The Trinity, simply and honestly: what the Bible says, why comparisons fall short, and how the church learned to put the mystery into words.
Christians believe in one God. Yet they pray to the Father, worship Jesus and speak of the Holy Spirit as God. How does that fit together? The honest answer starts with an admission: we cannot fully understand God. A God who fits in one sentence would be smaller than we are. But we can say what the Bible shows, and what the church has confessed about it together for sixteen centuries.
There is only one God. And yet He is Father, Son and Holy Spirit. That is a great mystery, bigger than our heads. You don't have to understand it all to love God, just as you can't fit the sea in a bucket and can still swim in it.
One God, in three persons: the Father, the Son and the Holy Spirit. Not three gods. Not one person with three masks. Not three parts that together make God. Each of the three is fully God, and yet there is only one God.
The building blocks from the Bible
The Bible gives no formula, but five things that together make up the picture.
1
There is only one God
This is the heart of Israel's faith, prayed every day in the 'Hear, Israel'. Jesus Himself calls it the first commandment. Christians never let go of it: the Trinity is not an expansion to three gods.
Nobody questions that. Jesus teaches us to pray to 'our Father', and Paul writes: for us there is one God, the Father.
yet to us there is one God, the Father, of whom are all things, and we for him; and one Lord, Jesus Christ, through whom are all things, and we live through him.
John opens his gospel with: the Word was God, and the Word became flesh. Thomas calls the risen Jesus 'my Lord and my God', and Jesus does not correct him.
In the beginning was the Word, and the Word was with God, and the Word was God.
Whoever lies to the Holy Spirit lies to God. The Spirit is everywhere, knows the depths of God and gives life: things that are said of God alone.
While you kept it, didn’t it remain your own? After it was sold, wasn’t it in your power? How is it that you have conceived this thing in your heart? You haven’t lied to men, but to God.”
At the baptism of Jesus the Son stands in the water, the Spirit comes down and the Father speaks from heaven: three at once, not one after the other. Jesus has people baptised in 'the name' (singular) of the Father, the Son and the Holy Spirit. And Paul blesses with the grace of the Lord Jesus, the love of God and the fellowship of the Spirit.
Go,and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit,
Familiar images, well meant. But each of them slides towards an old error that the church rejected early on.
Water: ice, liquid and steam
One substance in three forms.
Why it falls short
Water is never fully ice, liquid and steam at once in the same drop. It changes form. Then God would be Father now, Son later, Spirit after that. But at the baptism of Jesus all three are there at the same time, and the Son prays to the Father.
Leads to: Modalism
The teaching that God is one person who shows Himself in three guises one after another, like an actor with three masks. In the third century it was linked to Sabellius and Praxeas, and the church rejected it.
An egg: shell, white and yolk
Three parts, together one.
Why it falls short
A shell is not an egg, and neither is a yolk. Then each of the three would be only a piece of God. But the Bible says that in Christ the whole fullness of God dwells, not a third of it.
Leads to: Partialism
The idea that Father, Son and Spirit are each a part of God and only 'whole' God together. It is less a historical movement than a trap that comparisons with parts fall into.
A shamrock with three leaves
One plant, three leaves.
Why it falls short
It suffers from the same thing as the egg: one leaf is not the whole clover. The story that Saint Patrick explained it this way does not come from his own writings, by the way: it was only written down centuries later.
Leads to: Partialism
Each leaf is only a part. Useful for saying that God is three and one, not how.
The sun, its light and its warmth
One source, and what goes out from it.
Why it falls short
Early church fathers used images like this, and the creed calls the Son 'light from light'. But whoever goes too far makes light and warmth into something less than the sun itself: a radiance, not a person.
Leads to: Subordination
If the Son and the Spirit are less God than the Father, you end up with Arius: the Son as the highest creature. The Council of Nicaea rejected that in 325.
Three people in one team
Three persons, one goal.
Why it falls short
This picture takes the three persons seriously, but turns them into three separate beings who happen to agree. Then you have three gods.
Leads to: Tritheism
Belief in three gods. Christians have always rejected it: there is one God, with one will and one being.
Every comparison falls short, and that is fine: God is not like anything else. It helps more to see what the Bible says, and to accept that the mystery is greater than our understanding. Whoever thinks this way stands in a long line: the church fathers themselves said that their words fence in the mystery, they do not explain it.
From the apostles to Nicaea and Constantinople
The word came later than the faith. A short line through the first centuries.
c. 50–95
The apostles
The New Testament does not have the word 'Trinity', but it does have the thing: the baptismal command, blessings and letters name Father, Son and Spirit in one breath.
An early handbook for congregations prescribes baptism 'in the name of the Father and of the Son and of the Holy Spirit', as Jesus had said.
c. 180
A word for the mystery
Theophilus of Antioch is the first known writer to use the Greek word trias, a group of three, for God. Shortly after 200 Tertullian uses trinitas in Latin, in a work against Praxeas, who taught that the Father Himself had suffered on the cross.
325
Council of Nicaea
The priest Arius teaches that the Son was created, the highest of creatures. More than two hundred bishops reject this: the Son is 'of one being' (homoousios) with the Father, begotten, not made.
c. 360–380
The Cappadocians
Basil the Great, Gregory of Nazianzus and Gregory of Nyssa work out how to speak of the Spirit: one being (ousia) in three persons (hypostases). Basil writes a book on the Holy Spirit.
381
Council of Constantinople
The creed of Nicaea is expanded on the Spirit: He is Lord and gives life, proceeds from the Father, is worshipped and glorified together with the Father and the Son, and has spoken through the prophets. Catholics, Orthodox and many Protestants still pray this text.
589–1014
East and West: the filioque
In the West a word was added to the creed: the Spirit proceeds from the Father 'and the Son' (filioque), first at a synod in Toledo in 589, in Rome only around 1014. The Eastern churches do not accept the addition. It remains a difference today, though the churches have sought much rapprochement over it in their conversations.
Today
What all the great churches confess together
Catholics, Orthodox and Protestants confess the Trinity together, with the same ancient creed. Groups that deny it stand outside that shared confession; you can read more under the church traditions.
How the church later branched out, you can see under Traditions.