With Tertullian’s philosophy out of the way, I want to turn to areas where he seems to have influenced matters of Christian Doctrine and Dogma. Keep in mind while reading these that I am not an expert on religious history or modern Christianity. If I’ve come across something and it seems relevant I’ll mention it but there are areas where something may have been accepted as Doctrine by the Catholic but not the Eastern Orthodox Church, or something that a Protestant Church or Churches decided wasn’t doctrine after The Reformation (the big one of the 16th century, not any of the other ones). I’ll be doing well if I can keep what’s Doctrine separate from Dogma separate from what ended up being points of discussion/conflict. Fortunately, for this first topic it’s easy as this is Doctrine accepted in every Christian Church that I know of (with the exception of a few heresies).
Setting aside his influence on Augustine, which I can’t begin to quantify at this point, I think Tertullian’s area of greatest impact was on the nature of the Trinity. The Godhead had been described in Trinitarian terms for quite some time. Ignatius makes references to it and Justin Martyr does as well. Theophilus of Antioch takes this one step further in referring to God as a Trinity. 1
While early Christian authors clearly recognize that the Godhead consists of three entities, they have trouble expressing exactly what they mean. In some cases God comes across as three beings, in others as one being with three aspects. Christians were accused, particularly by Jews, of being polytheists. And Romans/Pagans never seemed to have much of an idea exactly what was being talked about. Tertullian tackles this and I have to give him his props – he does it brilliantly.
Around 206 it appears that Montanists were either driven out of the Church or their beliefs were declared invalid. An individual by the name of Praxeas appears to have been significant in this event and a few years later Tertullian wrote, Against Praxeas as a personal attack. In it, Praxeas is accused of being Monarchist; believing that the Godhead is made of one being with three aspects. To be fair, it’s unclear is Praxeas actually believed this; he may have been lumped into this category with other anti-Montanists, but this is unimportant compared with Tertullian’s argument.
I’ll try to cover Tertullian’s key points. As he keeps coming back to and adding to them, I’m not going to try to cite every single place where he discusses them, just specific parts of the text where I think you can figure out what he meant. If you’re interested in the development of Trinitarian Doctrine, Against Praxeas is essential reading. You can find an online version on Roger Pearse’s site, The Tertullian Project. You can also find the Ante-Nicene Fathers version online if you want to read the same thing I did.
The entire treatise could have as easily been been titled, On the Trinity as this is almost exclusively what it is about. Tertullian opens with a statement ridiculing the fact that certain Christians have been inspired by the Devil and have fallen into error in believing that the Christian Godhead is a single individual, “He [the Devil] says the the Father Himself came down into the Virgin, was Himself born of her, Himself suffered, indeed was Himself Jesus Christ.” (Against Praxeas, I) Pretty strong stuff (unfortunately Tertullian goes on for another several hundred words, IMO he could have quit right there).
Tertullian spends the next thirty chapters on his Trinitarian theory. I’ll briefly cover his main points.
1. The Father, the Son, and the Holy Spirit are three individual entities, but inseparable from each other:
“… one cannot believe in One Only God in any other way than by saying that the Father, the Son, and the Holy Ghost are the very selfsame Person. As if in this way also one were not All, in that All are of One, by unity (that is) of substance; while the mystery of the dispensation is still guarded, which distributes the Unity into a Trinity, placing in their order the three Persons—the Father, the Son, and the Holy Ghost: three, however, not in condition, but in degree; not in substance, but in form; not in power, but in aspect; yet of one substance, and of one condition, and of one power, inasmuch as He is one God, from whom these degrees and forms and aspects are reckoned, under the name of the Father, and of the Son, and of the Holy Ghost.” Against Praxeas, II
2. The Son is equivalent to God’s Word. While begotten, He was present with the Father from the Beginning, as God always had his Word, though this Word was not revealed until the world was created and there was something to reveal it to. Tertullian spends a lot of time on this in Against Praxeas – Chapters 5-8 and 12. Obviously I can’t include all of this here but there are a few key quotes I think will help:
“Yet even not then was He alone; for He had with Him that which He possessed in Himself, that is to say, His own Reason. For God is rational, and Reason was first in Him; and so all things were from Himself. This Reason is His own Thought (or Consciousness) which the Greeks call λόγος, by which term we also designate Word or Discourse … and therefore it is now usual with our people, owing to the mere simple interpretation of the term, to say that the Word was in the beginning with God; although it would be more suitable to regard Reason as the more ancient; because God had not Word from the beginning, but He had Reason even before the beginning; because also Word itself consists of Reason, which it thus proves to have been the prior existence as being its own substance.” Against Praxeas, V
So for eternity God had Reason with him. And his reason became God’s Word:
“Whatever you think, there is a word; whatever you conceive, there is reason. You must needs speak it in your mind; and while you are speaking, you admit speech as an interlocutor with you, involved in which there is this very reason, whereby, while in thought you are holding converse with your word, you are (by reciprocal action) producing thought by means of that converse with your word. Thus, in a certain sense, the word is a second person within you, through which in thinking you utter speech, and through which also, (by reciprocity of process,) in uttering speech you generate thought. The word is itself a different thing from yourself. Now how much more fully is all this transacted in God, whose image and likeness even you are regarded as being, inasmuch as He has reason within Himself even while He is silent, and involved in that Reason His Word! I may therefore without rashness first lay this down (as a fixed principle) that even then before the creation of the universe God was not alone, since He had within Himself both Reason, and, inherent in Reason, His Word, which He made second to Himself by agitating it within Himself.” Against Praxeas, V
The Son is the Word of God and so, while begotten, has been with him from the beginning:
“Then, therefore, does the Word also Himself assume His own form and glorious garb, His own sound and vocal utterance, when God says, ‘Let there be light.’ This is the perfect nativity of the Word, when He proceeds forth from God—formed by Him first to devise and think out all things under the name of Wisdom — ‘The Lord created or formed me as the beginning of His ways;’ then afterward begotten, to carry all into effect — ‘When He prepared the heaven, I was present with Him.’ Thus does He make Him equal to Him: for by proceeding from Himself He became His first-begotten Son, because begotten before all things; and His only-begotten also, because alone begotten of God, in a way peculiar to Himself, from the womb of His own heart—even as the Father Himself testifies: ‘My heart,’ says He, ‘hath emitted my most excellent Word.'” Against Praxeas, VII
3. The Holy Spirit proceeds from the Father through the Son:
“The same remark (I wish also to be formally) made by me with respect to the third degree in the Godhead, because I believe the Spirit to proceed from no other source than from the Father through the Son.” Against Praxeas, IV. He also covers this in Apology, XXI.
4. A very key concept which I’ve not seen expressed by earlier authors is that while the Trinity are three individuals, they are of the same substance. He opens with this in Against Praxeas, II (see above) and expands on this throughout. In Against Praxeas, VIII he provides some useful analogies to illustrate this. The sun gives off rays, a stream flows from a fountain and a tree grows from the root. In each of these cases you can look at the rays, stream and tree as the offspring of the sun, fountain and root, respectively. Yet they are never separate from their source and are of the same substance.
There are still problems with this when viewed with later developments in mind. Tertullian’s order of precedence was a point of contention, particularly the Son proceeding from the Father, and is not part of the Nicene Creed. Overall this is a very significant text. Tertullian uses much of the language which would become part of the Nicene Creed:
“… we believe Him to have suffered, died, and been buried, according to the Scriptures, and, after He had been raised again by the Father and taken back to heaven, to be sitting at the right hand of the Father, and that He will come to judge the quick and the dead …” Against Praxeas, II
You can also find similar language in Prescription Against Heretics, XIII.
And then there is this:
“Thus Christ is Spirit of Spirit, and God of God, as light of light is kindled.” Apology, XXI
Maybe these ideas were already present in the Church and he’s simply the first to write about them but nobody prior to Tertullian even began to describe the Trinity in these terms. Much of his language found its way into the Nicaean Creed. In looking at the impact of Tertullian on the development of Christianity, this is huge.
1 Ignatius is unclear (to me anyway) on whether he considers the Holy Spirit to be completely separate from Christ. For example, in his Letter to the Magnesians, XV, he concludes the letter with, “Fare ye well in harmony, ye who have obtained the inseparable Spirit, in Christ Jesus, by the will of God.” Also see, Letter to the Philadelphians, IV & VI, and Letter to the Smyrnaeans XII. Justin makes more of a distinction, as in his First Apology V. For Theophilus see, To Autolycus II.XV.
Roberts, Alexander & Donaldson, James, eds., Ante-Nicene Fathers Volume 1: The Apostolic Fathers, Justin Martyr, Irenaeus. Peabody, MA, USA: Hendrickson Publishers (2004), ISBN: 1-56563-083-1.
Roberts, Alexander & Donaldson, James, eds., Ante-Nicene Fathers Volume 2: Fathers of the Second Century: Hermas, Tatian, Athenagoras, Theophilus, and Clement of Alexandria (entire), Peabody, MA, USA: Hendrickson Publishers (2004). ISBN: 1-56563-084-X.
Roberts, Alexander & Donaldson, James, eds., Ante-Nicene Fathers Volume 3: Latin Christianity: Its Founder, Tertullian: I. Apologetic; II. Anti-Marcion; III. Ethical. Peabody, MA, USA: Hendrickson Publishers (2004), ISBN: 1-56563-086-6.
Roberts, Alexander & Donaldson, James, eds., Ante-Nicene Fathers Volume 4: Latin Christianity: Its Founder, Tertullian, Part Fourth: Minucius Felix; Commodian; Origen, Parts First and Second. Peabody, MA, USA: Hendrickson Publishers (2004), ISBN: 1-56563-086-6.
Schaff, Philip and Wace, Henry, eds., Nicene and Post-Nicene Fathers Second Series Volume 3: Theodoret, Jerome, Gennadius, Rufinus: Historical Writings, etc. Peabody, MA, USA: Hendrickson Publishers (2012), ISBN(for series): 978-1-56563-116-8.
Schaff, Philip and Wace, Henry, eds., Nicene and Post-Nicene Fathers Second Series Volume 6: The Principal Works of St. Jerome. Peabody, MA, USA: Hendrickson Publishers (2012), ISBN(for series): 978-1-56563-116-8.