Trinity, doctrine of the

Trinity, doctrine of the. The central Christian dogma that the one God exists in three Persons and one substance, Father, Son, and Holy Spirit. The God who reveals Himself to mankind is one God equally in three distinct modes of existence, yet remains one through all eternity.

Though the word ‘Trinity’, in its Greek form τριάς, was first used by Theophilus of Antioch (c. AD180), Christian theologians have seen adumbrations of the doctrine in the Bible. The appearance of three men to Abraham (Gen. 18) was held to foreshadow the revelation of the threefold nature of God. Besides the reference to the three Persons in the baptismal formula in Mt. 28: 19, there are held to be Trinitarian overtones in other NT passages, such as the Pauline benediction in 2 Cor. 13:14.

Finding appropriate concepts to develop the doctrine was difficult and many 2nd and 3rd-cent. Christians adopted views which were later considered unorthodox. These included the so-called ‘economic Trinity’, in which the distinctions between the Persons depended solely on their functions (or ‘economies’) towards the created universe; also various subordinationist propositions. At the Councils of Nicaea (325) and Constantinople (381) the doctrine was defined in outline by negative rather than positive pronouncements, affirming against Sabellianism the real distinction of the Divine Persons, and against Arianism and Macedonianism their equality and co-eternity. The Persons differ only in origin, in that the Father is ungenerated, the Son is generated by the Father, and the Holy Spirit proceeds from the Father. Some E. Fathers understood the Spirit to proceed from the Father through the Son; others are less explicit or deny any ‘double procession’. From the time of Photius, belief in the procession of the Spirit from the Father alone was characteristic of E. theology.

In the W. the doctrine developed somewhat differently. Latin theologians started, not from the difference of the Persons, as did many of the Greeks, but from the unity of the substance. The procession of the Spirit was attributed both to the Father and the Son. St Augustine compared the generation of the Son to an act of thinking on the part of the Father (an idea based on Tertullian) and explained the Spirit as the mutual love of the Father and the Son. This so-called ‘psychological theory of the Trinity’ was developed by the Schoolmen.

The Trinitarian doctrine elaborated by the Schoolmen was challenged in the 17th cent. by Socinianism and Unitarianism, but has remained the central strand of W. theology. In the 20th cent. J. Moltmann developed a distinctive doctrine of the social Trinity, reviving the patristic theory of circumincession to express the self-differentiation of God as the crucified God.