One of the three great Cappadocian Fathers (with his close friend Gregory of Nazianzus and his younger brother Gregory of Nyssa) and one of the most consequential theologians of the post-Nicene period. Born at Caesarea in Cappadocia to a wealthy and notably Christian family (his grandmother Macrina the Elder had been a disciple of Gregory Thaumaturgus; his parents Basil the Elder and Emmelia raised ten children, of whom five became canonized saints including Basil, his brother Gregory of Nyssa, his brother Peter of Sebaste, his sister Macrina the Younger). Trained at Caesarea, Constantinople, and Athens 350-356 (where Gregory of Nazianzus was his fellow student and close friend). Returned to Cappadocia; baptized and entered monastic life (357); founded coenobitic monasteries in Pontus and composed the Longer and Shorter Rules (the foundational monastic rule of Eastern Orthodox tradition, comparable in influence in the East to the Rule of Benedict in the West). Ordained presbyter at Caesarea (364); consecrated archbishop of Caesarea (370); served as archbishop until his death (379, on the eve of the First Council of Constantinople that would vindicate the Cappadocian Trinitarian theology). Basil's principal contribution is the systematic articulation of the Trinitarian doctrine of the Holy Spirit, particularly his treatise On the Holy Spirit (375), which defended the full deity and consubstantiality of the Holy Spirit against the Pneumatomachian (Spirit-fighter) party that denied the Spirit's full deity. Basil also produced the Hexaemeron (a set of homilies on the six days of creation), extensive other homilies, hundreds of letters, and influential liturgical work (the Liturgy of St. Basil remains a periodic liturgy in Eastern Orthodox use alongside the more common Liturgy of St. John Chrysostom). Called the Great for his combined theological, monastic, pastoral, and ecclesial-political contributions.