As promised, here are some more reasons for the importance of the trinity, taken from chapter 1 of Dr. Bruce Ware's book...Father, Son, & Holy Spirit: Relationships, Roles, and Relevance. The first three reasons are stated without the extra thoughts, and then three more have been added (each with part of Dr. Ware's elaboration of the reason).
TEN REASONS TO FOCUS ON THE WONDER OF THE TRINITY
1. The doctrine of the Trinity is one of the most important distinguishing doctrines of the Christian faith and therefore is deserving of our careful study, passionate embrace, and thoughtful application.
2. The doctrine of the Trinity is both central and necessary for the Christian faith to be what it is. Remove the Trinity, and the whole Christian faith disintegrates.
3. Worship of the true and living God consciously acknowledges the relationship and roles of Father, Son, and Holy Spirit.
4. The Christian's life of prayer must rightly acknowledge the roles of Father, Son, and Spirit as we pray to the Father, through the Son, in the power of the Spirit.
If Jesus taught us to pray to the Father, then we ought to do this. For one reason or another, we sometimes follow a different practice. We may encourage our children, especially, to open their prayers with, "Dear Jesus," despite the fact that Jesus said to pray "Our Father in heaven"...we should pray to the Father through the Son. Jesus Christ is the mediator. He is the one through whom we address the Father. He is the one who brings us access to the Father. Our prayers bring spiritual benefit only when we pray in his name. And prayers that bring fruit in the kingdom are those offered in the power of the Spirit. We pray as the Spirit prompts and urges us to pray. So prayer rightly understood - Christian prayer - is prayer to the Father, through the Son, in the power of the Spirit. To pray aright, we need a deep appreciation for the doctrine of the Trinity.
5. The Christian's growth in Christlikeness or sanctification is rightly understood and enriched when seen as the work of the triune God.
First, the Father ordains and secures our holiness...Ephesians 1...This ordained plan then moves toward becoming reality in the lives of sinners as the Son lives [a holy life]...and then dies to pay for and defeat our sin...But even with the plan of the Father and the saving work of the Son, we are not declared holy or remade until we put our faith in Christ. Then, by faith, we begin the life-long process of conformity into his likeness, and here the Spirit [works]...in opening our eyes to see the glory of the Son (2 Cor. 4:6) and in making us like Christ (2 Cor. 3:18). So our sanctification is done by the triune God, with Father, Son, and Holy Spirit each participating in different but completely complementary ways.
6. The triune relationships of the Father, Son, and Holy Spirit cause us to marvel at the unity of the triune God.
The three persons are never in conflict of purpose, never jealous over another's position or specific work, never prideful over one's own position or work, and they are always sharing fully the delight in being the one God accomplishing the unified purpose of God...Each divine Person accepts his role, each in proper relation to the others, and each works together with the others for one unified, common purpose.
Check back on Friday for the last four reasons that the doctrine of the Trinity is so important.