Basil the Great lived and worked in a most contentious age – between the Council of Nicaea (325) and the Council of Constantinople (381). At issue was the Christian revelation of God. Basil’s opponents were the semi-Arians, Sabellians, and the Pneumatomachi (Spirit-fighters), all of whom denied the equal divine nature of the Holy Spirit with the Father and the Son, thereby denying the doctrine of Holy Trinity.