Theory of everything: How Trinitarian love explains the whole Christian faith
[Homily for the Solemnity of the Most Holy Trinity, 2025]
One Sunday each month, the duty of preaching all the homilies at all the Masses here at Our Lady of Sorrows falls to my brother deacon Walter and me, and our priests get a break from preaching. This month it just so happens that the Sunday our priests left the preaching duties to us deacons is … Holy Trinity Sunday. Hmm. (sidelong look at priest celebrant)
Now, I’m kidding! Far from having any kind of anxiety about preaching the Holy Trinity, which I guess is a thing, years ago I said that that if I had to choose just one topic to preach about for the rest of my life, I would pick the Holy Trinity and it wouldn’t be close! This is not because I just have so much love for theological mysteries that defy our understanding: one God in three Persons, Father, Son, and Holy Spirit. Rather, it’s because the Holy Trinity is the key that unlocks literally every other aspect of our faith. It’s like C.S. Lewis’s famous remark about the sun: While we can’t directly see the sun, by the sun we see everything else. In a similar way, no one can fully understand the Trinity, but without the Trinity we can’t begin to make sense of the rest of the Catholic faith!
I’m sure many of you have heard the saying that you don’t really understand a thing if you can’t explain it simply—like, to a child. Often credited to Einstein, or some other scientist, and you see this in science: the deeper you go, the more unified things become. Without getting too far into the weeds—I want to avoid weeds today—physicists tell us that all known physical processes can be explained in terms of just four fundamental forces, and one of the great goals of physics is to try to explain all four forces in a single, unified theory, a theory of everything. (Stay tuned!)
What does this have to do with the Holy Trinity? Well, let’s begin with the most basic and practical of religious questions: What does God expect of us? How should we live? What does it mean to be a good person? This question was of great interest in Jesus’ day, and attempts to answer it could get complicated. As some of you may be aware, according to Jewish tradition, if you total all the commandments in the Torah, the law of Moses, there are 613 of them. That’s a lot of commandments!
Now, throughout the Old Testament scriptures you see efforts to express God’s will more simply. For example, the Ten Commandments, which both Jews and Christians have traditionally used as a framework for all moral questions. But are even ten commandments simple enough? The Old Testament prophet Micah famously summarized God’s expectations in three ideas: Do justice; love mercy; walk humbly with God. Three. That’s pretty good.
Our Lord Jesus does it in one. Just one thing God wants of us. He formulates it in two commandments: Love the Lord your God with your whole being, and love your neighbor as yourself. But this is fundamentally one commandment, as St. Augustine daringly put it: “Once and for all, I give you this one short command: love, and do what you will.”
Now, the love Augustine refers to is divine love, spiritual love, the love that Latin writers like Augustine called caritas, or charity, and the New Testament writers called agape in Greek. This love is not just a feeling; it goes beyond emotions and passions. It is radically unselfish; it actively wills the good of the other; it is gift of self to the other; it embraces the other and welcomes the other’s embrace. This kind of love doesn’t come naturally to us; it’s a supernatural gift of God, a theological virtue, a fruit of the Holy Spirit, and we who have received this gift are called to grow in it all our lives.
Love like this is not just what matters most; it’s literally all that matters. Why? Why is this? Why is agape love the be-all and end-all of Christian ethics? Saint Augustine answers in the same homily: Because God is love. The New Testament teaches that in 1 John. And what does it mean to say that God is love? Ah, now we’re talking about the Trinity.
Love is relationship. Love exists between persons. We believe in one God. We also believe that God is love, which is to say, God is relationship, God is a divine community, an eternal society, which Christ, the Scriptures, and the Church teach us to name as Father, Son, and Holy Spirit. What exactly it means to say “one God in three Persons,” and how we explain that theologically and philosophically, are very important questions that I am not going to pursue today. More weeds I’m not getting into! My burden today is simply that this most central and most mysterious of dogmas is what makes sense of everything else in the Catholic faith. Because only the Triune God is love.
I’m holding a copy of the Catechism of the Catholic Church—800 pages long, over 2800 numbered paragraphs, 250,000 words, thousands of indexed topics. It seems our faith is very complicated! But the Catechism organizes all of this content into four major headings, or pillars:
the articles of our creed, the faith we will profess in a few moments;
how we worship in liturgy and sacrament, as we’re doing right now;
how we’re called to live in Christ out there in the world; and
Christian prayer.
Four pillars. That doesn’t seem too bad. But these four pillars are not separate, unrelated things. It’s all one thing: it’s all love. Trinitarian love, gift of self, explains the whole Catechism. That’s our theory of everything!
Why did God create the heavens and the earth? Why did he create us in his image? Because God is love.
Why did the Son of God become human? Why does he feed us with his body and blood?
Why are marriage, family, and community so important? Why is it important to be here together on Sunday mornings?
Why are selfishness, tribalism, deceit, corruption, resentfulness, and indifference to the suffering of others so corrosive to the spirit?
Why is the duty to forgive so essential?
How do we dare to call the unfathomable Creator of the heavens and the earth “Our Father”?
What is the eternal happiness to which we aspire, that we call heaven?
So many questions; just one answer: Trinitarian love. The Triune God is love. This explains everything.
Pope Leo XIV, in his Pentecost homily last week, proclaimed that the Holy Spirit teaches us
before all else the commandment of love that the Lord has made the center and summit of everything. Where there is love, there is no room for prejudice, for “security” zones separating us from our neighbors, for the exclusionary mindset that, tragically, we now see emerging also in political nationalisms.
Pope Leo speaks in this homily about the Holy Spirit “opening borders” in our hearts, in our relationships with others, and between people. Where love unites us and we “view others as our brothers and sisters,” he says,
differences no longer become an occasion for division and conflict but rather a shared patrimony from which we can all draw, and which sets us all on journey together, in fraternity.
Look around at our divided world, our troubled Church, our suffering families, our divided hearts. We have our work cut out for us. The love of the Holy Trinity calls us all to unity and harmony, as individuals, families, communities. One Church, one human family on earth. The obstacles may seem insurmountable, but love never fails. In this Jubilee Year of Hope especially, we are called to “journey together” in hope—and “hope does not disappoint.”
We gotta good pope. If Francis hadn't found him, we wouldn't have him.
Wonderful, Steve; thank you!