The New Catholic Encyclopedia: "The formulation ‘one God in three persons’ was not solidly established, certainly not fully assimilated into Christian life and its profession of faith, prior to the end of the 4th century. But it is precisely this formula that has first claim to the title the Trinitarian dogma. Among the Apostolic Fathers, there had been nothing even remotely approaching such a mentality or perspective." – (1967), Vol. XIV, p. 299.
For many years I have struggled to understand the doctrine of the trinity. To say it is a mystery that we are not expected to comprehend simply doesn't cut it for me. Some time ago I discovered that in the original formulation of the trinity, the word in Greek which we traditionally have interpreted to mean "persons", as in "three persons in one God" is actually the same word used to designate the mask worn by actors in Greco-Roman theater. We cannot call this a "person" but we can certainly call it a "persona". This insight has put a totally new spin on the entire concept for me. We finite creatures cannot possibly hope to describe our transcendent God, but we can speak of the modes or roles or personae that assist our understanding. God as creator/father, God as spirit/sustainer, and the glimpse of God we obtain in the life and teaching of Jesus. In other words, trinity is not a description of God but is, rather, a description of the human experience of God in the language of fourth century Greek speaking Christianity. We are not limited to just these three. Any persona that promotes our understanding of and our relationship to God is completely acceptable. God could be mother as well as father. God could be Wisdom / Sophia / Word / Allah / Krishna / Manitou. God's possibilities are endless. These are merely our human images of God. God is, as always, ONE.