Gloria tibi, Trinitas aequalis, una Deitas!

Benedicta sit sancta Trinitas atque indivisa unitas:
Blessed be the holy Trinity, and undivided unity:

Te toto corde et ore confitemur, laudamus atque benedicimus:
tibi gloria in saecula!

With all heart and voice we confess, praise and bless You:
to You be glory forever!

Fr Geoffrey Preston, OP, in his book, 'Hallowing the Time', offers some thoughts for today's great Solemnity and encourages all to celebrate the One whom we worship, love and serve, to delight in the mystery of the Triune God and to experience God as Father, Son and Spirit:

"In the Dominican tradition Trinity Sunday is the day when the brightest theologian in the house, the Regent of Studies, the 'primus doctor', preaches the sermon at the liturgy of the brethren. How quickly that can lead to talk about talk, to use words to say what are the appropriate words to use about the Blessed Trinity. For today's feast is a feast of orthodoxy, a celebration of the correct ways of talking about the God who can scarcely be talked about. Here at least lie the origins of the feast in the Calendar, for St Thomas Becket introduced it at a time when theology in England was vigorously alive, when people loved to talk about the central concerns of the faith and about none more than the Trinity, and when the theology of the triune God was again attracting the attention of brilliant minds after lying dormant for centuries. The feast of the Trinity was a feast for the theologians in the narrow sense, an occasion for the bright boys to let go.

It would be a pity to underplay that by underestimating the importance of right belief. What a man believes is not incidental to how a man lives, granted always that it is a question of what a man really and truly believes and not purely and simply of what he is prepared to say he believes. How you live depends in fact on what you really believe, on what you are prepared to put your trust in, and to stake yourself on. Perhaps it is all to the good that once in a while we should celebrate not, as in the usual Christian tradition, some concrete historical event which has changed our lives but simply the One who is the source of those events. Gently contemplating him in whom we put our faith we can let the words we utter about the Three-in-One and One-in-Three bemuse and bewitch us. We can deliberately let ourselves get lost, once in a while, in the paradoxes of the language of orthodoxy, for going beyond reason is part of the significance of 'metanoia', repentance.

Christianity is an historical religion through and through. It is concerned with the events God has brought about for our well-being, as St Thomas would say, to make us happy. For us and for our happiness the Word of God became a man of flesh and blood, altogether one of us. That is what we celebrated at Christmas and on the Epiphany. For our sakes too, the Word of God made flesh was crucified, suffered death and was buried in the time of Pontius Pilate. This is what we commemorate in Holy Week. Then for our well-being the Word who had become man and who had been killed was raised again in the Holy Spirit from amongst the dead. We celebrate that in the fifty days of Easter. And then, so that we might be fully happy, the Father sent the Spirit through the Son. That is what we concern ourselves with at Pentecost. But when we keep Trinity Sunday it seems that we are not really being encouraged to remember anything in this way at all. You can only remember what is, in one sense at least, in the past. Today we concern ourselves instead with what happens in time out of time. We look to how God happens, to how God is in himself. It is true that we could never know how God is in himself if we knew nothing of what he had done, but knowing that, we do know God in himself. There is nothing extraordinary about that condition of knowing God. After all, we only know what one of our fellow men is like by looking at what he or she does. Through this characteristic behaviour of God we rejoice to know that he is good and loving and true. Deeper still, in how God is God, we delight in the mystery of his being Father, Son and Holy Spirit.

A mystery, we are told, is beyond reason. That suggests that the more we reason the closer we approach it, although it always lies on the further side. But that is not the meaning of 'mystery' in this context. Of course we have to try and understand as thoroughly as possible what it is we believe. We have a duty laid on us to love God with all our mind, as well as with all our heart and soul and strength. But while problems are there to be solved by brain-power, mysteries are to be lived with, lived from and lived out... The Trinity, on the other hand, is a mystery which cannot be solved for there is no problem about it. It is too flat a view of reality which assumes that all we encounter in life are problems to be solved. People, for instance, may have problems yet people are not problems. Every human being is a mystery in his or her own right, and woe betide us if we treat other people or ourselves as jumbles to be sorted out. We have always to live with one another as people beyond our control and manipulation. And equally, we have always to live with ourselves as the mystery which we are... As for each human being, so for the origin and ground of all things, for God. That off-putting language about 'one and three, persons and natures' is there to remind us that we must not attempt to solve the Trinity as though God were a problem. We are being told, in the classical formulae of Christian faith, that we have to say apparently contradictory things about God if we are to get anywhere near the truth...

Our best approach [may be] to live with the experience we are baptized into sharing, praying to the Father, with the Son, in the Holy Spirit and leaving it to the threefold Lord to show us in the future how his name is one. As the Athanasian Creed has it: 'Now the Catholic faith is this - that we worship one God in Trinity and Trinity in Unity.'"

The images above, all from my own collection of photographs, show artistic attempts to depict and teach this divine mystery of the Trinity: the stone relief from St Paul's church in Salamanca, the 'shield' of the Trinity in stained glass from All Saints' church in Cambridge and the illumination by the Dominican illuminator, John Siferwas, taken from the 15th-century Sherborne Missal.