While Augustine was working on his book “On the Trinity,” he was walking by the seaside one day, meditating on the difficult problem of how God could be three Persons at once.

He came upon a little child. The child had dug a little hole in the sand, and with his hands was scooping water from the sea into a small hole he had dug into the sand. Augustine watched him for a while and finally asked the child what he was doing. 

The child answered that he planned to empty the sea into the hole he had dug in the sand. “What?” Augustine said. “That is impossible. Obviously, the sea is too large to empty into that small hole”

“Indeed,” said the child, “but I will sooner empty the sea into this hole than you will succeed in comprehending the mystery of the Holy Trinity with your limited, human understanding.” 

And vanished.1

The story teaches us that the reality of the Triune God is mysterious beyond comprehension. However, it’s not beyond defense.

In this post, we will defend the reasonability of God’s Triune nature by employing an analogy.2

Pens and Persons

God must be One, there is no doubt. The Catholic Church has never claimed otherwise.

But God is also three. And here’s why. 

To begin, let’s take a pen. I can see the pen on the table in front of me; not only with my eyes, but also in my mind, by imagining it. If I close my eyes and picture the pen, the picture doesn’t do it justice. It doesn’t do it justice because there are things about the pen that I just can’t imagine.

For example, I can’t imagine the pen in all 3 of its dimensions (pictures are 2D), nor can I “picture” its weight. But the pen on the table does have 3-dimensions and does have a particular weight. Thus, my image of the pen is imperfect. 

But, if my imagined pen was perfect, then it would be a pen.

I would be able to take it out of my mind and write with it because there would be nothing missing in the mental-pen that is also in the pen setting on the table.

Analogously, when God thinks about Himself, that thought is perfect. And being perfect, the thought does not lack anything to be found in God. Hence, the thought itself is God.

Yet, it is also distinct (as thoughts are distinct from their thinkers), as well as contained within the One (since thoughts remain within their thinkers).

Thus far, we have discovered Two within the one God: “Two” of what though? 

Taking the usual definition of a person (an individual substance of a rational nature), then these “Two” are, at the very least, personal.

Therefore, we arrive at two persons within the One God.

The Word

Who is this second person? We know by revelation that He is called the “Word,” which makes a lot of sense because a mental word is a thought, and since words must come from someone, even here, we see the unity as well as distinction within the One.

Scripture illustrates this unity and personal distinction in the prologue of St. John’s Gospel:

In the beginning was the Word, and the Word was with God, and the Word was God…(John 1:1) (emphasis added).

Now, two persons imply a relationship, and because God is perfect, this relationship must also be perfect; and, as we know from experience, the most perfect relationships are loving ones.

Moreover, since love is “willing the good of the other,” and a perfect love wills a perfect good, then the “willed good” between these two persons must also be perfect: namely, God—the third person within the One. 

This third person, “shared” and “exchanged” within the One God, is termed, by Divine revelation, the Holy Spirit.

The Holy Spirit is “Holy” because it is God. It is termed “Spirit” to invoke the similarity between this Person and the breath shared between lovers. Spirit also evokes the notion of movement, since love tends to move those held captive by it.

In essence, if God knows Himself perfectly, then that knowledge must also be God: distinct and yet contained within the Knower. Moreover, if there are two persons within the One, then there is a relationship; a perfect relationship shares perfect love, which must also be, itself, God. 

Food For Thought

Such is a way to defend the reasonability of the Trinity by analogy (albeit no analogy comes close to capturing the Triune God), and it goes without saying that one cannot deduce the Trinity from natural reason. 

Yet, with what we can grasp, let us rejoice in the Triune mystery, and meditate on its implications for our lives. To help us do so, we close with this short reflection from Joseph Ratzinger:

To him who believes in God as triune, the highest unity is not the unity of inflexible monotony. The model of unity or oneness toward which one should strive is consequently not the indivisibility of the atom, the smallest unity, which cannot be divided up any further; the authentic acme of unity is the unity created by love (Introduction to Christianity, Chpt. V, T.1).

This reflection is inspired by, and partly indebted to Frank Sheed’s, “Theology and Sanity.”

1. Story adapted from medievalists.net.

2. Although, we can’t actually prove that God is Triune by reason (see the first Aquinas quote below), reason can make some legitimate strides (see the second quote).

Therefore, by natural reason we can know what belongs to the unity of the essence, but not what belongs to the distinction of the persons. Whoever, then, tries to prove the trinity of persons by natural reason, derogates from faith in two ways. Therefore, we must not attempt to prove what is of faith, except by authority alone, to those who receive the authority; while as regards others it suffices to prove that what faith teaches is not impossible (ST., I, Q.32, A.1).

In the Platonic books also we find, “In the beginning was the word,” not as meaning the Person begotten in God, but as meaning the ideal type whereby God made all things, and which is appropriated to the Son. And although they knew these were appropriated to the three persons, yet they are said to have failed in the third sign—that is, in the knowledge of the third person, because they deviated from the goodness appropriated to the Holy Ghost, in that knowing God “they did not glorify Him as God” (Rom. 1:21)(ST., I, Q.32, A.1, R. 1).


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