A recent announcement by a leading pastor in Australia's third largest church that Jesus is not God, but merely a great man, has not caused him to be disciplined as a heretic. The reason given was that no action could be taken unless someone made a formal complaint. A number of church leaders have left the path of orthodox Christianity and the view that Jesus is God the Son. They have zero credibility to represent Christianity in my opinion. So, why do I believe in the Trinity?
First of all, I do believe in God's oneness which is supported in Deuteronomy 6 and Exodus 20. God is described as the Father in 1 Corinthians 8:4,6. Christ is also described as equal to God in Philippians 2:5-11; the Son is described as being the express image of God in Hebrews 1. He is also described as God with us in Matthew 1:23. The most convincing argument to me is the fact that we call Jesus Lord. In the Septuagint, the Greek Old Testament that Jesus often quoted, the Greek word for Lord was used to describe YHWH, God. This is most specifically addressed when Jesus is called my Lord and my God in John 20:28. What about the Holy Spirit? He is spoken of interchangeably with God in Acts 5:3-4. Jesus was God the Father's Son yet that which was conceived in Mary was of the Holy Spirit according to Matthew 1:20.
So how do we get three in one? It is important to note that no serious scholar uses 1 John 5:7 to prove the Trinity, because it is of doubtful origin. There is plenty else to support the logical conclusion. Linguistically, we can also see from Genesis 2:24 that a man and a woman are spoken of as one. This is the same word describing God as one in Deuteronomy 6:4. We also note that in Matthew 28:19-20 the Father, Son and Holy Spirit are given one name. Even more convincing is John 1:1 where Jesus, the Word was God.
So how does all this work? We are human and cannot fully understand God, but there have been a number of Trinity theories over the centuries. The so-called economic view is that which we find in Scripture, where details are left to logical analysis. Modalism was also a theory that God is one person with three names. This was rejected because of examples such as Jesus praying to Father. God the Father would not need to pray to himself. He is not schizophrenic. Tritheism, the idea of three gods was also rejected because it basically contradicts the idea of God being one. The Orthodox position logically summarizes a 2,000 year long discussion on the topic as "one ousia in three hypostases" – one Godhead indivisible and yet three persons.
Why is it important that Jesus is God? If a mere man died for you and me, then our faith is in vain. Christianity is not a philosophy like some eastern religions. It is not about a man entering a cave without witnesses and claiming to be God's prophet. It is our self-sacrificing God entering our world to show us his love in a very impactful way, by dying for us and rising the third day with thousands of witnesses. If Jesus was merely a godly man and not Immanuel, God with us, then that sacrifice and resurrection save nobody.