The Trinity

The doctrine of the Trinity is very important in Christianity. But people who are not Trinitarians, even non-Trinitarians who believe in the Bible and in Jesus, might wonder, what’s the reason for believing in the Trinity? Is the idea of the Trinity motivated from Biblical texts or was it something that came out of Greek philosophy or Greek culture in early Christianity? How did Christians come to understand things in this way? And why has this understanding persisted in Christian history?

With this episode I’d like to get into some more systematic theology. In a previous episode I went over the nature of God as it has been formulated in the theological and philosophical tradition of classical theism. The topic of this episode, the Trinity, is also about the nature of God but more especially about the uniquely Christian understanding of the nature of God as the triune God, God as Trinity: Father, Son, and Holy Spirit.

The doctrine of the Trinity is very important in Christianity. But people who are not Trinitarians, even non-Trinitarians who believe in the Bible and in Jesus, might wonder, what’s the reason for believing in the Trinity? How did Christians come to understand things in this way? And why has this understanding persisted in Christian history? Is the idea of the Trinity motivated from Biblical texts or was it something that came out of Greek philosophy or Greek culture in early Christianity? Or even more basic, what is the doctrine of the Trinity, really? I think these are good questions and quite common questions. So it’s a topic worth looking at.

I’ll go through this topic in seven sections: (1) a definition of the Trinity, (2) some misinterpretations of the Trinity, (3) the scriptural motivation for the doctrine of the Trinity, (4) some of the cultural and philosophical background, (5) some useful theological terms, (6) some history of the development of the doctrine, and (7) the significance of the doctrine of the Trinity to the whole Christian faith.


One definition of the Trinity I think is quite good is one with the following seven parts.

The Father is God.
The Son is God.
The Holy Spirit is God.
The Father is not the Son.
The Son is not the Holy Spirit.
The Holy Spirit is not the Father.
There is only one God.

I picked up this definition from Phillip Cary in his Teaching Company course The History of Christian Theology. And he adapted this from Augustine of Hippo (354 – 430). This definition is quite straightforward, I think. And we’ll see later how there are scriptural motivations for each of these statements. Each of the statements, taken individually, isn’t hard to understand. It’s trying to understand how they can all fit together that gets challenging. And that’s where a lot of the additional terms and concepts come in; like substance, persons, generation, and procession. But the most basic content of the definition, which all these other concepts are based on, consists of these very basic ideas. God is Father, Son, and Holy Spirit. Each of them is God. They are not the same person. And there is only one God.


That’s what the Trinity is. It’s also good to understand what the Trinity is not. There are two major misunderstandings of the Trinity, that make the mistake of either confounding the persons or dividing the essence. These two misinterpretations are modalism and tritheism.

Modalism is the view that the Father, Son, and Holy Spirit are all the same person. That each is merely a mode that God can take on. One proponent of this view in history was a man named Sabellius in the third century A.D. So this idea is also sometimes called Sabellianism. I think this is a pretty common misunderstanding of the Trinity, for both non-Trinitarians and even many Trinitarians. It’s easy to see where this comes from. If there’s only one God and the Father, Son, and Holy Spirit are God, then just say they’re all the same person. But this is quite clearly scripturally untenable, as we’ll see in the next section. We shouldn’t try to imagine that Jesus prayed to himself or spoke of himself in the third-person as if he were his own Father.

Tritheism is the view that there are three Gods: the Father, Son, and Holy Spirit. It’s also easy enough to see where this comes from. If the Father, Son, and Holy Spirit are God, then just say there are three Gods. But this is also quite clearly scripturally untenable. Monotheism is one of the most emphatic teachings of both the Old and New Testaments. Granted, the Ancient Israelites were not very good at following this and were almost irrepressible relapsing polytheists. But the prophets of the Lord were uncompromising and zealous monotheists, continually reproving the people and calling them to repent and to forsake polytheism. While there are other divine beings like angels in the Bible, they are subordinate to the one creator God. There’s no room for three such capital G Gods in the scriptures.

Scriptural Motivation

More than any other source, more than tradition, reason, or culture, the most important and authoritative source of doctrine in Christianity is in scripture. The doctrine of the Trinity is not explicitly taught in the Bible. But the doctrine is scripturally motivated. If we ask, “what is it that motivates Christians to formulate the doctrine of the Trinity?” we can find those motivations in scripture. It doesn’t come from nowhere.

There are two main groups of scriptures that motivate the doctrine of the Trinity. First, scriptures that affirm that there is only one God. And second, scriptures that affirm that Jesus is God. Other kinds of scriptures include those that affirm that the Father is God, that the Holy Spirit of God, and that they are not all the same person.

The most significant of the monotheistic passages is the Shema in Deuteronomy 6:4.

“Hear, O Israel: The Lord our God, the Lord is one!”

This is a kind of first article of faith for the religion of Israel. It’s the one Jesus called the first and greatest commandment (Matthew 22:38). The first of the Ten Commandments are similar.

“I am the Lord your God, who brought you out of the land of Egypt, out of the house of bondage. You shall have no other gods before Me.” (Exodus 20:2-3)

Among the Old Testament prophets Second Isaiah is especially emphatic in his monotheism:

Isaiah 43:12
“You are My witnesses,” says the Lord,
“And My servant whom I have chosen,
That you may know and believe Me,
And understand that I am He.
Before Me there was no God formed,
Nor shall there be after Me.”

Isaiah 44:6
“Thus says the Lord, the King of Israel,
And his Redeemer, the Lord of hosts:
‘I am the First and I am the Last;
Besides Me there is no God.’”

That’s the monotheistic foundation. One God, the Lord God of Israel. As we come to the New Testament we find passages of scriptures that indicate that this same God is actually three persons. After his Resurrection, at the moment of his Ascension, Jesus commissioned his apostles in Matthew 28:19.

“Go therefore and make disciples of all the nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit”

Interesting that it’s the name, singular, ὄνομα (onoma), of the Father, Son, and Holy Spirit, rather than the names. This baptismal formula calls for baptism in the name of the three persons of the Trinity. We see elsewhere that the three persons are invoked in blessing, as with Paul in 2 Corinthians 13:14.

The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Spirit be with you all. Amen.

In the scriptures Jesus doesn’t ever say explicitly, “I am God”. Some conclude from this is that the early Christians actually didn’t believe that he was God and that this idea developed later. I don’t think that theory works, but that’s another topic. Even without that kind of direct statement there are many reasons to conclude from the scriptures that Jesus is God.

The Gospel of John opens placing Christ at the Creation of all things in the prologue of John 1:1-5.

In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things were made through Him, and without Him nothing was made that was made. In Him was life, and the life was the light of men. And the light shines in the darkness, and the darkness did not comprehend it.

Paul also taught of an exalted origin when he quoted what appears to have been a very, very early Christian hymn about Jesus, in Philippians 2:5-11.

Let this mind be in you which was also in Christ Jesus, who, being in the form of God, did not consider it robbery to be equal with God, but made Himself of no reputation, taking the form of a bondservant, and coming in the likeness of men. And being found in appearance as a man, He humbled Himself and became obedient to the point of death, even the death of the cross. Therefore God also has highly exalted Him and given Him the name which is above every name, that at the name of Jesus every knee should bow, of those in heaven, and of those on earth, and of those under the earth, and that every tongue should confess that Jesus Christ is Lord, to the glory of God the Father.

That’s quite exalted language. The name which is abovery name. Jesus Christ is Lord. Lord is the word traditionally substituted for the name of God, YHWH. “Jesus is Lord” is probably the earliest Christian confession. Essentially another version of “YHWH is Lord”.

Paul has similarly exalted language for Jesus when he says in Colossians 2:9.

For in Him dwells all the fullness of the Godhead bodily.

In the Gospel of John Jesus makes a number of conspicuous “I am” statements, basically invoking the name of God as revealed to Moses in Exodus 3:14, “I AM THAT I AM”. For example in John 8:58.

Jesus said to them, “Most assuredly, I say to you, before Abraham was, I AM.”

And Jesus’ disciple Thomas actually calls him God in John 20:27-28.

Then He said to Thomas, “Reach your finger here, and look at My hands; and reach your hand here, and put it into My side. Do not be unbelieving, but believing.” And Thomas answered and said to Him, “My Lord and my God!”

In John Jesus also teaches about his oneness with the Father. In John 10:30.

“I and My Father are one.”

And in John John 14:9-11.

He who has seen Me has seen the Father; so how can you say, ‘Show us the Father’? Do you not believe that I am in the Father, and the Father in Me? The words that I speak to you I do not speak on My own authority; but the Father who dwells in Me does the works. Believe Me that I am in the Father and the Father in Me, or else believe Me for the sake of the works themselves.

This unity notwithstanding, it is clear from multiple instances in the scriptures that the Father and the Son are not the same person. For example at Jesus’ baptism in Matthew 3:16-17.

When He had been baptized, Jesus came up immediately from the water; and behold, the heavens were opened to Him, and He saw the Spirit of God descending like a dove and alighting upon Him. And suddenly a voice came from heaven, saying, “This is My beloved Son, in whom I am well pleased.”

The Father, Son, and Holy Spirit are all spoken of distinctly here. Jesus is also always praying to the Father, with no indication that he is in any way praying to himself. Even in their intimate unity there is distinction, as shown wonderfully in John 17:20-23.

“I do not pray for these alone, but also for those who will believe in Me through their word; that they all may be one, as You, Father, are in Me, and I in You; that they also may be one in Us, that the world may believe that You sent Me. And the glory which You gave Me I have given them, that they may be one just as We are one: I in them, and You in Me; that they may be made perfect in one, and that the world may know that You have sent Me, and have loved them as You have loved Me.”

These and other scriptures indicate that: there is only one God, that the Father, Son, and Holy Spirit are God, and that they are not all the same person.

Cultural and Philosophical Background

Christianity developed in a highly Hellenized, Greek-speaking environment. Even important Jewish leaders of early Christianity, like Paul of Tarsus, spoke and wrote in Greek and were immersed in Greek culture. The Jewish scripture for many outside of Judea was the Septuagint, a Greek translation of the Hebrew scriptures. An important Jewish theologian and philosopher of the time period, Philo of Alexandria (20 B.C. – 50 A.D.) wrote all his works in Greek and he was well-versed in Platonic philosophy.

There is a line of thought that Greek culture and philosophy was the real source of many Christian theological developments, rather than scripture. One prominent proponent of this view was Adolf Von Harnack (1851 – 1930). I happen to think this position is overstated and agree with Robert Louis Wilken that “the time has come to bid a fond farewell to the ideas of Adolf von Harnack” and that rather than positing the Hellenization of Christianity “a more apt expression would be the Christianization of Hellenism” (The Spirit of Early Christian Thought, xvi). Greek culture and philosophy are sometimes thought to have invaded and supplanted the original Hebrew foundation. But this world was already immersed in Greek influence, even the Jewish part of it. Certainly Jews and Christians drew from the ideas available to them in the surrounding culture, but in a way that was subordinate to and in the service of scripture. Robert Louis Wilkin made this observation of the writings of the Early Church Fathers:

“To be sure, many of the best minds in the early church were philosophically astute and moved comfortably within the intellectual tradition of the ancient world… But if one picks up a treatise of Origen or Basil of Caesarea and compares it with the writings of the philosopher Alcinous or the neo-Platonist Plotinus, it is apparent at once that something else is at work. For one thing… they turn always to the Bible as the source of their ideas. No matter how rigorous or abstruse their thinking–for example, in dealing with a complex and subtle topic like the distinctive identity of each person of the Trinity–Christian thinkers always began with specific Biblical texts. I have found that it is not possible to read the church fathers without the Bible open before me. The words of the Scriptures crowd the pages of their books and essays, and their arguments often turn on specific terms or phrases from the Bible. But one can detect something else in their writings, at once closer to experience yet more elusive. On page after page the reader senses that what they believe is anchored in regular, indeed habitual, participation in the church’s worship, and what they teach is confirmed by how they pray.”

This has also been my experience in reading the Early Church Fathers.

Something interesting that we get from Greeks are philosophical ideas that are quite amenable to monotheism, converging on a similar idea that we get through revelation in the Old Testament. Greek pagans, among the regular folk, were polytheists. But the more educated, intellectual, and philosophical Greek pagans tended to trace everything back to some single ultimate source. For Plato (c. 428 – c. 348 BC) this was The Good, for Aristotle (384 – 322 BC) this was the Unmoved Mover, for Plotinus (c. 204 – 270 AD) this was The One. Both reason and revelation pointed to the reality of a single first principle or God over all things. Early Church Fathers well-versed in both scripture and philosophy, like Justin Martyr (100 – 165), Origen of Alexandria (185 – 253), and Clement of Alexandria (150 – 215), could find both sources quite harmonious. Both reason and revelation were important sources in support of the foundational idea of the doctrine of the Trinity: that there is only one God.


It’s possible to define the Trinity in very simple terms, like the seven listed earlier. Those simple terms are sufficient for many purposes. They certainly were for the earliest Christians. Still, as Christians have thought more deeply about the Trinity they have found it helpful to expand their vocabulary to cover more sophisticated concepts and to distinguish them from heretical views. Before people had these terms available to them they might ask questions about the Trinity like “one what?” and “three whos?” What kinds of things are we talking about here? There weren’t terms available to tag these sorts of concepts to get a hold of them. There aren’t terms in scripture to use for these sorts of philosophical questions. But they are interesting questions. They’re terms that we can use if we want to take things to the “next level”. Let’s look at five such terms.

Substance, Homoousion, Essence

This is a term for the “one what?” question. The Greek term οὐσία (ousia) is essence or substance. The Council of Nicea used this term to describe what it is in their essence as God, that the Father, Son, and Holy Spirit share. They are the same in essence, ὁμοούσιον (homoousion), one ousia.

Persons, Hypostases

Hypostasis (ὑπόστασις) is a term for the “three whos?” question. This is an especially good example of a term that was appropriated and repurposed to make a fine distinction that wasn’t conceptualized previously. (It’s quite interesting how language can extend our thinking in this way). Hypostasis had meant something very similar to ousia. But it was later made distinct to refer to that in the Trinity which should not be confounded, the persons of the Father, Son, and Holy Spirit. Using the terms ousia and hypostasis the Trinity can be described as three hypostases, one ousia; three persons, one essence.


Perichoresis (περιχώρησις) is a term to used to refer to the relations between the three persons of the Trinity. It means “going around” and when used to describe the Trinity it refers to their particular interrelation or interpenetration. As used historically in the writings of theologians like Maximus Confessor (c. 580 – 662), Gregory of Nazianzus (329–389), and John of Damascus (c. 675 – 749) it conveys a sense of motion, dynamism, even a kind of eternal dance between the Father, Son, and Holy Spirit. This idea has special currency for the mystical side of Christianity, in pursuit of direct, experiential, and personal relationship with the Triune God.

Eternal Generation, Eternal Begetting

The Nicene Creed states that Christ is “begotten, not made”, γεννηθέντα, οὐ ποιηθέντα (gennethenta, ou poiethenta). The point being that the Son is not a creature, not created by the Father. But he is begotten, or put another way, generated by the Father. Is this a distinction without a difference? No. Unlike any created being, the Son exists necessarily and eternally, just like the Father. Each has life in himself. “For as the Father has life in Himself, so He has granted the Son to have life in Himself”. (John 5:26) There’s a relation of begetter and begotten. But this is something more akin to a logical process than a process in time.

A geometrical analogy of generation that comes to mind is the relation of the center point of a circle to all the points on its circumference. By definition all points on a circle are equidistant from the center of the circle. In a sense the center point generates all the points on the circle. But which part comes first? Well neither really comes first. The relation doesn’t even come to be in any kind of temporal process. There’s a relation there but it’s just there, without needing to have ever started, much less one part before another.

One philosophy contemporary with the Council of Nicea, Neoplatonism, certainly provided intellectual tools to come up with this kind of idea. In the metaphysics of Plotinus (204 – 270) all things are understood to derive from a single great source, an absolute One. The first level of emanation from this One is the Divine Mind. The One eternally generates the Divine Mind in a way very similar to the way Christian theologians understood the Father to generate the Son.


In the Nicene Creed it is said that the Holy Spirit “proceeds from the Father”, τὸ ἐκ τοῦ Πατρὸς ἐκπορευόμενον (to ek tou Patros ekporeuomenon). Catholics and Protestants also say that the Holy Spirit proceeds from the Father and from the Son. Filioque in Latin. One example from scripture for this idea is John 14:23,

But the Helper, the Holy Spirit, whom the Father will send in My name, He will teach you all things, and bring to your remembrance all things that I said to you.


A key historical moment for the development of the doctrine of the Trinity was the Council of Nicea in 325. The Council was a response to the teachings of Arius (265 – 336). Arius taught that the Son, Jesus Christ, was a creature, a creation of the Father, the first and greatest of God’s created beings, but still a created being. The key idea of this doctrine was that “there was a time when he was not”.

Arius’ teachings were very influential, not just among clergy and theologians but even among regular folks. Gregory of Nyssa (335 – 395) described the controversy in this way:

“The whole city is full of it, the squares, the marketplaces, the crossroads, the alleyways; rag dealers, money-changers, food-sellers, they are all busy arguing. If you ask someone to give you change, he philosophizes about the Begotten and the Unbegotten; if you inquire about the price of a loaf, you are told by way of reply that the Father is greater and the Son inferior; if you ask, “Is my bath ready?” the attendant answers that the Son was made out of nothing.” (“On the Deity of the Son” PG xlvi, 557b)

Πάντα γὰρ τὰ κατὰ τὴν πόλιν τῶν τοιούτων πεπλήρωται͵ οἱ στενωποὶ͵ αἱ ἀγοραὶ͵ αἱ πλατεῖαι͵ τὰ ἄμφοδα· οἱ τῶν ἱματίων κάπηλοι͵ οἱ ταῖς τραπέζαις ἐφεστη κότες͵ οἱ τὰ ἐδώδιμα ἡμῖν ἀπεμπολοῦντες. Ἐὰν περὶ τῶν ὀβολῶν ἐρωτήσῃς͵ ὁ δέ σοι περὶ γεννητοῦ καὶ ἀγεννήτου ἐφιλοσόφησε· κἂν περὶ τιμήματος ἄρτου πύθοιο͵ Μείζων ὁ Πατὴρ͵ ἀποκρίνεται͵ καὶ ὁ Υἱὸς ὑποχείριος. Εἰ δὲ͵ Τὸ λουτρὸν ἐπιτήδειόν ἐστιν͵ εἴποις͵ ὁ δὲ ἐξ οὐκ ὄντων τὸν Υἱὸν εἶναι διωρίσατο. Οὐκ οἶδα τί χρὴ τὸ κακὸν τοῦτο ὀνομάσαι͵ φρενῖτιν ἢ μανίαν͵ ἤ τι τοιοῦτον κακὸν ἐπιδήμιον͵ ὃ τῶν λογι σμῶν τὴν παραφορὰν ἐξεργάζεται.

So the Church had to ask, what do we say about this? Is this right? The First Council of Nicea (325) and the Nicene Creed were the result. The Nicene Creed was later adjusted further in the First Council of Constantinople (381) to the version in use today. In response to Arius the Nicene Creed affirmed that Jesus Christ is:

“Begotten of the Father; Light of Light, very God of very God, begotten, not made, consubstantial with the Father”

The key being that Jesus is God. That was the line drawn.

There were also some very significant theologians and texts written following the council that have been important in the history of Christian theology, especially theology of the Trinity. Some theologians of special note are

Athanasius of Alexandria (296 – 373)
Basil the Great (330 – 379)
Gregory of Nyssa (c. 335 – c. 395)
Gregory of Nazianzus (329–389)
Augustine of Hippo (354 – 430)
Hilary of Poitiers (310 – 367)

Arianism continued to be a prominent view, sometimes supported by the Roman Empire. And many of the Barbarian kingdoms in the West were Arians. These theologians worked diligently to teach the orthodox view against Arianism.

One of the most significant texts of this period was Augustine of Hippo’s On the Trinity (De Trinitate). It’s not only an impressive theological defense and explanation of the Trinity but it also ends up being a fascinating work on the philosophy of the mind and personal identity. This was because Augustine pursued the idea that human beings, being created in the image of God, must be created in the image of the Trinity and therefore bear features of the Trinity in themselves and in their minds.


In his Intercessory Prayer in John 17:3 Jesus said to the Father:

And this is eternal life, that they may know You, the only true God, and Jesus Christ whom You have sent.

Knowing God is foundational to Christian life. This means knowing both the Father and his son Jesus Christ. And also the Holy Spirit, who testifies of both. This brings home the importance of Jesus Christ to Christian faith.

This is what makes Christianity unique. There are other monotheistic religions and even monotheistic philosophies. But the unique and special revelation of Christianity is the one we find in Jesus Christ.

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