Sermon for Trinity Sunday

The curious thing about Trinity Sunday is that it’s one of the few festivals in the Church calendar that celebrates a doctrine. Many feasts of the liturgical year commemorate events recorded in Scripture – and very often on the date or during the season of the year when we believe them to have happened. Easter falls in the spring around Passover, the time of year when Jesus died and rose again. And following the New Testament chronology exactly, Ascension comes forty days and Pentecost fifty days after Easter.

The date of Christmas is admittedly arbitrary, and appropriately occurs on the date of an old Roman midwinter holiday celebrating the triumph of light over darkness around the time of the winter solstice. But then the Church coordinated the dates of the Annunciation, the Visitation, and the Nativity of Saint John the Baptist to fit in chronologically with the putative date of Christ’s birth at Christmas. Likewise, we keep most saints’ days on the anniversary of the saint’s death: his or her “birthday into heaven.”

But Trinity Sunday is different. We could really observe it at any time of the year, for the mystery it celebrates is timeless. Such events as the Birth of Christ, the Baptism of Christ, and the descent of the Holy Spirit at Pentecost all represent definite historical moments in God’s revelation of himself to his people. For this reason, theologians sometimes speak of the cumulative record of these moments as “salvation history.” But there is no single historical moment when God revealed himself as Trinity. Rather, over several centuries of sustained reflection on the biblical revelation, the Church developed the doctrine of the Trinity – as summarized in the Nicene and Athanasian Creeds – as the only way of speaking about God that could adequately account for the reality of people’s actual experiences of the Father, the Son, and the Holy Spirit.

So, why do we celebrate Trinity Sunday when we do? The reason is simple: For the past six months, from Advent Sunday through the Day of Pentecost, we’ve been retracing the history of God’s self-revelation to his people, from the preaching of the Old Testament prophets, through the Incarnation, death and Resurrection of Christ, to the outpouring of the Holy Spirit upon the Church. Today, we step back and do precisely what the early Christians did: we reflect on what we’ve learned. And the whole history of revelation that we’ve been recapitulating these past six months adds up to this picture of the Triune God given expression by the Trinitarian doctrine.

The word Trinity never occurs in Scripture. It appears to have been coined by the Second Century Roman theologian Tertullian. But the Christians of the first four centuries found that the doctrine made sense of so much: such as the threefold “Holy, Holy, Holy” of the cherubim in the vision of Isaiah; and God’s strange use of the first-person plural in the opening chapter of Genesis: “Let us make man in our own image.”

Most important of all, the doctrine of the Trinity helped the early Christians understand the words and actions of Jesus, who was himself God Incarnate and yet spoke of his Father in heaven and of the Holy Spirit he would send down upon the Church after his Ascension. Moreover, Trinitarian language helped them make sense of their own experience of God: for at one and the same time they had a vivid sense of God as their heavenly creator and father; of Jesus as their Lord, Savior, friend, and brother; and of the Holy Spirit as the guiding and empowering divine presence within. God was indeed one in being, and yet had revealed himself as three Persons.

A good exercise on Trinity Sunday, rather than trying to resolve the paradox of how God can be one and three at the same time, is to ask ourselves how we’ve experienced the three Persons of the Trinity in our own spiritual lives: In what ways have we known God as our Father in heaven; as Jesus our Savior; and as the Holy Spirit who indwells us and gives us inner counsel and strength?

Most of all, the doctrine of the Trinity speaks to us of God’s very nature and being as love. Our God is not a solitary monad subsisting in splendid isolation, but rather a community of three Persons eternally united in mutual relations of perfect self-giving love. And because God has created us in his image, it follows that we find the fulfillment of our nature not in rugged individualism, but rather in relationship and community. In other words, because God is love, we realize our God‑given purpose in life by learning to love and to be loved! And our eternal destiny in Christ is to be caught up forever into that perfect circle of divine love that is God’s own inner life.

So, Trinity Sunday remains a superb way to wrap up and summarize the completed cycle of the liturgical year before we move into Ordinary Time. And it invites us to celebrate the most unique aspect of the Christian revelation: our faith in God who is one in three and three in one, whose very nature and essence is love.