But in the case of the Trinity.... it's really true. It is quite an unfathomable mystery to understand how God can be one and yet subsist in three persons. We do get SOME help from the New Testament, although it's also an theological axiom of that although the Trinity is present all through the Christian Scriptures, the word "Trinity" itself never occurs.
The short scripture reading (1 Cor. 12:4-5) for Morning Prayer in Liturgy of the Hours struck me anew today because of this very subtlety.
"Now there are varieties of gifts, but the same Spirit,
and there are varieties of service but the same Lord;
and there are varieties of working but the same God
who inspires them all in every one."
There you have it ....the inner life of the Father, Son and Spirit as He works himself out in the life of the believer. He comes as gift, as service and as energizing power. Kinda neat, even if it is a little understated for those of us who are used to reading systematic theology.
I went to the full text of 1 Corinthians 12 to discover the immediate context. The verses before this passage deal with a creed, the shortest and perhaps earliest creed "Jesus is Lord!" The verses immedately following this indicate why all this is happening- for the common good.
So, I am heartened to note how the life of the Trinity has an external setting- our thought life and what we believe. There is intellectual content and assent involved. But there is also a social context- an effect on how we behave toward and exist with others. Belief in the Holy Trinity is not a brainiac convention, but is acutally part of the outward move of God in self giving service to the world.
We're called to be attentive to both fronts.
We will never understand fully how this mystery works in our lives. All of the saints know this, whether or not they expressed the thought in a concrete way. That inability guarantees our unceasing dependence on God, who calls us to journey all our lives, and only to arrive at Home once.
Saint Teresa of Avila (1515-1582), Carmelite, Doctor of the Church was one who put this idea into concrete expression.
"God gave me to see clearly the truth of the most Holy Trinity. It is just as learned theologians told me, but I did not understand it as I do now... What I have seen is this: three distinct Persons, each one visible and who speaks and to whom we can speak. Afterwards I thought how the Son alone took human flesh, which shows clearly that the three Persons are distinct. The Persons love each other, communicate and know each other. But, if each one is distinct, how can we say that the three are one essence? For this is what we believe.
This is deepest truth, and I would die for it a thousand times. In these three Persons there is but one will and one power and one might; neither can one be without the others. There is one sole Creator of all created things. Could the Son create an ant without the Father? No, because their power is one. The same is to be said of the Holy Spirit.
Thus, there is one God Almighty, and the three Persons are one majesty. Is it possible to love the Father without loving the Son and the Holy Spirit? No, for those who please one of the three Persons please all three Persons, and those who offend one offend all. Can the Father exist without the Son and without the Holy Spirit? No, for they are one in being, and where one is, there are the three; they cannot be divided.
How is it, then, that we see that the three Persons are distinct? And how is it that the Son, not the Father, nor the Holy Spirit, took human flesh? This is what I have never understood; theologians know it. What I know is that the three were there when that marvellous work was done.
I do not busy myself with much thinking about this; all my thinking comes down to this: God is almighty, that he has done what he would do, and can do what he wills. The less I understand it, the more I believe it, and the greater the devotion it excites in me. May he be blessed for ever! Amen."