Gregory of Nazianzus was a 4th-century Archbishop of Constantinople. He is widely considered the most accomplished rhetorical stylist of the patristic age. As a classically trained speaker and philosopher he infused Hellenism into the early church, establishing the paradigm of Byzantine theologians and church officials. Gregory made a significant impact on the shape of Trinitarian theology among both Greek- and Latin-speaking theologians, and he is remembered as the "Trinitarian Theologian". Much of his theological work continues to influence modern theologians, especially in regard to the relationship among the three Persons of the Trinity. Along with the two brothers Basil the Great and Gregory of Nyssa, he is known as one of the Cappadocian Fathers. Gregory is a saint in both Eastern and Western Christianity. In the Roman Catholic Church he is numbered among the Doctors of the Church; in Eastern Orthodoxy and the Eastern Catholic Churches he is revered as one of the Three Holy Hierarchs, along with Basil the Great and John Chrysostom. Gregory's most significant theological contributions arose from his defense of the Nicene doctrine of the Trinity. He is especially noted for his contributions to the field of pneumatology—that is, theology concerning the nature of the Holy Spirit.In this regard, Gregory is the first to use the idea of procession to describe the relationship between the Spirit and the Godhead: "The Holy Spirit is truly Spirit, coming forth from the Father indeed but not after the manner of the Son, for it is not by generation but by procession, since I must coin a word for the sake of clearness."