Wednesday, 16 February 2011

Question 39 - The Persons in Comparison to the Essence


Aquinas has now spent some time investigating the Persons of the Trinity as Persons. For the rest of the Trinitarian treatise, he will investigate the relationship between the Persons and various other aspects of the Trinity. In this question, he investigates the relationship between the Persons and the essence; in Question 40 a detailed inquiry is made into the Persons and the relations and properties; in Question 41 the characteristic acts of the Persons are considered; in Questions 42 the Persons are compared with one another; and in Question 43 the missions of the Persons are considered.

Why this Question Matters.

The Christian doctrine of the Trinity is prone to the opposite errors of tri-theism (where the Persons are seen as individual Gods) and of modalism (where the Persons are “collapsed” into the divine essence and are seen merely as “modes of being” of the divinity). In the first article Aquinas recalls that divine simplicity implies that the Persons and the divine essence are the same reality; but that there is a real distinction between the Persons because they are subsistent relations. With this apparently paradoxical situation explained through our analogical understanding of God, the rest of the question is devoted to how we may speak of, and understand, the Persons in relation to the divine essence without falling into error.

The Thread of the Argument

A1: Returning to the theme of how we are to understand the idea of God as being three persons in one essence, Aquinas asks whether the essence in God is the same as a Person. At first sight, this proposition would seem to be nonsense: for example, if the persons are distinct then this would imply distinction in the essence which contradicts the unity of God’s essence. Similarly, identifying Person and essence would seem to mean that each Person (or subject) would have its own nature; again a problem.

Aquinas returns to Divine simplicity in his answer: simplicity implies immediately that the essence of God can be identified with each Person. However, this answer is troubling in that we’ve spent many questions demonstrating the distinction between the Persons and now we seem to be saying that really they are the same. Some theologians, recognising this difficulty, proposed that we can find some way to distinguish between Person and essence. Aquinas rejects this saying that the relations in God (which define the Persons) are the Divine essence because of Divine simplicity. We must affirm that essence and Person are the same reality whilst simultaneously holding that there is a real distinction among the Persons. To reconcile this apparent paradox we remember that a Person is a relation subsisting in the Divine nature; the distinction between the Divine essence and the Persons is not a real distinction but a conceptual one.

This conceptual distinction between Person and essence allows us to affirm something of the essence while denying it of the Persons. Therefore we can simultaneously affirm the unity of the essence and the distinction of the Persons. The strangeness of this position arises from the fact that in God the relations are subsistent; in created things this is never true and therefore analogies that we might attempt with creatures break down. Thus, as far as created natures are concerned, individuals are individuated as subjects by matter. When we use the notion of “subject” or “hypostasis” when referring to God by analogy with created subjects we have to remember that the principle of individuation that gets us the notion of “subject” is different. To think of three blobs of “stuff” within God pushes the analogy too far; although they are analogous, individuation by relation is different from individuation by matter.

A2: Aquinas continues this theme of naming Divine realities by analogy with created realities when he turns to the question of whether we can say that the three Persons are “of one essence”. In creation the nature of a species is individuated by matter; this means that we perceive the nature of a thing through its form and its individuality through its being a subject having that form. By analogy we talk of the essence as being the form of the three Persons. Now when we use the genitive “of” with created things we are happy to say that a form is “of” the subject that has the form. So we refer to the “health of John”. We don’t say that the thing is “of” the form; “John of health” (or “John is of health”) without a qualifying adjective (“John is of good health”) simply doesn’t work. Similar considerations allow us to say both “the essence of the three Persons” and “three Persons of one essence”, with emphasis on the unity of the essence.

A3: We can claim that the essence of God is the same as a Person and that the three Persons are of one essence; we can go even further than this and name an individual Person “God”. But when we do this are we using the name “God” in the same way as when we use the name “man” in the sentence “Socrates is a man”? In the latter, when we say that “Plato, Socrates and Cicero are each men” we mean that that there are three men under consideration. When we say that “The Father, the Son and the Holy Spirit are each God”, are we saying that there are three Gods? The objections suggest that that is precisely what we mean; but of course Deuteronomy demands “Hear oh Israel! The Lord your God is One God”.

To resolve this, Aquinas considers the more general question of how any name applied to the essence of God can be applied to each of the Persons individually. He immediately distinguishes between names that signify the essence as nouns and names that are adjectives and claims that such nouns are predicated of the Persons in the singular only (so that saying “The Father, the Son and the Holy Spirit are each God” only refers to one God). Adjectives, however, can be predicated in the singular or the plural. To see this, we recall that substances (signified by nouns) are those things that exist in and of themselves and that accidents (signified by adjectives) have their existence in some substance. Hence nouns are put into the singular or the plural according to the form corresponding to the substance; adjectives then agree grammatically with their nouns.

When we consider creatures, the only case where there is single form for a multitude is where we have a collection and this is signified by a collective noun which is in the singular (“a profession”). When described adjectivally (“professionals”) we get the plural, however. It is different when we consider God: we’ve seen in the last article that the divine essence has a signification like a form and this form is most definitely a unity. Therefore nouns that signify the divine essence are predicated of the Persons only in the singular. (Socrates, Plato and Cicero are three men that share the form of a human being and are each individuated by matter, but Father, Son and Holy Spirit, individuated by relative opposition, are not three Gods but one God.)

Adjectives are predicated in the plural because of the plurality of Personal subjects. An example from the Athanasian Creed illustrates the difference between the divine nouns and adjectives: using adjectives we speak of three who are eternal, uncreated, and immeasurable; but we speak of them as the eternal, the uncreated, and the immeasurable.

A4: In a sentence like “drink another cup, my friend” the word “cup” really refers to the wine that the cup contains; we’re not being asked to suppose that someone is literally to consume a cup! In the terminology of medieval logic the “signification” of the word “cup” in this sentence is a cup, but the “supposition” is the wine that the cup contains; we are “supposed” to infer that the sentence is referring to the wine rather than to the cup. This distinction between signification and supposition facilitates the precise analysis of how we use certain types of sentences in language.

In this question Aquinas asks whether concrete names for the substance of God can have a Person as their supposit. As the Nicene Creed identifies the Son as “God from God” it would appear that we have to allow for this. Aquinas rejects some contemporary theories as inadequate, claiming that the name “God” signifies the divine essence as existing in the one that has that essence; this wider understanding of the word “God” allows it to supposit for a Person. We therefore have to be careful to recognize when the word “God” supposits for the essence and when it supposits for a Person in a given sentence.

In replying to the objections, Aquinas distinguishes between the way that words work when applied to the created and to the uncreated. For example, when we use the word “man” in a sentence, its natural supposit is to an individual person, and something extra has to be in the sentence in order for it to be understood in the sense of “humanity”. This is because we infer the conceptual notion of humanity from the collection of individuals. In contrast, the word “God” is naturally associated with the common nature and we have to have something added to it in order to understand the supposition as referring to a Person (So in “God from God” the “from” shows that a procession is involved, which is characteristic of a Person.) This observation gets us out of the conundrum caused by the two sentences “God generates” (referring to the Father) and “God does not generate” (referring to the Son) offered in the third objection. Here, the first sentence contains the characteristic act of generation that identifies that the supposition of the sentence is the Person of the Father. The second sentence does not contain such a characteristic act (it would have to read “The God who is generated does not generate” in order to supposit the Person of the Son).

The replies to the fourth and fifth objections give extended examples of how to apply Aquinas’s teaching to unravel various apparent paradoxes caused by careless inference about the supposition of the word “God”.

A5: We have certain concrete names for the divinity, such as “God”, but we also have more abstract names like “essence”. Aquinas can now ask the same question as Article 4 for such abstract names; can they supposit for a Person? This time the answer is that they cannot. In answering this question, Aquinas is following the lines of a medieval controversy involving Joachim of Fiore, who had attacked the opinion of Peter Lombard, and whose opinions were promptly condemned by the fourth Lateran council in 1215. In following the line laid down by the council, Aquinas has to be sensitive to the use of language by the Church Fathers who had been willing to say that “essence is from essence”.

Aquinas points to Joachim’s mistake as being the fact that he has not understood that to understand a proposition, one must not only take into account what is signified but also the way in which things are signified. In this case a word like “God” signifies (or supposits) in a different way to a word like “essence” even though in reality God is the same as the divine essence. “God” signifies the divine essence as existing in one who has it, therefore it can signify in a way that refers to a Person. “Essence” on the other hand, signifies the divine essence as an abstract form and cannot therefore signify a Person.

The objections fall into two themes: the use by the Church Fathers of expressions that do apparently supposit a Person with abstract names for God; and apparent paradoxes caused by careless attention to detail.

Aquinas, following his usual reverential exposition of the Fathers, claims that they sometimes expressed things more strongly than their terminology would support. Now that terminological precision has been achieved, one should read the Fathers with the appropriate translation of terms or by disambiguating such expressions with the addition of appropriate terms. So a phrase in Augustine like “essence from essence” should be read as “The Son, who is the essence, is from the Father, who is the essence”.

As an example of one of the paradoxes, the fifth objection observes that since the Father is the essence, “the essence generates”. Therefore if “the essence does not generate” (as this article would assert), we obtain a contradiction. To resolve this paradox, Aquinas distinguishes between substantival names (like “Julius”) which automatically point to concrete particulars and adjectival names (like “Caesar”) which do not. An adjectival name requires a substantival name conjoined to it in order to signify (“Julius Caesar”). Since names like “essence” are adjectival, they cannot supposit for a Person. We would need to say something like “the essence is the God who generates” in order for the supposit to work. Hence there is no paradox because the word “essence” in the two sentences is not working on the same way.

A6: A brief article covers the question of whether propositions like “God is three Persons” or “God is a Trinity” make sense. In such propositions, the Persons are taken as predicates of the concrete essential names. Aquinas affirms that this can be done, by building on the analysis of Article 5, recalling the difference between adjectival names of the Persons (that cannot be predicated of the essence) and substantival names (which can). We then have to recall that not only is the divine essence the same as one Person, but also is the same as two or three Persons; therefore any combination of the Persons can be predicated of the essence. As we saw in Article 4 the name “God”, by its very nature, supposits for the essence. Therefore just as “the essence is three Persons” is true, so is “God is three Persons”.

A7: Nouns can be either common nouns (that name items in general) or proper nouns (that name particular items). So “apostle” is a common noun whereas “Paul” is a proper noun. But notice that we sometimes refer to the apostle Paul as “the Apostle”; when we do this, using a common noun as a proper noun, it is called “appropriation”. In the context of Trinitarian theology, appropriation is the ascription of common (and therefore essential) names to one of the Persons. In this Article, Aquinas notes that we do appropriate essential names to the persons (he gives the example “Christ, the power of God and the wisdom of God” from 1 Cor. 1:24) and provides a justification for this practice.

We can come to know of the essential attributes of God by the light of natural reason, and Aquinas has spent some effort in working this approach out in the treatise on the One God, using analogies of the Divine with the created. However, the attributes proper to each Person are beyond natural reason and are known only to faith. Aquinas argues that, as the Personal properties are so obscure, it is fitting that essential attributes be appropriated to the Persons in order to make the Faith manifest. However, as the objections point out, this is not without its dangers. Aquinas identifies two valid types of appropriation: in the first case by way of similarity (for example, things to do with the intellect are assimilated to the Son, who proceeds as the Word); and by way of dissimilarity (for example, power is appropriated to the Father in contrast to the way in which human fathers get weaker with age). Appropriation by similarity is much the more common of the two.

In appropriating essential attributes to the Persons, Aquinas is clear that we do not understand these attributes to be proper to the Persons, but that the process helps to make the Persons better known to us though similarity and dissimilarity to created things known to us. In doing so, we do have to be careful not to fall into error: for example, we must remember that the Father is not wise through the wisdom of the Son but rather is wise by the wisdom that is the Divine essence.

A8: Aquinas now turns to particular examples of appropriations made by some of the Fathers of the Church in their writings. The selection appears to have been made according to their importance in medieval controversies and Aquinas’s aim is to justify these appropriations against objections drawn from such controversies.

This final article is laid out in an unusual form for the summa. We have the usual section of objections laid before us first, attacking a series of appropriations, but then the rest of the question is taken up with Aquinas’s extended answer which lays out a series of principles for appropriation and then takes each objection in turn within the body of the answer. The result, very much longer than the usual respondeo section, reads a little bit like an individual academic paper embedded within the body of the summa. Because of its length, we will not attempt to prĂ©cis all of the arguments and counter arguments for each of the appropriations mentioned, but will merely describe the principles that Aquinas lays out.

Aquinas begins with an important reiteration of how we know God by analogy with how we know His creatures; and of how we know creatures themselves. Our first grasp of a created object is through its very being; we first grasp that it is. The second step is for us to understand the created object as a unity; it is not simply a being, but a being that makes sense to be identified as a unified thing. We then grasp the thing insofar as it has a power to act and to cause in the world. Finally, we understand the thing in relation to what it causes; indeed, we could not claim much knowledge of a thing unless we knew how it fits into the causal structure of the world. We can see in this division a relation to the structure of much of the first part of the summa: QQ. 2-10 deal with God in his being as known through analogy with His creatures; Q. 11 deals with God’s unity; QQ. 14-26 deal with God’s operations; and QQ. 44ff. deal with God’s relationship to creatures.

From the point of view of this question, however, Aquinas takes this division of the modes of knowing creatures (and thereby knowing God, by analogy) to point to different ways in which appropriation can be applied to God. We can apply appropriation from the point of view of God’s being; this gives us the Father-Son-Holy Spirit triad “eternity”, “species” and “use” that is the subject of one of the objections. We can consider appropriation from the point of view of God’s unity; this gives us the triad “unity”, “equality” and “harmony”. From the point of view of God’s power of causation we obtain the triad “power”, “wisdom” and “goodness”. Finally, considered in the light of God’s relationship to creatures, we obtain “through Him”, “with Him” and “in Him”, corresponding to efficient, formal and final divine causality.

Handy Concepts

  • The distinction between the Divine essence and the Persons of the Trinity is not a real distinction but a conceptual one.
  • Within God, the principle of individuation of the Persons is by relation, in contrast to the individuation of created objects by matter. Although analogous, we have to remember that individuation by relation is different from individuation by matter.
  • When considering a sentence in a language, we can talk about the signification of a term (which is what the term might be taken as pointing literally to) and the supposition of the term (which is what the term is really pointing to).
  • When talking about creation we infer “humanity” from examples of individual human persons. But when talking about divinity we infer the individual Persons from the common divine essence.
  • The process of using a common noun as a proper noun is called appropriation. In the context of Trinitarian theology, appropriation is the ascription of common (and therefore essential) names to one of the Persons.
  • Appropriation helps to make the Persons better known to us though similarity and dissimilarity to created things already known to us.


  • Much of this question might be seen as simply a defence of “how things are done” and of what was accepted and rejected by the Fathers of the Church. It is, of course, worth asking whether the principles that Aquinas used correspond to the principles that the Fathers used. One might also ask whether what we have here is a theory that designed to fit the facts rather than a theory that will predict the facts. But in defence of Aquinas one must also surely recognize that what he presents is principled and coherent with an organic relationship to what has gone before him.


  1. sunsetmike said...

    I recently was marked down on a theology exam for stating, "Aquinas explains that in terms of the Eternal Godhead, essence and person are the same."

    Am I wrong?

    Please help


  2. Hi sunsetmike,

    I think that if this was *all* that you wrote about how essence and person inter-relate than you would get marked down. The question is very subtle and what you've related above requires an explanation of why the answer does not fall into the error of modalism.

    I've attached your comment to this question, as it's the one in which Aquinas deals in detail with this inter-relationship.

    It might also be worth pointing out that the recent Dominican translation identifies the teaching of the 4th Lateran council against Joachim of Fiore (Denz. 803-4) as proximate background to the first two articles of this question.