This is an excerpt from remarks on Trinity Sunday.

Today throughout the world the Church is celebrating the great Solemnity of the Most Holy Trinity, when the Church invites us pause in wonder to ponder the great mystery of the Triune God who has revealed himself as the centre of the universe and of history.

This feast places before us the central mystery of our Catholic faith: that God is one in his divinity but three in his persons. This is not some “added extra” to who God is. The Trinity is not some kind of “mathematics of the Deity” or puzzle. Without at least some grasp of the mystery of the Trinity we fall short, very short, of understanding who God really is. In fact, “God in his greatness cannot be anything but a mystery for us, yet he revealed himself.

Recently at confirmation at a local parish I asked the boys and girls “how many gods are there?” They all answered correctly, “one.” And then to the question, “how many persons?” they answered “three.”

Then I asked how many understood this. Most – a little to my surprise – hands shot up. “Lucky them,” I thought. Instead I said “this is a great mystery, who God is, and if we could understand him completely, then we would be God ourselves.”

But thanks to the Holy Spirit, who guides us to the whole truth of divine revelation believers can know, at least in a limited way, something about the inner life of God himself. There is one God in three persons. He is the Creator and merciful Father; he is the Only-Begotten Son, who died and rose for us; he is the Holy Spirit through whom “God’s love has been poured into our hearts” (Rom 5:5). We must admit that without Revelation, we would not know this. The mystery is simply too great, too unfathomable for us to grasp had it not been revealed.

There are some today who would not be upset if we dropped the Trinity from our belief. For one thing, they would say, it would help dialogue with the Jews and Muslims, who profess faith in a God who is strictly one.

Scripture tells us otherwise. His Name – “Love” – clearly expresses that “the God of the Bible is not some kind of primary deity closed in on itself and satisfied with his own self‑sufficiency but he is life that wants to communicate itself, openness, relationship.

Words like ‘merciful,’ ‘abounding in steadfast love and faithfulness’ speak to us of a relationship, in particular, of a vital being who offers himself, who in the words of Pope Benedict wants to fill every gap, every shortage, who wants to give and to forgive, who desires to establish a solid and lasting bond.

There is no such thing as love of nothing, a love that is not directed at anyone.  

Christians believe that God is triune because they believe in the revelation that God is love! If God is love, then he must love someone. There is no such thing as love of nothing, a love that is not directed at anyone. So we ask: Who is it that God loves so that he is defined as love?

A first answer might be that God loves us! But men and women have only existed for a few million years. Who did God love before that? God could not have begun to love at a certain point in time because God cannot change.

Another answer might be that before he loved us, he loved the cosmos, the universe. But the universe has only existed for a few billion years. Who did God love before that so that he can be defined as love? We cannot say that God loved himself because self-love is not love, but egoism, or, as the psychologists say, narcissism.

How does Christian revelation answer this question? God is love in himself, before time, because there is eternally in him a Son, the Word, whom he loves from an infinite love which is the Holy Spirit.