Some think that Gregory spent a certain time in retreat before his consecration as bishop, but we have no proof of the fact. His extant letters make no mention of such retirement from the world. Nor are we better informed of the circumstances of his election to the See of Nyssa, a little town on the banks of the Halys, along the road between Cæsarea and Ancyra. According to Gregory of Nazianzus it was Basil who performed the episcopal consecration of his brother, before he himself had taken possession of the See of Sozima; which would place the beginning of Gregory of Nyssa's episcopate about 371. Was this brusque change in Gregory's career the result of a sudden vocation? St. Basil tells us that it was necessary to overcome his brother's repugnance, before he accepted the office of bishop. But this does not help us to an answer, as the episcopal charge in that day was beset with many dangers. Moreover in the fourth century, and even later, it was not uncommon to express dislike of the episcopal honour, and to fly from the prospect of election. The fugitives, however, were usually discovered and brought back, and the consecration took place when a show of resistance had saved the candidate's humility. Whether it was so in Gregory's case, or whether he really did feel his own unfitness, we do not know. In any case, St. Basil seems to have regretted at times the constraint thus put on his brother, now removed from his influence; in his letters he complains of Gregory's naive and clumsy interference with his (Basil's) business. To Basil the synod called in 372 by Gregory at Ancyra seemed the ruin of his own labours. In 375 Gregory seemed to him decidedly incapable of ruling a Church. At the same time he had but faint praise for Gregory's zeal for souls.
On arriving in his see Gregory had to face great difficulties. His sudden elevation may have turned against him some who had hoped for the office themselves. It would appear that one of the courtiers of Emperor Valens had solicited the see either for himself or one of his friends. When Demosthenes, Governor of Pontus, convened an assembly of Eastern bishops, a certain Philocares, at one of its sessions, accused Gregory of wasting church property, and of irregularity in his election to the episcopate, whereupon Demosthenes ordered the Bishop of Nyssa to be seized and brought before him. Gregory at first allowed himself to be led away by his captors, then losing heart and discouraged by the cold and brutal treatment he met with, he took an opportunity of escape and reached a place of safety. A Synod of Nyssa (376) deposed him, and he was reduced to wander from town to town, until the death of Valens in 378. The new emperor, Gratian, published an edict of tolerance, and Gregory returned to his see, where he was received with joy. A few months after this (January, 379) his brother Basil died; whereupon an era of activity began for Gregory. In 379 he assisted at the Council of Antioch which had been summoned because of the Meletian schism. Soon after this, it is supposed, he visited Palestine. There is reason for believing that he was sent officially to remedy the disorders of the Church of Arabia. But possibly his journey did not take place till after the Council of Constantinople in 381, convened by Emperor Theodosius for the welfare of religion in that city. It asserted the faith of Nicæa, and tried to put an end to Arianism and Pneumatism in the East. This council was not looked on as an important one at the time; even those present at it seldom refer to it in their writings. Gregory himself, though he assisted at the council, mentions it only casually in his funeral oration over Meletius of Antioch, who died during the course of this assembly.
An edict of Theodosius (30 July, 381; Cod. Theod., LXVI, tit. I., L. 3) having appointed certain episcopal sees as centres of Catholic communion in the East, Helladius of Cæsarea, Gregory of Nyssa and Otreius of Melitene were chosen to fill them. At Constantinople Gregory gave evidence on two occasions of his talent as an orator; he delivered the discourse at the enthronization of St. Gregory of Nazianzus, also the aforesaid oration over Meletius of Antioch. It is very probable that Gregory was present at another Council of Constantinople in 383; his "Oratio de deitate Filii et Spiritus Sancti" seems to confirm this. In 385 or 386 he preached the funeral sermon over the imperial Princess Pulcheria, and shortly afterwards over Empress Flaccilla. A little later we meet him again at Constantinople, on which occasion his counsel was sought for the repression of ecclesiastical disorders in Arabia; he then disappears from history, and probably did not long survive this journey. From the above it will be seen that his life is little known to us. It is difficult to outline clearly his personality, while his writings contain too many flights of eloquence to permit final judgment on his real character.
1 -[Saint Gregory of Nyssa]
2 -[Saint Gregory of Nyssa : Life]
3 -[Saint Gregory of Nyssa : Works]