Writing against Praxeas, who taught Monarchians viz., the Father, the Son and the Holy Spirit are one and the same person, Quintus Septimius Florens Tertullianus’(c. 160 – c. 225 AD) gave one of the earliest and robust defense of one and only God in three distinct persons. Tertullian contended:

Bear always in mind that this is the rule of faith which I profess; by it I testify that the Father, and the Son, and the Spirit are inseparable from each other, and so will you know in what sense this is said. Now, observe, my assertion is that the Father is one, and the Son one, and the Spirit one, and that They are distinct from Each Other. […] Father and the Son are demonstrated to be distinct; I say distinct, but not separate.[He explained further that its “on the ground of Personality, not of Substance—in the way of distinction, not of division”]

Quoting Isaiah 42:1, 45:1 61:1(Luke 4:18) 53:1-2, Psalms 71:18, 3:1, 110:1, Tertullian argued:

Still, in these few quotations the distinction of Persons in the Trinity is clearly set forth. For there is the Spirit Himself who speaks, and the Father to whom He speaks, and the Son of whom He speaks.

He went further to contend:

If the number of the Trinity also offends you, as if it were not connected in the simple Unity, I ask you how it is possible for a Being who is merely and absolutely One and Singular, to speak in plural phrase, saying, “Let us make man in our own image, and after our own likeness;” whereas He ought to have said, “Let me make man in my own image, and after my own likeness,” as being a unique and singular Being?

In the following passage, however, “Behold the man is become as one of us,” He is either deceiving or amusing us in speaking plurally, if He is One only and singular. Or was it to the angels that He spoke, as the Jews interpret the passage, because these also acknowledge not the Son? Or was it because He was at once the Father, the Son, and the Spirit, that He spoke to Himself in plural terms, making Himself plural on that very account? Nay, it was because He had already His Son close at His side, as a second Person, His own Word, and a third Person also, the Spirit in the Word, that He purposely adopted the plural phrase, “Let us make;” and, “in our image;” and, “become as one of us.” For with whom did He make man? and to whom did He make him like? (The answer must be), the Son on the one hand, who was one day to put on human nature; and the Spirit on the other, who was to sanctify man.

With these did He then speak, in the Unity of the Trinity, as with His ministers and witnesses In the following text also He distinguishes among the Persons: “So God created man in His own image; in the image of God created He him.” Why say “image of God?” Why not “His own image” merely, if He was only one who was the Maker, and if there was not also One in whose image He made man? But there was One in whose image God was making man, that is to say, Christ’s image, who, being one day about to become Man (more surely and more truly so), had already caused the man to be called His image, who was then going to be formed of clay—the image and similitude of the true and perfect Man.

Tertullian assembled John 1:1-3, Psalms 45:6-7, 110:1, and Isaiah 53:1 to argue that “the Father is Lord, and the Son also is Lord”(Lord = Yahweh). He went on to expound:

A much more ancient testimony we have also in Genesis: “Then the Lord rained upon Sodom and upon Gomorrah brimstone and fire from the Lord out of heaven.” Now, either deny that this is Scripture; or else (let me ask) what sort of man you are, that you do not think words ought to be taken and understood in the sense in which they are written, especially when they are not expressed in allegories and parables, but in determinate and simple declarations?

Tertullian believed that He was following the apostle Paul teaching of Romans 9:5.

I shall follow the apostle; so that if the Father and the Son, are alike to be invoked, I shall call the Father “God,” and invoke Jesus Christ as “Lord.” But when Christ alone (is mentioned), I shall be able to call Him “God,” as the same apostle says: “Of whom is Christ, who is over all, God blessed for ever.”

Oneness Apostolic, also known as “Jesus Only”, do uphold Praxeas teachings today. A teaching which, I believe, Tertullian strongly and successively refuted. The doctrine of Trinity is the rule of faith that early Christians taught and believed.

Question: Did you know that the doctrine of Trinity was taught by Ante-Nicene Church fathers?

Bibliography:

Tertullian. (1885). Against Praxeas P. Holmes, Trans.). In A. Roberts, J. Donaldson & A. C. Coxe (Eds.), The Ante-Nicene Fathers, Volume III: Latin Christianity: Its Founder, Tertullian (A. Roberts, J. Donaldson & A. C. Coxe, Ed.) (603-8). Buffalo, NY: Christian Literature Company.(paragraphs added)

Image Credit: Ressonância Trinity Symbol