Saturday, 13 November 2010

Question 29 - The Divine Persons


Aquinas has now established that there are real relations in God and that, as a consequence of divine simplicity, these relations are substantial. He has also identified the connections between the notions of procession and relations. Having dealt with these highly abstract concepts, Aquinas now devotes Questions 29-38 to an understanding of the idea of “persons” within the Godhead, connecting this notion with those of procession and relation, and providing a detailed discussion of each person. In Questions 39-43 he will then discuss in more detail the relations between the persons of the Godhead.

Why this Question Matters.

Aquinas is now aiming at a metaphysical elucidation of the classical Christian affirmation that God is three persons (Gk. hypostases) in one substance (Gk. ousia). The next step in this process is for him to address the question of what is meant in this context by a “person”. Aquinas has available to him a number of different definitions of personhood current in medieval theology; the one he favours is that of Boethius: “The person is an individual substance of a rational nature”. One of the major strengths of this definition is that it applies not only to human persons but can also be applied, by analogy, to angels and to divine persons; it is an expansive and inclusive definition. However, Aquinas has to explain carefully what the terms of the definition mean as it is easy to misunderstand what it is driving at. Having established a metaphysical definition of “person” he then has to discuss the various Greek and Latin terms used in Trinitarian theology, as to avoid later confusion. Finally, Aquinas delves into how the notion of person applies analogically to God: from this discussion will emerge the critically important idea that the persons within the Godhead are the subsistent relations identified in the previous two questions.

The Thread of the Argument

A1: Aquinas first addresses the suitability of Boethius’ definition of person. He observes that if we consider substances in general (i.e. the genus of substance) then we quickly recognize the fact that we can identify individual substances. Individual substances have the property that they subsist in themselves: they do not require some other substance to specify their being. Contrast an individual substance like a ball with the whiteness of the ball: the ball subsists in itself, but the whiteness (which we are quite entitled to call this whiteness) depends for its being on the ball. Aquinas identifies such substances as primary substances or hypostases. Further, there is a more perfect mode of particularity to be found amongst those substances that are rational; they are in control of their actions. These rational individual substances are what we call persons.

The objections to this article mostly focus on technical issues involved with the definition. For example, if we are taking “substance” in the definition to refer to primary substance, then it would seem redundant to refer to an individual substance. Aquinas replies that the addition of the word “individual” is justified because it adds the property of “not being assumable by another”. Although this may seem odd, Aquinas is thinking of the special case of individuated human nature in Christ: from the definition of Chalcedon we know that Christ is not a human person; His personality is that of the second person of the Trinity. Similarly one might object (on Aristotelian grounds) that the definition should use “essence” instead of “nature”. Aquinas replies that the sense in which “nature” is being used here (slightly different from Aristotle’s use), which is the essence of each particular thing, is better appropriate that the more general term “essence”. The reply to the fifth objection looks forward to Aquinas’ teaching on the soul: a separated substance (such as the soul of a human after death) is an individual with a rational nature but is not a person. Aquinas replies that the soul is a part of a human person and therefore cannot be identified as being a primary substance. It may be an individual, but it is not an individual substance.

A2: Terminology has always provided an obstacle to the understanding of Trinitarian theology. Even when the Doctrine of the Trinity was approaching its definitive conciliar form there was confusion between different theological schools that were using the same words to mean subtly (and sometimes not so subtly!) different things. Therefore, it is always a good idea, before embarking on Trinitarian speculation, to have a session devoted to the defining of terms. In the objections to this article Aquinas gathers together arguments and counter-arguments to suggest that a person, an hypostatis, a subsistent and an essence are really the same things. In a twist of scholastic humour, Aquinas gathers arguments for and against this position from a single author, Boethius, who is also the author from whom he has acquired his definition of person!

In his reply, Aquinas identifies two senses of the word “substance”. In the first sense, the substance of a thing tells us what that thing is: it is a thing’s what-ness or its quiddity. In this sense, substance is the same as the Greek ousia and can be identified with essence. (As an example of this use, in the creed we affirm that the Son is consubstantial with the Father; consubstantial is translating the original Greek term homoousios).

The second sense of the word “substance” is a bit more complicated, but basically refers to an individual thing within the genus of substance. As such, it can be described in a number of different ways. It can be referred to as a suppositum, which is a logical term referring to the thing that underlies some attributes (so, for example, the ball is the suppositum that underlies the property of roundness). Secondly a substance can be called subsistent insofar as it exists as a thing-in-itself and not in another (so the ball subsists but the roundness does not, as it exists in the ball). Thirdly, a substance is a thing-with-a-nature (the ball exhibits the nature of what it is to be a ball). Fourthly, a substance is called a hypostatis or substance in that it underlies its accidents (so the ball underlies the whiteness of the ball).

All that is left to Aquinas now is to specialize these words to the genus of rational substances.

A3: The Athanasian Creed explicitly attributes personhood to the Father, Son and Holy Spirit, but one might ask whether this is a reasonable thing to do. Aquinas replies by saying that subsisting in a rational nature is the most perfect thing in the created world and by the teaching of Question 13 Article 3 it is therefore quite reasonable to attribute personhood to God. We do, of course, have to remember that such an attribution is by way of analogy and that the personhood attributed to God is attributed in a far more excellent way than it is to creatures. Aquinas’s answer to the question set in this article is quite straightforward; the bulk of the interest comes in his replies to the objections.

First of all, one might object that scripture gives us various words and formulations to describe God and that we should not go beyond these. Aquinas admits that “person” is not said of God in scripture but he claims that what personality describes is used many times of God. Moreover, if heretics are to be refuted, then new ways of expressing the ancient faith are quite appropriate. In a similar line, one might object to the very word “person” because its etymological derivation is quite inappropriate to God. But this is to fall into the etymological fallacy; because a word originates in one way this does not imply it necessarily retains such a meaning (especially when it is being used, as here, in a technical sense).

In the reply to the third objection, Aquinas adds an important qualification to what he said about hypostatis in Article 2. In the created world, a substance is called a hypostatis insofar as it underlies its accidents: but in God there are no accidents, so surely we cannot apply the notion of hypostatis to God. Aquinas replies that, when applied to God, we are not thinking of hypostasis in this way but in terms of signifying a subsistent entity. He also relates some history of the terminological arguments in the early Church: as the Greek term “hypostasis” used to be translated as the Latin “substantia” (that is, “substance” or “essence” rather than the later understanding of “subsistence”), confusion arose as the Latins thought the Greeks were attributing three essences to God.

Objection 4 collects together some terminological problems. A rational nature would seem to imply discursive cognition, which is not true of God (Question 14 Article 7); individuation would seem to imply individuation by matter, again not applicable to God; God does not have any accidents, so how can we call Him a substance? Aquinas answers the first and third of these by pointing out that rationality can be thought of in a much wider sense and that substance refers, more fundamentally, to per se existence. In answering the second objection, Aquinas introduces the important idea of individuation as incommunicability. An individual is one for whom it makes no sense to attribute its properties to something else. So, for example, it would make no sense to attribute my thoughts to some other person.

Aquinas’s answers to objections 2-4 emphasize the importance of understanding that in Trinitarian theology terms are borrowed from the metaphysics of created reality and are given subtly modified technical definitions when applied to divinity. Failure to realize this will lead to failure to understand the analogical way in which personhood is applied to God.

A4: Aquinas leaves the hardest problem until last! How are we to understand personhood when it is applied to God? How does the analogy with created personhood work? The fundamental problem lies with our use of the word “person” in everyday language: when I talk about “that person, John”, I am referring to a concrete individual, to a primary substance. When I talk about a “group of people”, I am pointing to a plurality of individuals; the concept of relation doesn’t seem to enter into view at this point. Aquinas recognizes this and recalls that some theologians (including St. Augustine) took the word “person” as signifying the essence in God. They took the relational aspects defined by conciliar decree as a sort of ad-hoc “add-on” intended to confute heretics. Aquinas is not satisfied with this explanation, arguing that it simply leaves the door wide open for further misconceptions.

Another way of looking at the use of the word “person” when applied to God is to consider that it simultaneously points to both substance and to relation. The question remains as to which is primary: does “person” signify substance primarily and relation indirectly, or does it signify relation primarily and substance indirectly? Aquinas is happy with neither of these approaches but affirms that the second is closer to the truth; still, more work needs to be done.

To do this, Aquinas notes that we have to distinguish between what we signify when we talk about a “human person” (“this flesh and these bones and this soul which are the principles that individuate a man”) and what we signify when we talk about a “divine person”. When we talk about divinity, we remember that there are no accidents in God: the divine relations subsist in exactly the same way that the divine essence subsists. Therefore Divine Paternity (relation) is God the Father (person) is divinity (essence). Therefore, “divine person” signifies a relation as subsistent. For Aquinas, when we are talking about divine personhood, relation and essence are tightly interwoven and although we might assign priority to one, we have to remember that such identification is wrapped around with provisos.

So, Aquinas notes that his solution is, in a sense, consistent with the two previous ideas about relation and essence suggested above. However, it is important to note that he has welded the two ideas of relation and essence together much more closely than the previous theological solution would have it. It is true that “person” signifies relation directly and essence indirectly but we must note that it signifies “relation” as an hypostatis when we are talking about divinity. Similarly, it is correct to say that “person” signifies essence directly and relation indirectly but we must remember the proviso that this is insofar as hypostasis and essence coincide.

Handy Concepts

  • Aquinas adopts the definition of Boethius: “The person is an individual substance of a rational nature”. It’s a good definition from his point of view as it is (i) accurate and (ii) amenable to a strategy of analogical predication.
  • Individuals are characterized by their self subsistent existence. They are also characterized by the property of incommunicability.
  • It is important to grasp the technical meaning of the terms used in Trinitarian theology and to recognize that their analogical use when applied to divinity can mislead us if we are not careful.
  • Personhood in God corresponds to subsistent relation. Later on we will see that, in a sense, we should say that God is Father not because he has brought forth a Son; rather He has brought forth a Son because He is Father.
  • In article 4 Aquinas challenges St Augustine and corrects him. It’s interesting to note the way in which he does this: he has the confidence to take on an argument of one of the greatest of the Church Fathers but he also has the humility to do this is in a very gentle way. Augustine is correct insofar as he is using the theological language available to him, but Aquinas sees the need, and has the ability, to develop what the saint has done. This is a recurring pattern in Aquinas’s work.


  1. Thanks so much for your thoughts in clarifying part 1 q. 30. Today being Trinity Sunday, I was trying to understand 'person' as applied to God better. You have been helpful to me; God bless.

    Do we have to accept St Thomas' explanation of 'person' as being de fide? Or do we merely need to confess in English that God is three persons? If we are only obliged to do the latter, we still need to qualify the term 'person' in some way. Have others besides St Thomas proposed other clarifications which are acceptable to the Church?


  2. Welcome Yan! You ask a tricky question about the doctrinal status of St. Thomas's explanation of person.

    When the Church, in its doctrinal definitions, uses the term "person" (and I'm thinking especially of the 11th council of Toledo, of the confession of the 4th Lateran Council and of the decree for the Jacobites of the Council of Florence) one is obliged to understand the term in the way that the authority that promulgated such definitions intended it. So "hypostasis" means an individual complete substance existing in itself, and a "person" is a hypostatis of a rational nature.

    But one has to observe that each of these words is defined in terms of further concepts and that these concepts (especially in Aquinas) are derived by abstraction from our sensation of the material world, and then applied analogically to God.

    So I think that you do have to take the meanings of words (or their intended meaning) within de fide doctrinal definitions to have the same de fide status as the definitions themselves. After all, a de fide statement is irreformable by its nature. This doesn't, however, preclude doctrinal development strictly within the scope of the definition - and that may include further refinement (but not redefinition!) of the meanings of the words used.

    If anyone else wishes to jump in and correct me; welcome!

    As to your final question about other definitions, I'm not really sure. I have read alternative approaches to trinitarian theology, but I personally have found them lacking in comparison to Aquinas. You have to remember that the Church encourages theological speculation and rarely steps in to condemn error; and only when it is vital to do so. There may be plenty of theories that are out there that are "acceptable" in that they haven't been condemned!