A Lesson on the Trinity

Note: This article is adapted from lesson notes for a teaching I did on the Trinity a few years ago. The class was following McGrath’s Christian Theology, so some of this follows his thought, some of it is my own.

This article is longer than usual, so if you enjoyed reading even part of this this please leave a like. I am trying to determine what to focus on post-seminary now that my health is improving and your feedback is essential in making this decision. Thanks.

Photo by Ben Turnbull on Unsplash

When we try to describe the Trinity we have set before ourselves a difficult task because attempting to describe the transcendent using human language is a bit of an impossible task. One theologian has likened it as an attempt to pour the ocean into a cup. This task is made even more difficult by the fact that we are limited to what God has revealed about Himself, which is to say that we do not know everything about God; we only know what God has revealed about Himself to us. But nonetheless God has revealed Himself to us and we must try to grasp and understand this revelation as best we can.

A common question that is asked these days regarding the doctrine of the Trinity is its relevance to everyday life. Even lifelong, committed Christians ask this question! The answer to this is that it matters because it is how God has revealed Himself in history (some of which is recorded in Scripture) and in our own lives. It matters because it corresponds to reality. It matters because it’s true.

We were created by someone (the Father). We were redeemed by someone (the Son). We are being sanctified by someone (the Holy Spirit). But these are not three separate actions by three separate gods, but one unified action by one Triune God. It is in the doctrine of the Trinity that we find the cohesion necessary to make sense of reality. Without this doctrine Christianity becomes an incoherent mess.

We must understand that this is not only what Scripture reveals to us, but also that beneath the surface of the complexities of the history of salvation and our own human experience lies one God and one God only. There are not multiple gods involved in the creation and redemption of humanity. There is only one God, and there is only way to Him.

The Basics

There are two ways to approach describing the Trinity: economically or immanently. When we describe the Trinity economically we are describing how God has made Himself known in redeeming humanity in history. An example of this can be found in Irenaeus:

“God the Father uncreated, who is uncontained, invisible, one God, creator of the universe; this is the first article of our faith … And the Word of God, the Son of God, our Lord Jesus Christ … who, in the fullness of time in order to gather all things to himself, he became a human being amongst human beings, capable of being seen and touched, to destroy death, bring life, and restore fellowship between God and humanity. And the Holy Spirit … who, in the fullness of time was poured out in a new way on our human nature in order to renew humanity throughout the world in the sight of God.” – Irenaeus, Demonstration of the Apostolic Preaching, 1.6. 

Or in other words. God the Father created the universe; God the Son became incarnate and redeemed humanity; and God the Holy Spirit indwells, sustains, and sanctifies Christians as they follow Christ.

When we approach the Trinity immanently (also called “essentially”) we are attempting to describe God as He is in Himself, that is, outside of the limiting conditions of time and space. A typical way to describe the Trinity in this manner is: There is one God comprised of three persons: Father, Son, and Holy Spirit. These three are all equal and all are God, but they are also separate from each other.

This approach is also found in the Athanasian Creed (c. 500):

“Now this is the catholic faith, that we worship one God in Trinity and Trinity in unity, without either confusing the persons or dividing the substance. For the Father’s person is one, the Son’s another, the Holy Spirit’s another; but the Godhead of the Father, the Son, and the Holy Spirit is one, their glory is equal, their majesty coeternal.”

Visually the immanent approach to describing God can be represented like this:

This doctrine is also reflected in the Nicene Creed: “We believe in one God, the Father almighty…and in one Lord, Jesus Christ, the only begotten Son of God, begotten of the Father before all ages; God of God, Light of light, true God of true God, begotten not created, of one substance with the Father…and in the Holy Spirit, the Lord and giver of life, who proceeds from the Father (and the Son) who with the Father and the Son together is worshiped and glorified…”

When we attempt to describe the Trinity we should not choose one approach or the other because God has revealed Himself in both ways and both approaches are necessary.

These formulations were developed in response to various heresies and challenges that arose during the first centuries of the Church. They made sense of the Biblical data and put it into a format that was theologically coherent. So these traditional formulations of the Trinity are not something you want to depart from because you will probably very likely open the door to theological errors. To be sure there are other theological topics where it is perfectly fine to develop your own doctrine or formulation, but the Trinity isn’t one of them.

If you wish to know more about the Biblical data as well so how this came to be formulated as such continue reading.

Old Testament

If we are going to claim that Christ and Christianity are the fulfillment of the Messiah and His Kingdom promised in the Old Testament, then we must show that there is continuity between it and the New Testament. The goal here is not to prove the formulation of the previous section, but simply to show that the Old Testament reveals a single God, but also plurality within that single God.

A common argument for the Trinity from the Old Testament is to appeal to Deuteronomy 6.4, “Hear, O Israel: The Lord our God, the Lord is one” and say that “one” (echad) denotes composite oneness, and so the Trinity is compatible with the Old Testament. The word (yachid) would have more forcefully excluded the possibility of plurality within God and is not used to describe divine oneness.

This is not an altogether bad argument. Yachid is only used 12 times in the Old Testament and in those uses does mean “only, only one, solitary” and it is indeed never used to describe God. However, echad is used over 900 times in the Old Testament and has a wide range of possible meanings, including “only” (see Joshua 22.20; 1 Kings 4.19; Song of Songs 6.9; Zechariah 14.9). Furthermore, the clause in Deuteronomy 6.4 has no verb in Hebrew, which leaves us with at least 5 translation options:

  1.             “Yahweh is our God; Yahweh is one.”
  2.             “Yahweh our God, Yahweh is one.”
  3.             “Yahweh our God is one Yahweh.”
  4.             “Yahweh is our God, Yahweh alone.”
  5.             “Our one God is Yahweh, Yahweh.”

So the argument is a plausible one, but due to the wide range of possible meanings with echad and the Hebrew syntax it is not the best.

What is unquestionably clear though from this text is that there is only one God: Yahweh.

What is also clear in the Old Testament is that there are multiple divine agents portrayed as coming from God, and thus being dependent on Him, but also as having an independent existence.


Sometimes in the Old Testament “wisdom” simply refers to the learned skill of human beings living in accordance with God’s commandments. Sometimes it refers to a primary attribute of God. But sometimes it is portrayed as a person with an existence apart from, yet dependent upon God. This independent, yet dependent existence is most evident in Proverbs 8.1-31, especially in verses 22-23:

“The Lord possessed me at the beginning of his work,
the first of his acts of old.
Ages ago I was set up,
at the first, before the beginning of the earth.”
(See also Psalm 104.24; Proverbs 3.19; Jeremiah 10.12)

In the New Testament this personification is applied to Christ by Paul in 1 Corinthians 1.24:

“but to those who are called, both Jews and Greeks, Christ the power of God and the wisdom of God.” (See also 1 Corinthians 1.30; Colossians 2.3)

Most church fathers also interpret the Wisdom in Proverbs 8 to refer to Christ, (see Justin Martyr, Dialogue with Trypho, 61.129; Tertullian, Against Praxeas, 6; Origen, On First Principles, 1.2.1– 5, 8, 12), but some interpret it to refer to the Holy Spirit (e.g. Irenaeus, Against Heresies, 4.20.1, 3).

The Word of the Lord

The word of the Lord refers to God’s speech going out into the creation to accomplish His will. Sometimes this is to bring guidance, judgment, and salvation as in Isaiah 55.10-11:

“For as the rain and the snow come down from heaven
and do not return there but water the earth,
making it bring forth and sprout,
giving seed to the sower and bread to the eater,
so shall my word be that goes out from my mouth;
it shall not return to me empty,
but it shall accomplish that which I purpose,
and shall succeed in the thing for which I sent it.”
(See also Psalm 119.89; 147.15-20).

Or to create the universe as in Genesis 1 and Psalm 33.6, 9:

“By the word of the Lord the heavens were made,
and by the breath of his mouth all their host…

For he spoke, and it came to be;
he commanded, and it stood firm.”

The Spirit of the Lord

The spirit of the Lord refers to God’s presence and power within the creation as seen in Psalm 139.7-10:

“Where shall I go from your Spirit?
Or where shall I flee from your presence?
If I ascend to heaven, you are there!
If I make my bed in Sheol, you are there!
If I take the wings of the morning
and dwell in the uttermost parts of the sea,
even there your hand shall lead me,
and your right hand shall hold me.”

It gives life, order, and beauty to creation (Genesis 1.2; Job 33.4; Psalm 104.30); will be present in the expected Messiah (Isaiah 42.1-3); and is portrayed as being the agent of a new creation (Ezekiel 36.26-27; 37.1-14). Thus it shows a strong correspondence with the New Testament and a Christian theology of the Holy Spirit.

Conclusion from the Old Testament

In the Old Testament then we see that there is only one God (Deuteronomy 6.4) and that there are multiple divine entities coming from that one God.

New Testament

There are 2 primary Trinitarian texts in the New Testament:

“Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit…” – Matthew 28.19

“The grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with you all.” – 2 Corinthians 13.14

However, there are at least 115 more passages in which deity is attributed to at least one of the members of the Trinity. Some of these are discussed below.

Deity of the Father

The deity of the Father isn’t in dispute, but nevertheless it is affirmed in the New Testament in numerous places, some of which include: John 20.17; Romans 1.7; 1 Corinthians 1.3, 8.6, 15.24; 2 Corinthians 1.2-3, 11.31; Galatians 1.1, 3, 4; Ephesians 1.2-3, 17; Philippians 1.2, 2.11; Colossians 1.2-3, 3.17; James 1.27; 1 Peter 1.2-3; 2 Peter 1.17; 2 John 3; Jude 1.

Deity of Jesus

There are numerous passages that attribute deity to Jesus, but among the most important are what are called the “high Christological passages.” They include John 1.1-18; Romans 1.2-5; Philippians 2.6-11; Colossians 1.15-23; Hebrews 1; 1 John 1.1-3.

Deity of the Holy Spirit

The deity of the Holy Spirit is not as obvious as that of the Father and the Son, and so some explanation of the various passages will be necessary.

Sometimes the Holy Spirit is used interchangeably with God as in Acts 5.3-4 where in v.3 Peter rebukes Ananias and said he has lied to the Holy Spirit, and then in v.4 says he has lied to God. Or again in Acts 28.25-27 where Paul says the Holy Spirit spoke through Isaiah and then quotes Isaiah 6.9-10, but Isaiah speaks after hearing “the Lord” (adonai). Or yet again in Hebrews 10.15-17 where the author says “The Holy Spirit also bears witness to us…” and then quotes Jeremiah 31.33-34, but Jeremiah declares the words of Yahweh, thus equating the Holy Spirit with Yahweh.

The Holy Spirit possesses the attributes of God, such as: knowing the thoughts of God (1 Corinthians 2.10-11; John 16.13).

The Holy Spirit possesses the power of God. This can be seen in the virgin birth (Luke 1.35); Paul’s ministry accomplishments (Romans 15.19); convicting the world (John 16.8-11); and spiritual regeneration (John 3.5-8; Titus 3.5), a power which Jesus said belongs to God (Matthew 19.16-26).

The Holy Spirit is eternal like the Father and the Son (Hebrews 9.14).

The Holy Spirit is associated with the Father and the Son as an equal in Matthew 28.19 and 2 Corinthians 13.14 (see above).

Conclusion from the New Testament

The result of all these verses is the same as the Old Testament: one God, but multiple divine entities coming from that one God.

Patristic Development

It was during the Patristic period (roughly from 100A.D.- 600A.D.) that the doctrine of the Trinity we know today came about (see the beginning of this article). As should be clear from the Biblical data above the theologians of this period were not developing the doctrine in the sense of inventing something new, but were developing in the sense of putting into a clear and precise model how God revealed Himself both in Scripture and in reality.

One of the most formative and influential theologians in Western Christianity is Tertullian, and he is likely responsible for the development of the distinctive Trinitarian terminology we use today. First, he invented the term Trinity (Trinitas). Second, he used the term Person (Persona) to translate the Greek hypostasis (usually translated “substance” or “essence”). Scholars debate what Tertullian meant by this term. The Greek term refers to the basic nature or structure of an entity, but the Latin (Persona) literally means “a mask,” such as one worn by an actor in a Roman drama. It is possible by using this term that Tertullian wanted his readers to understand the idea of “one substance three persons” to mean that the one God played three distinct yet related roles in the great drama of human redemption. Third, he used the term Substance (Substantia) to express the fundamental unity within God, that is, what the members of the Trinity have in common.

By the second half of the fourth century it had been concluded that the Father and Son were of one substance, thus condemning the Arian view as heresy and establishing a consensus within the church (although Arianism itself didn’t go away and still remains today, e.g. Jehovah’s Witnesses). What was not settled however is the relationship between the Father and the Spirit. Western theology has tended to begin from and emphasize the unity of God, but Eastern theology (found in the Eastern Orthodox churches, e.g. Greek Orthodox, Russian Orthodox, etc) has tended to emphasize the distinct individuality of the three persons. The Eastern approach could logically lead to three independent beings doing quite different things, but two later developments: perichoresis and appropriation  excluded this possibility.

An Aside

These two different tendencies were bound to conflict and eventually exploded in 1054 with the Western church and Eastern church anathematizing one another over the addition of “and the Son” (Filioque) to the Nicene Creed. Originally the Nicene Creed said the Holy Spirit proceeds from the Father only, but later the West added “and the Son” so that the Holy Spirit proceeded from both the Father and the Son. For the West this didn’t cause much of a problem theologically due to its emphasis on the unity of God. However, this was (and remains) a huge problem for the East because in order to safeguard the unity of God against their emphasis on the distinctness of the three persons they stress that both the Son and the Spirit proceed from the Father, thus the unity is found in the Father, who is the “Fountainhead of Divinity.” So in their view if you have the Spirit proceeding from both the Father and the Son you have denigrated the Spirit and have created two Gods (the Father and the Son) thus destroying the unity and equality between the persons of the Trinity.

Perichoresis and Appropriation

The term perichoresis is often found as “mutual interpenetration” in English. It refers to the mutual indwelling of the members of the Trinity in one another, but still maintains the individuality of each of them. Logically following from this idea is appropriation, which responds to the modalist heresy. Modalism argued that at different points in the redemption of humanity God existed in different “modes” of being. So at one point God was Father and created the world, and then at another God was Son and redeemed it.  Against this appropriation insists that the works of the Trinity are a unity; whatever one does, the other two members do as well, a logical extension of their mutual indwelling. A helpful image for grasping these two concepts might be a dance, where each member maintains their individuality, but is involved in whatever another member does.


Hopefully this has been helpful in not only understanding the essential basics of the Trinity, but also in understanding how the doctrine has come to be articulated as such and why we should adhere to the traditional formulations for this doctrine.

If you enjoyed reading this please leave a like. I am trying to determine what to focus on post-seminary now that my health is improving and your feedback is essential in making this decision. Thanks.


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