Well, it’s Trinity Sunday, our annual chance to hear how poorly catechized our priests are. This year the priest was a really good one, but the homily was just as bad. Sure we should live in unity as the Father Son and Holy Spirit live in unity. But (a) if we don’t know what the Trinity is, we have no idea what it means to be like them, (b) that’s not the point of the feast, and (c) the point of John 17 is that we are bound together because we have entered into the life of the Trinity. If we’re not interested in the Trinity in itself, than there’s no point talking about sharing in Trinitarian unity.
So here’s six points to ponder on Trinity Sunday.
(1) Trinity Sunday is the octave of Pentecost. It is the culmination of that feast, not just a random Sunday in the year.
(2) Trinity Sunday is about God. Given than the Trinity is no more or less than the Christian doctrine on God, it wouldn’t hurt to think of this as “God Sunday.” This is the one time of the year that we are specifically enjoined to think about God himself. In traditional Catholic spirituality, from the Eastern mystics of the first millennium to the Spanish Carmelite mystics of the second, the Trinity is seen as the goal of our faith. This is not something to skim over on our way to more interesting things. The Trinity is the height of contemplation, and Trinity Sunday is the Sunday specifically given to contemplation. Homilies are supposed to make doctrine practical, to be sure. But the practical application here is prayer. Christianity without contemplation—and a Christianity that can never once, even on Trinity Sunday, think about God in himself—is no Christianity at all. That’s the point of the feast.
(3) We have only the faintest idea what Trinity, three-in-one, means. That implies, first of all, that we shouldn’t use the Trinity as a jumping-off point for other metaphors. We don’t say, for example, that since the Trinity is three-in-one, our families and communities should be too! We don’t know what that means! Above all, what should be stressed on Trinity Sunday is that God is beyond our grasp. Trinity means that God is not domesticated, not within our ken. Intelligible, to be sure. But not to us. Trinity Sunday is our time to realize that God is greater than the limits of our minds.
(4) Trinity Sunday is Christological. Historically, the doctrine of the Trinity arose out of controversies about the person of Jesus. Is he less than God? Sort of like God? A separate God? Just the one God sort of doing a new thing? No, Jesus is the eternal Second Person of the Most Blessed Trinity. It is surely very hard and obscure to preach about how God is three in one. But this is not so hard to preach about. Jesus is God. He is the Son of God, and equal with God, and one in being with the Father . He was in the beginning with God. To talk about the Trinity is to talk about who Jesus is in his most deepest self, in his divinity. And to talk about who Jesus is is to talk about the Trinity. Jesus is God: there's a good homily.
(5) Trinity Sunday is about the Holy Spirit. Everything said about Jesus goes for the Holy Spirit too. In this sense, Trinity Sunday is about soteriology. Jesus can reconcile us to God because he is God. If he were less than God, he could not bring us into full contact with God. And if he were just the One doing something new, instead of an eternal person within the Trinity, there would be no relation to enter into: we would either have to melt into the sheer unity of God, or stay utterly removed. To say Jesus is the Son of God is to say that we can enter into divine sonship: that we can be divinized, as the Eastern Fathers say (and St. Thomas repeats). If you can't preach about this, you can't preach about Christianity, because divinization is Christianity. This is what it's all about.
How are we divinized? Jesus sends his Spirit, who dwells in our hearts. And like Jesus, that Spirit is not something less than God, nor some emanation of God, but God himself. The Trinity means that the Spirit who dwells in our hearts is God himself: and so we are elevated into the life of God. This is not abstract, and this is not obscure stuff about doctrines that don't effect us and that we can't understand. Real preaching about the Trinity is preaching about divinization, about the Spirit bringing us into conformity with Christ so that we can enter into the life of the Trinity. If, as John 17 says, we are to be one as the Father and the Son are one, it is only because we are to enter into that very Trinitarian life, through the Spirit dwelling in us.
And so, to return to the first point, Trinity Sunday is the culmination of the Pentecost octave. On Pentecost Sunday we celebrate a historical event, the opening of the apostolic age. We celebrate the manifestation of the Spirit through charismatic gifts. But on the octave, we celebrate the deeper meaning of this manifestation. We celebrate that what we receive is not just the gift to speak in foreign tongues, or to heal, or to preach, or to be caught up in some ecstasy. We receive the very life of God himself. This is the heart of Christianity. It's a shame no one's told our priests.