The Trinity, also called Trinitas in Latin, is a Christian belief about the nature of God. It teaches that there is one God who exists as three eternal, equal, and sharing-the-same-nature divine persons: God the Father, God the Son (Jesus Christ), and God the Holy Spirit. These three persons are distinct but share one essence, or nature, known as "homoousion."

The Fourth Lateran Council explained that the Father is the source of the Son, the Son is born from the Father, and the Holy Spirit comes from both. In this belief, the one essence describes what God is, while the three persons describe who God is. This shows both their differences and their unity. All creation and spiritual gifts are seen as a shared action of the three persons. Each person shows unique qualities in the Trinity, proving that everything comes "from the Father," "through the Son," and "in the Holy Spirit."

This belief is called Trinitarianism. People who follow it are called Trinitarians, while those who disagree are called antitrinitarians or nontrinitarians. Many mainline Christian groups consider nontrinitarians not to be Christian. Nontrinitarian views include Unitarianism, binitarianism, and modalism. The study of the Trinity is called "triadology" or "Trinitarian theology."

Although the full Trinity doctrine is not clearly stated in the New Testament, the Gospel of John offers ideas that support it. The New Testament includes a three-part understanding of God and has several Trinitarian formulas. The Trinity was first clearly explained by early Christians and church leaders in the mid-2nd century and later, as they studied the relationship between Jesus and God in their religious texts and traditions.

Old Testament

The Old Testament has been understood by some people to mention the Trinity in several places. For example, in the Genesis creation story, the use of first-person plural pronouns in Genesis 1:26–27 and Genesis 3:22 has been used to support the idea of God being one being in three persons. These verses include lines such as:

"Then God said, 'Let us make man in our image, after our likeness.'"

"Then the LORD God said, 'Behold, the man has become like one of us in knowing good and evil.'"

Some Christians believe these pronouns refer to more than one person within God. A biblical scholar named Victor P. Hamilton explains that some people think these pronouns do not refer to other persons in God but instead to the "heavenly court" mentioned in Isaiah 6. Scholars like Meredith Kline and Gerhard von Rad support this view. Von Rad explains that the use of the plural ("Let us") helps avoid making God’s image too directly connected to God the Lord. Instead, God is shown as part of a group of heavenly beings, which hides His identity. Hamilton notes that this idea may conflict with a statement in Isaiah 40:13–14, which says no one can give advice to God. If the plural pronouns in Genesis suggest God consults a heavenly court, this might contradict Isaiah’s claim that God seeks no one’s counsel. Hamilton believes the best explanation is one that hints at the Trinity but uses less direct language. He also mentions that the plural in Genesis 1:26–27 might reflect a "duality within the Godhead," which connects to the "Spirit of God" mentioned in Genesis 1:2. He argues that the author of Genesis likely understood the idea of a "plurality within unity" and that the Trinity was revealed more clearly in the New Testament.

Another example is Isaiah 9, where the Messiah is described as "Wonderful Counselor, Mighty God, Everlasting Father, Prince of Peace." Some Christians believe this verse refers to the Trinity because "Counselor" is a title for the Holy Spirit (John 14:26), "Mighty God" is a title for God the Father, and "Prince of Peace" is a title for Jesus. This verse is also used to support the belief that Jesus is divine.

The divinity of Jesus is also suggested in the Book of Daniel, where a figure described as "one like a son of man" is given eternal rule over all nations. This is similar to a statement in Psalm 145:13, which says God’s rule is eternal. Some writers also see hints of the Trinity in Old Testament references to God’s word (Psalm 33:6), God’s Spirit (Isaiah 61:1), and Wisdom (Proverbs 9:1), as well as in stories like the three men who visited Abraham in Genesis 18. However, most scholars agree that connecting these Old Testament ideas directly to the Trinity would go beyond what the Old Testament intended.

Some early Church leaders believed that prophets and holy people in the Old Testament had knowledge of the Trinity. They saw figures like the divine messenger in Genesis 16:7, Genesis 21:17, Genesis 31:11, Exodus 3:2, and the "Wisdom" in the sapiential books as representing Jesus, and "the spirit of the Lord" as the Holy Spirit.

Other Church leaders, like Gregory Nazianzen, argued that the revelation of the Trinity was gradual. He believed the Father was clearly shown in the Old Testament, but the Son was only hinted at because it was not safe to openly declare the Son’s divinity when the Father’s identity was not yet fully understood.

In Genesis 19, two angels visited Lot in Sodom. This created confusion for those who believed in one God in three persons. Some, like Justin Martyr and John Calvin, believed the God who visited Abraham was Jesus, the second person of the Trinity, while others, like Augustine, thought the three visitors were the three persons of the Trinity. Augustine noted that Lot addressed the visitors as one because they shared the same nature despite being three separate persons.

Christians also interpret theophanies, or appearances of the Angel of the Lord, as moments when a distinct person, different from God, was revealed. This person was still called God. This idea was present in early Christianity and was also discussed by Jewish thinkers like Philo. These appearances were seen as Christophanies, or preincarnate appearances of the Messiah.

New Testament

According to Larry Hurtado, the New Testament does not clearly explain the Trinity as it is understood today, but it does show a three-part view of God. Some important statements that mention all three parts of God include Matthew 28:19, 2 Corinthians 13:13, Ephesians 4:4–6, 1 Peter 1:2, and Revelation 1:4–6. Scholars Harold W. Attridge and C. K. Barrett note that the Gospel of John contains ideas that helped shape the Trinity. James Barker says that parts of the Trinity are present in the New Testament, especially in the Gospel of John. Early Christians studied verses like the Great Commission, which says, "Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit," and Paul’s blessing, which says, "The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all." These verses led early Christians to think about how the Father, Son, and Holy Spirit are connected.

Over time, the many references to God, Jesus, and the Holy Spirit in the New Testament were combined into the idea of the Trinity—one God who exists in three persons but is one in being. This idea was used to explain how the three parts of God are connected and to show that the church did not worship more than one or more than three gods.

Modern Bible scholars agree that 1 John 5:7, which says, "There are three in Heaven that testify—the Father, the Word, and the Holy Spirit—and these three are one," was not in the oldest Greek or Latin texts. This verse, called the Johannine Comma, was added later by someone copying the text. It appears in some later Latin texts and translations like the King James Version, but not in older translations such as those in Ethiopic, Aramaic, Syriac, or early Armenian. The verse was used by many Latin-speaking writers in the Middle Ages and later appeared in printed Bibles like the Textus Receptus.

In the letters of Paul, early Christians worshipped Jesus in ways that show they believed he had a special place in God’s plan. This is called a "binitarian" pattern, where both God and Jesus are honored. For example, people prayed to Jesus, called his name in worship, were baptized in his name, and shared meals in his honor. Jesus is described as being in the same form as God and having the fullness of God in his body. Some verses even call Jesus "God."

Many scholars believe the Synoptic Gospels (Matthew, Mark, and Luke) show Jesus as divine. For example, Jesus forgives sins, which some people think only God can do. When Jesus did this, some religious leaders said he was claiming to be God. After his resurrection, Jesus received worship from his followers, a sign of respect and devotion usually given to God. This is seen in Matthew 28:16–20, where Jesus is called "Emmanuel," meaning "God with us," a name connected to God’s presence in the Old Testament.

In the book of Acts, early Christians called on Jesus’ name, a practice similar to calling on God’s name in the Old Testament. People were baptized in Jesus’ name, and Stephen, a Christian, called out to Jesus before he died. Acts also describes Jesus appearing to Paul as a divine presence, like the way God appeared to the prophet Ezekiel.

The Gospel of John focuses on Jesus’ divinity, calling him the Logos, or Word, who existed before creation and was with God. John 1:1 says, "In the beginning was the Word, and the Word was with God, and the Word was God." Thomas, one of Jesus’ followers, called Jesus "My Lord and my God!" in John 20:28. Scholars agree these verses show Jesus is identified with God. Some scholars, like Philip B. Harner, have questioned the traditional translation of John 1:1, suggesting it might mean the Word shared the same nature as God. Others disagree. John also describes Jesus as the creator of the universe.

Some people believe John’s Gospel shows a hierarchy, but the text does not explicitly support this idea.

Early Christianity

The idea of the Trinity began to take shape as early Christians tried to understand how Jesus and God are connected in their religious writings and traditions. Margaret Baker explains that Trinitarian beliefs have roots in ideas about angels that existed before Christianity.

An early mention of the three "persons" of the Trinity appears near the end of the first century. Clement of Rome, in a letter he wrote, asked why some people in the Christian community were not living properly. He wrote, "Do we not have one God, and one Christ, and one gracious Spirit that has been poured out upon us, and one calling in Christ?" A similar idea is found in the Didache, an early Christian text that tells people to "baptize in the name of the Father and of the Son and of the Holy Spirit."

Around AD 110, Ignatius of Antioch also wrote about the Father, the Son, and the Holy Spirit, encouraging people to obey all three. The book called the "Ascension of Isaiah," written between the end of the first century and the start of the third century, includes a "proto-Trinitarian" view. It describes people in heaven praising "the primal Father and his Beloved Christ, and the Holy Spirit."

Justin Martyr, who lived from around AD 100 to 165, used phrases that later became common in Trinitarian theology. He described the Son and the Father as the same "being" but also different "faces," which helped shape later ideas about the Trinity. He compared the Son to a fire that comes from a torch, showing how the Son comes from the Father. Justin also wrote that Christians worship Jesus as the Son of God and the Holy Spirit as the third part of the Trinity. He explained that baptism is done "in the name of God, the Father and Lord of the universe, and of our Saviour Jesus Christ, and of the Holy Spirit."

Some scholars say Justin's writings focused more on two persons, not three, and the same is true for some writings by Tertullian and Eusebius of Caesarea.

The first person recorded to use the word "Trinity" was Theophilus of Antioch, who lived in the late second century. He described the Trinity as God, his Word (Logos), and his Wisdom (Sophia), using the early Christian idea that the Holy Spirit is the Wisdom of God.

Tertullian, who was born around AD 150–160, was the first to clearly define the Trinity as the Father, the Son, and the Holy Spirit. He defended this idea against someone named Praxeas, even though many people at the time disagreed with him.

St. Justin and Clement of Alexandria mentioned all three parts of the Trinity in their writings, and St. Basil also did this when lighting lamps in the evening.

Origen of Alexandria, who lived from AD 185 to around 253, was sometimes thought to believe the three persons of the Trinity were not equal. However, some modern researchers think he might have supported the idea that all three are equal, which influenced later theologians.

The idea of the Trinity developed over the first four centuries as early church leaders responded to other beliefs, such as Adoptionism, Sabellianism, and Arianism. In 269, church leaders in Antioch criticized Paul of Samosata for his Adoptionist ideas and also rejected the use of the term "homoousios" (meaning "of the same being") in a certain way.

In the fourth century, Arianism taught that the Father existed before the Son, and that the Son was not God but a created being. In 325, the First Council of Nicaea created the Nicene Creed, which described Jesus as "God of God, Light of Light, very God of very God, begotten, not made, being of one substance with the Father." It also mentioned the Holy Spirit as the one through whom Jesus was born to the Virgin Mary. The creed used the term "homoousios" (meaning "of the same being") to describe the relationship between the Father and the Son. After many years of debate, this term became a key part of accepted Christian belief, leading to the idea of "three persons, one being."

The Nicene Creed from 325 said little about the Holy Spirit. At that time, the focus was on the relationship between the Father and the Son, with no clear statement about the Holy Spirit. The creed stated:

"We believe in one God, the Father Almighty, Maker of all things visible and invisible. And in one Lord Jesus Christ, the Son of God, begotten of the Father… Light of Light, very God of very God, begotten, not made, being of one substance with the Father… And [we believe] in the Holy Ghost."

The Nicene Creed from 325 is considered to have a binitarian focus (focusing on two persons), even though it briefly mentions the Holy Spirit.

Later, at the First Council of Constantinople in 381, the Nicene Creed was expanded into the Niceno-Constantinopolitan Creed. This version said the Holy Spirit is worshiped and glorified with the Father and the Son, showing that the Holy Spirit is also "of one substance" with them. The creed now read:

"We believe in one God, the Father Almighty, Maker of heaven and earth, and of all things visible and invisible. And in one Lord Jesus Christ, the only-begotten Son of God, begotten of the Father before all worlds… Light of Light, very God of very God, begotten, not made, being of one substance with the Father… And in the Holy Ghost, the Lord and Giver of life, who proceedeth from the Father, who with the Father and the Son together is worshiped and glorified, who spake by the prophets…"

The idea that the Holy Spirit is divine and a person was developed by Athanasius in the last years of his life. He helped improve the Nicene Creed. By the end of the fourth century, under the guidance of Basil of Caesarea, Gregory of Nyssa, and Gregory of Nazianzus (called the Cappadocian Fathers), the doctrine of the Trinity was nearly complete.

These three men explained that the differences between the three persons of the Trinity are only in how they relate to each other within God. There are not three gods, but one divine being in three persons. Some of the Cappadocian Fathers used social examples to explain the Trinity, while Augustine of Hippo used a psychological example. He believed that since humans are made in the image of God, they are made in the image of the Trinity. Augustine compared the Trinity to the parts of a human mind: memory, understanding, and will. In short, Christians can think of God as one person, not three.

Theology

Baptism is usually given using the Trinitarian formula, "in the name of the Father, and of the Son, and of the Holy Spirit." Trinitarians believe this formula represents the Christian faith into which baptism is an initiation. For example, Basil the Great (330–379) said, "We must be baptized using the terms we received, and we must believe using the same terms." The First Council of Constantinople (381) stated, "This is the faith of our baptism, which teaches us to believe in the name of the Father, the Son, and the Holy Spirit. According to this faith, there is one Godhead, power, and being of the Father, the Son, and the Holy Spirit." This suggests that the Trinitarian formula was used in baptism from the early days of the Church. Other Trinitarian formulas in the New Testament include 2 Corinthians 13:14, 1 Corinthians 12:4–6, Ephesians 4:4–6, 1 Peter 1:2, and Revelation 1:4–5.

Oneness Pentecostals disagree with the Trinitarian view of baptism and focus on being baptized "in the name of Jesus Christ" only, which they believe is the original apostolic formula. For this reason, they often look at baptisms described in the book of Acts. People who emphasize Acts’ baptisms often question whether Matthew 28:19 is authentic. However, most New Testament scholars accept Matthew 28:19 as genuine because there are no differences in the text, and early Christian writings like the Didache and works by Ignatius, Tertullian, Hippolytus, Cyprian, and Gregory Thaumaturgus support it.

Gerhard Kittel wrote about Matthew 28:19: "The relationship between the Father, Son, and Holy Spirit soon became clear in formulas like 2 Corinthians 13:14 and 1 Corinthians 12:4–6. This formula first appears in the baptismal instruction in Matthew 28:19. It is clear that the Father, Son, and Holy Spirit are connected in a close, unbreakable relationship."

The term "immanent Trinity" refers to who God is, while "economic Trinity" refers to what God does. The Catechism of the Catholic Church explains: "Theology refers to the mystery of God’s inner life within the Trinity, and economy refers to how God reveals himself and shares his life. Through God’s actions, we learn about his inner life, and understanding his inner life helps us understand his actions. Just as people show who they are through their actions, knowing a person better helps us understand their actions. The entire work of God is done by the three persons of the Trinity. The Trinity has one nature and one work: 'The Father, the Son, and the Holy Spirit are not three creators, but one.' Each person does the work in their own way. The Church teaches, following the New Testament, 'one God and Father, from whom all things come; one Lord Jesus Christ, through whom all things come; one Holy Spirit, in whom all things come.' The Son’s Incarnation and the Holy Spirit’s gift especially show the roles of the Trinity’s persons."

Ancient theologians argued that the Trinity always works together with one will. The three persons of the Trinity always act as one God. The Son’s will cannot differ from the Father’s because it is the Father’s. They share one will and one being. Otherwise, they would not be one God. St. Basil wrote: "When Jesus said, 'I have not spoken on my own,' and 'As the Father said to me, so I speak,' and 'The word you hear is not mine, but the Father’s,' it does not mean he lacked purpose or power. He used these words to show that his will is closely connected to the Father’s. Do not think of the Father’s commands as orders given to a subordinate. Instead, understand them as a sharing of will, like a reflection in a mirror, without time, from the Father to the Son."

Thomas Aquinas said the Son prayed to the Father, became lower than angels, became human, obeyed the Father as a human, but remained God in his divine nature. "The fact that the Father glorifies, raises, and exalts the Son does not mean the Son is less than the Father, except in his human nature. In his divine nature, the Son is equal to the Father, and their power and work are the same." Aquinas stated that believing in the Son’s mystery requires faith in the Trinity.

Athanasius of Alexandria explained that the Son is eternally one with the Father in being, but in his human life, he chose to be subordinate. Human traits should not be applied to the eternal Trinity. The Cappadocian Fathers also said there is no inequality in the Trinity’s actions. Basil wrote: "We see the Father, Son, and Holy Spirit acting as one, with no differences. From this unity of action, we know their nature is one."

The traditional theory of "appropriation" says certain names, qualities, or actions are linked to one Trinity person, not to exclude others but to emphasize them. This idea was developed by Latin theologians like Hilary of Poitiers, Augustine, and Leo the Great. In the Middle Ages, scholars like Bonaventure taught it systematically.

Augustine connected the Trinity to human life, saying humans reflect the Trinity because they are made in God’s image. He used the idea of mutual love between people to explain the Trinity. In De trinitate, he wrote: "We must ask if love itself is triune. Augustine said it is, and it includes three parts: the lover, the beloved, and the love itself."

Thomas Aquinas reaffirmed the belief that "One of the Trinity suffered in the flesh." He explained that Jesus suffered and died in his human nature, but not in his divine nature. "The command to suffer belongs only to the Son’s human nature. Christ was raised in the same way he suffered, in the flesh, as 1 Peter 4:1 says."

Architecture

The design of Gothic cathedrals includes many details that reflect religious beliefs. Features such as the cross-shaped layout, the use of light, sculptures, and symbols like the Trinity in trefoils and the four evangelists in quatrefoils show decisions made to express theological ideas. Whether the architecture is complex or simple, and whether the building was originally made for Christian use or not, spaces used for Christian worship show religious meanings and values.

Many Christian churches have three doors to represent the Trinity. Other parts of the building, such as windows or steps, are also grouped into three for this reason. This practice began in churches that were built using materials from older, non-Christian holy structures. Examples include the three royal doors inside Eastern churches and the three doors on the front of many cathedrals. A triangle-shaped floor plan can also symbolize the Trinity, as seen in the Heiligen-Geist-Kapelle in Austria.

Artistic depictions

The Trinity is often shown in Christian art with the Holy Spirit represented by a dove, as described in the Bible's account of Christ's baptism. The dove is usually shown with its wings spread wide. Sometimes, artists use three human figures to represent the Trinity, though this is less common in most periods of art.

The Father and the Son are often shown with differences in age and clothing, but this is not always the case. The Father is frequently shown as an older man with a white beard, a style that may come from the Bible's description of the "Ancient of Days." This image is sometimes used to support this representation, though in Eastern Orthodoxy, the "Ancient of Days" is usually understood to refer to God the Son, not the Father. In early Byzantine art, Christ was often shown as the "Ancient of Days," but this style became rare over time. When the Father is shown in art, he may have a triangular-shaped halo instead of a circular one. The Son is often placed at the Father's right side, as described in the Bible (Acts 7:56). He may be shown as a symbol, such as a lamb (agnus dei) or a cross, or on a crucifix, leaving the Father as the only full-sized human figure. In early medieval art, the Father was sometimes shown as a hand emerging from a cloud, offering a blessing, as seen in scenes of Christ's baptism. Later, in Western art, the "Throne of Mercy" (or "Throne of Grace") became a common image. In this style, the Father (sometimes seated on a throne) is shown holding a crucifix or a slumped, crucified Son, similar to the Pietà, with the Dove hovering above or between them. This image remained popular until at least the 18th century.

By the late 15th century, most depictions of the Trinity, aside from the "Throne of Mercy," became standardized. The Father was shown as an older man in simple clothing, Christ was often shown with part of his torso bare to reveal the wounds from his crucifixion, and the Dove was placed above or around them. In earlier art, both the Father and the Son were more likely to wear elaborate robes and crowns. At times, only the Father wore a crown or even a papal tiara.

In the later part of the Christian Era, during the Renaissance in Europe, the "Eye of Providence" began to be used as a clear image of the Trinity, linked to the idea of Divine Providence. In 17th-century art, the Eye of Providence was sometimes shown surrounded by clouds or sunbursts.