Trinity Sunday, Year A

God reveals himself in the depths of our being
(Readings: Exodus 34:4-6, 8-9; 2 Corinthians 13:11-13; John 3:16-18)
Introduction to Mass
Today is Trinity Sunday. Our Christian belief that God is a “trinity” of persons is one of the basic mysteries of faith - like Jesus being human and divine, or God’s presence in the sacraments – which we can only understand in and through faith, in and through our contact with God.
We’ll never fully grasp God’s nature until we see him face to face in eternity. But the partial grasp that we do have has come to us through centuries of experience and reflection, going back to the earliest days of the Hebrew people. The readings for today’s feast show how our knowledge of God developed and grew over time.
As we prepare to celebrate Mass together…
The Trinity is always described as a great mystery of Christian faith but that's not because it's impossible to explain or because it doesn't make any sense. The Bible doesn't give an explanation of God's nature in what we would recognise as modern scientific language. The Bible isn't that kind of literature, and after all, knowledge of God isn't that kind of knowledge. What the Bible gives is a description of the experiences, first of all of the Chosen People, and then of the disciples and the early followers of Christ, as they gradually learned more and more about who God was and what he was actually like.
As far as we can tell from the Bible, in the earliest days of their existence as a distinct nation, the Chosen People believed in a number of gods, like the pagan countries around them. They might have seen their God as the top God but he was still one out of many, and it was only later on, long after their experience of being liberated from slavery in Egypt, after settling in Canaan in the Holy Land, that they came to the understanding that there's only one God, the creator of the world and of everything that exists.
Nowadays we tend to assume that religious belief means belief in a God – a single being. Even people who don't believe in God think in terms of denying the existence of a single God, not a whole collection of them. But at the time when much of the Old Testament was written this believe in one God, who created the universe was what made the faith of the Jewish people different from the other people around them. Or it was one of the main things.
Another thing that the Chosen People came to understand about God, which also distinguished their religion from the other religions at the time, was the fact that God wasn't just a projection of purely human qualities. He wasn't just a reflection of human emotions and jealousies and so on, as in so many of the stories and myths about the pagan Gods. The God of Israel was a moral God. His nature was love – "a God of tenderness and compassion, slow to anger, rich in kindness and faithfulness" says the book of Exodus. He was free from all the familiar human vices and weaknesses.
And being a moral God, he gave the people he had made laws and commandments, so that the image of the creator would, so to speak, impress itself on his creatures. These laws and commandments weren't only an expression of God's identity and God's character. They were an expression of the identity and the character that his people were called to have as well.
So for the Chosen People, as their knowledge and understanding of God grew and developed, their understanding of themselves developed as well. That's the first point I'd like to try to make.
The second point is that this advance or this progression in knowing and understanding God didn't stop in the Old Testament, of course. It was fulfilled, or brought to its highest point, in the person of Jesus - and not only his person, but, we would have to say, in his mission, his proclamation of the Kingdom of God.
Back in the Old Testament period, the Israelites only learned what God was like slowly, over the course of centuries, under pressure of events and the experiences that they had, the preaching of the prophets and so on. For the disciples, and for the first groups of Christians, the advance in their understanding of God had to move a bit more quickly.
Immediately after Christ's Resurrection, the first Christians reached the conclusion that the God they had always known and prayed to had been made present in the man Jesus. This was the conclusion that they reached after their experience of seeing Jesus alive after his crucifixion. And then again, later on, after the experience of Pentecost, they knew that God had made himself present in another way as well - in the Spirit that they received. That Spirit was the God that they had always worshipped as well.
The New Testament doesn't give any explanations, in modern scientific language, of how God is present in these three persons - the Father, Christ the son, and the Spirit. What the New Testament does do is it describes the experiences the disciples had - their experience of Jesus' rising from death, then his leaving them and the coming of the Holy Spirit.
And the New Testament relates the conclusion they drew from their experiences: that their understanding of God had to move on. Now they had to speak about God as three persons. The word 'Trinity', as we know, doesn't appear anywhere in the New Testament. But the belief - and more important, the experience of the Trinity - does appear, and it appears right at the start of the Church's existence. That's the second point I want to try and make.
And the final point is this. What was true for the Israelites in the period of the Old Covenant with God is true for Christians - for us - in the period of the New Covenant. Our knowledge and our understanding of God gives us our understanding and knowledge of ourselves. The key to our identity lies in God's identity. If God is a community of love, the meaning of our human life lies in living alongside each other and for each other as well. We are all members one of another, as St. Paul says.
This isn't the spirit of the society we live in, though. From the low-level boorishness and inconsiderateness that has become part of everyday social life, the verbal and physical belligerence which has become commonplace, through to the ruthless commercial priorities that mark people's working lives and the economy at large, the atmosphere we live in now is one where people are separated and alienated from each other and competitors against each other rather than “members one of another” as God intends.
Our belief in the Trinity tells us that that isn't an adequate vision of what it means to be human. The love that makes up God's nature, and makes up ours as well, has to reach beyond the small private circle that we might belong to, and has to mark all our other relationships as well. That's our vocation, at any rate, that's what we're called to, even if sinfulness and weakness make us think of it as impractical.
So the feast of the Holy Trinity is about God's identity, of course, but it's not only about God's identity. It's also an opportunity for us to reflect on our true identity as revealed to us by our Christian tradition - persons made in God's image, giving of ourselves to each other, and receiving from each other, in whatever ways our circumstances invite us to.
That's what the Father and the Son and the Spirit do, and that's what we're supposed to do as well.