It used to be standard practice to divide the summa into a number of “theological treatises” and on that account, we are now moving from the “Treatise on the One God” to the “Treatise on the Blessed Trinity”. It’s now less fashionable to make such a hard and fast division, and more in keeping with the times to emphasise the unity in the work as a whole and the intimate connections between the different parts. There’s truth in both approaches: to cut the summa up into pieces risks losing the unity that is undoubtedly there; but equally we must note that the character of the work changes at certain key points, which Aquinas himself often signposts. At this point in the summa, Aquinas tells us that we are now to turn from considering the oneness of the divine essence to those things that pertain to the Trinity of persons in God.
It is important to note that, although this is not a hard division, we are moving from the realm of “natural theology” (where metaphysics can conclusively demonstrate facts about the existence and being of God) to the realm of “revealed theology” where facts about God are discerned by reason applied to the data of revelation. Aquinas firmly believed, in opposition to a number of prominent theologians of his time, that the truths of the Trinity cannot be demonstrated by means of metaphysics; they are purely truth of revelations. This does not mean that he believes that metaphysics has no role to play; on the contrary, the role of metaphysics is to show that arguments against the truths of faith are not proofs. Metaphysics can be used to show that the truths of the faith can be explained in a rationally coherent way consistent with other scientific (in the widest sense of the word) truths.
One consequence of this is that there may be many ways of approaching and expressing the truths of the Trinity; unfortunately not every way of approaching the Trinity, however attractive it may be, is rationally consistent in this way with the truths of faith and of reason. Aquinas will spend much of his time in this part of the summa showing how it is possible to misunderstand the data of revelation and how this has led people into error throughout the ages.
Aquinas’s presentation of the doctrine of the Trinity does not arise out of thin air. He is indebted to the Fathers of the Church who came before him and especially to St Augustine (in the West), the Cappadocian Fathers (in the East) and the some of the documents of the early ecumenical councils. However, it is also true to say that Aquinas produces a creative synthesis out of the tradition that is handed on to him that goes deeper and further than that tradition.
Why this Question Matters.
One of the most fundamental questions in the consideration of the Trinity is: where to start? What are we to make of the data of revelation; what in it is most foundational for Trinitarian theology? The Christian doctrine of the Trinity is revealed in scripture but, as is well known, it took some centuries before the Church was able to elaborate and define what it meant by the claim that God is one substance in three persons, by an extended reflection on the meaning of scripture. St. Thomas starts his teaching on the Trinity by identifying that the most fundamental notion that scripture gives us is that of an “immanent procession” in the Godhead. We are quite used to the creedal claim that the Holy Spirit “proceeds from the Father and the Son”; what Aquinas notes is the scriptural teaching that, in sense, both the Son and the Holy Spirit “proceed” from the Father and that the “procession” of the Holy Spirit has a double meaning (which he will elaborate in later questions). In this question, Aquinas starts his meditation on the Trinity by elaborating the notion of “procession” and by introducing two ancient and fundamental heresies (Arianism and Sabellianism) that demonstrate how misunderstanding the idea of procession can lead to theological shipwreck.
The Thread of the Argument
A1: Following his standard practice, Aquinas first of all asks whether it makes any sense to talk about “processions” in God. The idea of this question, of course, is to understand the correct meaning of the word in this context and to point out how it can be misunderstood. In everyday life, “procession” usually means something like “a going out from”. The objections build on this observation to claim that such a notion of procession is incompatible with the divine essence. There is no motion in God, so there cannot be a “going out”; if something “goes out”, it is different from what it goes out from, but there is no diversity in God; if God goes out from God, it would seem that the first “God” referred to cannot be a first principle. The sed contra observes that scripture tells us about this “going out” from God; what then does it mean?
In his answer, Aquinas introduces a distinction between what we now call the “immanent” and the “economic” processions in the Trinity. To do this, he introduces us to the Arian heresy, which took the Son to be first among the Father’s creatures and the Sabellian heresy which took the Father, Son and Holy Spirit to be different modes of existence of the one God. He does this because he identifies the root of their mistakes to lie in their identification of procession purely with “economic procession”. This latter refers to the going out of the Son and the Holy Spirit into the created world from the Father. Aquinas claims that what the Arians and the Sabellians missed was the fact that this economic procession is founded in an “immanent procession", a procession that goes on within the Godhead itself. To help us visualize this idea, he gives us the analogy of the intellect understanding something; such an understanding, in a sense, both goes out from the intellect but also stays within the intellect itself. The intellect may present such understanding to the will so that (economic) action may follow upon this immanent understanding. Later on, Aquinas is going to push this analogy further; here he hints at by introducing the phrase “the word in the heart” to describe such a process of understanding. That Aquinas intends the reader to make the connection with the opening of St John’s Gospel should be clear.
The answers to the objections should be clear; the objections make the same mistake of identifying the economic processions of this world with the immanent processions within the Godhead. However, the reply to the third objection hints at a future theme. We’ve already seen that creation goes forth from God’s creative knowledge; itself a kind of procession. It is no coincidence that Aquinas will consider creation immediately after his teaching on the Trinity, as he sees the creation as an act of the whole Trinity.
A2: Having established the fundamental nature of procession within the Godhead, Aquinas immediately turns to the tasks of specializing this notion to the cases of the Son and of the Holy Spirit and of relating procession to the other words that scripture and tradition use to describe the relations between the persons of the Trinity. In this article, he looks at the description of the Son as “begotten of the Father before all worlds” (as the Nicene Creed puts it); the notion of “begetting” or “generation”. Applying the notion of “generation” to the Son might appear troublesome: we use the word “generation” to refer to the coming to be (and decay) of material things, this would clearly not work as far as the Son is concerned. Similarly, if Aquinas is going to push his analogy of procession with the conception of an idea (or word) in the mind of God, then how does he explain that we simply don’t apply the word “generation” to this mental process? Finally, if something is generated from another thing, it receives its existence from the latter. But if the Son is fully God, then He must be self sufficient existence and not receive His being from another.
Aquinas points out that “generation” can be used with a very wide meaning corresponding to a general notion of coming into existence and going out of existence but that it can also be used to refer to a process whereby something living comes into existence with the same nature as that that generated it. It is this latter use that carries over by analogy to the case of the Son being “generated” by the Father.
Replying to the objections, Aquinas points out that the first objection is founded upon the wider meaning of the word “generation”. The second objection is trickier. When we form an idea in our minds, that idea does not have the same nature as our minds, so in this sense the analogy fails. However, God’s act of understanding is His very being; hence the Son that is generated in this sense does have the same nature as the Father. Finally, and trickiest of all, one has to accept that the analogical use of the word “generation” has its limits. When we are talking about the generation of the Son, we have to understand that whilst He is generated by the Father, He doesn’t receive existence into some subject but rather He receives His existence as from some principle. The concern here is to avoid any notion of “subordination” in the Trinity (that the Son and the Holy Spirit are in any sense inferior to the Father) whilst recognizing that there are relations of order in the Trinity (so that the Father can be said to be the principle of both the Son and the Holy Spirit).
A3: Aquinas has connected the fundamental notion of procession with the generation of the Son and now he turns to the procession of the Holy Spirit. There are objections to the idea of more than one procession in the Godhead: if two, then why not three and four and so on? There is only one nature of the Godhead to be communicated, so how can there be more than one procession communicating that nature? The third objection is an excellent example of Aquinas anticipating an objection to the solution that he is going to propose: the procession of the Son corresponds to the going forth of a word in the intellect of God; the only other similar possibility would seem to be that the procession of the Holy Spirit corresponds in some way to the will of God. But in God, the Will and the intellect are the same thing, therefore there cannot be two processions.
Aquinas does indeed turn to the will of God as the solution to this question. In our minds, the intellect proposes something to the will as a good and the will is drawn by its nature to this good: there is a coming forth of love, immanent to the will, towards that good. By analogy, the immanent procession of the Holy Spirit corresponds to the procession of love towards the word in the intellect of God. The first objection is met as there is naturally within the Godhead, this structure of intellect and will, and no more. However, Aquinas will devote Article 5 of this question to a further consideration of this issue. The second objection is met by observing that what is true in the created word is not necessarily true of God. In God, any procession would be a means of communicating the divine nature.
The third objection goes to the heart of the difficulty of the doctrine of the Trinity; it challenges any notion of there being “structure” within God, as everything in God is in some sense “convertible”. Aquinas, of course, spent a lot of time showing that we can talk about things like intellect and will in God and that these notions, though imperfect, have some correspondence with reality. So here he is not going to give up so easily! Nothing can be loved by will unless it is conceived in mind so these processions, although they are related in being the same substance, are distinct as processions.
A4: Having established that it is fitting that the procession of the Son be called generation, Aquinas now has to face the awkward consequence of his argument that one might also call the procession of the Holy Spirit generation as well. This would be rather embarrassing, as Christian tradition (here Aquinas quotes the Athanasian Creed) holds that generation is unique to the Son. To answer this, Aquinas points out that intellect and will differ from one another in the following way. The intellect understands something when there is a likeness of the thing in the intellect for it to ponder. The will wills something not because the something is present in likeness but because it tends towards that thing. Therefore the procession that corresponds to the intellect carries within itself the very notion of likeness and thus corresponds naturally to the notion of generation (whence like comes from like). The procession corresponding to the will, on the other hand, carries with it the notion of tending-towards. We don’t have a particular name for this procession immediately to hand, but scripture indicates that we can liken this to the breathing of a spirit and so we can call it “spiration”.
A5: Returning to the first objection to Article 3 above, Aquinas now shows why there are only two processions in the Trinity. Given the way that Aquinas has explained the notion of procession, he seems open to the objection that over and above intellect and will we might attach a procession to God’s power or to His goodness. Similarly, we observe that created minds have many more than one single idea and therefore surely God must have many ideas, each of which would correspond to a procession. To meet these objections Aquinas returns to emphasize the fact that we are considering immanent processions in this question. We will see later that many things do proceed from the Godhead externally but as for immanent processions, he observes that in spiritual beings (and therefore by analogy in divine beings) there are only two actions that remain within the agent, those of intellect and will. Consequently there can only be two immanent processions that correspond exactly to these.
- The fundamental data of revelation concerning the Trinity lies in the notion of immanent procession within the Godhead. Although our experience in the world is of the action of the economic Trinity, we do not have to work backwards from this (as we did when we inferred God’s existence from his action in the world) to the immanent Trinity as the latter is revealed directly in scripture.
- Two of the “great” early Christian heresies were rooted in a misidentification of the economic Trinity with the immanent Trinity. Plus ça change, plus c'est la même chose.
- The procession of the Son corresponds to the idea of a word in the intellect; the procession of the Holy Spirit corresponds to the loving movement of the will towards that word.
- The procession of the Son can fittingly be called “generation”.
- In the case of the Holy Spirit, the word “procession” is overloaded. The word is used in common with the procession of the Son but is also used as a particular name for the procession of the Holy Spirit (which can also be called “spiration”).
- The idea that we can use the methods of metaphysics in order to discern truths contained purely in revelation (as opposed to natural theology) may seem troubling, if not repugnant. Aquinas was well aware of this objection and gives an extended apology for his approach in the opening two questions of his commentary Boethius’s “On the Trinity”.