Following upon these elucidations, St Thomas examines the name which Christians give to God: Trinity. The discussion of this term sometimes takes up a very large place in the scholastic Trinitarian treatises.20 The mid-thirteenth-century authors generally recognize that this is a relative name.21 Thomas confines himself to a rapid exposition, emphasizing both the plurality of the persons (numerically three) and their essential unity. The word Trinityrefers to 'the determinate number of persons'. Otherwise put: what the word plurality states vaguely, the name Trinity puts into a determinate form. Applied to God, the name Trinity refers in a precise way to 'the number of persons having one single essence'. It does not precisely signify the relations, but rather the number of persons who are mutually referred to one another through the relations.22 We will lay out the question of 'number' in more detail further on.
The plurality of persons, to which the word Trinity refers, implies a genuine alterityamongst the persons. St Thomas pays serious attention to the connection between plurality and alterity. The occasion is furnished by a conventional scholastic debating-point: 'is the Son ''other'' (alius) than the Father?'23 The Summa Theologiae brings together two problems which the Sentences consider separately: what is the alterity of the persons, and can one speak of a diversity of persons?24
Philosophically, according to Aristotle, the 'plural' is that which is 'divisible' or 'divided'.25 To account for the multiplicity, one must turn to the cause or explanation of the division. And this is not identically the same in things which are secondary and composed, and in those which are primary and simple. The cause of the division of secondary and composed things is the diversity of that which is simple and primary. This latter presupposes a plurality amongst primary and simple things. So the first 'division' comes from affirmation and negation (being and non-being). If there is alterity in things, it is because the negation of the one is in some way included in the other.26 The explanation of the alterity of creatures is connected to a reflection on being and non-being, on 'division' and diversity.
20 For instance, the Summa of Alexander of Hales dedicates seven chapters or questions to it (Book I, ed. Quaracchi, vol. 1, nos. 441-447).
21 Albert, I Sent. d. 5, a. 6, ad 1; Summa fratris Alexandri, BookI (ed. Quaracchi, vol. 1, no. 443).
22 ST I, q. 31, a. 1, sol. and ad 1; cf. I Sent. d. 24, q. 2, a. 2.
23 ST I, q. 31, a. 2. cf. Augustine, De Civitate Dei XI, X, 1.
25 Super Boetium de Trinitate, q. 4, a. 1; cf. Aristotle, Metaphysics X, ch. 3 (1054a22).
26 Super Boetium de Trinitate, q. 4, a. 1; St Thomas is discussing here how best to understand Boethius' statement that: 'the principle of plurality is alterity' (Boethius, De Trinitate 1, Leonine edn., vol. 50, p. 69).
When one turns to Trinitarian theology as such, the study of the plurality of persons will require a special kind of analysis, and fresh conceptual instruments. It also requires that one fine-tunes the terminology: not 'division' but 'distinction through relations'; not 'diversity' but 'distinction'.^ As to relation itself, it doesn't follow from distinction; relation is what entails distinction and personal alterity.M
By the end of the chapter, we should be able to see how to get hold of the Trinitarian plurality. But making our start with a consideration of the theological vocabulary used for plurality will enable us to stake out the question much better. Following his constant method, with which we are by now familiar, Thomas begins from the Trinitarian heresies which he wants to avoid, and concludes by indicating the path which gives an accurate view of things:
Now in speaking of the Trinity we must beware of two opposite errors, proceeding along a crest lined up between Arius' error in allocating three substances to the three persons, and the error of Sabellius, in attaching one single person to the single divine essence.29
The genuine distinction of the persons and their plurality requires that one recognize a genuine personal alterity in God. The Son is 'an other' (alius) from the Father, but he is not 'something else' and the Holy Spirit is 'an other' from the Father and the Son without being 'something else' than the Father and the Son are. We find here once again a double-mapping in our path to the mystery of the Trinity, or the double aspect which was brought out in our study of what relation is in God. The alterity of the Father, the Son, and the Holy Spirit is an alterity of 'supposits', an alterity of persons based on a relation-distinction, but not an alterity of essence, nature, or substance.3° Not acknowledging the personal or hypostatic alterity would backfire on us as Sabellianism; conceding an alterity of essence leads to Arianism.
Thus, the pitfalls of the heresies require us to take care about the words we use, so easily do they conceal ambiguous fault-lines. Paying attention to terminology is not a second-rate pastime. It expresses a very vivid sense of the rigour which it takes, whether in theology or catechesis and preaching, to express the faith authentically. The words we use have an enormous impact, since we refer to faith through them. Thomas recalls this in his appropriation of an ancient warning, made by Jerome at the time of the sensitive Trinitarian
28 De potentia, q. 8, a. 3, ad 12; see above, in Chapter 6, 'Relation the Heart of Trinitarian Theology'.
29 ST I, q. 31, a. 2. Cf. what Thomas already says in the Sentences, Book I, d. 24, q. 2, a. 1.
3° ST I, q. 31, a. 2; I Sent. d. 9, q. 1, a. 1, sol. and ad 2; De potentia, q. 9, a. 8; cf. Inloan. 14.16
controversies of the fourth century: 'careless words are a slippery slope to heresy'. Here more than anywhere else, it is necessary to take care to speak prudently or with circumspection (cautela).M Reflection on the two main heresies calls for the elimination of certain words from our Trinitarian language.
To avoid the error of Arius, one avoids speaking of diversity (diversitas) or difference (differentia) in God; that would destroy the unity of essence. But we can use the word 'distinction', on account of relative opposition. So if we come across a reference to diversity or difference of persons in any authoritative text, we take it to mean 'distinction'. Then, to safeguard the simplicity of the divine nature, it is necessary to avoid the words separation (separatio) and division (divisio) which are a matter of a whole divided into parts. To safeguard equality we avoid the word disparity (dispar-itas). To safeguard the likeness [of the persons] one avoids the words alien (alienus) and divergent (discrepans), following Saint Ambrose... and Saint Hilary____
On the other hand, to avoid the error of Sabellius, one avoids the words singularity (singularitas) so as not to negate the communicability of the divine essence; this is why Hilary says it is sacrilege to call the Father or the Son a single God. We must also avoid the term unique (unicus) so as not to negate the plurality of persons: Hilary also says that the idea of someone singular and unique is inapplicable to God. If we speak of 'the only Son' that is because there are not several sons in God. But we do not call him 'the only God' since the deity is common to several [persons]. We also avoid the term conflated [confusus] lest we endanger the order of nature amongst the persons. Ambrose thus writes: What is one is not 'conflated', and what is undifferentiated cannot be manifold. We must also avoid 'solitary' (solitarius) in order to respect the fellowship of the three persons; for Hilary says, We should profess beliefin neither a solitary nor a diversified God. 32
This discussion goes back over the rules for terminology which he gave in the Commentary on the Sentences and in the Questions De potential This list of proscribed words is not peculiar to him. It is an expression of the attention paid to the quality of words, within the context of respect for language which typifies scholastic theology. Such a glossary is significant to us because of the way it is organized. Using a well-known method, St Thomas has pulled his language together with the object of side-stepping Arianism and Sabellianism.34 One can also observe the references to the Fathers of the
31 ST I, q. 31, a. 2; cf. I Sent. d. 24, q. 2, a. 1; De potentia, q. 9, a. 8: 'it is necessary to speak of God in such a way that one never creates an occasion for error'.
33 I Sent. d. 24, q. 2, a. 1; De potentia, q. 9, a. 8.
34 This includes a study of antithetical parallelisms: there are thus four groups of words to avoid in relation to Arianism, and also four for Sabellianism, as Thomas explains in his Commentary on the Sentences (I Sent. d. 24, q. 2, a. 1) and in his Disputed Questions De potentia (q. 9, a. 8).
Church (Western, as it happens, because the issue is Latin terminology) together with whom Thomas draws out the rules of Trinitarian language.
It is especially notable that 'difference' is excluded from this language. Today, it has become a common practice to indicate the Trinitarian plurality in terms of'difference', or 'unity within difference'. Thomas does not invite us to speak like this. Although he does use the notion of 'difference' in some explanations requiring a philosophical vocabulary (speaking of 'difference' is often introduced by an objection), he does not recognize 'difference' amongst the divine persons. The reason is simple: the word difference implies a 'distinction of form',35 which is to suggest a distinction within the nature or essence of the divine persons. In fact, according to a classic patristic exegesis of Philippians 2.6-7 ('Christ Jesus, though he was in the form [morphe; forma] of God... poured himself out, taking the form of a slave') 36 if we often use the language of accommodation to speak of 'form' within God, this is to designate the divine essence. The word diversity is even more serious, because diversity derives from substantial forms and so implies a difference in essence.37 But Thomas would have come across the word differentia in his reading of the Fathers, for instance in the Latin translation of John of Damascus' De fide orthodoxa3 He invites us to explain such formulae as 'difference of persons' as an expression of Trinitarian distinction (distinctio): one must take different to mean distinct. This is a recognizable example of the method of expositio reverentialis, from which, at opportune moments, Thomas did not refrain.39
Within the work as a whole, and both in its practice and in its theory, the investigation into Trinitarian plurality gives a central place to the language of distinction. The reason for selecting this word is obvious: in itself, distinction
35 De potentia, q. 9, a. 8, ad 2; ST I, q. 31, a. 2, ad 2.
36 Cf. Thomas, In Phil. 2.6 (no. 54): 'one calls the nature of a thing its ''form'' '. The meaning of morphe (which St Paul only uses in this one passage) is discussed; although it is also necessary to hold on to its sense of a 'manifestation of being' and of 'image', the anti-Arian controversy usually led patristic exegesis to find its meaning in nature or substance. See for instance Hilary of Poitiers, De Trinitate VIII. 45-47 (SC 488, pp. 450-455); Basil of Caesarea, Contra Eunomius I.18 (SC 299, pp. 236-237). Cf. P. Grelot, 'La traduction et l'interprétation de Ph 2.6-7. Quelques éléments d'enquete patristique', NRT93 (1971), 897-922 and 1009-1026.
37 De potentia, q. 9, a. 8, ad 2; ST I, q. 31, a. 2, ad 1. It is commonplace to proscribe attribution of'diversity' to God: see for instance Bonaventura, I Sent. d. 19, p. 1, a. un., q. 1, ad 4; d. 23, dubium 4.
3s See the passage cited in ST I, q. 32, a. 2, sed contra, and also De potentia, q. 9, a. 8, arg. 2. Cf. John of Damascus, De fide orthodoxa, versions of Burgundio and Cerbanus, ed. E. M. Buytaert, New York, 1955, p. 183.
39 De potentia, q. 9, a. 8, ad 2; cf ST I, q. 31, a. 2, ad 2. On this topic, see Y. Congar, 'Valeur et portée oecumeniques de quelques principes hermeneutiques de St Thomas', RSPT 57 (1973), 611-626; J.-P. Torrell, 'Autorites theologiques et liberte du theologien. L'exemple de St Thomas d'Aquin', Les Échos de Saint-Maurice NS 18 (1988), 7-24.
does not designate a difference of essence or substance, and it is thus perfectly suitable to express the alterity of persons sharing a single essence. Thomas uses distinction as much as he does relation to pinpoint the way in which the plurality of this world is a causal reflection of the plurality of the divine persons, which in turn confers an eminently positive character on the many-ness of creatures.40
St Thomas very seldom either refers to the Father as 'first person', or uses the phrase 'second person' to name the Son; he designates the Holy Spirit as 'third person' a little less rarely, but it is not a repeated formula within his Trinitarian vocabulary. This is despite the fact that, at least from Tertullian onwards,41 such language is common in the Latin tradition. So, for instance, the Trinitarian treatise in the Summa does not use the 'first' or 'second person.' The phrase 'third person' appears in one argument, and in the response to it, where the terminology is determined by the sources of the discussion,42 and in the response to one other argument, where Thomas shows that the Holy Spirit is not an 'intermediary' or 'mediate' person within the Trinity, but that he is the 'third person'.43 One can see that this way of speaking is rather peripheral. To our knowledge, St Thomas' complete works only contain one single text which uses the three formulae all at once, as in 'the first, second, and third person'; this passage, which comes from an argument in a disputed question, clearly presents the manner of speaking which was current in the school rather than the language habitually chosen by St Thomas himself.44
The accurate meaning of the expressions, 'first, second, third person' excludes any kind of priority of one person over another. One must be yet more precise than that, if one wants to render the consubstantiality of the Trinity. Taken in an absolute sense, 'where there is unity, there is no relationship (ordo) of first or of third'. So one cannot say that the Son is 'the second God', or that the Holy Spirit is 'the third God'. One can only say that the Son is the 'second person' or that the Holy Spirit is the 'third person'; this usage is recognized 'because of the plurality of persons'^5 Such expressions, which Thomas seldom employs, designate the order of origin or 'order of nature' in God, conforming to the baptismal and credal formulae. Otherwise put, the
40 I Sent. d. 26, q. 2, a. 2, ad 2; see below, in Chapter 14, 'Trinity and Creation: the Meaning of the Plural'.
41 See Tertullian, Contra Praxeas 6.1; 11.7; 12.3; 18.2 (CCSL 2, pp. 1165, 1172, 1173, 1183), etc.
42 ST I, q. 32, a. 1, arg. 1 and ad 1; cf. Bonaventure, I Sent. d. 3, p. 1, a. un., q. 4, arg. 2.
44 Depotentia, q. 10, a. 4, sed contra 2 (one can see a related expression in q. 9, a. 9, sed contra 3).
meaning of these formulae is just the 'number' we signify when we refer to many persons in their standing order: one, two, three, persons. So we need to examine more closely the idea of 'number' within the Trinity.
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