Using the elements which we have just brought to mind (the common and the proper), and in line with the project of thinking about faith which we sketched in the previous chapter, Thomas' thesis aims at giving an account of the divine persons who are the one God (the common essence), each of whom is characterized by a personal property (the distinction of persons). The notion of person as 'subsistent relation'—which we will look at in detail later on4s— is thus the synthesizing principle of Thomas' treatise about God. Since the divine person is to be conceived as a subsistent relation, the study of person must be preceded by a study of relation: and since our minds perceive procession as the foundation of relation, the theory of relation requires a preliminary study of procession. As we try to think about the mystery of the Trinity, the order in which we conceptualize things will thus be as follows: (1) the processions; (2) the relations; (3) the persons. Here again one finds the fundamental elements of this meditation, as St Thomas developed them in his
46 Theology does not restrict itself simply to repeating the thinking of philosophers, for human reason easily commits 'numerous errors' about God (STI, q. 1, a. 1). At the conclusion of his study of the essential attributes of God, in the Compendium Theologiae, St Thomas observes: 'That which we have taught about God has been treated with Wnesse by many pagan philosophers, even though some have commited errors on this topic' ( CT I, ch. 36). St Thomas was not satisWed with borrowing and using other people's philosophy: he created a philosophy.
47 ST I, q. 12, a. 12. This does not refer to everything which could be said about the divine essence: the treatise on the Trinity will show this by making further reWnements about the relation of the essence with the divine persons.
4s See below, Chapters 6 and 7.
Disputed Questions De potentia. Following the explanations given in the prologue of the treatise on the Trinity in the Summa, the study of 'that which concerns the distinction of the persons' is presented like this:
I. THE ORIGIN OR THE PROCESSIONS (q. 27)
II. THE RELATIONS OF ORIGIN (q. 28)
(a) The persons, considered absolutely (qq. 29-38)
1. The persons in their common properties (qq. 29-32)
- The plurality or 'number' of the persons (q. 30)
- Consequences of the plurality of the persons (q. 31)
- Our knowledge of persons (q. 32)
2. The persons in the features which are proper to each of them
(b) The persons, considered in comparison (qq. 39-43)
1. The persons compared to the essence (q. 39)
2. The persons compared to the properties (q. 40)
3. The persons compared to notional acts (q. 41)
4. The persons in their mutual relations (qq. 42-43)
- The persons' relations of equality and of similarity (q. 42)
This structure does not reflect the order of our discovery of the Trinitarian mystery, as one would find it in the Summa Contra Gentiles or the biblical commentaries.49 And it does not offer an historical approach which reflects the centuries-long genesis of the Church's confessions of the Trinity. The Summa Theologiae proposes a speculative understanding of the faith (intel-lectus Wdei) which exhibits the notions, so to speak, in the inverse order to that in which we would find them out.5o This method of exposition consists in treating procession, relation, and person in their conceptual sequence, so that
49 A comparison of the two Summas shows that, in the Summa Theologiae, the exposition is mainly dedicated to notions which, in the Summa contra Gentiles, are aimed at giving an account of the faith in the face of arguments against Trinitarian faith.
50 In faith, we know God through his action in the world and we confess the three divine persons; then theology refines that the persons, in virtue of the processions (generation of the Son, procession of the Spirit), are distinguished by relations. The Summa Theologiae in a sense follows the reverse order: processions, relations, persons (including the foundations of creation and grace which are studied in a detailed way in the rest of the Summa).
the reader can benefit at each stage from the elements conditioning our understanding of each of the notions. We reminded ourselves in the previous chapter that the only purpose of this speculative doctrine is to take us back to the profound teaching of revelation, conveyed by Scripture. To read the treatise on the Trinity in the Summa requires knowledge of biblical revelation, of the liturgy, and, to an extent, knowledge of Christian tradition.
The investigation of the three persons is structured in a similar way: each point of doctrine is situated in such a way that it draws on the preceding expositions and illuminates the subsequent scene. The study of the persons is the centre of the treatise on the Trinity. If one leaves out the two first questions dedicated to processions and to relation, the whole Trinitarian treatise comes under the heading: 'the divine persons' (qq. 29-43). St Thomas' teaching about the Trinity mainly concentrates on the reality of the Trinity itself, that is, on Father, Son, and Holy Spirit. So, Thomas first of all explains the notion of 'person', the meaning of this word and our knowledge of divine persons (qq. 29-32), then he studies each of the divine persons one at a time (qq. 33-38), in order finally to compare the persons (qq. 39-43). These comparisons are diverse. The study of some of them is mainly aimed at organizing the different aspects of our knowledge of the Triune mystery and of our language: it is a matter of comparing the person with the essence, with the properties, and with the notional acts of generation and spiration (qq. 39-41). The others concern the mutual relations of person to person, either at the heart of the immanent life of the Trinity (equality, relation of principle, order of origin, perichoresis: q. 42), or in the Trinity in its gracious action, when the Son and the Holy Spirit are sent to the saints (mission: q. 43).
The placement of the last question about the divine missions means, on the one hand, that, in studying the sending of the Son and the Holy Spirit, the theologian never takes his attention off the intra-Trinitarian mystery. On the other hand, it means that the divine persons are sent and given in their personal distinction, that is in their distinctive properties. Trinitarian doctrine, in illuminating our knowledge of the divine persons in the bosom of the eternal Trinity, furnishes the elements required to appreciate creation and to grasp the salvation effected by the sending of the Son and the gift of the Spirit. In this light, the treatise on the Trinity provides the foundation of the whole teaching which the rest of the Summa Theologiae offers. The Trinitarian treatise is thus constructed in a way that will disclose the three divine persons in their subsistence, in their properties, in their relations, and in their actions on our behalf. The fundamental structure of this theological exposition expresses Thomas' determined option for the central place of the person and for the role of relation in grasping the meaning of person.
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