The Trinity is So Simple, it's Hard to Explain!
The Holy Trinity is a tremendously difficult concept to explain. When I was in the seminary, we would sometimes jokingly refer to Trinity Sunday as “heresy Sunday” since it was the weekend when most newly ordained deacons would preach their first homilies. It was (and still is!) very hard to try to steer clear of all the incomplete and imprecise ways to speak about the relationship and activity of the Triune Godhead.
The basic concept that has always guided my reflection on the Trinity is that they always function together. For example, when God the Father creates in The Book of Genesis, The Son is also doing the work of creation as the Holy Spirit. In the Creed, we express this when we say that The Father, Son, and Holy Spirit are consubstantial – of the same substance as one another. While They are distinct Divine Persons, They are completely united in being and in action.
Ultimately, these activities are mysterious to us. But, while mystery can be puzzling to us, it is precisely the desire to experience a relationship with The One who beckons us forth yet eludes our complete understanding that increases our longing for Him. True love is often fashioned in longing for the other. Jesus, the Second Person of the Trinity and Word-Made-Flesh, deepens our understanding of God’s desire for us by giving Himself up to death so that our humanity might be caught up into the life of God Himself. He longs for us so much that God even mysteriously lays down his life so that we may come to live with and in Him!
At Mass, when we make acts of faith telling God that we believe in Him and that we love Him, even though we don’t quite understand the depth of that love, God responds by calling us deeper into relation with Him. How? This truly happens in the liturgy. More than just an empty external rite, the actions and prayer of the priest combined with the offering of the sacrifice of prayer by the people constitute a real exchange of love. This exchange is then consummated in our reception of Holy Communion — wherein the Triune God comes into communion with us and we with Him; a mystery to be sure! This perhaps is what causes St. John Vianney to exclaim, “If we really understood the Mass, we would die of joy.”