The Historical Development of the Trinity – From before Nicaea to the Reformation


Nicene Creed
Emperor standing behind the church fathers

The purpose of this article series is to trace the development of the Trinity theory through the centuries, commencing with the pre-Nicene fathers, though the tumultuous events of the fourth century, down to the Reformation.

In the year 325, the Council of Nicaea decreed that the Lord Jesus Christ exists as one substance (homoousios) and as co-equal with the Father.  The purpose of the first articles is to determine what Christians believed about Christ and the Trinity in the three centuries before Nicaea. 


Matt Slick is a prominent Trinitarian apologist.  To prove that Christians did believe in the Trinity during the first three centuries, his brief post, “Early Trinitarian Quotes,” provides a collection of proof texts from prominent second and third centuries theologians.

Sean Finnegan—a Unitarian (believing that the Father alone is God)—responded to Slick’s article with an article titled Trinity before Nicaea.  His purpose was to show that Christians in the first three centuries did not believe in the Trinity.  He discussed Slick’s articles but added further quotes.  Dr. Tuggy’s podcast 262 presents his response.  Dr. Tuggy is a well know Socinian Unitarian, which means that he believes that Christ did not exist before His human birth.  

The current article series analyzes the quotes from both these articles to see what the Christian authors believed in the first three centuries about the Father, the Son, and the Holy Spirit.  The purpose is not to determine whether what those early Christians were correct in their teachings, but rather to understand whether the Nicene and later creeds were consistent with the teachings of the early Christians.

To simplify these articles, many of the quotes below are summarized.  For the full quotes, refer to Finnegan’s article.

Trinity Defined


Slick’s definition of the Trinity, in summary, is as follows:

God is one, but is a Trinity of three distinct persons; the Father, the Son, and the Holy Spirit.  Each has a will and is self-aware, but they are not three beings. They consist of one substance.  Each person is the one God and is eternal, equal to the others and equally powerful.
Jesus, as a man, has both a divine and human nature.

In this definition, “each person is the one God.” This means that God = the Father = the Son = the Holy Spirit.  This sounds like Modalism, where the Father, Son, and Holy Spirit are not three different Persons, but three modes of the same Being. But then Slick also says that they are “three distinct persons.”

The three-ness of God is expressed as three separate wills and self-awareness.
The one-ness of God is expressed as a single substance, understood as a single Being.

Historical Development

The conceptual progression and historical development of the Trinity theory can be described as follows:

Jesus is God.

Worship JesusBased on the High Christological statements in the Bible, Trinitarians believe that Jesus is God as much as the Father is God.  This was the main point of the Nicene Creed of the year 325, which identified the Son as “true God from true God.”

Three Persons in One Being

This creed caused much dispute and controversy in the church for the next 50 years, for the Bible is clear that only one God exists (monotheism).  Trinitarians, therefore, developed the concept that the Father, the Son, and the Holy Spirit are a single Being; together they are the one God of the Bible. However, since there are differences between the Father, the Son and the Holy Spirit, such as that the one is begotten and the other not, the thought developed that they are three different Persons within the one single Being.  The Three Person in One Being theology was clearly enunciated by the first council of Constantinople in the year 381.

The word Trinity has two possible meanings.  With a lower case, “trinity” simply means a group of three.  But we currently use the word “Trinity,” with a capital “T,” as a proper name for the single Being who consists of three divine Persons.

Two Natures

But then, Christ Jesus, when He was on earth, did not know the day and hour of His return, and said that only the Father knows that.  And in many other ways, He indicated that He is subordinate to the Father.  For example, He was sent by the Father and that the Father gave Him what to say and what to do.  Trinitarians, therefore, developed the thought that Jesus had both a human and a divine nature.  In His human nature, He did not know the day or die hour, but in His divine nature He knows all things.  This “two natures” theory was articulated at the council of Chalcedon in 451.

The conclusion that the Son is God as much as the Father is God is, therefore, the foundation on which the Trinity theory rests.  Both the One Being/Three Persons and the dual nature theories simply are secondary attempts to reconcile the Bible with the conclusion that the Son is God. 

The concepts in this section will be brought out in more clarity in the articles that will follow.


AriusIn the fifty years after Nicaea, that creed was rejected by most church leaders.  Arianism was the main competitor for the Trinity theory and held the sway until the year 381.  This theory is analyzed in a later article.  In summary, Arianism argues that the Son is not equal to the Father, but was begotten by the Father before time and that God created all things through the Son.  In other words, in the infinity beyond time, the Father was before the Son, using the word “before” metaphorically. 


The articles below discuss the Christologies of Polycarp, Justin Martyr, Ignatius of Antioch, Irenaeus (bishop of Lyons), Tertullian and Origen; the greatest and most influential Christian theologian before Augustine.  The purpose is to evaluate the following aspects from the definition of the Trinity against their works:

1. The Son is God.
2. The three Persons are equal.
3. The Holy Spirit is self-aware.
4. The three Persons consist of one substance.
5. Jesus has both a divine and human nature.

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