Gregory of Nazianzus
St. Gregory of Nazianzus (b. 330, died 390) the Archbishop of Constantinopal known as Gregory the Theologian, was instrumental as an Early Church leader. His contribution to the theological definition of the Trinity and the nature of Christ are considered a masterpiece, also known as the Five Theological Orations.  He strongly opposed Arianism and helped prevent an Arian schism in the diocese. Saint Gregory, along with Saint Basil and Basil's brother Gregory of Nyssa, are jointly known as the Cappadocian Fathers. Proclaimed Doctor of the Church by Pope Pius V in 1568.
Born in Arianzus, a village of Cappadocia (modern day Turkey) to father Gregory, Bishop of Nazianzus and Saint, and mother Nonna also was a Saint. Gregory had siblings, his brother St. Caesarius and his sister St.Gorgonia. He was educated in Caesarea of Palestine where he studied rhetoric under Thespesius, studied in Alexandria, and then in Athens. He dedicated his life to God after surviving a violent sailing trip. In Athens, he studied with fellow friend St. Basil and shared class with Prince Julian, future Emperor of Rome. Gregory would observe of him, "What an evil the Roman State is nourishing." As Emperor, he was called the Apostate because he denied Christ and did all in his power to restore paganism.
St. Gregory lived the monastic life for a time in the hermitages of Pontus, along with St. Basil. His father ordained him presbyter of the Church of Nazianzus. During St. Basil's dispute with the emperor, consecrated him unwillingly as Bishop of Sasima, archdiocese of Caesarea. This would lead to conflict with Basil and the relationship soured. Following the death of Arian emperor Valans, Gregory went to Constantinopal. The city just witnessed thirty years of Arianism and paganism. The orthodox did not even have a church. Gregory converted his house and held services there. There he preached the Five Theological Orations for which he is best known, a series of five sermons on the Trinity and in defense of the deity of Christ. People flocked to hear him preach. Gregory became Bishop of Constantinople the following year in 381. 
His request was granted, and his cousin Eulalius, a priest of holy life to whom he was much attached, was duly appointed to the See of Nazianzus in 383. Gregory withdrew to Arianzus where he spent the remaining years of his life in retirement, and in the literary labors. Before leaving Constantinople he made his will, in which he bequeathed all his property to the Deacon Gregory for life, with reversion to the poor of Nazianzus.  Died in peace 25 January 390.
Gregory's had voluminous writings, and a great reputation as an orator and a theologian.
Orations- 45 in total
- The Five Theological Orations -in defence of the Church’s faith in the Trinity, against Eunomians and Macedonians.
- The Two Invectives against Julian -present us with a very dark picture of his character.
- Moral Orations
- treatise on the Priesthood
- Festal Orations
- Panegyrics on Saints
- Funeral Orations on Eminent People
- Occasional Orations
Letters numbering 243
Poems totaling 507
- "Let us not esteem worldly prosperity or adversity as things real or of any moment, but let us live elsewhere, and raise all our attention to Heaven; esteeming sin as the only true evil, and nothing truly good, but virtue which unites us to God."