TRINITY. Trinitarian doctrine touches on virtually every aspect of Christian faith, theology, and piety, including Christology and pneumatology, theological epistemology (faith, revelation, theological methodology), spirituality and mystical theology, and ecclesial life (sacraments, community, ethics). This article summarizes the main lines of trinitarian doctrine without presenting detailed explanations of important ideas, persons, or terms.

The doctrine of the Trinity is the summary of Christian faith in God, who out of love creates humanity for union with God, who through Jesus Christ redeems the world, and in the power of the Holy Spirit transforms and divinizes (2 Cor. 3:18). The heart of trinitarian theology is the conviction that the God revealed in Jesus Christ is involved faithfully and unalterably in covenanted relationship with the world. Christianity is not unique in believing God is "someone" rather than "something," but it is unique in its belief that Christ is the personal Word of God...