On the night of the Last Supper, Jesus spoke words that included important teachings about the Trinity. Through these words, we can gain some understanding of the Trinity, although this doctrine is so complex that it is impossible to reach a fully satisfying explanation. No one in history has perfectly explained this doctrine, which is why it remains so challenging. Still, I will try to explain it as clearly as I can.
During the early Christian era, when the apostles were active, there was no established definition of the Trinity, and the term "Trinity" itself was not yet in use. However, similar concepts appear in the Bible, such as Jesus’ command:
“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.” (Matthew 28:19, WEB)
And Paul’s blessing:
“The grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit, be with you all.” (2 Corinthians 13:13, WEB)
Additionally, early Christian documents, such as Clement of Rome’s writings from the 1st century, also hint at this concept by mentioning God, the Lord Jesus Christ, and the Holy Spirit together. For example, he writes, “As God lives, and the Lord Jesus Christ lives, and the Holy Spirit (who are) the faith and the hope of the elect...” (1 Clement 58:2).
To describe this difficult idea, the early church father Tertullian first used the term “Trinitas” around the 2nd to 3rd centuries. Although he later leaned toward the Montanist heresy, his term was useful for explaining the relationship between God, Jesus, and the Holy Spirit as described in the Bible. The doctrine of the Trinity was formally established at the First Council of Nicaea in 325 AD, reaffirmed at the First Council of Constantinople in 381 AD, and further developed at the Council of Chalcedon in 451 AD.
Simply put, the doctrine of the Trinity teaches that God exists as three persons—Father, Son, and Holy Spirit—but shares the same essence and is one being. This means that while God is one in essence, He is distinguished as three persons, and the relationship among these persons is eternally equal and coexistent.
This concept is difficult to grasp fully. If it were easy, there would not have been so many heretical theories throughout church history. Examining these heresies can help us understand what is wrong with them, so let’s start with that.
The heretical views about the Trinity can be broadly divided into tritheism and unitarianism.
Tritheism claims that there are three gods with different essences and ranks. This is similar to subordinationism, which sees Jesus and the Holy Spirit as subordinate gods under the Father. Tritheism directly contradicts biblical passages such as:
“Know therefore this day, and consider it in your heart, that the LORD is God in heaven above, and on the earth beneath: there is none else.” (Deuteronomy 4:39, WEB)
“That all the people of the earth may know that the LORD is God, and that there is none else.” (1 Kings 8:60, WEB)
“I am the LORD, and there is none else, there is no God besides me.” (Isaiah 45:5, WEB)
“Surely God is in you; and there is none else, there is no God.” (Isaiah 45:14, WEB)
“I am the LORD; and there is none else.” (Isaiah 45:18, WEB)
“There is no God else beside me; a just God and a Savior; there is none beside me.” (Isaiah 45:21, WEB)
“Look to me, and be saved, all the ends of the earth: for I am God, and there is none else.” (Isaiah 45:22, WEB)
“Remember the former things of old: for I am God, and there is none else; I am God, and there is none like me.” (Isaiah 46:9, WEB)
For these reasons, tritheism was condemned as heresy from the time of the Council of Nicaea.
Unitarianism asserts that there is only one person with one essence. This includes adoptionism and modalism. Adoptionism suggests that Jesus was a human chosen by God to be His Son. Modalism claims that one God takes on different roles in different situations. For example, a man can be a father at home, an employee at work, and a church member at church; or water can exist as solid, liquid, or gas. Similarly, modalism might suggest that God acts as the Father in the Old Testament, as the Son in the New Testament, and as the Holy Spirit after Pentecost. However, this is incorrect because the Bible shows all three persons working together, not one God acting differently at different times. A heresy derived from modalism is Patripassianism, which claims that God the Father died on the cross. Attempts to simplify the Trinity often lead to modalistic explanations, such as comparing God to the sun or a tree.
So, what is the correct understanding of the Trinity?
Generally, theologians use terms like perichoresis (mutual indwelling, mutual interpenetration, mutual complementarity) to describe the Trinity, meaning that the three persons of God dwell within each other and work together. I plan to explain it from this perspective as well, by showing all relevant biblical passages related to the Trinity to aid understanding.
