One God, Three Persons
Isn't "three in one" a contradiction?
Main teaching: De fide
The big question
Christians say they believe in one God. They also say the Father is God, the Son is God and the Holy Spirit is God. To many people that sounds like bad arithmetic: either there are three gods, or “three” is just a figure of speech. Is the Trinity a contradiction, or a puzzle the Church has never solved?
What the Church teaches
There is one God in three really distinct Persons: the Father, the Son and the Holy Spirit. Each Person is the one God, whole and entire. They are not three gods, and they are not three parts of God (Lateran IV, DH 800, 804; Athanasian Creed, DH 75; CCC 253–255).
The Son is consubstantial with the Father, “of the same substance”, true God from true God (Nicaea, 325; DH 125).
The Holy Spirit is God, the Lord and giver of life, who with the Father and the Son is worshipped and glorified (Constantinople I, 381; DH 150).
How sure is this? De fide. These are among the most solemnly defined truths of the faith. See CCC 232–256.
The Trinity is a mystery in the strict sense. Reason could never have discovered it, and even once revealed, it cannot be fully understood (Vatican I, Dei Filius ch. 4; DH 3015; CCC 237).
Where it comes from
Scripture. The Old Testament insists there is one God: “Hear, O Israel: The LORD our God is one LORD” (Deuteronomy 6:4). The New Testament never retracts that. Yet it speaks of three, each acting as God.
- Together. Jesus sends the apostles to baptise “in the name of the Father and of the Son and of the Holy Spirit” (Matthew 28:19): one name, three Persons. St Paul blesses the Corinthians with “the grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit” (2 Corinthians 13:14). At Jesus’ baptism the Father speaks, the Son is baptised, and the Spirit descends (Matthew 3:16–17).
- The Son is God. “In the beginning was the Word, and the Word was with God, and the Word was God” (John 1:1). The Word is with God, so distinct from the Father, and is God. Jesus says, “I and the Father are one” (John 10:30).
- The Spirit is God. When Ananias lies to the Holy Spirit, Peter tells him, “You have not lied to men but to God” (Acts 5:3–4). Jesus promises “another Counselor” (John 14:16), a Person, not a force.
The early Church. Tertullian (died about 220) was the first to use the word Trinity in Latin, and the formula “three Persons, one substance”. St Athanasius (died 373) spent his life defending Nicaea against Arius. The Athanasian Creed, a Latin creed from about the fifth century, put the whole teaching in one sentence: we worship one God in Trinity and Trinity in unity, “neither confounding the Persons nor dividing the substance”.
How theologians explain it
One and three answer different questions. A contradiction would be to say God is one and three in the same respect. The Church does not say that. God is one in nature: there is one divine “what”. God is three in person: there are three divine “whos”. Ask “what is the Father?” and the answer is God. Ask “who is the Father?” and the answer is the one who begets the Son. The same goes for the Son and the Spirit.
Each Person is the whole of God. The Father is not one third of God, with the Son and Spirit making up the rest. Each Person possesses the one divine nature completely. That is why the three are equal: none is greater or older than the others.
The three classic errors. The Church’s teaching was sharpened against three ways of getting it wrong:
| Error | What it says | Why it fails |
|---|---|---|
| Modalism (Sabellius, 3rd century) | One Person, who appears in three ways or “modes”, like an actor wearing three masks | It cannot explain the Father speaking to the Son, or the Son praying to the Father. The Persons are really distinct. |
| Arianism (Arius, 4th century) | The Son, and then the Spirit, are creatures: the greatest creatures, but not God | Scripture calls the Word God and gives him divine honour. Nicaea defined that he is “of the same substance” as the Father. |
| Tritheism | Three separate gods who work together | Scripture and the Creed insist there is one God. The three share one nature, not just one purpose. |
Above reason, not against it. The Trinity cannot be proved by reason; we know it because God revealed it. But reason can show that it is not a contradiction, by showing that “one” and “three” refer to different things (nature and person). That is what theologians mean by calling it “above reason but not against reason”.
Philosophy bridge
The philosophy course distinguishes a thing’s nature, what it is, from a person, an individual who has a rational nature. Among human beings, each nature belongs to one person, so we never meet one nature in three persons. In God, the one infinite nature is possessed whole by three Persons. The distinction makes the doctrine statable without contradiction; it does not make it comprehensible.
What the Church does not claim
- Not that 1 = 3. God is one in one respect (nature) and three in another (person).
- Not that the Father came first. The Son and Spirit are as eternal as the Father. “Father” and “Son” describe a relation, not a sequence in time (Lesson 3.2).
- Not that the Son is less than the Father. When Jesus says, “the Father is greater than I” (John 14:28), the Church has always read it of his human nature, which is a creature.
- Not that the popular analogies explain it. Water, ice and steam suggest one thing appearing in three forms, which is modalism. A three-leaf clover suggests three parts of one thing. Both are errors the Church rejected. The Trinity has no real likeness anywhere in creation.
Check your understanding
- State in one sentence what the Church teaches about the Trinity.
Show answer
There is one God in three really distinct Persons, the Father, the Son and the Holy Spirit, each of whom is fully God.
- Why is the Trinity not a contradiction?
Show answer
Because God is one and three in different respects: one in nature (what God is) and three in person (who God is). A contradiction would require one and three in the same respect.
- Name the three classic errors about the Trinity and say briefly what each claims.
Show answer
Modalism: one Person appearing in three ways. Arianism: the Son (and Spirit) are creatures, not God. Tritheism: three separate gods.
- Explain how John 1:1 shows both that the Word is distinct from the Father and that the Word is God.
Show answer
“The Word was with God” means the Word is distinct from the one he is with, the Father. “The Word was God” means the Word is himself God.
- Why does the water, ice and steam analogy mislead?
Show answer
It suggests one thing appearing in three different forms, which is the error of modalism. In fact the three Persons are really distinct and exist at the same time, each fully God.