Unity and Uniqueness
Polytheism (the belief in many gods) dominated the ancient Mediterranean world, with its gods and goddesses. But one culture – the Jews – stands out for its uniquely developed commitment to monotheism (the belief in one God).
Great emphasis was placed on God’s uniqueness in the Old Testament. “Hear, O Israel: The Lord our God, the Lord is one. You shall love the Lord your God with all your heart and with all your soul and with all your might” (Deut. 6:4-5). The Lord Himself commanded: “You shall have no other gods before Me” (Exodus 20:3). ‘Before Me’ means ‘in My presence,’ and the presence of Yahweh extends throughout the entire creation. The greatest threat to Israel was the corruption that came from pursuing false gods. Israel needed to remember there was no God except its God.
The doctrine of the Trinity is established by the New Testament. This doctrine does not teach “tri-theism” – a belief in three distinct gods – Father, Son, and Holy Spirit. The New Testament speaks of three distinct persons who together are one God.
The deity of the Son of God is expressed in John 1:1-4: “In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things were made through Him, and without Him was not anything made that was made. In Him was life…”
Notice that the Word is distinct from God – “the Word was with God.” But the Word is also identified with God – “the Word was God.” The Word is identified with the Creator. To say “in Him was life,” is to say that the Word is the source of life!
When Christ appeared and showed His wounded hands to Thomas and invited Thomas to put his hand into His wounded side, Thomas cried out, “My Lord and my God” (John 20:28). Jesus accepted the worship of Thomas!
In similar fashion the NT attributes deity to the Holy Spirit (Matt. 12:32; Heb. 9:14). The divinity of the Holy Spirit is demonstrated, for example, when He is placed on the same level with the Father and Son, as in the baptismal formula in Matthew 28:18-20 or Paul’s benediction in 2 Corinthians 13:14: “The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Spirit be with you all.”
A Paradox is not a Contradiction
A paradox is something that appears to be contradictory until closer examination reveals it is not so. The law of non-contradiction states that something cannot be what it is and not be what it is at the same time and in the same relationship. The doctrine of the Trinity does NOT state that God is one in essence and at the same time three in essence, or that God is one in person and at the same time three in person. Rather, the historic teaching is that God is one is essence and three in person.
Essence and Person
What is the stuff that distinguishes a human being from an antelope, an antelope from a grape, or a grape from God? It is the essence of the thing, its ousios, a Greek word that means “being” or “substance.” The stuff of deity, the essence – the ousios – is what God is in Himself. When the church declared that God is one essence, it was saying that God is not partly in one place and partly in another. God is only one being.
Our English word “person” comes from the Latin word persona, which referred to actors who played more than one role in a play; and the actors distinguished their characters by speaking through masks, the Latin word for which was persona. So when Tertullian first spoke of God as one being, three persons, he was saying that God simultaneously exists as three roles or personalities – Father, Son, and Holy Spirit. This is indeed mysterious, but it is not contradictory.
Existence and Subsistence
The terms existence and subsistence are used to make a distinction among the persons of the Trinity. The concept of existence refers to pure being that depends on nothing for its ability to be. It is eternal. It has power of being within itself. It is by no means creaturely. Creaturely existence is characterized not by being but by becoming, because the chief trait of all creatures is that they change. God is being, not becoming or changing. He is eternally the same, so we say He is one being.
The term subsistence is a difference within the scope of being, not a separate being or essence. Each person in the Trinity subsists or exists under the presence of deity. There are not three existences or beings but rather three subsistences within that one eternal being.
[Adapted from Everyone’s a Theologian by R.C. Sproul]