When I was young, my family spent snow days and summer afternoons conducting science experiments. We would examine the properties of fire and its need for oxygen, calculate the number of calories in a peanut, or determine the best way to drop an egg from a ladder without cracking it. Some might call us ‘nerdy’, but we were curious to figure out the world around us. If we had a question, we assumed there was a concrete answer for it, and our experiments helped us find the answers we wanted.

It is good for us to investigate answers to our questions, but some aspects of God remain incomprehensible to us as created man. The nature of God is one of those aspects that is both knowable and unknowable at the same time. While there is much we can understand about God’s nature, there is still much of God that our human minds cannot fully comprehend. The doctrine of the Trinity lands squarely in the middle of this gap between the omniscience of God and the limitation of man as something we can begin to grasp but only partially.

What Is the Trinity?

The word “trinity” never appears in Scripture. It was first coined by a theologian named Tertullian, who used the Latin phrase trinitas to explain what he saw in Scripture. The term gives us helpful vocabulary to distinguish between the three persons of the Godhead without believing falsely that there are three distinct Gods (the heresy known as “tritheism”). So, while “trinity” never shows up in the biblical text, the word conveys a concept or doctrine that is found throughout the text—that God is both three and one.

Trinity means simply the “tri-unity” of God. It means that there is one God, who is also three distinct persons: God the Father, God the Son, and God the Spirit. The three persons within the Godhead are unified in their God-ness yet distinct in their role and personhood. We often try to conceptualize how this “tri-unity” works by using illustrations, yet each illustration breaks down in significant ways because God is incomparable to anything else in our created world. He is His own category, and we must recognize our inability to categorize this God who is extraordinarily different from everything within His creation.

While we may struggle to describe or explain the Trinity, the doctrine of the Trinity includes three key concepts that we can know for sure: God is three distinct persons, there is only one God, and each person of the Trinity is fully God.

God Is Three Distinct Persons

God exists as three distinct persons: the Father, the Son, and the Spirit. We see this throughout Scripture, as each person of the Godhead appears in the text, serving specific functions and displaying their God-hood. For instance, Matthew 3:16-17 shows all three persons of the Godhead at work at one time. God the Son was baptized, the Spirit of God descended and rested on Him, and God the Father spoke, saying, “This is my beloved Son, with whom I am well pleased.”

Similarly, Jesus tells His disciples to, “make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit” (Matthew 28:19). Jude 20-21 instructs believers to, “Pray in the Holy Spirit; keep yourselves in the love of God, waiting for the mercy of our Lord Jesus Christ.” Scripture clearly shows us God’s activity in the world, performed by three distinct persons through their work in creation, salvation, incarnation, and resurrection.

Let’s look at God’s work in creation specifically: God the Spirit hovered over the waters (Gen. 1:1), God the Father spoke (Gen. 1:3), and God the Son was present at creation and all things were made through Him (John 1:1-3). God Himself affirms the plural nature of His personhood by using a plural pronoun in Genesis 1:26, saying, “Let us make man in our image, after our likeness.” God is distinctly Father, Son, and Spirit—each one unique from the other.

Yet, immediately after Genesis 1:26 and its plural pronoun, we see in Genesis 1:27 that God is also one: “So God created man in his own image, in the image of God he created him; male and female he created them.” God is distinctly three persons, but He is also one God.

There Is Only One God

Scripture explicitly states that there is only one God. While there are three distinct persons of the Trinity, all three persons of the Godhead are one in nature or essence. Deuteronomy 6:4 states that, “the LORD is one.” God speaks in Isaiah 45:5, saying, “I am the LORD, and there is no other, besides me there is no God.” Paul confirms this in the New Testament, stating that “God is one,” (Rom. 3:30) and “There is one God” (1 Tim. 2:5).

We worship the one God, who, though distinct in personhood, is unified in one nature. This is difficult to understand. As humans, we do not exist in relationships like this; the closest similarity we have is evident in marriage, where a husband and wife as two persons become one flesh. Yet, ask any married couple and they will tell you that they still possess distinct wills! The Trinity is different as the Father, Son, and Spirit possess the same will and nature. They are distinct persons who are distinguished by the ways they relate with each other and to the created world, yet they are also of the same nature and will. God is one, and there is only one of Him.

Each Person of the Trinity is Fully God

Some have attempted to explain away this three-in-oneness by assuming that only God the Father is fully God, but the Son and Spirit are not actually God. However, Scripture is also clear that each person of the Trinity is fully God.

The Son is explained to be fully God in John 1:1-4, which states that, “In the beginning was the Word, and the Word was with God, and the Word was God.” We see Thomas express the Son’s God-hood as well in John 20:28, where Thomas answers, “My Lord and my God!” in response to Christ’s miraculous resurrection. In short, the Son is fully God.

In addition, the Spirit is fully God, which we see in Acts 5:3-4. In this passage, Peter questions why Ananias lied to the Holy Spirit, and Peter states, “You have not lied to men but to God.” We also see that God’s qualities of deity are shown by the Spirit in several places: God’s omnipresence in Psalm 139:7, His omniscience in 1 Corinthians 2:10-11, and His omnipotence in Luke 1:35-37 are all attributed to the Spirit. These are characteristics of God that are fully divine. If the Spirit is not God, He could not possess these incommunicable attributes of the divine God.

Why Does This Matter?

Wayne Grudem explains in his book, Christian Beliefs, “If Jesus is not both fully God and a separate person from God, then he could not have borne the complex wrath of God, died, and risen from the dead.” Our salvation has no power to save if Jesus is not indeed God. Similarly, if the Spirit is not fully God, then He possesses no power or authority to sanctify the believer. At the same time, if God is not one in nature, then we worship three separate Gods and break God’s own commandment to worship Him alone (Ex. 20:3-6).

It matters that we get the Trinity correct because it pertains to the God we love and worship, and we want to worship Him rightly.  The doctrine of the Trinity deals with the God of the universe. He is infinitely greater than all of us, and there should be aspects of His character that our human minds cannot fathom. Yet, it still matters that we understand His nature to the best of our abilities in order that we might know best how to serve and worship Him in His fullness. We may struggle to understand it, but as Grudem explains, “The Trinity is one of those mysteries we can only describe in part,” so don’t lose heart. Over the next several weeks, we’re going to dig into a study of the Trinity, but let’s not forget to appreciate the beauty and complexity of God as one who is ultimately beyond our ability to comprehend fully.

Editor's Note: This originally published at Thinking & Theology.