This week's question deals with the Oneness of God in comparison to the Trinitarian doctrine. Gary D. writes "Would you comment on the chasm between 'Trinitarian Christians' and 'Oneness Christians?'"
The notion of the Trinity has its roots in the early history of the Church. Tertullian, an early church writer, is generally credited as being the first to use the term "Trinity" to describe God. However, it wasn't until the fourth and fifth centuries that the doctrine was officially adopted by the Church and recognized as a part of Orthodox Christianity.
In short, the doctrine of the Trinity is the belief that God is three simultaneous and separate manifestations of God all wrapped up into one. In other words God the "Father," Jesus, and the Holy Spirit are different manifestations of the God-head, but they are also at the same time a unity. If this seems obtuse or difficult to understand, you're not alone. The whole of the Trinity doctrine is considered to be a "mystery" by the Church: a concept that is not understood, but must be accepted. Infinity is another example of "mystery" because our finite linear minds have great difficulty grasping the notion of forever and no end or beginning, so we just accept it.
There is evidence in the New Testament to support the teaching of the Trinity. The writer of Matthew understood there were three separate manifestations of the Divine when he wrote that the disciples should baptize in the names of "the Father, the Son, and the Holy Spirit" (Matthew 28.19). Further, in the gospel of John we read Jesus promising God will send the Holy Spirit sometime after Jesus' death (John 14.6). Thus in both of these passages we see the three manifestations of God set forth.
To further support the notion of the Trinity, Jesus says that "The Father and I are one" (John 10.30). This verse was one of the key passages used to support the doctrine when the Church Councils met in the fifth and sixth centuries. And so, although there is no clear expression of the Trinity doctrine in the Bible, some evidence and nearly 2,000 years of Church tradition supports it.
On the other hand, there is a large body of believers who do not embrace the Trinitarian doctrine. These un-orthodox Christians can be found in most churches, although most simply choose not to discuss the matter unless pressed. There are also several denominations/faiths that choose to reject the Trinity outright, the Jehovah's Witnesses being one of the most prominent. However, the notion that the Trinity is a human construct has haunted the Orthodox Church from early on. Arius of Alexandria taught in the third and fourth centuries that although Jesus was divine, he was neither equal nor the same as God. For most Christians this teaching today seems blasphemous. However, there is a body of scripture to support the view.
In the Old Testament we read that "God is one" (Deuteronomy 6.4). In fact, Jesus quotes this passage in Mark 12.29. This suggests that God could not be three-in-one, but is one only. In another instance, when someone approaches Jesus and calls him "good," Jesus responds: "No one is good but God alone" (Mark 10.18b). Some suggest Jesus clearly isn't claiming equality with God. Further, Paul wrote that Jesus subjected himself to God (1 Corinthians 15.28) and in Hebrews we read that Jesus didn't exalt or glorify himself, but was obedient to God who in turn glorified the Son (Hebrews 5.5-10). All of these passages have been used to show that the Trinity should not be an orthodox teaching.
And so, as Gary points out, there is a chasm of belief between those who believe God is One and those who believe God is One-in-Three. To make matters worse, both camps claim the other is apostate at best.
So, how do we reconcile the two? Probably we can't -- intolerance seems to be a dominant human trait -- even in the Church. On the other hand, according to many denominations and faiths there is only one primary tenet of orthodoxy: that "Jesus is the Christ, the Son of the Living God" (adapted from Matthew 26.63) and that "God has raised him from the dead" (Romans 10:9b). If we could get every Christian on board with this affirmation, and then if Christians would get busy loving God, loving their neighbor, and making disciples (the two Great Commandments and the Great Commission) non of us would have time to seriously disagree anyway.