Tuesday, 12 October 2010

Question 28 - The Divine Relations

Why this Question Matters.

In the previous question, Aquinas identified as foundational to the explication of the Trinity the scriptural affirmation of processions within the Godhead. The fundamental points were made that these processions are immanent to the Godhead and that mistaking these immanent processions for the economic activity of the Trinity was at the root of the two important ancient heresies of Arianism and Sabellianism. Aquinas is now faced with the task of putting metaphysical flesh on the bones of this traditional interpretation of scripture. The basic tool that he has available to him is that of the category of relation. The strategy is quite straightforward: the processions within the Godhead define relations; as there are no accidents in God, these relations must be substantial rather than accidental; these relations are the persons within the Trinity. Aquinas will lay out the foundations for this strategy of persons-as-relations in this question and will complete it and elucidate the detailed consequences in the subsequent questions. All the while, he will navigate between the heresies of Arianism, Sabellianism and Tritheism.

The Thread of the Argument

A1: Aquinas is immediately faced with a fundamental problem in applying the category of relation to the processions in the Godhead. In the Categories, Aristotle identified relation as an accidental category. We know there are no accidents in God; hence such a category is inapplicable to God. This problem was well known by the time of Aquinas and had led to a realization that Aristotle’s notion of relation (set out in the Categories) had to undergo development and modification if it was to apply to the divine substance. Therefore Aquinas’s first question: “Are there any real relations in God?” is an entirely natural one to address. The objections home in on the obvious problems: there can be no accidents in God and it looks as though the relations involved here are actually “relations of reason” rather than “real relations”. The sed contra points out that if paternity and sonship are not real relations then God is not the Father or the Son in reality but only as a construct of our minds; an obvious lapse into a form of Sabellianism. In his reply, Aquinas observes that it is only in the category of relation that we find terms that express what is conceptual as opposed to real. Sometimes the relations between things are of the very nature of the things involved; sometimes, though, they are simply because of our understanding of the world. The processions in God are of the former type, because what proceeds from the Father has the same nature as the Father; this is paradigmatically a real relation.

A2: Having established that there are real relations in God, Aquinas now spells out the consequences of this by asking whether these relations are identical with His nature. One might doubt that this is so because in the normal course of events relations are something different from the substances in which they inhere. One might also point out that if God’s nature is fundamentally relational, this would seem to make His nature dependent upon something other than itself, which is clearly wrong. The sed contra points out that anything that is not the divine nature is a creature and yet, in the liturgy, we worship these relations as co-equal to God.

Aquinas briefly discusses two aspects of the accidental categories when we are talking about created things: their inhering in a subject (that is, their being is a being-in) and their specific character (or their essence). In the accidental categories other than relation, the specific character of an accident also inheres in its subject. So the accident of height inheres in a subject and is to do with the subject alone. For the accident of relation, though, things are different: the relation inheres in a subject but its specific character is associated with being directed to something outside the subject. One possible mistake to make here (which St Thomas ascribes to Gilbert de la Poirée as the reason for the latter’s condemnation by the Synod of Rheims) is to take account only the essence of a relation whilst neglecting its being-in a subject. If one does this, then a relation appears to be something that is not intrinsically associated with a subject.

Once one has realised this double aspect of the accident of relation, then the consequences of transferring this notion from creatures to the divine substance is that the being of a real relation can no longer be accidental, it has to be substantive. Therefore a real relation in God has the being of the divine essence and is therefore the same as the divine essence.

It might be objected at this point that in identifying the being of the real relations in God to be identical with His essence we have collapsed the persons of the Father, Son and Holy Spirit into one another. But we have to remember here the dual aspect of relations: they have a being-in a subject (which has here been identified with the divine essence) but they also have a specific character to do with going-out-to (or pointing-to) something (its “relational opposite”). So the being of the relations are the same, but their pointing-to their relational opposites differ. This fact is taken up explicitly in the next article.

A3: It would appear that since the relations in God are identical to His substance, then they cannot be distinct. Similarly, one might view the only real relation in God to be that of procession (or origination); any two examples of such could not be really different, but only conceptually so. Aquinas’s answer is disarmingly simple: if we attribute something to a thing then we attribute to it everything that is contained in the definition of the attribution. In the case of relation, the definition doesn’t only include the being-in of the relation but also the pointing-to of the relation. It is by the latter that the relations within God are distinct. Therefore we can quite happily affirm that when we think of the being of God, then unity follows on this being; when we think of the relations in God, distinction follows.

A4: Having established that there are real relations in God, now is the time to count them. Aquinas has already implied that there are four: those associated with Fatherhood, Sonship, Spiration and being-Spirated. The objections list a number of putative examples which would seem to suggest a multiplication of relations even as far as infinity. Equally one might object that Fatherhood and Sonship (respectively Spiration and being-Spirated) go together as a pair and should therefore only be counted once, giving us less than four.

When Aristotle discussed relations in the Metaphysics (as opposed to the Categories) he identified that relation is either founded on quantity or upon action (or being acted upon). As there are no quantities in God, the real relations in God must be founded upon action. Therefore the real relations in God are founded upon the internal processions in God (because the external relations with creatures do not define real relations in God). Therefore, from the investigations of Question 27, there can only be two opposite relations each corresponding to the two immanent processions within God. The procession of the Son from the Father gives us the relations of Paternity and Filiation; the Procession of the Holy Spirit gives us Spiration and being-Spirated). These pairs of opposed relations are genuinely distinct as each member of a pair has a different pointing-to. The examples of possible other relations presented in the objections fail, as they each boil down to a misunderstanding of God in His single act of being.

Handy Concepts

  • Following the tradition that he inherited, the fundamental metaphysical tool that Aquinas uses to build his theology of the Trinity is the notion of relation. Although the category of relation is not the most immediately given datum of revelation (that place belongs to the processions), Aquinas sees it as inevitable that any orthodox theology of the Trinity will necessarily be resolvable to one of relation.
  • The real relations in God correspond to the procession revealed in scripture.
  • In the created world, relations do not only have their being in some subject, they also have a going-out-to or pointing-to their “relational opposite”. We can distinguish between their being and their specific character. This twofold aspect of relations becomes critical for distinguishing the persons in the Trinity, when we generalize the notion of relation to the divine substance.
  • In using relations in this way, Aquinas has explained the unity of the substance (their being-in is the same) as well as the distinction of the persons (their pointing-to is different).
  • There are four real relations in God because that is what scripture reveals to us.
  • The connection between the real relations in God and the person of the Father, Son and Holy Spirit will be made in the next question.


  • It was well known by the time of Aquinas that Aristotle’s conception of relation as set out in the Categories needed to be developed in order to deal with the divine substance. (Indeed, Aristotle himself carried on developing the theory in the Metaphysics.) It is reasonable to ask whether the theory of relation was adequate by the time Aquinas applied it in his Trinitarian theology. Some would argue that his conception of relation was inadequate; others would say that it’s been downhill all the way since his time.

Saturday, 9 October 2010

Question 27 - The Procession of the Divine Persons


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.

Handy Concepts

  • 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”.

Thursday, 7 October 2010


One of the important metaphysical concepts that Aquinas makes use of is that of a “relation”. He uses the concept in Ia q.13 in talking about how we are related to God and how God is related to us. When he comes to consider the Trinity, the notion of a relation becomes central. Aquinas will develop an exposition of the Trinity that maintains metaphysical coherence between the idea of God as “one” and God as “three” by identifying the “hypostases” (or “persons”) within God as “subsisting relations”.

This article is intended to give a brief overview of how medieval philosophers thought about relations as an aid to understanding how Aquinas uses the notion.

There is a superb article on “Medieval Theories of Relations”, by Jeffrey Brower, over at the online “Stanford Encyclopedia of Philosophy”.

In many ways, this article simply condenses and simplifies what is said there, so if the reader finds what is written here intriguing, puzzling or simply infuriating, relief may be had by going on to read Brower’s article.

We’re thoroughly used to using the notion of a relation in everyday language. For example:

  • “James is taller than Richard.”
  • “This potato is heavier than that tomato.”
  • “Hannah is my daughter.”

These examples seem quite benign, but when one starts to consider the metaphysics underlying such expressions of relation one is rapidly exposed to some surprising difficulties. For example, it would seem quite reasonable to think that “James is taller than Richard” expresses an objectively real fact about the world rather than simply being a consequence of how our minds organize their thoughts about the world. This being so, it would seem that a relation has to be some sort of real thing in the world as opposed to something that only exists in the mind. Where then does this relation exist? What is it? Does it have form and matter?

Medieval philosophers started their thinking about relations from Aristotle’s treatment in the Categories (which we mentioned in our Introduction to Metaphysics). In this work, Aristotle divided what we can express about things into two classes: substance and accident. Aristotle characterises substance as that which cannot be predicated of anything or said to be in anything – “primary substances”; or as that which can be predicated of something but cannot be said to be in anything – “secondary substances”. On the other hand, accidents are predicated of things in the sense of being (or inhering) in things. There is a primary division between being in a subject (accident) versus not being in a subject (substance).

So, for example, when we say that “that cat is white”, we are predicating something (whiteness) of some thing (“that cat”). The whiteness inheres in the cat as an accident, whereas the phrase “that cat” points to that particular cat rather than being predicated of it, and certainly does not inhere in the cat. So in our sentence, “that cat” points to a primary substance and “white” is an accident inhering in that particular cat. Similarly, in the sentence “that animal is a cat”, “that animal” points to a primary substance and “cat” is a secondary substance, a universal.

In the Categories, Aristotle went on to divide up the class of accidents into nine subclasses. One of these subclasses is what we are considering here, the notion of “relation”. Aristotle’s original Greek described “relation” as “pros ti” (“towards something”) and this description gives us an important clue about the metaphysical opportunities and problems associated with relation. The other eight accidental categories are all naturally associated with a thing-in-itself: we can happily say that “the ball is big” (the category of quantity) or “the ball is in the sandpit” (the category of place) but when we come to talk about relations involving the ball, we need something else there as well: the thing that enters into the relation with the ball: “the ball is bigger than the ant”.

When we think of our original examples, a sentence like “James is taller than Richard” seems to involve a number of aspects. First of all, each of the participants in the sentence has a particular height; the relation between the heights of James and Richard is said to be founded in the heights of each individual. Next, there is a comparison between the heights that dictates whether the relation holds or not. Finally there are the questions of where this relation exists as an accident and the sense in which we can say that the existence of this relation is real.

In the Categories, Aristotle held that a relation is not a separate thing to which the participants in the relation are jointly attached but is really explained by the foundational accidents involved. This idea bears a sort of similarity to Aristotle’s approach to universals; universals are instantiated in their exemplars, there is no Platonic third realm of universals where they have a totally separate existence. However, for Aristotle, relations (as universals) are still real entities with their own existence.

In the Middle Ages, although philosophers followed Aristotle in teaching that relations are real entities explained by foundational accidents, there was a dispute between those that held that relations amounted to no more that these foundational accidents (“reductive realism”) and those who held that although relations were founded on these foundational accidents, relations were sui generis accidents (“non-reductive realism”). These latter (including Aquinas) held that we should distinguish between such a thing as the accident of height and the accident of pointing-towards other heights founded upon the accident of height.

There’s a major distinction to be made between some modern approaches to relations, where they are considered to be things that hold between two or more things and the Aristotelian (and medieval) approach in which they inhere in one thing pointing towards another.

Medieval philosophers were also willing to recognize a distinction between propositions and situations that define real relations (so called “relations according to being” or “relationes secundum esse”) and propositions and situations that simply express relative terms (“relations according to speech” or “relationes secundum dici”). In other words, a distinction was made between what serves to relate things and what simply stands in some relation. For example, if we were to come across a decapitated body with its head by its side, we might say “this is a head” and “this is a body”. “Body” and “head” would appear to be relative terms related to each other, but do “this is a head” and “this is a body” express real relations? The problem is that if so this would appear to identify substances with relations, but according to Aristotle relations are accidents. The solution is to recognize that these relative statements are describing parts of substances and not relations. If we were to go on and say “this is the head of that body” we would now be expressing a relation between two substances whose accidental situation indicates that they originally came from one substance. Aquinas refers to this distinction in Ia q.13 a.7 ad1.

Let’s consider another problem: think about the relation of “equality”. “James is the same thing as James” seems to express an obvious fact about reality. If this relation is a real thing, which we’ll call “R1”, then we can immediately observe that “R1 is the same thing as R1”. This is itself a real relation which we’ll call “R2”. We can then apply this reasoning to R2 to get R3, and so on. We soon see that our simple notion of the relation of equality implies an infinite sequence of “real things” associated with one apparently simple relational statement! This would seem the sort of hopeless mess that would have William of Ockham rubbing his hands in glee. The way out of this conundrum is to observe that when we say “James is the same thing as James”, we’re not really saying anything about James. We could quite happily substitute the word “James” with any “x” that named a substance and we’d still have a true statement. Statements like this do not express real relations (“relationes reales”) but what the medieval philosophers called “relations of reason” (“relationes rationes”). In this example, we notionally posit a relation founded on the unity of the substance concerned.

There are also problems in other directions and Aristotle seems to have identified some of these problems in his Metaphysics, suggesting that he himself knew that the treatment in the Categories would not ultimately be sufficient for all circumstances. Much of the medieval debate about relations amounts to a debate about how to relate the theory of relations given in the Categories with that advanced in the Metaphysics and then how to square this resolution with the data of revelation about God.

As we saw, our original examples given above seem to be based on accidents in both the objects appearing in the relations concerned. “James is taller than Richard” depends upon a fact about James’ height and a fact about Richard’s height and a comparison between the two. However, this need not be the case.

  • “Richard is thinking about Fiona.”

This sentence seems to express a relation between Fiona and Richard that only depends upon some fact about Richard (that he is currently thinking about Fiona). There would seem to be nothing about Fiona that is involved in this relation. (If one argues that “Fiona is known by Richard” is the underlying fact about Fiona that grounds this relation, one should consider that this is just another way of saying “Richard knows Fiona”).

  • “I have arrived at a position to the right of the column”.

Similarly, this sentence provides another example where it is a fact about me that founds the relation rather than any fact about the column. In both of these examples there is a profound asymmetry. Medieval philosophers dealt with these examples by using the idea of a “relation of reason” that we saw above. They considered that even if there were no case for considering one side of the relation being real (or extra-mental) we should consider it as if it were so, projecting the mental relation onto the subject concerned. In examples such as these, there is both a real relation and a relation of reason involved. Philosophers such as Aquinas were quite happy to consider that certain relations did not introduce something in extra-mental reality. The discussion in Ia q.13 a.7 gives a clear example of Aquinas exercising these concepts of real relation and relation of reason simultaneously.

  • “I am thinking about those two chairs.”

This sentence would seem to set up a relation between two chairs (as well as a relation between me and the two chairs). But surely this relation expresses no facts inherent in the chairs themselves. Here we have an example where the relations involved are purely those of reason.

Finally, we come to the examples that motivated much discussion in the middle ages about the nature of relation and about whether the notion of relation put forward by Aristotle was adequate when dealing with the metaphysics of theism.

  • “God the Son is the son of God the Father.”
  • “The Holy Spirit proceeds from the Father and the Son.”

We already know from Aquinas that when we talk about God, we often talk analogically. Does this apply here, when we talk about relations involving God? Or are these statements literally true, and if so, how are we to understand them?

If we take the statement “Jesus is the Son of God” as being true, then it appears to set up a relation between God the Father and the God the Son. If we were to consider this relation to be purely one of reason, then we would fall into the heresy of Sabellianism (the idea that the distinction between the persons of the Trinity is purely notional). If we were to suggest that the relation is real in the Son and a relation of reason in the Father, then we would be falling into the error of Arianism (that the Son of God is a creature) because the reality of the relation in the Son would correspond to an accident in the Son which would imply that the Son was a creature. If the relation were real in both God the Father and in God the Son then we would seem to have set up accidents in both of them, contrary to the doctrine of divine simplicity.

Aquinas’s solution is simple and bold: when we consider relations concerning the divine persons, those relations can correspond to substances rather than accidents. Aquinas will spend much of Questions 27-43 of the first part of the summa developing the idea that the persons of the Blessed Trinity are subsisting relations within the Godhead.