The Trinity in Christianity, three Persons in one God. The doctrine, central to Christianity, is considered a supernatural mystery, known to man only by the revelation of Jesus in the New Testament. According to the traditional understanding of the revelation, the three Persons are really distinct from one another; yet each Person is identified with the one divine nature, and therefore there is only one God. The First Person, called the Father, is said to have eternally begotten the Second Person, the Son of God. The Son assumed a human nature in time and was called Jesus. The third Person, called the Holy Spirit, is believed to proceed eternally, according to Western theology, from the Father and the Son. According to Eastern theology the Holy Spirit proceeds from the Father alone. Christians believe that despite the eternal processions within the Divinity, there is no subordination; the three Persons are equally divine, uncreated and uncaused, eternal, and omnipotent.
In the early centuries of the Church many theologians tried to explain the Trinity in a way that would reconcile belief in Jesus with belief in only one God. Some groups, such as the Gnostics, said that the Son was a divine emanation of the Father; others, such as the Arians, said that the Son was simply a man created by the Father. In 325 a.d. the Council of Nicaea stated the orthodox doctrine in the form of the Nicene Creed, considering Christ both fully God and fully man. Later the doctrine was elaborated by St. Augustine and St. Thomas Aquinas.
There are also trinitarian concepts in Hinduism, Buddhism, and Taoism.