The idea of there being three in God only emerged gradually, until about the 4th century when the doctrine was defined. Jesus, like the Jews among whom He lived, believed in one God. This was different from nearly all the other nations around – who had a variety of gods. The Jews – and Jesus was a Jew – saw God as a heavenly father, as in the original patriarchal and nomadic structure of their society. Jesus, in His little village grew up as a faithful Jew. But as an adult He was critical of the corruptions that had developed in this society. There were the priests, many of whom liked to think of themselves as important leaders in their religious society. There were also the Sadducees and Pharisees who also had ‘inappropriate’ ideas of their religion and their nation. Even among the ordinary folk there were some who thought their God should free them from Roman domination and restore them as a nation again – free from foreign dominance.
Jesus was separate from all of these groups; He was in Himself and somewhat in the eyes of His supporters, an almost new and ideal Jew – loving all – like a true son of their patriarchal origins. He seemed most comfortable with simple folk and even with those often classed as sinners or who were sufferers of some illness or disability. He also showed concern for those seen as lepers, and for non-Jewish folk such as Samaritans and Romans. These aspects of Jesus’ life and His enthusiasm were significant and important to his close followers and even to those who became His followers after His death. The first Christians, as we would call them, saw in Jesus’ life that He was like a true son of God, in His way of life and regard for others.
It was this way of life, that the first followers tried to take on themselves, that was viewed by the early Christians as expressing the very Spirit of God . And this was a dynamism of spirit that they needed in order to survive in the Roman society and when they were persecuted for their beliefs and attitudes – rejecting the Roman tolerance of all sorts of gods and ways of life.It was throughout these circumstances and trials that the notions of God expanded to not just seeing God as their father, but seeing Jesus as His very Son and the motivation of their religious lives as the Spirit of God seen in the life of Jesus. From these ideas evolved the notion of the Trinity – of the patriarchal Father, of the devoted sonship of Jesus’ life, and of the vitality and enthusiasm of His Spirit. We, believers in all this, must seek to live in the world as Jesus would, with the dynamism of the Spirit and acknowledging the patriarchal overview of the Father.
iseeitmyway 
I think, unique in all the sermons I’ve read and heard about the Trinity, is the absence of the word “person”. You explain beautifully the evolving notion of how God created, then joined and continues to sustain this world of ours. In avoiding any discussion of “three persons in one” I think you have wisely moved away from a dead-end discussion and talk of “mystery to be revealed at the end of time”.
The mystery is all around us: the created world; the Word of God that speaks to us in multiple ways beyond mere words; and the Spirit of God that breathes with us as we breathe in and out.
As always, you manage to cut through the theological thicket to show us what is both simple but also profound. Bless you.