What is the Trinity?

A classic formula is “one God in three persons.” God is one in being, or substance, and three in persons. Historic Christian theology insists on both points at once: rejecting any idea that the three persons are merely masks or modes of one person, and rejecting any idea that they are three separate gods.

The word “Trinity” does not appear in the Bible. Christians developed it to summarize what they believed the Bible teaches about God. The early Christian writer Tertullian used the Latin term trinitas around the year 200.

No. Christianity is a monotheistic religion, and the Trinity is understood as a way of describing one God. Christian theologians have used many analogies to explain this, such as water existing as ice, liquid and steam, but they have also warned that every analogy falls short and that the Trinity is ultimately a mystery beyond full human understanding.

Jews and Muslims have often criticized the doctrine as compromising God’s oneness. Christians respond that the Trinity describes the inner life of the one God rather than adding gods to God.

The Father is the source of all things, to whom Jesus prayed and whom he called “Abba.” The Son is the eternal Word of God who became human in Jesus Christ. The Holy Spirit is God present and active in the world, who inspired the prophets, descended on the apostles at Pentecost and dwells in believers.

Christian theology describes the relationships between the persons in specific terms: the Son is eternally begotten of the Father, and the Spirit eternally proceeds. These relationships distinguish the persons without making any of them less divine.

The earliest Christians were Jews who worshipped one God, yet they also worshipped Jesus as Lord and experienced the Holy Spirit as God’s presence. The New Testament contains passages that name the three together, such as the command to baptize “in the name of the Father and of the Son and of the Holy Spirit” in Matthew 28:19.

In the fourth century, controversy arose when Arius, a priest in Alexandria, taught that the Son was a created being. The Council of Nicaea in 325 affirmed that the Son is “of one being” with the Father. The Council of Constantinople in 381 expanded the creed and affirmed the full divinity of the Holy Spirit. The result, the Nicene Creed, remains the most widely accepted Christian creed.

Catholic, Orthodox and mainstream Protestant churches all affirm the Trinity as defined by the early councils. Baptism is administered in the name of the Father, Son and Holy Spirit, and the Trinity shapes liturgy, prayer and hymns across these traditions.

The best-known difference is the filioque. The Western church added to the Nicene Creed the phrase that the Spirit proceeds from the Father “and the Son.” The Eastern Orthodox churches reject this addition, holding that the Spirit proceeds from the Father. The disagreement contributed to the split between Eastern and Western Christianity in 1054.

Outside the historic mainstream, some groups that identify as Christian reject the Trinity. These include Unitarians, Jehovah’s Witnesses, Oneness Pentecostals and the Church of Jesus Christ of Latter-day Saints, each of which understands God and Jesus differently.

In Trinitarian Christianity, yes. Jesus is the second person of the Trinity, the Son, who became human. The Council of Chalcedon in 451 described him as one person with two natures, fully divine and fully human. Christians therefore pray to Jesus and worship him as God, while also saying that he prayed to the Father during his earthly life.

For Christians the Trinity is not only an abstract doctrine. It shapes how they pray: often to the Father, through the Son, in the Spirit. It shapes baptism, the Eucharist, blessings and hymns. Many theologians also see in the Trinity a picture of God as relational love, which informs Christian ideas about community and relationships.

The Trinity is not Father, Mother and Son; the Holy Spirit is not Mary. It is not three gods sharing power. It is not one person who changes roles over time, a view known as modalism, which the early church rejected. And it is not believed by Christians to be a later replacement of biblical monotheism, but an explanation of it.

The Trinity is the Christian belief that the one God exists eternally as Father, Son and Holy Spirit, three distinct persons who are each fully God and together one God. It was formally defined by the councils of Nicaea and Constantinople in the fourth century and is shared by Catholic, Orthodox and most Protestant Christians.