The recognition of the plurality of the persons is the counterpart of the unswerving affirmation of the identity of person and essence. This identity was emphasized earlier in the scrutiny of the notion of 'person' (q. 29). Thomas comes back to this examination when he deals systematically with the relationships of persons and essence, much later in the Summa Theologiae
65 De potentia, q. 9, a. 7. The transcendental multiplicity thus consists in one aYrmation and two negations.
«« De potentia, q. 9, a. 7, ad 4. «7 ST I, q. 30, a. 3, ad 3.
(q. 39). The point of this question is to show that the divine persons each have their own prerogatives and simultaneously to bring to light and consider every possible aspect of the authenticity of Trinitarian monotheism. This thesis entails making numerous refinements to the way we speak about faith and to our grasp of the Trinitarian mystery. It will bring out once again the benefits of the theory of subsistent relations.
Recalling the historical origins of this question takes us back first of all to the twelfth century, and Gilbert de la Porrée. In order to safeguard the unity of the divine nature of the three persons, Gilbert declared that the relations are 'positioned from outside' or 'externally imposed'. St Thomas replied by distinguishing two aspects within relation, and he showed that relation in God is really identical to the divine nature.68 A further question has now to be asked, not in regard to relation, but to person. Is the person diVerent from the essence? Gilbert de la Porrée had taken over from Boethius the distinction between abstract forms (that through which a thing is what it is) and concrete subjects (the concretely existing individual), and he posited an analogous distinction within God. So people criticized him for introducing a diVerence between God (to which we refer in the concrete) and the divine essence (to which we refer in the abstract: that through which God is God) and of creating an apparent diVerence between the divine person, the Father for instance, and the relation or property, for example, paternity, as that through which the Father is Father. Pope Eugene III gave his doctrinal sanction to this latter foreboding. Theologians must not cast a division between God's essence and the persons. The divine essence is not just 'that through which' God is God, it is God himself.69 Gilbert's stalwart opponent, Peter Lombard, gave a lot of space to the debate in his Sentences.?0
Thomas' doctrine of subsistent relation enables him to tackle the problem in an eirenic way. As regards person and essence, he begins by referring to the historical aspect of the question:
Because, as Boethius says, it is relation which multiplies the persons of the Trinity, some have affirmed that in God the person differs from the essence. This difference derived from the fact that, as they thought, the relations are 'added on' (assistentes) to the essence; effectively seeing in the relations nothing but the idea of reference to another, forgetting that they themselves are realities.^
68 ST I, q. 28, a. 2. See above, in Chapter 5, 'The Being of Divine Relations'.
69 For more detail and bibliographical material, see our own brief exposition: 'Trinite et Unite de Dieu dans la scolastique, XIP-XIV siècles', pp. 201-204; Trinity in Aquinas, pp. 9-12.
70 Peter Lombard, Sentences, Book I, dist. 33 and 34.
71 ST I, q. 39, a. 1; cf. I Sent. d. 33, q. 1, a. 1; d. 34, q. 1, a. 1.
One can see in this the criticisms which he had earlier directed at the school of Gilbert de la Porree in his investigation of relations.72 On this basis, he can easily show the identity of person and essence in God, in a discussion which provides a remarkable synthesis of his theory of the person. In order to create this synthesis, all of the by now well-known features of the problem are drawn up: the exclusion of accidentality from God, the twin aspects of relation, relative opposition, and subsistent relation. Thomas remarks:
But as it was shown above (q. 28, a. 2) just as relations in created things inhere [in a subject] in an accidental way, so relations in God are the divine essence itself. It follows from this that in God the essence is not really distinct from the person even though the persons are really distinguished from one another. In eVect, as we also showed above (q. 29, a. 4), person signifies relation in so far as this relation subsists in the divine nature. But, considered in comparison to essence, relation only diVers from it conceptually; and, in comparison to the opposed relation, it is really distinguished by virtue of this relative opposition. Thus there is one essence and three persons.73
So the theory of relation enables one to respect God's simplicity in the very act of disclosing God's authentic plurality. Simplicity lays itself down as a fundamental rule of Trinitarian doctrine: God is his own essence or nature,74 and the persons themselves are this nature.
This meditation began as a criticism of Gilbert de la Porree, but that is not the whole of what it is aiming to achieve. On a deeper level, it is about the faith professed against Arianism at the Council of Nicaea: the Son is begotten 'of the substance of the Father' and he is 'coessential' or 'consubstantial' with the Father.75 Once he has completed his appraisal of Gilbert de la Porree, Thomas immediately raises the question of the unitary essence of the three persons: 'Must it be said that the three persons are of a single selfsame essence?'76 In short, 'the word homoousion, which the council of Nicaea adopted against the Arians, means that the three persons are of one essence'.77
Following the lead of Athanasius, Hilary of Poitiers, and Augustine, St Thomas strongly applies the 'numerical unity' of the essence to the three persons. The essence of the three persons should be 'one in number' (una numero).78 This phrase means that the three divine persons are not just of one
73 ST I, q. 39, a. 1; cf. I Sent. d. 34, q. 1, a. 1.
75 'Consubstantial' and 'coessential' are the two translations of Nicaea's homoousios which Thomas uses (Super IIDecret.; Leon. edn., vol. 40, p. E 41).
77 Ibid., sed contra. Like Athanasius of Alexandria in his own time, St Thomas extends what Nicaea says about the Father and the Son to the Holy Spirit.
78 Super II Decret.; cf. ST I, q. 33, a. 2, ad 4; q. 39, a. 5, ad 2.
specific nature, like the human persons in whom one recognizes 'the same nature' because they have the same humanity. In the Triune God, the essence is not 'multiplied' by the three persons, but the three persons are one and the same identical essence. St Thomas came upon this claim in his reading of Scripture.79 This numerical unity is an absolute prerequisite for maintaining the confession of the unity of God and crediting Son and Holy Spirit with their authentic divinity.80 St Thomas sees it as a strict exigency of the Niceno-Constantinopolitan Creed; the theory of the immanent processions of the Word and of Love enable one to disclose this precise numerical unity.81 Thomas states that,
Since the Father, the Son, and the Holy Spirit are not distinguished through their divine nature but solely by their relations, it is therefore appropriate that we do not call the three persons 'three gods', but confess one single, true and perfect God. And if, among human beings, three persons are called three men and not one single man, that is because the human nature common to the three is theirs in a different way, divided up materially amongst them, which could not take place in God. This is because, since three men have three numerically different humanities, only the essence of humanity is common to them. But it must be the case that in the three divine persons, there are not three numerically different divinities but one single and simple deity,82 since the essence of the Word and of Love in God is nothing but the essence of God. So, we do not confess three Gods but one sole God, because of the single, simple deity in the three persons.83
St Thomas is looking at the fact of distinction by means of relation alone, making it play a role analogous to that of a 'principle of individuation'. In physical beings, the principle of individuation is the material which renders an individual, in relation to the species whose nature the individual has.84 All of them have, of course, the nature appropriate to the human species, but this humanity is, as it were, 'multiplied' in each one of them.85 It works out differently in the Triune God. The divine essence is numerically one: the essence is absolutely one and the same identical reality in the three persons.
79 See for instance In loan. 14.10 (nos. 1887-1888,1891); 15.9 (no. 1999); 16.28 (no. 2161), etc.
80 SCG IV, ch. 7 (no. 3421); ch. 14 (no. 3502); ch. 8 (no. 3427).
82 'Deity': deitas. As so often with Thomas, the word is used here with a meaning equivalent to 'divinity' (divinitas), so as to designate the divine nature, despite the subtle difference between these two terms: 'divinity' can refer to participated divine being, whereas 'deity' refers exclusively to the divinity possessed through essence (I Sent. d. 15, exp. text: dist. 29, exp. text).
83 De rationibus fidei, ch. 4.
84 Cf. for instance SCG III, ch. 65 (no. 2400): 'There is such a thing as this man (hic homo) from the fact that human nature is in this material (in hac materia), which is the principle of individuation.'
What makes the persons of the Trinity plural is not the common essence but relation as a personal property, a 'quasi principle of individuation'. One of the outstanding benefits of the doctrine of the immanent processions is that its perception of the origin of the Word and Love in the Trinity shows this: the Word and Love proceed within the unity of the divine nature. Relative opposition as to origin makes the relations really distinct from one another, but each of them is really identical to the single divine essence or substance.86 In sum, this body of ideas (the person, relative opposition, Word and Love, and subsistent relation), coheres around the depiction of the Trinitarian unity of God.
5. PERSON AND ESSENCE: A PROBLEM RAISED BY JOACHIM OF FIORE
Once the controversy created by Gilbert de la Porree was over, a different misapprehension led to a more precise articulation of the relation between the Trinity and Unity of God. It came about in Joachim of Fiore's polemics against Peter Lombard. Peter Lombard's Sentences take up a radically different position on this from what we described earlier as being Roscelin's stance. Doubtless with Gilbert de la Porree in mind, the Lombard affirmed the absolute prerogatives of the unity of God: the Triune God is 'a single, once-off supreme reality'.87 Since the divine essence is an 'unitary, sovereign reality', Peter Lombard refuses to accept formulae like 'the Father engenders the divine essence', or 'the divine essence engenders the Son'. Since the essence or divine substance is the unitary reality of the Triune God, Peter Lombard figured that one cannot say the essence engenders, or is engendered, or proceeds: this would mean that the essence engenders itself, that is, that the Trinity engenders itself. It does not belong to the essence or to the substance but to the person to be the subject of generation and procession.88
This understanding of the three persons aroused both deep incomprehension and steely opposition in Joachim of Fiore (+1202). Joachim was attached to different formulae from these, which did use the words 'substance' or 'essence' to mean the person or hypostasis (and patristic precedents for these are not uncommon). So he rejected the terminology which Peter Lombard had imposed. Failing to grasp the way the Lombard's analysis
87 Peter Lombard, Sentences, book I, dist. 25, ch. 2, n. 5 (vol. I/2, p. 194).
88 Peter Lombard, Sentences I, book I, dist. 5, ch. 1 (vol. I/2, pp. 80-87).
distinguishes the reality from the ways our language works (like Thomas after him, Peter Lombard does not attribute generation to the substance but to the person who has this substance), Joachim could not accept a 'supreme reality which does not engender, which is not engendered, and does not proceed'. In his eyes, such a 'supreme reality' would be a fourth reality, alongside the 'reality which engenders', the 'reality which is engendered', and the 'reality which proceeds' (Father, Son, and Spirit). So he thought Peter Lombard's doctrine put forward a 'quaternity' in God, creating a synthesis which allies Arianism to Sabellianism.89
In 1215, the Fourth Lateran Council sharply rejected Joachim of Fiore's interpretation of Peter Lombard. The Council condemned the treatise in which Joachim formulated his accusation of heresy against the Lombard; and, not without generating yet another misunderstanding, it criticized Joachim for conceiving the divine unity like a collective union, that is, in the way that many men are one single people.90 As a result, the Council propounded a profession of faith in the unique divine reality which does not engender, is not engendered, and does not proceed, since each of the persons is this divine reality.
St Thomas commented on the Lateran IV decree Damnamus. He also mentions Joachim's diYculties in the Summa Theologiae.91 Joachim 'has not properly understood the formulae of Master Peter Lombard',92 'he is mis-taken'.93 On this basis, Thomas repeats that 'the divine essence is not something other than the three persons; so there is no quaternity in God'. Likewise, 'there is no distinction of the divine essence in the three persons'.94 The distinction is purely a matter of the divine persons in their mutual relations. This is a strict requirement of the Nicene Creed.95
As far as our language is concerned, Thomas recalls this fundamental rule: we speak of God not after the mode of God himself, but in a creaturely modality, and it is from this that we structure the words which we use to name God. This is why, in our language about God, we signify the essence as if we were referring to a form: we signify 'that through which' God is God, even though, in the divine reality itself, the divine essence is nothing other than the person (there is in God none of that composition of form and supposit which
89 For the references to Joachim's works and for the bibliographical references, see our exposition, 'Trinite et Unit*; de Dieu dans la scolastique XII e-XIVe siecles', pp. 204-205; Trinity in Aquinas, pp. 12-14.
90 Decress of the Ecumenical Councils, 2 vols., ed. Norman P. Tanner, Washington DC, 1990, vol. 1, pp. 231-233; Denzinger, nos. 803-807.
91 ST I, q. 39, a. 5. 92 Super II Decret. (Leon edn., vol. 40, p. E 41).
93 ST I, q. 39, a. 5. 94 Super II Decret. (Leon edn., vol. 40, p. E 43).
characterizes corporeal creatures96). And we signify the person as the concretely existing subject or subsistent, even though the person has no other reality than the divine essence itself. Our words cannot do any better than this. The different ways of signifying the essence and the person follow from this. For this reason, because of the mode in which it is signified in our speech, the essence cannot take the place of the person: that which properly belongs to the person is thus not attributed to the essence. Since the divine acts are performed by the supposits, that is, the persons, one does not say that the 'essence engenders', even though the Father who engenders is nothing other than the divine essence. The entire discussion is governed by what it means to be a divine person.97
But Thomas' reading of the Fathers had put him in contact with the 'essentialist' figures of speech, which attributed divine generation to the divine essence or substance (speaking of 'the engendering essence', 'the engendered essence', and so on). In the texts he had at his disposal, he found this especially in Athanasius of Alexandria, from whom Hilary passed it on to the West, and even in Basil of Caesarea.98 It is notable that when he focuses on Cyril,99 he has to explain that 'the Fathers sometimes impelled their language beyond the borders of terminological precision'. Because of the real identity of the essence and the person in God, Cyril sometimes overlooks the terminological proprieties, swapping one of them for another. When we read in the Fathers that the 'essence engenders' or that 'the essence is engendered', Thomas suggests that we take it as meaning that, through generation, the Father has given his own essence to the Son. Thomas concludes that these figures of speech have to be interpreted before one makes any generalizations on their basis.100
The same hermeneutic rules are applied to more important figures of speech. We have already remarked upon the outstanding case in point, the formula 'three persons of a single selfsame essence'. This formula is a direct consequence of the terms 'consubstantial' and 'coessential', put forward by the Council of Nicaea. In this phrase, we mean the essence as 'that through which' the three persons are the same God, whereas we refer to the persons as supposits or subjects possessing this essence. Such a distinction does not exist within God's own reality, but in our way of understanding and talking about the mystery of God. Since in God the essence is single and the persons
97 ST I, q. 39, a. 5; cf. I Sent. d. 5, q. 1, aa. 1 and 2; De unione Verbi incarnati, a. 1, ad 12.
98 For the texts which Thomas had from the Greek Fathers, see CEG I, ch. 4. Peter Lombard was doubtless unaware of the extent of the linguistic tradition by which Joachim was so captivated. Hilary's position was more well known in the West, and Peter Lombard had brought it into the discussion of this question (see the Sentences, book I, dist. 5).
100 ST I, q. 39, a. 5, ad 1; CEG I, ch. 4. On the method of reverential exposition, see above, n. 39.
plural, our dogmatic formulae profess the consubstantiality of the three persons like this. It works in the same way when we say that 'the Father and the Son are of the same nature'.i°i
The person and the essence are identical in reality, even though our respective notions for them are not precisely the same. We meet again the two sides to our language for God, which is not neutral or interchangeable. Observing this enables us to explain why one attributes certain properties to the person which one does not ascribe to the divine essence: even though the essence is not distinct, the person is distinct; the essence does no engendering, but the person of the Father engenders the Son. On this basis, it is the theory of subsistent relation which supplies an understanding of the conceptual distinction between the person and the essence and likewise of their identity in the reality of God.i°2 The essence is not something additional on top of the three persons, and is thus in no way a 'fourth' thing alongside the three persons. When it is added to the linguistic analysis which Thomas never lets out of sight, the theory of subsistent relations enables one to present a genuinely Trinitarian monotheism.
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