My main problem with the Trinity is that nowhere in the NT is the teaching made explicit, and I cannot imagine the failure to do so of such a central doctrine. The word "Trinity" does not even appear, nor do phrases like "God the Son," or "Three in one," and so on. You only infer it from suggestions that can be interpreted many ways.
It seems reasonable to me that a century or so after the Gospels were born comparisons between this Jesus and other cult-heads started being made, and Jesus was seen to come off poorer, so they developed the teaching in comparison with many other similar "trinities" that existed back then in order to "elevate" Jesus to godhood and make him more "salable." Now of course the way I just expressed it would not be what happened. Instead, these Christians felt an insufficiency, saw the trinities around them, and thought, "Now that is the way it must have been."
That is possible, yet the bible in certiain specific pasages and in overlall context strongly suggests a trinitarian type of god. For my personal comments based on my own experiences with god, see my previous post.
PAul/sau,l who reshaped the direction of early christianity, had an experience which illustrates the nature of the trinity. A part of god entered into him. And yet god remained the same . How did god "extrude" a part of his consciousness into a mortal man in a way as to be clear to that mortal man, and yet remain god. How did, indeed, god become a man on earth, imbuing that being with all the powers of god, and creating a man who could not die until he surrendered (quite clearly and verbally) the holy spirit? How could such a mortal shell be physically reborn, and at the same time transformed, unless a part of god could enter into him?
it is very difficult to accept the totality of biblical christianity unless you accept a form of trinitarian god. Otherwise you have to see the holy spirit and christ as entirely separate entities, and yet they are not always so.
Christ is called the son of god, and christ on earth (materially) was the physical son of god (according to scripture) but the equivalent of christ -not as a man, but as an entity in heaven was not the son of god but a part of him (the word) As to the spirit. jn 4 24 says that god is a spirit, yet the bible also says that god walked the earth as a man, and appears in other physical shapes and forms, a moving finger, fire, light, etc.