The Triune God: Oneness and Threeness


The baptismal formula in Matthew 28:19 is my favorite place to begin teaching on the Trinity. Before most of us have any idea what it means to confess that God is Trinity, we are baptized in the triune name. From day one, we are immersed in the life of the Trinity (read “Immersed in the Trinity from Day One“). Explicit teaching on the Trinity is about “unpacking a comprehensive reality in which we already find ourselves as Christians” (Fred Sanders). In fact, all “Christian teaching is best thought of as a commentary on baptism. It has the happy task of trying to explain what baptism in the triune name means” (Thomas Oden).

In Matthew 28:19, Jesus 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.” We are baptized in the name, singular—there is something one about God. But this one name is the name of the Father, Son, and Holy Spirit—there is something three about God. The word Trinity simply means threeness. The Athanasian Creed states, “the catholic faith is this: That we worship one God in Trinity, and Trinity in Unity.” Oneness and threeness must be confessed.

The Oneness of God

Let’s start with the oneness of God. Deuteronomy 6:4 (the Shema) was Israel’s fundamental confession: “Hear, O Israel: The Lord our God, the Lord is one.”

There is only one God. Christianity, like Judaism and Islam, is a monotheistic faith (mono = one; theos = God). There are not many gods, as polytheistic religions like Buddhism or Hinduism claim (poly = many; theos = God). There are not two gods or three gods or ten gods. There is one God.

This one God is one in his very essence. In other words, the one God is without parts. We can say, “I have one pizza,” but a pizza may be cut into eight or more parts (slices). God is not like this. God’s being is simple or without parts. There are not two parts or three parts or ten parts in God. We do not add up the attributes of God (holiness, love, justice, etc.) and arrive at God. The Lord is one: his being is perfect oneness. We confess the name of God: one name for one God who is one in his being.

When we talk about the Father, Son, and Holy Spirit, we must never forget the oneness of God. The Father, Son, and Spirit are not parts of God. It is not as though God is like an egg, where the yolk + the white + the shell = an egg. The Father, Son, and Spirit are not different things that, when you put them together, make up God. This is a heresy called partialism. It undermines God’s oneness.

The Threeness of God

Now, let’s consider the threeness of God: the Father, Son, and Holy Spirit. It’s equally important that when we talk about the oneness of God, we do not forget what is three in God.

Some people think that the Father, Son, and Spirit are just three different ways that the one God reveals himself to us. In high school, I worked at a grocery store and met a Oneness Pentecostal who tried to tell me that sometimes God puts on the “Father” hat, and other times he wears the “Son” or the “Spirit” hat. In other words, there’s one Johnathan Arnold, but sometimes I act like a father (when I’m around my little boy), other times I act like a son (when I’m around my parents), and other times I act like a pastor (when I’m preaching). But this is a dangerous and heretical way of thinking about God. It tries to preserve what is one about God, but it undermines what is three about God. The Father, Son, and Spirit are not just three hats or masks that God puts on. The Father sends the Son and the Spirit. It makes no sense to say that Daddy Johnathan sends Son Johnathan or Pastor Johnathan because these three are the same person. I can’t send myself—that doesn’t make any sense. This kind of thinking is based in a heresy called modalism. It undermines God’s threeness.

Modalism is a bit harder to get one’s head around than partialism. It helps to consider another illustration. It’s sometimes said that God is like a water molecule: it can exist as a liquid, solid, or gas, but it’s still the same substance (H2O). The one H2O molecule exists in three different modes or states. But when liquid H2O becomes solid H2O, it stops being liquid. The H2O molecule cannot be liquid and solid at the same time. This illustration cannot be used to explain the exact way in which God is three and one. God never stops being the Father, Son, and Spirit. Modalism undermines what is three about God. The Father, Son, and Spirit are not three modes of God’s being nor are they three parts of God.

The created world reflects the triunity of the Creator, but there is nothing in creation that is three and one in the exact same way that God is three and one.

Illustrations for the Trinity fall apart very quickly and promote ways of thinking about God that are unworthy of him. If you say that God is like a three-leaf clover (one clover, but three leaves), you’re back to partialism: the three leaves are parts of the one clover. The same is true of a flower: the stem, leaves, and petals are parts of the one flower.

So if God is not like a flower, a three-leaf clover, an egg, or H2O, what is he like? He’s not exactly like anything. There is nothing in creation that is three and one in the exact same way that God is three and one. Isaiah asked, “To whom then will you liken God, or what likeness compare with him?” (Isa. 40:18). The doctrine of God’s incomprehensibility must be kept ever before us as we study the deep things of God. We need a more careful way to talk about the oneness and the threeness of God.

Labeling the One and the Three

To help us speak about what is one in God and what is three in God, the church over time settled on the terms nature and persons. There is one divine nature and three divine persons. The Father and the Son are of the same nature, but they are distinct persons.

We should not push this too far. These terms aren’t packed with meaning. They are just ways to distinguish between what Scripture reveals as one in God and what it reveals as three in God. Fred Sanders makes the essential point:

Notice that the terms as used in the doctrine of the Trinity are not especially thick or content-bearing terms. They are not richly descriptive terms that were ready at hand to apply to God, and they do not bring with them clarifying specifications that serve the theological purpose of naming the one and the three. It is enough if they are concise labels that are useful for picking out things we already knew from the actual revelation: the sender and the sent have something in common and something else that distinguishes them.

When we say that Jesus is the Son, we are talking about who Jesus is: he is the second person of the Trinity, the Son of the Father. When we say that Jesus is God, we are talking about what Jesus is: he is of the same nature as the Father. Everything that God is, Jesus is. This is why the great Christian catechisms ask “What is God?” instead of “Who is God?” The word “what” points to the essential nature or substance of God.

The terms “nature” and “persons” aren’t packed with meaning. They are just ways to distinguish between what Scripture reveals as one in God and what it reveals as three in God.

The words substance and essence are synonyms for nature. The Father and the Son are of the same substance, and that substance is very God. It’s not as though the Son and the Father are made of different stuff (to put it crudely). They are of the same “stuff,” the same spiritual substance. According to the Nicene Creed, the Son is “God of God, Light of Light, very God of very God.”

At this point, we can begin to make sense of the next few lines in the Athanasian Creed:

…we worship one God in Trinity, and Trinity in Unity;

4. Neither confounding the persons nor dividing the substance.

Don’t confound or confuse the persons of the Trinity. God does not put on three hats or show up in three modes or forms. He is three in his persons, and these persons shouldn’t be confused. The Father is not the Son. The Son is not the Spirit. The Spirit is not the Father. They are distinct persons (Mt. 3:16–17; Jn. 15:26).

    1. For there is one person of the Father, another of the Son, and another of the Holy Spirit.

On the other hand, don’t divide the substance. The Father, Son, and Spirit are not three parts in God. Whatever is true of the divine nature (“the Godhead”) is true of the Father, Son, and Spirit.

    1. But the Godhead of the Father, of the Son, and of the Holy Spirit is all one, the glory equal, the majesty coeternal.
    2. Such as the Father is, such is the Son, and such is the Holy Spirit.

Applying the Nature to the Persons

Whatever is true of God (the divine nature) is true of the Father, Son, and Spirit. The Father is God (Gal. 1:1); the Son is God (Jn. 1:1); the Spirit is God (Acts 5:3–4). This means that we can study the attributes of God’s one nature and apply these attributes to each person of the Trinity.

So, what do we know about God?

  • God is uncreated — no one created God; he is self-existent (aseity).
  • God is incomprehensible — no creature can fully understand the Creator.
  • God is eternal — he has no beginning; he is timeless.
  • God is almighty — he is all-powerful (omnipotence).
  • God is Lord — he rules over all (sovereignty).

We could go on. The Athanasian Creed applies these truths about God to the persons of the Father, Son, and Spirit while being careful never to undermine God’s oneness. The Creed teaches us to confess:

    1. The Father uncreated, the Son uncreated, and the Holy Spirit uncreated.
    2. The Father incomprehensible, the Son incomprehensible, and the Holy Spirit incomprehensible.
    3. The Father eternal, the Son eternal, and the Holy Spirit eternal.
    4. And yet they are not three eternals [eternal beings/natures] but one eternal [being/nature].
    5. As also there are not three uncreated nor three incomprehensible, but one uncreated and one incomprehensible.
    6. So likewise the Father is almighty, the Son almighty, and the Holy Spirit almighty.
    7. And yet they are not three almighties, but one almighty.
    8. So the Father is God, the Son is God, and the Holy Spirit is God;
    9. And yet they are not three Gods, but one God.
    10. So likewise the Father is Lord, the Son Lord, and the Holy Spirit Lord;
    11. And yet they are not three Lords but one Lord.
    12. For like as we are compelled by the Christian verity to acknowledge every Person by himself to be God and Lord;
    13. So are we forbidden by the catholic religion to say; There are three Gods or three Lords.

Since the Son is God, he is uncreated and eternal: the Father did not create the Son, for there was never a moment in time when the Son began to exist.

Whatever is true of God is true of the Son.

The most problematic heresy in the early church was the heresy of Arianism (taught by Arius). It was even more problematic than modalism (taught by Sabellius). Arius claimed that the Son was made by God the Father before the world began, and that the Father then used the Son to create the heavens and the earth. But this denies that the Father, Son, and Spirit are of the exact same nature, since the divine nature is eternal and uncreated. In another article, we will talk more about this heresy and how it relates to the confession that the Son is eternally begotten by the Father and the Spirit eternally proceeds from the Father and the Son.

Oneness and Threeness in Being and Works

When it comes to carefully preserving the oneness and the threeness of God, Saint Agustine serves as an excellent teacher. In On The Trinity, Augustine summarizes the church’s consensual teaching on the Triune God. He begins with a strong statement on the oneness of God:

All those Catholic expounders of the divine Scriptures, both Old and New, whom I have been able to read, who have written before me concerning the Trinity, Who is God, have purposed to teach, according to the Scriptures, this doctrine, that the Father, and the Son, and the Holy Spirit intimate a divine unity of one and the same substance in an indivisible equality; and therefore that they are not three Gods, but one God:

We must be careful to avoid “dividing the substance,” as Augustine demonstrates. But we must be equally careful to avoid “confounding the persons.” Augustine goes on to ground the distinction of the persons in their eternal relations of origin (the subject of an upcoming article):

…although the Father hath begotten the Son, and so He who is the Father is not the Son; and the Son is begotten by the Father, and so He who is the Son is not the Father; and the Holy Spirit is neither the Father nor the Son, but only the Spirit of the Father and of the Son, Himself also co-equal with the Father and the Son, and pertaining to the unity of the Trinity.

Augustine then shows that these distinctions which have eternally existed in God (the immanent Trinity) are manifested in the distinct roles of the Father, Son, and Spirit in our redemption (the economic Trinity). To preserve the threeness of God, we must not confound the persons in our redemption (i.e., by collapsing the divine economy), since it is the economic Trinity that reveals the immanent Trinity:

Yet not that this Trinity was born of the Virgin Mary, and crucified under Pontius Pilate, and buried, and rose again the third day, and ascended into heaven, but only the Son. Nor, again, that this Trinity descended in the form of a dove upon Jesus when He was baptized; nor that, on the day of Pentecost, after the ascension of the Lord, when “there came a sound from heaven, as of a rushing mighty wind,” the same Trinity “sat upon each of them with cloven tongues like as of fire,” but only the Holy Spirit. Nor yet that this Trinity said from heaven, “Thou art my Son,” whether when He was baptized by John, or when the three disciples were with Him in the mount, or when the voice sounded, saying, “I have both glorified it, and will glorify it again;” but that it was a word of the Father only, spoken to the Son;

After this strong statement upholding the threeness of God, Augustine ends with a final, qualifying statement on the oneness of God:

although the Father, and the Son, and the Holy Spirit, as they are indivisible, so work indivisibly. This is also my faith, since it is the Catholic faith.

The persons of the Trinity “work indivisibly” (the doctrine of inseparable operations): “Father, Son, and Spirit are inseparably united in every act of redemption, but they act distinctly according to their distinct personal characteristics” (Peter Leithart). Even as we strive to preserve the threeness of God in his external works, we must never forget his oneness. 

Next time, we’ll discuss what it means for Jesus to be the only begotten Son of God and what it means for the Spirit to proceed from the Father and the Son. For now, we worship one God in Trinity, and Trinity in Unity:

Glory to the Father, and to the Son, and to the Holy Spirit,
As it was in the beginning, and now, and ever shall be, world without end. Amen.

Johnathan Arnold
Johnathan Arnold
Johnathan Arnold is President and Founder of Holy Joys. He serves as a preaching and teaching pastor in Newport, PA, where he lives with his wife Alexandra and son Adam. You can connect with him on Twitter @jsarnold7.