Aquinas believes that the fact that God is Trinity is purely a truth of revelation indemonstrable by human reason. However, although indemonstrable it is not unreasonable, as he has shown in previous questions. So far, we have seen how a metaphysical picture of God as Trinity can be built up consistent with (and possibly implied by) the data of revelation. This still leaves open questions about what we can know of the underlying reality of God as Trinity (the question of epistemology rather than ontology). In this question, Aquinas introduces facts about God that allow us conceptual access to the Persons of the Trinity; the notions in God that allow us to characterize and distinguish between the Persons.
The Thread of the Argument
A1: Aquinas has shown (in question 12) that our natural knowledge of God (i.e. the things that we can know about God in the absence of revelation) is derived purely from our knowledge of creatures. This means that our natural knowledge of God is restricted to what we can know of Him as causing the being of creatures. However, God’s creative power is common to the entire Trinity and is therefore associated with His essence rather than with the distinction of the Persons. Hence, our natural knowledge of God does not extend to a demonstrable knowledge of the Persons.
Aquinas goes further, saying that attempts to prove the Trinity of Persons are actually damaging to the faith. On the one hand, truths that are purely of the faith by their very nature surpass and excel human reason; to bring them down to our level is to undermine their dignity. On the other hand, attempts to prove such truths of faith (which are bound to have metaphysical holes in them) bring the faith into disrepute amongst unbelievers because it would appear to the latter that Christians base their beliefs on nonsense. Truths of the faith, such as the Trinity of Persons in God, should be received only through authority; theologians should concentrate their arguments on showing that such faith is not metaphysically impossible.
In the replies to the objections, Aquinas gives a forward reference (Question 39) to the idea of the appropriations: some attributes of God which are really associated with His essence can be appropriated to one of the Persons of the Trinity with which this attribute has a special affinity. We appropriate God’s power to the Father, His wisdom to the Son and His goodness to the Holy Spirit, for example. Aquinas is willing to admit that philosophers are able to infer the existence of such essential properties amenable to appropriation to the Persons.
In the reply to the second objection, Aquinas discusses the nature of explanation. In doing so he gives a nice illustration of a sophistication in medieval science that some may find surprising. He points out that an “explanation” can, on the one hand, have the nature of a proof or, on the other hand, it can simply provide a consistent description of matters of fact and that there may be other equally valid consistent descriptions. As an illustration of the former, Aquinas claims that the uniform motion of the celestial bodies is amenable to proof. For the latter, he describes the fact that although epicycles and eccentrics give a consistent explanation of the observed behaviour of astronomical objects, some other explanation may be superior.
A2: Aquinas now introduces the twin ideas of the Properties and the Notions in God. Simply put, the properties in God are what belong to each Person, as a Person, which allow them to be distinguished one from another; the notions are these distinguished characteristics inasmuch as they are known by us and allow us to distinguish the Persons (with a technical caveat concerning the common spiration of the Holy Spirit by the Father and the Son). This article considers whether it makes sense to posit notions (and therefore properties) in God. The usual objections can be made: scripture does not talk explicitly of such things therefore neither should we; such ideas confuse the already complex distinction between essence and personhood in God; one shouldn’t start to posit such things about a purely simple being. Despite the objections, Aquinas is able to rally patristic support in favour of the idea of the properties and notions: we simply do recognize that there are paternal, filial and processional properties and that we can know about them.
In the medieval period there were a number of solutions to this question offered by a variety of theologians. The “classical” position had been put forward in the standard textbook of the time by Peter Lombard. This stated that there are five such notions in God: the Father’s unbegottenness (or innascibility) and paternity; the Son’s filiation; the procession of the Spirit and the spiration of the Spirit common to the Father and the Son. Aquinas begins his answer by introducing the figure of Praepositonius of Cremona (Chancellor of the University of Paris at the start of the thirteenth century) as representative of those theologians denying such notions in God. Praepositonius identified statements such as “the Father distinguishes Himself from the Son through paternity” as simply being the equivalent of “the Father is the Father”. Statements such as the former are simply ways of speaking that actually say no more than that the Persons are distinct and that God is one.
Aquinas will have none of this! He recalls that we name in the way that we understand and that we understand things as concrete realities (named by concrete words) or as principles or forms of such things (described by abstract words). Applying our use of language to God does not destroy Divine simplicity: we can still apply abstract names when we talk of God’s essence and concrete names when we talk of the subsisting relations. If we were unable to do this, then we would be completely unarmed to argue against Trinitarian heretics: we need to be able to talk of God’s substance as a “what”; of the Persons as a “who”; and of the relations as a “that by which”. Within the Father there is no real difference between what He is, who He is and that through which He is; but in order to understand and describe Him we must be able to perceive and distinguish these three. A further consideration is that if we were unable to distinguish notions in such a way, we would not be able to distinguish between the two relations that the Father has with the Son and the Spirit respectively. However, it’s important to note that the filiation and the spiration are not distinct realities within the Father so the corresponding notions do not divide the Father but simply distinguish His relations.
A3: Having introduced the notions in the previous article, Aquinas now sets about defending the “classical” list. In order to account for the notions, Aquinas claims that Divine Persons are multiplied by their origin and that this can arise in two ways: by being source of another or by being from another. The Father is known by being not from another, the notion of innascibility (or unbegottenness). He is also known by the facts that the Son and the Spirit are from Him and these give us the notions of Paternity and Common Spiration. Similarly the Son is known by His Filiation and also by the Common Spiration and the Spirit is known by the Procession. There are thus five notions in God, only four of which are relations (innascibility is not relational, for which, see Question 33, Article 4). Similarly, only four of the notions are properties (as the common spiration is not a personal property). Aquinas completes his account with the rather obscure distinction between “notions of persons” and “personal notions” (which will be explained further in Question 40, Article 1) to claim that three of the notions are personal (Paternity, Filiation and Procession) whereas the other two are simply notions of persons.
A4: It might have seemed so far that Aquinas defends the notions in God as being of the Faith itself, especially in the light of his argument in favour of the notions based on the need to be able to refute heretics. But this would leave Aquinas in a difficult position: many distinguished theologians of the recent past disagreed with the account that Aquinas gives. Does this mean that Aquinas considers them all heretics?
In order to address this problem, Aquinas makes a distinction. One can identify those things that pertain directly to faith as revealed to us. For example, that God is both one and three. To deny any of these truths would be to fall immediately into heresy by the very nature of the denial. On the other hand, there are matters that pertain indirectly to the faith rather than directly. For example, a denial that Samuel was the son of Elkanah is not a direct denial of a truth of the faith, but the denial implies the proposition that sacred scripture errs in places which is a direct denial of the faith. In this case, the inference is pretty straightforward but in many cases the chain of reasoning from a particular proposition to a direct denial of the faith may be highly complex (and, indeed, inaccessible to many people). If this is so, then one cannot accuse of heresy those who hold such mistaken beliefs because the proof of their erroneous nature was not available to them.
- Our knowledge of God, derived from created causes, reveals the essence of God, but not the Persons as created causes are actions of the entire Trinity.
- The notions are distinct characteristics of the Divine Persons by which we can distinguish between them. We can go on to distinguish notional acts (where we think of the Divine Nature from the point of view of its relations) and essential acts (where we think of the Divine Nature absolutely).
- Cajetan identified that “This question does not concern the reality considered absolutely in itself, but the reality insofar as it is described and apprehended by us”.
- One cannot accuse of heresy those who were not in a position to be able to comprehend that a particular position implies a denial of the faith.
- Relations, notions and properties are all the same reality, differing from one another only conceptually. This distinction is not available to reason alone but is itself guided by revelation.