How can Christians affirm both the oneness of God and the Trinity? The Trinitarian nature of God is confusing and mysterious. Some have rejected the concept of the Trinity because the word “Trinity” is not found in the Scriptures. Some have created sects in their search for a proper Trinitarian understanding. Others have chosen to make the doctrine of the Trinity a secondary issue because of its complexity. Confusion over Trinitarianism has even led some to change the lyrics of esteemed hymns from “blessed Trinity” to “blessed eternally.” How then, should we understand the Trinity?
God is One
God is "one" (Deut. 6:4; 1Cor. 8:4,6). Paul said the nations have “many gods, yet for usthere is one God, the Father, from whom are all things and for whem we exist, and one Lord, Jesus Christ through whom are all things and through whom we exist” (1 Cor. 8:6). The simple singular nature of God is the foundation of the Christian system. The oneness of God refers to the singular divine essence (power, will, personality, perfection) which is completely and identically shared by the Father, Son, and Spirit. Because the Son shares this divine essence with the Father, he could be described as “Light of Light, very God of very God (Deum verum de Deo), begotten not made, being of one substance with the Father.”
The doctrine of the Trinity or the "three in oneness" of God, is difficult if not impossible to understand. The best we can do is to examine the Biblical data and believe what we are taught by God in the Word. First, we note that God is one. Jesus taught this in Matthew 4:10 from Deuteronomy 6:13. But does this mean that God is one in number or one in nature? Alexander Campbell wrote, “Some conceive of God as a mathematical unit; and as a thing cannot be both mathematically singular and plural—one and three, at the same time and in the same sense—they deny the true and proper divinity of the Son of God and the Spirit of God.”
God is Father, Son, and Spirit
How is the one God Triune? Augustine illustrated this grand reality this way: “But as there are two things (duo quædam), the mind and the love of it, when it loves itself; so there are two things, the mind and the knowledge of it when it knows itself. The doctrine of the Trinity is difficult to understand, but impossible to deny and eseential for Christianity.
When Jesus was baptized, Jesus was in the water, the Spirit descended in the form of a dove, and the Father spoke from Heaven. All three are present and distinct from the others. We are taught Jesus shares eternity with the Father, and fully like the Father (Jn. 1:1). Jesus was described as the one who relates to the Father as Son and Spokesman (Heb. 1:2). He is the Creator of the universe (Heb. 1:3). He is the "radiance of the glory of God and the exact imprint of his nature (Heb. 1:3); the One who upholds the universe (Heb. 1:3); the one who has made purification for sin and has been placed at the right hand of the Father (Heb. 1:3).
So, the Bible teaches that Jesus is fully equal with the Father, precisely like the Father, and distinct from the Father. We are also taught that the Holy Spirit is fully God (fully divine). Peter asked Ananias and Sapphira why they lied to the Holy Spirit and then referred to the Holy Spirit as God (Acts 5:3, 4). The Spirit is also listed with the Father and Son as authoritative and active in salvation (Matt. 28:19; 1 Pet. 1:2). The Father and Son dwell in the church through the Spirit (1 Cor. 3:16; 6:19; Acts 2:38; 5:32).
We have seen that the Bible teaches both that God is "one" and that the Father, Son, and Spirit are God. How can that be? Go back to Hebrews 1:3 where Jesus was described as "the exact imprint" of God's nature. In other words, Jesus is exactly like the Father. Jesus isn't just a lot like the Father. Jesus is exactly like the Father. There is absolutely no difference in the essence or nature of the Father from the Son or the Spirit. Jesus is described as "the Son" because that is how he relates to "the Father." The Spirit is described as the Spirit to differentiate him from the Son and the Father. There is no hierarchy, but there are intra-Trinitarian relations and identical persons.
Is God one? Yes. Are there three who are God? Yes. Are there three Gods? No.
God is one. The Father, Son, and Spirit are distinct persons who are identical
in their divine nature, will, and power. This is a mysterious yet, Biblical
doctrine of God. Therefore, when we come to God, we come to the Father in the
Son through the Spirit. This Triunity is the perfect display of perfect love.
We then should love our Triune God fully as we are welcomed into the presence
of the Triune God as the church—the bride of Christ indwelt by the Spirit to be
presented to the Father.
 The earliest theologians used the word “triad” to describe the Father, Son, and Spirit’s triune nature. The earliest known reference to “trinity” is in Tertullian (2nd century) who used the Latin form trinitas.
 Arianism taught that Jesus was a lower deity which the Father made. Some have taught that Jesus was an angel or prophet who was made into something like a demigod. Others still teach that the one “God” just has three names in which he manifests himself.
 Symbolum Nicaeno-Constantinopolitanum.
 Alexander Campbell. The Christian System. (Nashville: Gospel Advocate, rep. 1964): 8.