Of the Triune Godhead, Father, Son, and Holy Spirit, if we say anything, we must say:
Within the one being that is God, there exists eternally three coequal and coeternal persons (distinctive subsistences), namely, the Father, the Son, and the Holy Spirit. Genesis 1:1, 26, 3:22, 11:7, Isaiah 6:8, 48:16, 61:1, Matthew 3:16-17, 28:19, 2 Corinthians 13:14
1. the Father is God,
2. the Son is God,
3. the Holy Spirit is God,
4. the Father is not the Son or the Holy Spirit,
5. the Son is not the Father or the Holy Spirit,
6. the Holy Spirit is not the Father or the Son, and
7. The Father, Son, and Holy Spirit are not three gods, but one God.
The essence of something is that something’s being. The word essence has its root in the Latin, to be. When speaking of God, the question arises as to how God’s essence makes its existence known, for God is more than just having being or existence. Indeed, God is being, for He declared this to be so to Moses in Exodus 3:14-15. In the Exodus passage (see also John 5:26; Acts 17:24-25) God declares His self-existence (aseity), implying He is a boundless, ineffable, absolute, and transcendent being.
How does God's essence relate to the three persons of the Godhead?
God is a simple and uncompounded spiritual being. By simple we do not mean God is dim-witted. Nor do we mean that God is easy to understand. Simple, as a divine attribute, is the opposite of composite, the opposite of compounded. God is not made up of parts, composed of a genus (class), differentiations of species by attributes within a genus, and so on. The simplicity of God means God is not made up of goodness, mercy, justice, and power. He is goodness, mercy, justice, and power. Every attribute of God is identical with his essence.
So we cannot say love is more central to God than sovereignty, or vice-versa. Christians make this mistake all the time. You’ll hear people say, “God may have justice or wrath, but He is love.” The unstated implication: love is more central to the nature of God. But God is a simple being, not a composite being. So God is righteousness in the same way God is love.
In other words, the simplicity of God not only prevents us from ranking certain attributes higher than others, it allows God to have a distinct and infinite life of His own within Himself. God is not an abstract Absolute Idea who happens to have love, wisdom, and holiness, as if we first conceive of a being called God and then relate qualities to him. Rather, God in His very essence, within Himself and by Himself, is love, wisdom, and holiness. God is whatever He has, for He has nothing that He is not.
We can also say the same by stating, God is a simple and uncompounded spiritual essence. Essence is that by which something is what it is, that is, its nature. Generally speaking, essence and being are interchangeable in most discussions of God. Some also use nature and essence interchangeably.
Essence refers to the being of God, while person is used as subsistence within being. When something really exists we say this something possesses subsistence. When we speak of the characteristics of the Father, Son, and Holy Spirit, we are speaking about the individuated subsistences of the Father, Son, and Holy Spirit. These subsistences do not divide the essence of God. While there is but one essence of God, there are three distinctly different modes of subsistence in that essence, which we call Persons.
The divine essence does not exist independently along with the three persons. Which is to say, there is not some essence, "God", sitting over there somewhere, along with the three persons of the Godhead. The divine essence has no existence outside of and apart from the three Persons. For if the divine essence did, there would be no true unity, but a division that would lead into tetratheism (four Gods).
God’s indivisible essence is common to the three subsistences (Father, Son, Holy Spirit), each possessing the one divine essence as one undivided nature—‘as all the fullness of the Godhead dwells in Christ’, so also in the Holy Spirit; and of the Father. In other words, the personal subsistences are not dividing up the one divine essence, as in one-third for the Father, one-third for the Son, and one-third for the Holy Spirit. Rather, the Father, Son, and Holy Spirit are co-equal, co-participants of the one divine essence (the meaning of fullness in Col. 2:9).
The whole undivided essence of God belongs equally to each of the three persons. Thus the three persons co-inhere in the one divine essence existing simultaneously with one another as distinct subsistences or persons. This also means that the divine essence is not at one time entirely manifest as the Father (but not in or as the Son or Spirit), and then at another moment manifest exclusively as the Son, and yet again at another time solely as the Spirit. Rather, all three persons (subsistences) exist simultaneously.
AMR