is known to have been damned and so prayers are offered for absolutely all the dead, even for those who seem to have been great sinners. For this reason, Gregory of Nyssa is not listed as a Doctor of the Church, and his suspected Origenism accounts for why Gregory lacks an official liturgical commemoration in the Catholic Church. Moreover, writers in the Catholic Church have been reluctant to refer to him as "Saint" Gregory of Nyssa as he is sometimes noted simply as "Blessed" Gregory of Nyssa.
The Eastern Orthodox Church, on the other hand, venerates him as "Saint Gregory of Nyssa" on account of (1) his pedigree among other "Saints", chiefly his brother Basil and sister Macrina; (2) his work in the Second Great Ecumenical Council of the Church, especially in defense of the "Holy Spirit"; (3) his esteemed place among the "Cappadocian Fathers" because of his stalwart defense of the Holy Trinity; (4) the tacit veneration of St. Gregory by the 7th Great Ecumenical Council, especially the appellations "holy" and "doctor", as well as their inclusion of a biographical anecdote from Gregory's life which was used, in part, to support the Council's decision against the "iconoclasts"; (5) his holy life and example.
Gregory's Trinitarian doctrine can be found in his Why there are not three Gods and in a letter to his younger brother Peter ("On the difference between ousia and hypostasis") which has been erroneously classified as Basil's 38th letter. As well, in his catechetical work, "An Address on Religious Instruction" Gregory explicates his thought on the theistic differentiation between Christianity, Hellenism and Judaism. While he works out his notion of the Incarnation and the Atonement in his "An Address on Religious Instruction," one is also introduced to the ransom theory of atonement. Furthermore, his spiritual writings include Life of Moses, Life of Macrina (his older sister), the Life of Gregory Thaumaturgos, and 15 homilies On the Song of Songs. A large number of letters, sermons, philosophical works and short essays on a number of topics also survive.
Systematic publication of his works is proceeding in a collection, Gregorii Nysseni Opera, dominated by the work of the philologist, Werner Jaeger.
Several volumes of his writings have appeared in the Sources Chrétiennes collection, the first publication of which was Jean Daniélou's translation (later edition) of his Life of Moses (1941).
Friedhelm Mann (Ed.), Lesicon Gregorianum: Woerterbuch zu en Schriften Gregors von Nyssa, Brill. Leiden 1999-2008
Lucas Francisco Mateo-Seco and Giulio Mapser (Ed.) The Brill Dictionary of Gregory of Nyssa. Brill Leiden 2010
Phillip Schaff and Henry Wace (Ed.) Nicene and Post-Nicene Fathers. Eerdmans Grand Rapids 1974 (reprint)