Even though the Trinity is a mystery, it can be defined very simply: “There is one God who exists eternally in three persons.” While this paradox is hard to comprehend, we believe it because it is the only view of God that is faithful to everything God has revealed about himself in the Bible. That revelation starts with the oneness of God.

The Trinity starts with the concept, deeply rooted in the Jewish Scriptures, that there is only one God. 

Christianity was birthed out of Judaism, which is strongly monotheistic, based on the testimony of the Old Testament scriptures. Every day faithful Jews recited, “The Lord is our God, the Lord is one.” (Deuteronomy 6:4). This is the conviction Jesus’ disciples inherited and which they expressed in the New Testament. While people worship many different gods, only one God is real. Only one God created all things (1 Corinthians 8:5-6). As the first Christians wrestled with the identity of Jesus, they never wavered from the clear understanding that there is only one God (1 Timothy 2:5; Romans 3:30).

At some point in Christian history, each key part of the classic definition of the Trinity has been challenged. One challenge claims that the Father, Son and Holy Spirit are separate, distinct beings. Each has his own independent existence. This error takes the “three persons” part of the Trinity seriously, but it falls short on the “one God” side of the equation. This is a heresy called Tritheism. 

“Tri-theism” is a heresy that misses the oneness of God, teaching that there are three distinct gods who work closely together.

This view is very rare in Christian history, because the teaching of monotheism in the Bible is so clear. But one contemporary expression is Mormonism. They teach that Father, Son and Holy Spirit form one “godhead”, but not one God. The members of the godhead are one in purpose or will, but not in essence.

But in the Bible, God states, “I alone am God! I am God, and there is none like me” (Isaiah 46:9) and “You are my witnesses – is there any other God? No!” (Isaiah 44:8). This is an absolute statement. There are not three (or more) beings who can be called “God”. 

So what does it matter that God is one? How does this theological truth impact our daily lives? The answer is that the existence of one God gives us peace and certainty in a world that can often seem transitory and confusing. 

The existence of only one God helps us make sense of humanity, morality, and eternity. 

If there is only one God, then there is only one Creator of the entire human race. In the ancient world, each nation had its own deities. Nations claimed supremacy over other nations based on the supposed supremacy of their gods. But if there is just one God who made all people, then all humanity is one (Acts 17:26). We should not separate into competing tribes or claim superiority over other peoples.

If there is only one God, then there is only one Lord who has the authority to establish a universal moral code (Psalm 96:13). Since only one God rules the universe, every human being is answerable to him, and we will all be judged by the same standard.

If there is only one God, then there is only one Savior and one way to salvation. In the Bible, God says, “I alone am God. There is no other God – there never has been, and there never will be. I, yes I, am the Lord, and there is no other Savior” (Isaiah 43:11). There aren’t several pathways to eternal life, just one – because God is one.

The Bible undeniably teaches the oneness of God. That’s the starting point for the doctrine of the Trinity. 

The orthodox Christian doctrine of the Trinity has two basic parts: first, there is one God; and second, he exists in three persons. The most confusing part of this doctrine is that second part, and it has caused debate for thousands of years. To this day, average Christians often explain it with simple metaphors that mistakenly spread heresy! This lesson will help you get it straight for your own benefit, and for the benefit of those who are asking. Here’s what you need to know:

The Bible shows God existing in three distinct persons – the Father, the Son, and the Holy Spirit. 

The plurality of the one God is anticipated from the beginning of the Bible. In Genesis 1:26, “Then God said, ‘Let us make human beings in our image, to be like us.’” God (singular) says, “Let us (plural) make human beings…” This doesn’t prove or explain the whole concept of the Trinity, but it gives us a powerful hint of the direction the Bible will take us.

The multiple persons of God become more clear in the New Testament. At the baptism of Jesus (Mattew 3:16-17), Jesus is in the river, the Holy Spirit descends as a dove, and the voice of the Father speaks from heaven. All three persons are present in the picture at the same time.

This is why we believe that God encompasses both unity and distinction. To cover both ideas, we talk about the “being” of God versus the “persons” of God. When it comes to being or essence, there is one God. Yet when it comes to the persons of God, there is somehow a distinction. We use the word “persons” to capture the idea that Father, Son and Spirit interact with each other and with the world. It’s not a perfect word for the concept, but it’s the best one Christians have come up with. Remember: God is utterly different from us, and our finite minds struggle to comprehend his nature. When people try to make this easier to understand, they sometimes wander into heresy. 

One common error that denies the Trinity is the fallacy of “modalism” – that there is one God who appears in three different forms.

Modalism oversimplifies God and trades the truth of his personhood with an idea that’s off the mark: modes. Modalists explain that God appears sometimes as the Father, sometimes as the Son, and sometimes as the Holy Spirit. Modalists want to uphold the oneness of God, but this view falls short biblically because it can’t account for the times when the three persons (or even just two of them) appear in one scene, as in Jesus’ baptism or various times when Jesus prays to the Father (Luke 6:12; 10:21). The Bible clearly shows the Son in real relationship with the Father. As Jesus suffered in the Garden of Gethsemane, he spoke intimately to the Father and submitted his will to the Father’s will (Mark 14:36). This doesn’t make sense if the Father and the Son are merely forms God takes rather than real persons.

In fact, Modalism overall denies the important idea that relationship exists eternally within the Trinity. The Bible says that “God is love” (1 John 4:8). But in modalism, how can love be an essential quality of God’s nature? Before creation, there was nothing for the modalist God to love! By contrast, the Trinity explains how God is love from eternity past, because the three persons of the one God have always experienced love among themselves. And that leads us to one final point, where this doctrine becomes very personal to us:

We relate personally with each member of the Trinity as we discover their unique roles in creation, salvation, and prayer. 

All three divine persons are seen involved in the creation of the world. The Father planned the work of creation (Genesis 1:1), the Son did the work (John 1:3), and the Spirit energized the work (Genesis 1:2). The three persons also have unique roles in salvation. The Father initiated salvation, the Son died on the cross to accomplish it, and the Spirit brings forth the fruit of salvation in people (1 Peter 1:2). And think about prayer. All three persons of the Trinity are present when we pray, because God is one. Yet typically the Bible teaches us to pray to the Father (Matthew 6:9), through the Son (Hebrews 4:16; 10:19), and in the power of the Spirit (Ephesians 6:18). The whole thing comes full circle, because the Holy Spirit brings us into an intimate relationship with God as Father (Romans 8:15-16). 

So there is only one God, yet he exists in three persons. Understanding this rightly helps us to worship him in spirit and truth.

In this series, we have explored a simple definition of the Trinity: There is one God who exists eternally in three persons. This mystery is beyond human comprehension, but we believe it because the Bible supports each element of the definition. For example, we’ve seen how the Bible teaches the existence of only one God, and how it portrays the Father, Son and Holy Spirit as three distinct persons. In today’s topic, we’re going to add the final piece of biblical evidence that undergirds the doctrine of the Trinity, and here it is: At the heart of the Trinity is the claim that all three persons – Father, Son and Holy Spirit – are fully God. 

As we’ve seen, there is a tension between the ideas of “one God” and “three persons”. Many people feel a need to resolve the tension, and some have done so by denying that all three persons are fully God. Yet if all three persons do not share the full nature and attributes of God, the doctrine of the Trinity does not hold up. No one debates the deity of the Father, but historically the deity of the other persons has been contested. Yet the Bible supports the deity of both Jesus and the Holy Spirit. Let’s look at the Holy Spirit first:

The Holy Spirit has all the attributes of God. The Bible clearly equates the Spirit with God.

The Bible describes the Holy Spirit as having qualities that only God has. He is eternal (Hebrews 9:14), omnipresent (Psalm 139:7-10), all-knowing (1 Corinthians 2:10-11), and all-powerful (Luke 1:35). The Holy Spirit also does things that only God can do, such as creating the world (Genesis 1:2), authoring scripture (2 Peter 1:21), and imparting life (Romans 8:11).. 

No Bible verse flatly states that the Holy Spirit is God. But it does equate the Holy Spirit with God in Acts 5. In the early church, many people sold property and gave the money to the church to help the poor. When Ananias did that, he kept some of the money for himself, while claiming that he gave the full amount. In Acts 5:3, Peter confronted him about his deceit: “You lied to the Holy Spirit, and kept some of the money for yourself.” In the next verse, Peter added, “You weren’t lying to us but to God!” The apostle Peter clearly thought of the Holy Spirit as God.

There is even more evidence for the deity of the Son:

The biblical writers claim that Jesus is fully equal to the Father. Jesus himself makes the same claim.

The beginning of John’s gospel provides just one example of how the biblical authors viewed Jesus. John 1:1-3 opens by referring to someone called “the Word.” John says three key things about him. First, he existed with God from the beginning. Second, he himself was God. Third, together with the Father, he created everything. Then, in verse 14, John identifies who this is when he says “the Word became human” as “the Father’s one and only Son.” So “the Word” is revealed as Jesus, the second person of the Trinity, before his human birth. He was (and still is) God.

Other biblical writers agree. Romans 9:5 says, “He is God, the one who rules over everything and is worthy of eternal praise.” Hebrews 1:3 says that “the Son radiates God’s own glory and expresses the very character of God.” The Bible also attributes to Jesus works that only God can do, such as creating the world (Colossians 1:15-20; 1 Corinthians 8:6), forgiving sin (Matthew 9:2-7), judging humanity (John 5:22-30), and providing salvation (Titus 2:11-13).

The Bible’s writers believed this in large part because Jesus himself claimed equality with God. Several passages show this, including John 8. There Jesus is talking with Jewish leaders about their relationship with Abraham, the founding father of Judaism. In the climax of the conversation (John 8:58), Jesus declares “I tell you the truth, before Abraham was even born, I AM!” Thus Jesus claimed that he existed more than 2000 years prior, even before the time of Abraham. More strikingly, he called himself by one of the most important names of God in the Old Testament. In Exodus 3, God appeared to Moses and commissioned him to lead his people out of slavery. Moses asked, “Who shall I tell them sent me?” God replied, “Say this to the people of Israel: I AM has sent me to you” (Exodus 3:14). So Jesus identified himself as the same being who appeared to Moses. This was clear to the people he was addressing: “At that point they picked up stones to throw at him” (John 8:59). Death by stoning was the punishment for blasphemy. Jesus’ hearers understood that he was making himself equal to God. If that’s not what he meant, Jesus could have easily corrected their misunderstanding. But even though his life was threatened, he didn’t take back his claim.

There is no doubt that Jesus claimed to be God. But not everyone has accepted the implications of that claim.

Some try to resolve the paradox of the Trinity by denying that Jesus is fully God.

About 250 years after the ministry of Jesus, a debate about his nature and identity rocked the early church. A teacher named Arius claimed that Jesus was not fully God. His approach, called Arianism, asserted that Jesus was a special created being – but not equal to God. The council of Nicea rightly condemned Arianism, but it became very popular, not because it is biblical, but because it simplified the paradox of the Trinity. Groups today that also deny the deity of Jesus include Unitarianism and the Jehovah’s Witnesses.

In response to Arianism, advocates of the biblical doctrine made two important points that are still valid today. First, if Jesus is not fully God, then he is not worthy of our worship. It would be idolatry to offer worship to him as a created being. Yet Christians everywhere have always worshiped Jesus. More importantly, the Bible ascribes worship to him (Hebrews 1:6-8; John 20:28). Second, if Jesus is not fully God, then he is not able to save us. Salvation is always an act of God (Jonah 2:8-9). A lesser being could not have fulfilled all the requirements of righteousness on our behalf (Romans 8:3-4). Nor could a creature offer a sacrifice big enough to cover the sins of the entire world. An infinite sacrifice requires an infinite being. And as we saw above, only God can forgive sins. So if Jesus was anything less than God, he would not be a trustworthy Savior.

The testimony of the Bible is clear. The Father is fully God. The Son is fully God. The Holy Spirit is fully God. Yet there is only one God.

In this series, we have examined how to explain the doctrine of the Trinity as it is revealed in the Bible. The Trinity is hard to understand but easy to state: There is one God who exists eternally in three persons. As mysterious as this is, the idea of the Trinity is not just an abstract theological theory. It has the power to shape how Christians actually live every day. So let’s consider three applications of the Trinity in the Christian life.

The Trinity teaches us to live in humility. 

The idea of the Trinity certainly humbles us before God. The three-in-one God is a being we cannot comprehend. He is infinite; we are finite. He is powerful; we are weak. He is exalted; we are lowly. The fitting expression of this humility before God is worship. Psalm 99:1-5 calls us to “bow low before his feet, for he is holy.”

The Trinity also invites us to be humble toward each other. The relations between the three persons of the Trinity model mutual honor. For instance, the Holy Spirit does not glorify himself, but the Son (John 16:13-14). The Son does not glorify himself, but seeks to bring honor to the Father, while the Father gives glory to the Son  (John 13:31-32). Each of the three seek to promote and elevate each other, not themselves. We express this kind of humility when we serve each other. For example, in John 13, when Jesus spoke about glorifying the Father, he had just finished washing his disciples’ feet.

 This leads to the second way the Trinity is more than just an abstract theory:

The Trinity teaches us to live in community.

Because God is three persons in one being, he has always experienced community within himself. Relationship is built into the very existence of God. Obviously, the community of Christians is not the Trinity. Christians are not one in essence and we are imperfect sinners. But God’s love within himself is the basis and model for the love Christians have for each other. Consider four aspects of true community that God points us toward:

Loving unreservedly. 1 John 4:7 says, “Let us continue to love one another, for love comes from God.” The reason we love each other is because love is essential to the Trinity. This is because of God’s love for us (1 John 4:11), but also because of the example of God’s love within himself.

Forgiving freely. The members of the Trinity don’t need to forgive each other, because none of them has ever sinned. But the way God treats us models how we approach people in our lives who have sinned against us. Colossians 3:13 says, “Make allowance for each other’s faults, and forgive anyone who offends you. Remember, the Lord forgave you, so you must forgive others.”

Living peaceably. There is never conflict within the Trinity. Likewise, Colossians 3:14-15 invites us to live “together in perfect harmony…. For as members of one body you are called to live in peace.” To live in peace and harmony means that we must work to maintain reconciled relationships with each other.

Serving connectedly. The persons of the Trinity work together to fulfill different roles within a greater unity. 1 Corinthians 12:12 uses a similar analogy to describe unity and diversity in the church: “the human body has many parts, but the many parts make up one whole body.” Each part represents a different, vital function that the whole church needs, but within a larger unity of the one body. This deeper connection is greater than our diverse backgrounds (verses 13-14), so that the church – like the Trinity – is a unity with diversity. 

So God’s people are called to live in community that reflects the Trinity. As a Christian, you were never meant to go it alone. You need to connect with other Christians – through a small group, on a serving team, inviting others into your home or doing activities together. 

One more important application arises out of the relations between the persons of the Trinity:

The Trinity teaches us to live on mission.

Considering the roles within the Trinity, the Bible teaches that the Father sends the Son (1 John 4:14). Together, the Father and the Son send the Spirit (John 15:26). Again, this arrangement models something profound for the Christian life, because, having been sent by the Father, the Son sends the church with the help of the Spirit.

After Jesus rose from the dead, he appeared to his disciples and told them, “As the Father has sent me, so I am sending you” (John 20:21). The Father sent Jesus on his mission to be the Savior of the world. Similarly, Jesus sends us on our mission to tell people about Jesus’ mission (Matthew 28:18-20). We are the messengers who spread the good news that Jesus paid for human sin so that people can be right with God (2 Cor 5:18-21). We do our part by the power of the Holy Spirit (Acts 1:8), who lives within us.

Every Christ-follower is sent and empowered by the members of the Trinity to make salvation known to his fallen creation. Have you embraced your mission? The Father sent Jesus from his comfortable place in heaven to enter our messy world. He didn’t just send information. He sent a person who would engage others with compassion acts and truthful words. In the same way, Jesus sends us out of our comfortable existence to engage our neighbors in their world with both compassion and truth. You can do this because the Holy Spirit will empower you to point people to Jesus and his good news.

The biblical doctrine of the Trinity may be hard to understand, but it isn’t just esoteric speculation. Expect the reality of who God is to shape how you actually live as a Christian every day.