Three persons, one in being.
This principle for understanding the Trinity is drilled into the minds of all orthodox Christians. God is one in being yet three persons. The principle of three persons and one in being means that each of the persons is fully God: the Father is God. The Son, Jesus, is God. And so is the Holy Spirit.
Most of our attempts to grasp at this great truth only feebly explain how three can be one. Usually this is done by way of analogy. There are the simple everyday analogies, such as the three-legged stool and the shamrock. There are more profound analogies as well, such as St. Augustine’s insight that the memory, understanding, and will in the mind of a person are an imperfect image of the Trinity.
But we can take this line of thought one leap further.
Since each of the persons is fully God each is closely entwined with the other and even ‘abides’ or ‘dwells in’ the other. Jesus is in the Father. The Father is in Jesus. Because they have the same being or nature, the persons are not ‘outside’ each other but ‘inside’ or ‘abiding in’ each other.
This may sound strange, but it’s exactly what the Gospel of John says:
Do you not believe that I am in the Father and the Father is in me? The words that I speak to you I do not speak on my own. The Father who dwells in me is doing his works (John 14:10).
Likewise, Jesus declares:
Everything that the Father has is mine; for this reason I told you that he will take from what is mine and declare it to you (John 16:15).
The Holy Spirit is discussed in the same fashion:
But when he comes, the Spirit of truth, he will guide you to all truth. He will not speak on his own, but he will speak what he hears, and will declare to you the things that are coming. He will glorify me, because he will take from what is mine and declare it to you (John 16-13-14).
The late Church Fathers coined a unique term to describe this mutual interpenetration and indwelling of the divine persons: perichoresis. The use of the term in this context is typically traced back to St. John of Damascus, an eighth century Father. He described it this way:
The subsistences [persons] dwell and are established firmly [perichoresis] in one another. For they are inseparable and cannot part from one another, but keep to their separate courses within one another, without coalescing or mingling, but cleaving to each other. For the Son is in the Father and the Spirit: and the Spirit in the Father and the Son: and the Father in the Son and the Spirit, but there is no coalescence or commingling or confusion. And there is one and the same motion: for there is one impulse and one motion of the three subsistences, which is not to be observed in any created nature.
Just where does perichoresis come from? A popular explanation is that it derives from the Greek word for dance, whose root also led to our word chorus. As compelling an explanation as this is, the etymology is incorrect: in confuses two ancient Greek words that differ by one vowel. (For more on that, see here.)
Instead, perichoresis derives from perichōreō, which means to go around (sources here and here). This is a result of the prefix peri-, meaning around, and the verb chōreō, the word for making space or room or giving place, according to one lexicon. This verb, fittingly, is based on the noun chōra, defined as space or place. This etymology highlights the twofold meaning of the verb. As one author explains:
Therefore, [chōreō] in the meaning of space is conceived in the Greek language as she that receives and embraces everything, because basically the verb [chōreō] means to cede a place to or to make a room for something. However, someone might prefer to say that space is the greatest because it is the only thing that extends everywhere. [J]ust as the space can be perceived in two ways—now as something extending or spreading, and now as something receiving and containing—similarly, the verb [chōreō] also behaves in two ways. …
In other words, built into this idea of the Greek word for space is this dual notion of space extending everywhere and also receiving everything. This duality still is built into our English word space. We clean our homes to make space for someone or something. Space is also the great out-there, the infinite vacuum of the universe that holds all the stars and galaxies. (The addition of the prefix peri- seems to simply have underscored this notion of dual movement. My key source for the etymology and definition of perichoresis is here.)
In the context of the Church Fathers, perichoresis then could be defined as interpenetration and permeation: each of the persons penetrates into the other and fills Him completely. As the key source used here explains it:
[P]ermeation is a movement, for it is a process of penetration into something else and of extending itself in it (with the result of filling it completely), but at the same time it is receiving that into itself and holding it within itself.
Here we can see both the notion of space as expanding into something and the corollary notion of space making room for something else. In the context of Trinitarian theology, we could say that everything the Father has is in the Son—His divinity, His wisdom, His power, and so on. The fullness of the Father is in the Son—nothing is held back, otherwise, the Son would be less than the Father and less than true God, which would be heresy.
Conversely, the fullness of the Son is in the Father. Otherwise, the Father would have lost His wisdom and power in begetting the Son, which again would be heresy. (My emphasis on wisdom and power is intentional because it is very biblical and it is also touched upon by Sts. Thomas Aquinas and Augustine. See 1 Corinthians 1:24, On the Trinity, Book 7; and Contra Gentiles, Book 4).
Again, while this language may sound strange, it is firmly biblical. Again, John is clear on the mutual interpenetration of Father and Son. In John 17:1, Christ declares, “Father, the hour has come. Give glory to your Son.” Here is the notion of the Son receiving everything He has from the Father. But then Christ adds, “So that your Son may glorify you.” This last clause makes clear that the fullness of the Son is also in the Father. (Here, I am relying on the biblical understanding of glory as signifying the presence of God. For more, see here.)
Our familiar analogies of the Trinity—the stool, shamrock, and the tripartite mind—all deal with the issue of how three can be one.
But what about the question of how each of three can be in the other two? Is there another analogy—however inherently limited and feeble it must be—that could help us?
Here is one attempt: Think of music. There are the sheets of notes which a musician might read. But music can also be visualized on a computer screen, as a wave dipping up and down or a series of bars bouncing up and down. Then of course, there is the sound of the music itself. (I’m indebted to a scientist for this analogy, who applied it to a different question.) Each of these three is in the other. The sound is expressed in the visualization and the notes. And again: the notes are in the sound—certainly a discerning ear could pick them out.
Everything that is in the notes is in the visualization. And everything that is in the sound is coded in the notes. Yet they are distinct: no one would confuse the written notes for the sound, or the visualization for the written notes.
So there are these three: the sheet music, the visualization, and the sound. Each ‘interpenetrates’ and ‘permeates’ the other. But, of course, there is one ‘thing’ or ‘substance’: the music.
The truth of the Trinity is indeed a sort of divine music that calls out to us and captivates us. May we become ever more enchanted with its beauty as it draws us ever closer to the triune God.
