Summa Theologiae 1.27

Q. 27 “The Procession of the Divine Persons”

Thomas begins his “Treatise on the Trinity” with a prologue in which he says that, “Having considered what pertains to the unity of the divine essence, it remains to treat of what pertains to the Trinity of the persons in God.” So first comes unity, then plurality. Why? The answer has to do with the differences between faith and reason: for St. Thomas, God’s unity is a matter of rational demonstration—by natural reason alone man can determine the necessity of God’s absolute unity. The divine plurality, by contrast, is ultimately an article of faith: it is only because the doctrine of the Trinity has been revealed to man that we know the divine essence to subsist in a plurality of three persons. What this also means, however, is that plurality has a rational burden of proof that unity does not have. In the order of being, according to Aquinas, the unity of the divine essence is no more ultimate than the plurality of the individual persons, and yet it does seem to enjoy a certain priority in the order of reason, knowledge, or demonstrative explanation. But does this make sense?

What prompts Thomas’s discussion of the divine processions, accordingly, is not any rational consideration, but scripture itself, specifically, Jesus’s statement in the gospel of John that he “proceeded” from the Father. So it is a historically contingent revelation that informs us of the possibility of their being a procession within God, and hence which raises the present question. The first objection Thomas entertains in the first article to the position that there might be a procession in God is that the word procession signifies an “outward movement” (as we find, for example, in the case of Neoplatonic emanation theory); but in God, by contrast, there can be neither movement nor can there be something which is at once in him while being outside him. Thomas’s response to the objection, however, is rather remarkable, for it requires that the reader drastically rethink what is or at least can be meant by procession. To think of procession merely as an “outward movement,” after all, is fundamentally to think physically about procession: it is to think of procession, as Thomas puts it, “in the sense of local motion, or of an action tending to external matter, or to an exterior effect.” Now Thomas would admit that it is perfectly natural for one to think about procession in such physical terms, for as Thomas himself maintains, physical objects of our everyday sense-experience are what our minds know first and best. But natural human reason must make allowances for faith, for natural human reason by itself is limited by what is proper for the human mind to know, whereas the doctrine of the Trinity, for example, requires us to transcend  our usual ways of thinking about things. Thus, while the processions we are familiar with are exactly the kind of “outward movements” spoken of by Thomas’s objection, in the Trinity, by contrast, we seem to be confronted with an entirely new and different kind of processional possibility, a possibility, as we shall see, not fully grasped or exploited by Neoplatonic emanation theory; a procession in short, in which the act of procession terminates not outside of its source, but stays forever within its source.

Thus, what Thomas in fact confronts us with are not one but two different models for thinking about procession. But what exactly is meant by an “inward” procession? What analogies do we have for thinking about such a thing? In answer to this question, St. Thomas introduces Augustine’s famous psychological analogy for the Trinity. Just as in the human soul we find our concepts “proceeding” or “emanating” from the intellect, all the while remaining within the intellect, so the Son, as the Word of God, proceeds from the Father, all the while indwelling within him. Likewise, similar to human love which proceeds as a result of the soul intellectually grasping something as desirable, so the divine love of the Holy Spirit proceeds from the Father and the Son. The whole point of Aquinas’s use of Augustine’s psychological analogy, in summary then, is to provide a model for thinking about how Jesus can be correct in saying that he proceeded from the Father all the while leaving God one in his being.

Now, one of the things that is interesting to note about Thomas’s argument is how, in the very process of using the Neoplatonic concept of procession to explain the Trinity, Thomas ends up completely transforming Neoplatonism itself. As Thomas explains in his reply to the second objection,

“Whatever proceeds by way of outward procession is necessarily distinct from the source from which it proceeds, whereas whatever proceeds within by an intelligible procession is not necessarily distinct; indeed, the more perfectly it proceeds, the more closely it is one with the source from which it proceeds.” (ST 1.27.1 ad 2)

What Thomas is saying, in other words, is that because the thing which proceeds by means of an internal procession is more nearly like and united to the thing it proceeds from, internal procession is in fact a “more perfect” or higher form of procession than external processions. If we apply this same principle to Neoplatonism itself, however, we realize that the Neoplatonic hierarchy of being, by placing the external procession by which the One emanates into the divine mind above the internal procession whereby the divine mind is able to thinks itself, is in fact guilty of committing a grave metaphysical error: it privileges a lower form of emanation above the higher (in Christian terms, it is equivalent to saying that God’s outward act of creation is somehow prior to the inward act of the Father’s generation of the Son). In this way, by beginning with revelation, and yet using Neoplatonic concepts and rationality to help elucidate revealed teaching, Aquinas in the process effectively introduces a correction to Neoplatonism, and in a sense frees it to be more true to its own internal principles and logic.

A brief meditation on the two models of procession illustrated above. It is worth noting that the first, “physicalist” model also illustrates what, according to St. Thomas, is the human mind’s fundamental orientation in the act of knowledge: it is outward oriented. In order to understand the Trinity, however, or at least insofar as Thomas believes we can understand it, the human mind is in fact going to have to undertake the same kind of self-reflexive process or process of reversion that Thomas believes to be fundamentally involved in the processions of the divine Trinity. What this means, in other words, is that if the human mind is to come up with some analogy for thinking about how there can be a procession in God that nevertheless terminates within God, the human mind is going to have to refrain from doing exactly that which the doctrine of the Trinity denies of God’s own processions: namely, it is going to have to deny reaching for examples outside itself, and instead turn within itself. In this way the “procession” by which the human mind thinks about the Trinity comes to imitate or recapitulate the very procession within God that it seeks to understand.


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