Probably no area of Christian thinking has produced as much controversy as thinking on the doctrine of God. And this only makes sense. God is not like us. So we find it incredibly hard to speak about God.
But avoiding the discussion leads to more problems not less. In the first place, the doctrine of God is the primary foundation of Christianity. So not knowing how to talk about God places us in an awkward position. On top of that, most heresies start by talking about God in ways that conflict with the Bible’s meaning and right reflection on the Bible.
So we should know God and how to talk about God. For Christians, this means learning how to talk about the triune God. For the sake of knowing God, our faith, and avoiding error, consider then the following short dictionary of Trinity words.
Words that Define God as a Trinity
Aseity. The Latin phrase aseity derives from a + se and means “from itself.” Basically, it means that God derives from himself. He does not rely on some other being to create him. God has life from himself. He also has life in himself.
Life marks the inner-life of God. He eternally gives life to himself by eternally generating the Son (see below). Since God’s nature is life and the benevolent gift of life, he fittingly created the world and offers it eternal life through his Son Jesus Christ. That is who God is.
Eternal generation. God lives eternally, and he has given life eternally. From the beginning, the Word was with God (John 1:1; 17:24). And the divine relationship involves life-giving. Jesus explains, “For as the Father has life in himself, so he has granted the Son also to have life in himself” (John 5:26). Having life in himself, the Father grants the Son the same privilege. Yet since the Son has always been with the Father, then this grant of life in the Son must have occurred eternally—or without beginning.
God has always given life to the Son. He has eternally generated the Son. Like the Son, the Spirit too proceeds from the Father (and presumably has life in himself eternally from the Father as well).
Procession. Jesus explains that the Spirit “proceeds from the Father” (John 15:26). This procession corresponds to how the Spirit operates in Scripture (e.g., in Isa 63:11). It seems best to understand the Spirit’s relationship to the Father in ways similar to the Son’s relationship to the Father. The Holy Spirit eternally proceeds from the Father, while the Son eternally generates from the father. Since both the Son and Spirit proceed from the Father, we can also use the word spiration to describe the Spirit’s unique relationship to the Father.
Personal properties. Personal properties distinguish the Father, Son, and Spirit from each other. The Spirit proceeds from the Father, the Son begets from the Father, and the Father is unbegotten. This internal order to the Trinity fittingly plays out in history because the Father sends the Son into the world to save it (John 3:16). Then he sends the Spirit to perfect the work of the Son in the world (John 15:26).
No ontological subordination exists in the Trinity whatsoever. No eternal subordination exists in the Trinity. The distinguishing properties are unbegottenness, begottenness, and procession/spiration. Any claim that the Son eternally submits to the Father incorrectly defines the personal properties of the Trinity.
Simplicity and subsistence. Since God is simple, he has no parts or complexity. Each triune person subsists in God’s essence. God is one; a tri-unity. All that is in God is God. To subsist means to simply exist within the one nature of God such that each subsisting hypostasis can be identified as the one God. There are no parts to nor members of the Trinity; only subsisting persons.
Each triune person is the one God because persons are concrete instances of a nature. Persons are not natures. Persons do not have individual wills, minds, or emotions. Natures do (see below).
Hypostasis (persona, person). “The word hypostasis is a Greek word meaning a concrete instance of a nature— For example, Peter (hypostasis) is a concrete instance of humanity (nature). In the Latin Church, theologians used the word persona to mean something similar to hypostasis. Boethius (AD 477–524) defined person as “an individual substance of a rational nature.” In English, we use the word person” (quoted from here).
Applied to the Trinity, divine hypostases are three subsisting concrete instances of the divine nature.
Essence (nature, ousia, substantia). Essences or natures make up the essence of the thing. Human nature comprises body, spirit, mind, will, and intellect. Peter (hypostasis) is one concrete instance of human nature. He shares in common a body, spirit, mind, will, and intellect with all other human persons.
There is only one God, and so there is only one nature. Each subsisting hypostasis shares in the common nature of God, namely, his spiritual nature, mind, will, and intellect. Due to simplicity, Christian theology identifies each subsisting person as God—the one God. No one hypostasis in God can submit or command another since will belongs to nature, not hypostasis.
Yet God does act in a triune fashion. The Father sends, the Son acts, the Spirit perfects. Yet each works according to the one will of God. This is called the inseparable operation of God.
Inseparable operations. When one person works, all do. They work inseparably according to their personal properties. In the execution of God’s plan (the economy), the Father sends, the Son accomplishes, and the Spirit perfects. The Bible illustrates this order when Jesus says he has come from the Father (John 6:38) and when he says that the Father sends the Spirit as another comforter in his place (John 14:26; 15:26).
Economy. The Greek word economia means administration. Paul uses the word in Ephesians to speak of God’s “plan for the fullness of time, to unite all things in him, things in heaven and things on earth” (Eph 1:10). In theology, economia or economy refers to God’s plan of redemption in Christ that occurs in time.
Applied to the Trinity, Christ submits to the Father according to the economy. Yet according to divinity, the Son always has a united will with the Father. So the Father and Son together act to accomplish salvation (John 10:18), even salvation that required that Christ had to assume humanity in order to hand over his human will to the Father for our salvation.
How to Use Trinity Words
One reason to use Trinity words is to know God. They provide a big picture understanding of God based on the whole Bible and spiritual reflection on the Bible’s meaning. Since the Bible’s story unfolds over centuries and its themes unfold across sixty-six books, it can be hard to keep track of everything.
That’s why teachers use concise definitions to help us organize our minds. John the Apostle did this when he said, “God is love” (1 John 4:8). He summarized what he knew about the Bible and of Christ. Knowing that God is love feeds our faith. We can trust him to love and care for us because that is who he is.
Such definitions also protect us from error. Speaking about an eternal and infinite God is hard. So we need to do so with caution and in community. The Christian community (across the ages) has thought about God by the Spirit. We need to bounce our ideas and thoughts of them so that we do not fall into ruin.
That’s why the Spirit gave the church teachers (Eph 4:11). So don’t ignore Augustine, Calvin, or Bavinck. The living saints of all ages form our community of interpretation. And most importantly: so do your local leaders. Talk to them and try to work our your understanding of God to know him, to nurture your faith, and to avoid error.