by Matt Slick
The doctrine of the Trinity is that there is one God who exists in three distinct, simultaneous persons. It is a foundational doctrine of the Christian faith, but how does it apply practically to our lives right now? In order to answer the question, we first need to examine two doctrines that further clarify the Trinity.
The Ontological Trinity is the teaching that each member of the Godhead, the Father, the Son, and the Holy Spirit, possesses the same divine nature. In other words, the Father has the quality of being God as does the Son and the Holy Spirit. This is important because only God has this divine essence. We do not.
The Economic Trinity is the teaching that within the Godhead each of the members has a different role. The Father sent the Son (John 6:44; 8:18 ), but the Son did not send the Father. The Son came down from heaven not to do his own will but the will of the Father (John 6:38). The Father gave the Son (John 3:16), who is the only begotten (John 3:16), to perform the redemptive work (2 Cor. 5:21; 1 Pet. 2:24). Neither God the Father or God the Holy Spirit were given to the world to redeem it. The Father and Son sent the Holy Spirit, but the Holy Spirit does not send the Father or the Son. The Father, who chose us before the foundation of the world (Eph. 1:4), predestined us (Eph. 1:5; Rom. 8:29), and gave the elect to the Son (John 6:39). The elect are not given to the Holy Spirit or the Father. It was not the Father or the Holy Spirit who became incarnate--but only the Son. Therefore, within the Economic Trinity we can see a difference in function among its members. But, these differences do not mean that each member is not equally divine.
Practical Application, the Eternal Covenant of Redemption
Hebrews 13:20, "Now the God of peace, who brought up from the dead the great Shepherd of the sheep through the blood of the eternal covenant, even Jesus our Lord."
The Trinity is the most probable context for the Eternal Covenant spoken of in Hebrews 13:20. Since God is eternal, it makes sense to say that the Eternal Covenant must be a covenant made among the members of the Trinity. Therefore, many biblical commentators believe that the Eternal Covenant is the promise of the Father to the Son that the Father would give to the Son the elect (John 6:39) and that the Son would have to become incarnate and bear our sins in order to fulfill this promise (John 1:1, 14; 1 Peter 2:24). It is because of the inter-Trinitarian covenant that was made before the foundation of the world that we have redemption. This is perhaps the most important of all practical applications of the Trinity in that it provides a background for the eternal work of God in our redemption.
The Trinity and Salvation
To continue along the lines of salvation, we could make the case that without the Trinity we cannot be saved. Here's why. Our sin is against God; and because we are not able to undo our offense against God, due to our sinfulness and inability to perfectly keep His law, the only other party available to deal with our sin is God himself. After all, our sins are against Him, so He has to step in and do what we could not. That is exactly what happened. Jesus is God in flesh (John 1:1, 14; Colossians 2:9) who was born under the law (Galatians 4:4) and who never sinned (1 Peter 2:22). Since he was able to perfectly keep the Law of God where we could not, he was able to redeem us. We, Christians, are familiar with this gospel message; but what a lot of people don't realize is that in order for our redemption to be real, our Redeemer needed to have two natures: divine and human. We need a Savior who is divine in order to offer a sacrifice of divine quality by which God the Father is appeased. In addition, Jesus needed to be human, so he could fulfill the law and die for humans. This would mean that Jesus had to be under the Law (Galatians 4:4) and cooperate with the limitations of being a man (Philippians 2:5-8). This would further mean, to put it rather bluntly in a question, that when the Word became flesh (John 1:1, 14), then who is left, so to speak, to run the universe? This would mean that God the Father was operating in His full omnipresent, omniscience, and omnipotence while the Son cooperated with the limitations of being a man (Philippians 2:5-8), so he could be crucified and redeem us. So we could say that without God being a plurality of persons we would not be able to have the incarnation, and without the incarnation we would not be able to be redeemed.
The Trinity and marriage
Marriage is a covenant promise where a man and a woman enter into a legal contract. They commit themselves to mutual fellowship, financial sharing, sexual privileges, etc., with various exclusions to all other members of society. Within the marriage there is the husband, who is to love his wife (Ephesians 5:25) and who is also in spiritual authority over her (Eph. 5:23). But, when we consider the Trinity, we see that God the Father loved the Son (John 3:35; 5:20) and had headship over the Son since he sent the Son (John 4:34; 5:36). Therefore, when we see the positional authority of the Father over the Son and we also recognize that this does not mean there's a difference in nature or importance between them, we can apply this to marriage and recognize that the spiritual authority the husband has over his wife does not lessen her quality or importance. This is important, particularly since husbands sometimes oppress their wives instead of considering them as equal. If we understand that our wives are also made in the image of the triune God (Genesis 1:26) and like the Holy Spirit who is the helper (John 15:26), then we can properly appreciate the value of our wives as helpers who are our equal but in a different position of authority. Furthermore, since we can understand the hierarchical structure within the Trinity, it can help us to better understand the hierarchical structure within marriage. Just as the members of the Trinity all work in harmony, so, too, must the married couple work in harmony. Therefore, their marriage is to reflect the Trinitarian communion, equality, and difference of roles.
Communion with one another
Before the creation of the universe God always existed as a Trinity of persons. Therefore, we can say that the inter-Trinitarian communion has always been one of perfect harmony and fellowship. The model of the Christian church and our individual lives as Christians is to reflect this communion of God. It is this fellowship that ultimately emanates out of the very Trinitarian nature of God himself. As Christians, we are to have fellowship one with another, especially when the Holy Spirit indwells fellow believers (2 Corinthians 13:14). Likewise, this fellowship is to be enjoined within the church community and with Jesus (1 Corinthians 1:9). Therefore, because the doctrine of the Trinity allows for a true incarnation and our redemption, we can then be indwelt by the Holy Spirit (the third person of the Trinity) and can have fellowship with God and with others who are also indwelt by the Holy Spirit.
The Lord's Supper
When we take communion at church, we are participating in a covenant ceremony. The bread and the wine are the symbols of the covenant--but what covenant? As I mentioned above, there is the Eternal Covenant. This is the covenant between the members of the Godhead for our redemption. Therefore, when you are participating in the elements, you are participating in the manifestation of the Eternal Covenant. In other words, the inter-Trinitarian communion, which is necessarily without beginning and without end, would mean that God's thoughts for you are infinite in number. After all, he existed forever and covenanted within the Trinity to redeem people from a fallen world. This means that God has been considering you, thinking of you, and loving you forever. This knowledge can be very comforting and reassuring during times of difficulty.
You are not divine
God is divine. You are not. The Trinity is the only divine Being. We are not gods, nor can we become gods. Though there are heresies being taught in our world today that advocate our "inner divinity" or the potential of becoming divine, the truth is that only God the Trinity has the quality, nature, and essence of being God. When you realize this, you will have less of a tendency to exalt yourself. You will have less of a tendency to think more highly of yourself than you ought to. Hopefully, you will also learn to depend more on him then your possessions and abilities. Combine this with the notion that God in the inter-Trinitarian, Eternal Covenant has redeemed you and planned your redemption from before the foundation of the universe, and it should help you stay humble before God and dependent upon him as you trust his divine love for you.