The Holy Trinity, the God of Christianity, is complex. Clear language must be used and clear thinking deployed to grasp the Christian God. There are no backyard garden statues of the Holy Trinity like there are of Saint Francis of Assisi, because the Trinity is cerebral in a way that Saint Francis is not. On this solemnity, we celebrate the dogma of all dogmas because dogma matters. We sing songs to dogma, put flowers on the altar to dogma, and wear our best clothes for dogma. The Church’s thinking about God is not child’s play. Once we accept thoughts, they own us. At some point we no longer choose our thoughts, they choose us. So we must get God right so that we get everything else right—marriage, family, work, love, war, money, philosophy, humor, religion, fun, sports, etc. Bad people can be forgiven, but bad ideas less so. And bad ideas about God are dangerous. They caused skyscrapers to crumble to the ground. 

The Church believes that God is one in His nature and three in His persons. This means that if you were in a pitch black room and sensed a presence nearby, your first question would be “What is that?” “Is it the dog or the cat, my spouse, or the wind?” If it were God in the darkness, He would answer the question of “what” by saying “I am God.” Satisfied that the presence was a person and not an animal or the wind, the next question would be “Who are you?” And to that question, God would reply in three successive voices: “I am the Father. I am the Son. I am the Holy Spirit.” A nature is the source of operations, but a person does them. A statue has eyes but it is not its nature to see. It is not man’s nature to lay eggs or to breath under water, but it is the nature of a bird or a fish to do so. Our nature sets the parameters for what actions are possible for us. The daughter of a lion is a lioness and does what lions do. The son of a man is a man and does what men do. And the Son of God is God and knows and loves and acts as God does—perfectly. 

Our Trinitarian supernova is both a unity and a plurality, both one and many at the same time. This means that God does not exist alone but in a community of love. God is not narcissistic, admiring his own beauty and perfection. Instead, the love of the Father is directed toward the Son for all eternity. And the love of the Holy Spirit animates, and passes between, the Father and the Son. The Trinity’s three persons do not share portions of the divine nature, they each possess it totally. This theology means, by extension, that because man is made in the image and likeness of God, every person is created in order to model the Trinity by living with, and for, another, just as God does in His inner life. Because God is a Trinity of persons, then, His perfection is more fully embodied by an earthly community, such as a family, rather than by a lone monk.

The Trinity is not just scaffolding which obscures the true face of God. Nor are the Father, the Son, and the Holy Spirit three masks which conceal the one face of God. The one God exists as a Trinity. The Church’s belief in God and the Church’s belief in the Trinity stand and fall together. The Trinity is not just the summit of our faith, something we work toward understanding, but also our faith’s foundation. The truth of the Holy Trinity is learned early and often. Our God, distinct in His persons, one in His essence, and equal in His majesty, is solemnly invoked as the water spills on our heads at Baptism and as the oil is traced on our palms at our anointing. God, in all of His complexity and in all of His simplicity, is with us always in this world and, hopefully, in the world to come. 

Most Holy Trinity, we look to your three persons as a model of true love, knowledge, and community life. Help all marriages and families strive for the high ideal of perfection you set before the world, no matter the discouragement resulting from our sins and imperfections.

https://mycatholic.life/saints/saints-of-the-liturgical-year/first-sunday-after-pentecost-holy-trinity--solemnity/