Our father among the saints Gregory the Theologian, also known as Gregory of Nazianzus (though that name more appropriately refers to his father) and Gregory the Younger, was a great father and teacher of the Church. His feast day is celebrated on January 25 and that of the translation of his relics on January 19. With Sts. Basil the Great and John Chrysostom, he is numbered among the Three Holy Hierarchs, whose feast day is celebrated on January 30. St. Gregory is also known as one of the Cappadocian Fathers.
About the year 379, St. Gregory came to the assistance of the Church of Constantinople, which had already been troubled for forty years by the Arians; by his supremely wise words and many labors he freed it from the corruption of heresy. He was elected archbishop of that city by the Second Ecumenical Council, which assembled there in 381, and condemned Macedonius, Archbishop of Constantinople, as an enemy of the Holy Spirit. When St. Gregory came to Constantinople, the Arians had taken all the churches, and he was forced to serve in a house chapel dedicated to St. Anastasia the Martyr. From there he began to preach his famous five sermons on the Trinity, called the Triadica. When he left Constantinople two years later, the Arians did not have one church left to them in the city. St. Meletius of Antioch (see Feb. 12), who was presiding over the Second Ecumenical Council, died in the course of it, and St. Gregory was chosen in his stead; there he distinguished himself in his expositions of dogmatic theology.
Having governed the Church until 382, he delivered his farewell speech-the Syntacterion, in which he demonstrated the Divinity of the Son—before 150 bishops and the Emperor Theodosius the Great. Also in this speech he requested, and received from all, permission to retire from the See of Constantinople. He returned to Nazianzus, where he lived to the end of his life. He reposed in the Lord in 391, having lived some sixty-two years.
http://orthodoxwiki.org/Gregory_the_Theologian
