The Trinity is the doctrine that God is one in His being (nature/essence) but three in person (Father, Son and Holy Spirit). Although the word “Trinity” is never mentioned in the Bible, its constituent parts are found throughout Scripture. Hence, it is a biblical teaching which can be broken down in the following way:
- There is one God
- He exists as three distinct persons
- Each person is equally, eternally and truly God
- The Father is God
- The Son is God
- The Holy Spirit is God
Wayne Grudem defines it as such:
“God eternally exists as three persons, Father, Son, and Holy Spirit, and each person is fully God, and there is one God.”(Wayne Grudem)
There is one God
The Trinity does not teach that there are three gods (polytheism). The Bible consistently maintains that there is one God and He is one in His essence (Deuteronomy 6:4; Isaiah 44:6; 1 Timothy 1:17; 1 Timothy 2:5).
He exists as three distinct persons
God always has and always will exist as three distinct persons who are co-equal, co-eternal and all truly divine. The Father is God (John 6:27; Titus 1:4). The Son is God (John 1:1-4, 14, 18; 20:28; Colossians 2:9; Hebrews 1:3; Titus 2:13). The Holy Spirit is also God (Acts 5:4; 1 Corinthians 3:16; 1 Corinthians 6:19).
Equality with different roles
The three persons of the Trinity have distinct roles but remain equal. Their “three-in-oneness” can be seen through their respective roles in the singular events of creation and salvation.
In creation, the Father spoke the world into existence (Genesis 1:3-26). The Son was the means by which He created (John 1:3; Colossians 1:16) and by whose power the universe is sustained (Colossians 1:17). The Spirit was the breath (wind) of God who hovered over the waters, bringing order and life to His creation (Genesis 1:2).
In salvation, the Father initiated the plan and sent His Son into the world (John 3:16; Galatians 4:4; Ephesians 1:9-10). The Son obeyed and accomplished salvation for us (John 6:38; Philippians 2:5-8; Hebrews 10:5-7). The Spirit gave us new spiritual life (John 3:5-8). He sanctifies us (1 Peter 1:2) and applied this redemption to our lives, being the down payment of our salvation (2 Corinthians 1:22, 5:5, Ephesians 1:13-14).
What the Trinity is not
The Trinity is not modalism – the idea that “Father”, “Son” and “Holy Spirit” are three different names or manifestations of God. The Trinity is not three separate gods (polytheism), nor is it the denial of the full deity of Christ (Arianism). Instead, they are three persons who dwell in communion with one another, sharing the same nature, yet remaining distinct. This is not a contradiction either; “being” refers to what you are whereas “person” refers to who you are. This is a mystery, a paradox, but not a contradiction. We know God is triune because He has revealed Himself as such in Scripture. However, the exact intricacies of the three persons and how they subsist without being compounded is beyond our comprehension.
“We cannot conceive how a single, perfectly united being can also be three distinct persons, but that does not mean it is incoherent or impossible”(Roger E. Olson)
 Wayne Grudem Systematic Theology: An Introduction to Biblical Doctrine (1st edn Inter-Varsity Press, 1994) 226
 Roger E. Olson The Mosaic of Christian Belief : Twenty Centuries of Unity and Diversity (Inter-Varsity Press, 2002) 151