Mystery of the Trinity Part 1

Part 1: Knowing God and the Limits of Reason

Discussing God is never easy. He is not like anything else we know. All of our knowledge comes from the created world, through our senses and experiences. But God is not a creature. He is not part of the world. He is wholly other, and so our ability to speak about Him must be both careful and humble.

Still, that does not mean we can say nothing. On the contrary, reason can tell us much about God, though only what God is, not fully who God is. For that, we need revelation.

What We Can Know by Reason

St. Thomas Aquinas teaches that we cannot know God's essence directly, because our intellect begins with sense knowledge. But we can know that God exists, and certain things about Him, by reasoning from creation. We can see that there must be a necessary being, one who is pure act, utterly simple, uncaused, and infinite.

From these starting points, we can say with certainty that God is one. He cannot have parts, limits, or imperfection. He is Being Itself- ipsum esse subsistens- the fullness of all that is. Reason can tell us a great deal about God's attributes, and can even show that they are coherent and necessary.

But this knowledge is still limited. It tells us what God is in relation to creation, not who God is in Himself.

The Need for Revelation

There is a difference between natural theology and sacred theology. Natural theology considers what reason can discover from God's effects. Sacred theology begins with what God Himself has revealed: truths that go beyond reason’s grasp.

The Trinity is one of these truths.

No amount of reasoning could ever demonstrate that the one, infinite, simple God exists as three persons. That reality does not follow from God's effects, and is not evident in nature. But once it is revealed, reason can show that this mystery does not contradict what we know about God. In fact, it opens up a deeper understanding.

The God Who Reveals Himself

The Catechism reminds us that God has revealed the mystery of the Trinity for our salvation (CCC 257). He did not have to. He could have remained hidden, known only as Creator. But out of love, He chose to show us not only what He has done, but who He is from all eternity.

The Trinity is not a theory about God’s behavior. It is a revelation of God's own inner life, a communion of love between the Father, the Son, and the Holy Spirit. These are not roles or masks, but real persons, eternally distinct, yet sharing one divine essence.

God is not a solitary being who only begins to love once the world is made. He is, in Himself, a communion of love, eternally knowing and loving within the mystery of three persons.

Reason’s Role After Revelation

Although we cannot arrive at the Trinity by reason alone, that does not mean reason is useless. On the contrary, reason helps us avoid error, deepen understanding, and clarify what the Church teaches.

• Reason affirms that the Trinity is not illogical, even if it is mysterious.

• Reason shows how three persons can share one nature without division or confusion.

• Reason helps us speak about God in true and meaningful ways, even if analogically.

The more we understand God’s nature, the more we can see how divine simplicity does not conflict with the distinction of persons, and how the eternal processions of knowledge and love form the basis of divine personhood.

Looking Ahead

In the next part of this series, we will clarify what we mean by essence, nature, substance, and person. These are not technical distractions, they are necessary tools to speak meaningfully about the Trinity.

The Church does not ask us to explain the Trinity, but to confess it. And in confessing it rightly, we draw closer to the One who is not only truth, but love.

“O most blessed Trinity, Father, Son, and Holy Spirit, we praise You and glorify You, for You have revealed Yourself not only as Creator, but as eternal Communion.”