It is a commonplace that the holy Trinity doesn't connect with anything much in the life and worship of most Christians. One reason alleged for this is that what has been said about the Trinity by theologians is just so subtle, so extraordinarily difficult to understand, that, without an arduous apprenticeship in theology, one cannot begin to grasp what is at issue.
The irony is that the early theologians who devised difficult and abstruse language about the Trinity did so for no other purpose than to safeguard the truth that the God of Christian revelation does connect, and connect immediately, with the lives and worship of Christians.
It is because of this immediate connection of the Trinity with our life and worship that this feast of the Trinity falls when it does: at the completion of our celebration of the death, resurrection, and ascension of Jesus, and of the outpouring of the Holy Spirit; for it is in that Paschal mystery that the triune God connects with us, that we encounter the one God as Trinity.
The question of a Trinity arises for us because of what must be said about who it is that encounters us in the person of Jesus. And what must be said is that, in the person of Jesus, God encounters us. It was only when theologians began to ask themselves, and very properly too, what this might mean, that difficulties arose. After much laborious argument, the Church came to the conclusion that when we say that we encounter God in Jesus we have to mean God in the strict sense of the term.
It is part of the job of the doctrine of the Trinity to acknowledge that the problems which arise from this way of speaking are real problems. Jesus is God, and the Father is God, there is only one God, but Jesus is not the Father. This is a very mysterious way of talking.
The point is not that we should be puzzled by it, but that we should realise that the puzzle arises in the first place because God has revealed himself to us, and that is what, or rather, who, Jesus is: the revelation of God's own self to us.
So the Trinity has this tremendous impact on the lives of Christians, that the one God in whom we believe is not a God who lies hidden, but a God who can be seen and heard and touched in the person of Jesus: a God who pours himself out in love for us.
Nor is it only in Jesus that God encounters us. When we pray, as Jesus taught us, for the coming of God's kingdom, when we long eagerly for the whole of creation to be set free from futility, from its bondage to decay, we testify, St Paul says, to the presence of Christ's Spirit within us, that Creator Spirit, who bears witness with our spirit that we are children of God, and co-heirs with Christ.
To talk about the Spirit in this way means that our creation as human beings will not be complete until we are partly divine, until the spirit we call ours is in fact the Holy Spirit of God.
We have now the first fruits of the Spirit, a pledge of future glory. In this Spirit we long for the glory that is to be revealed in us -- for the fulfilment of God's plan in creating us in his image and likeness. That glory, which is nothing other than the glory of the triune God, will be revealed to us not as something to be observed externally, but within our own humanity.
What God destines for us is to be caught up in his own glory, conformed by the Spirit to the likeness of Christ, wrapped in the Father's light. That is what we hope for and long for now, in the Spirit. That is what we believe now, in Christ: that the God of love pours himself out for us, gives himself to us so as to be part of our very being, to draw us into the impenetrable mystery of the life he has as Father, Son, and Holy Spirit.