The hardest question
A man comes up out of a river. The sky opens. Something comes down on him like a dove, and a voice from heaven says: “This is my beloved Son, with whom I am well pleased.” Matthew tells the scene in two short verses, at Jesus’ baptism in the Jordan.
Count who is there. The Son, standing in the water. The Spirit, coming down on him. The Father, speaking from heaven. Three. Christians say each one of them is God. And Christians also say there is only one God.
So which is it? One, or three? For centuries this was the hardest question in the Christian faith. In the fourth century, bishops were sent into exile over it and emperors took sides. This article follows the question from the river to the councils that settled the words, and ends with one plain sentence you can use to explain it.
To get there, we start before the river, with a people who believed something almost nobody else in their world believed.
One God
The ancient world was crowded with gods. Egypt had hundreds. Rome had gods for the harvest, the sea, and war, and even a goddess of door hinges, Cardea. Centuries later, Augustine still found the list of Roman door gods worth a joke.
Israel was different. Deuteronomy gives the words that faithful Jews spoke when they lay down and when they rose up:
Hear, Israel: Yahweh is our God. Yahweh is one.Deuteronomy 6:4, World English Bible
Not one god among many. The only one. In Isaiah, God says it plainly: “I am Yahweh, and there is no one else. Besides me, there is no God” (Isaiah 45:5).
Keep this as the first rule. There is one God. What makes the next part strange is who the first Christians were. They were not pagans with many gods. They were Jews, and they prayed these same words.
Then Jesus
Within a few years of the crucifixion, these same believers were saying astonishing things about a carpenter from Nazareth. John’s Gospel opens: “In the beginning was the Word, and the Word was with God, and the Word was God.” A few lines later: “The Word became flesh, and lived among us” (John 1:1, 14).
When the risen Jesus shows Thomas his wounds, Thomas does not call him a great teacher. He says, “My Lord and my God!” (John 20:28).
The evidence is not only in the Bible. Around AD 112, a Roman governor named Pliny wrote to the emperor Trajan about the Christians in his province. He reported that they met on a fixed day before it was light and sang “a hymn to Christ, as to a god.”
And the Spirit? In Acts, the Holy Spirit does not behave like a force or a feeling. He speaks: “Separate Barnabas and Saul for me” (Acts 13:2). That gives the second rule. The Father is God, the Son is God, and the Spirit is God.
Who talks to whom
If all three are God, are they simply one person with three names? Listen to how they speak to each other. On the night before he dies, Jesus prays:
Now, Father, glorify me with your own self with the glory which I had with you before the world existed.John 17:5, World English Bible
With you, before the world existed. That is not a man talking to himself. In the same conversation Jesus promises: “I will pray to the Father, and he will give you another Counselor… the Spirit of truth” (John 14:16–17). Another one, not the same person in a new costume.
The Father sends, the Son prays, the Spirit comes. That is the third rule: the Father, the Son, and the Spirit are distinct. So there are three rules. One God. Each one is God. Each one is distinct. Any explanation of the Trinity has to keep all three standing. Drop one, and the whole thing falls.
Four ways to break it
Over the centuries, people found four ways to make it fall.
The first is that God is one person wearing three masks: first the Father, then the Son, then the Spirit, the way water can be ice, liquid, or steam. It breaks rule three. If the Father simply turned into the Son, who was Jesus praying to? This is called modalism. Around AD 200 a man named Praxeas taught a form of it in Rome, and Tertullian answered him with one of the sharpest lines in church history:
He put to flight the Paraclete, and he crucified the Father.Tertullian, Against Praxeas 1, translated by Peter Holmes
The second is three separate gods working together as a team, like a committee. It breaks rule one; it is many gods with Christian names. This is called tritheism.
The third is one God made of three parts, like a shamrock with three leaves, or an egg with shell, white, and yolk. But one leaf is not the whole shamrock, and the Bible never calls the Son one third of God. It breaks rule two: each one is fully God, not a slice. Teachers today sometimes call this partialism; it is a modern label, not an ancient movement.
The fourth is the big one. The Father is God, and the Son is the first and greatest thing God ever made: glorious, but created. It breaks rule two again, and it nearly took over the Roman Empire. The man behind it was named Arius.
A word for it: Trinity
The Bible gives all three rules, but it never uses the word “Trinity.” So where did the word come from?
Around AD 180, Theophilus, a bishop of Antioch, wrote about the days of creation and called the first three days “types of the Trinity, of God, and His Word, and His wisdom” (To Autolycus 2.15). His Greek word was trias. It is the first known use of the word for God.
A generation later, in Carthage in North Africa, Tertullian put it into Latin, trinitas, in his reply to Praxeas. He described three persons:
Yet of one substance, and of one condition, and of one power, inasmuch as He is one God.Tertullian, Against Praxeas 2, translated by Peter Holmes
The word was new, but the faith behind it was not. Christians had been baptizing “in the name of the Father and of the Son and of the Holy Spirit” since Jesus told them to (Matthew 28:19). The word was a tool, and about a hundred years later the church would need it badly.
Arius and the fight
Alexandria, Egypt, around AD 318. A popular priest named Arius began teaching that the Son had a beginning. A later historian, Philostorgius, says Arius even set his ideas to songs for sailors, millers, and travellers. His opponents summed up his teaching in one line, recorded in the council’s letter: “there was a time when he was not.”
If the Son was made, he is a creature. Then worshiping him means worshiping something God made, and all those Christians singing hymns to Christ, as to a god, were wrong. The argument spread across the empire. In 325, Emperor Constantine called the bishops to Nicaea. Somewhere between 250 and 318 of them came; tradition settled on 318.
They answered with one word. Not a similar substance: the same substance, in Greek homoousios. Their creed calls the Son:
God of God, Light of Light, very God of very God, begotten, not made, being of one substance (homoousion) with the Father.The Creed of Nicaea (325), translated by Henry Percival
Begotten, not made. A man makes a statue, but he begets a son, and what you beget shares your nature. Fifty-six years later, in 381, a second council at Constantinople completed the creed. It speaks of the Holy Spirit, “who is Lord and Giver of life,” and “who with the Father and the Son together is worshipped and glorified” (Schaff, § 129).
About three and a half centuries after the river, the church had found words for what it had believed all along.
One What, three Whos
Here is the promised sentence: God is one What and three Whos. It is a modern teaching phrase, not an ancient formula, but it says what the creeds say.
Ask what God is, and there is one answer: one divine nature, one being, one God. Ask who God is, and there are three answers: the Father, the Son, and the Spirit.
Medieval Christians drew it as a diagram called the Shield of the Trinity. Its earliest known copies are in manuscripts from around 1210. God is in the center and the Father, the Son, and the Spirit are on the corners. The inner lines say “is”: the Father is God, the Son is God, the Spirit is God. The outer lines say “is not”: the Father is not the Son, the Son is not the Spirit, the Spirit is not the Father.
Check it against the rules. One God: yes. Each one is God: yes. Distinct: yes. All three are still standing.
Love before the world
Why does any of this matter? The Bible says, “God is love” (1 John 4:8). Not that God has love, but that he is love. Love needs someone to love. If God were alone before creation, whom did he love?
Go back to the prayer on the night before the cross. Jesus says to his Father, “you loved me before the foundation of the world” (John 17:24). Before the universe, before anyone else existed, the Father loved the Son, in the Spirit. God was never lonely. He did not make the world because he needed company; he made it because his love overflowed.
There is an old story about Augustine. It is a medieval legend, not found in his own writings. Walking on a beach while thinking about the Trinity, he sees a boy pouring seawater into a hole in the sand. The boy says he is putting the sea into the hole. Augustine tells him that is impossible. The boy answers that it is no more impossible than fitting the Trinity into a human mind.
Perhaps that is the point. No one fits God into their head. One God, three persons, never alone.
