The Trinity is so controversial because it is truly beyond human comprehension. I have heard several analogies, about water and steam, eggs yolks and shells and other objects, all of which do not fully embody the existence of God, the Father, the Son and Holy Spirit as one being. The Bible teaches that the Father is God, that Jesus is God, and that the Holy Spirit is God and it teaches that there is only one God. As simply as can be stated, the Trinity is ONE God existing in three Persons. Deuteronony 6:4 and Galatians 3:20 as well as other Scriptures explain that there is only one God and God is only one. There is however indication of the three Persons of God in Genesis in the creation story of Genesis 1:1, Genesis 26 and in Jesus’ Baptism in Matt 3:16-17.
God the Father is distinguished from God the Son in Psalm 45. In John 14:16, Jesus speaks to God the Father about sending a Helper, the Holy Spirit. This demonstrates that Jesus who was God, was not God the Father and the Holy Spirit who is also God is another. Above and beyond anything, Jesus prayed regularly during his earthly walk. He was praying not to Himself, but to His Father. To those that contend that Christians believe in three gods as the Jehovah Witnesses contend, one can simply respond that the Bible speaks of God in three different beings, however it also speaks of their being only one God. To claim to understand God’s capabilities is quite arrogant and silly. He created us and the Creator is greater than that which he created. We may not understand it, but believe it based on faith. The doctrine of the Trinity is represented in the Bible, we know that God is the Father, Son and Holy Spirit, which is indicative of his great power and capacities greater than our understanding.