The following is the most interesting talk I've ever heard about the doctrine of the Trinity.
And weather you agree with the early Christians or not, I think you'll agree that what they believed is very interesting. (By early Christians I mean the Christians from before the time of the Emperor Constantine and the Nicene Creed.)
God does not need anything. He does not need to be entertained or praised. He was not bored. He was not lonely before he created. (Yet the Bible says he is a relational being.) If an eternal relationship has not always existed it makes no sense for God to create. Only if a perfectly loving relationship is in the uncreated does it make sense for him to create; for only then would he want others to enjoy the relationship he enjoys. Only love can explain the existence of this world.
Perfect love--a perfect relationship--is the eternal truth.