At the very end of Thomas Aquinas’ treatise on the Trinity (questions 27-43 of the first part of the Summa Theologiae), he deals with the way the Son and Spirit are sent into the world by the Father. That is, he takes up the subject of the divine missions.
It’s a brilliant discussion in its own right, and is especially nice for readers who have made their way through the often arid stretches of the previous questions. Thomas’ special genius is his ability to handle things abstractly; in fact, at the absolute limit of abstract clarity. But the doctrine of the Trinity is not all abstraction; the doctrine begins and ends with God the Father sending the Son and Spirit. So when Thomas finally gets to that part of the doctrine, he gets to put everything together and apply it to real experience.
My favorite passage in the whole treatise is in Question 43, article 2. All of it is good, but the central paragraph, where Thomas makes his own statement, is especially helpful (and his reply to the third objection adds a lot). It’s only a couple of hundred words in English, and fewer in Latin. But reading it with students this week, I realized that Thomas expresses himself so concisely here that his meaning is almost inscrutable. You can’t figure him out just from staring harder at the page, you have to have read widely in his sources and his commentators, and it helps if you’ve already pondered the things he is talking about.
To make matters worse, the standard English translations are mis-leading on this passage. It’s as if they’re not even trying to make a real translation into a language anybody has ever actually spoken. So for teaching this stretch of trinitarian theology, I wrote out an expanded paraphrase, maybe a hyper-meta-phrase, of these three paragraphs from the Summa. I don’t really know Latin, but I made educated guesses by comparing 4 translations (including Alfred Freddoso’s very helpful one), and drew on commentaries.
The result is a nearly thousand-word essay on trinitarian missions; it started as a paraphrase and ended up as whatever it is. And here it is.
The Son and the Spirit come from the Father, but we should pay close attention to the different things that “come from” might mean. Some of the words we use to talk about this “coming from,” like “proceed” or “go forth,” are only intended to draw our attention to the way the Son and Spirit are related to the Father from whom they come. These words are only words about their from-ness, and they only direct our attention to the origin-point, or the relation of the Son and Spirit to the One they are from.
But other words we use to talk about this “coming from” are more comprehensive, and they include not only that relation to the origin-point, but they also include the end-point or terminating-point that is on the other end of that “coming from.”
But what is the terminating-point that is out there at the other end of a “coming from?” There are two very different kinds of terminating-points. One kind is eternal. Since the Son is eternally begotten from the Father, his eternal terminating-point is the divine nature. Where does he eternally come from? The Father. Where does he eternally end up? In God (or, the divine nature). He comes from the Father and comes into the divine nature. Likewise the Spirit eternally comes from the Father as the one who is breathed out, and he also eternally ends up in God. (All of this “coming-from” and “ending-up-in” that we have to talk about is not any kind of motion from location to location. It refers to a way of being. See Question 27, article 1, “On Procession in God.”)
The other kind of terminating-point is time-bound: the incarnation of the Son, or the outpouring of the Spirit at Pentecost. But whenever we talk about these time-bound end-points that the Son and the Spirit come into as they come from the Father, we always include that relation to the point of origin. The words that make that connection clear are words like “mission” or “giving.” The terminating-points are very important, because the whole point of being sent is to arrive somewhere and exist in that other place, and the whole point of being given is that somebody can have you. And when we’re talking about the Son and the Holy Spirit being sent and being given to us creatures, we can describe that as them taking on new terminating-points. When they have these new terminating-points, they are still the eternal Son and Spirit existing eternally in the same relationships to the Father. They are eternal, and so are their relations to the One who is their origin. But their new, time-bound terminating-points are not eternal; they are temporal. When the Son and the Spirit are sent to us or given to us, these divine persons are existing in us creatures in a new way: new in us, not in God.
So here is the right way to use all these different “coming from” words: “being sent” and “being given” are words that only apply to God in terms of time. We can’t talk about an “eternal mission to creatures” or “eternal gift to creatures.” On the other hand, “generation” and “spiration,” since they are the relations of origin that make the Son the Son and the Spirit the Spirit, are special words that only apply to the eternal life in God. But there are some words that are more comprehensive, and take in both the eternal and the temporal: these words are “procession” and “going forth.” Think about the various ways we can say that the Son proceeds: Because He proceeds eternally he is God, but because he proceeds temporally he becomes man. His proceeding to the new, temporal terminus point of humanity is his visible mission, the special sending that is the incarnation. And the Son also “goes forth” in his invisible mission, when he is sent to dwell in humanity by grace.
(Reply to the third objection): “Mission” does not just refer to the way the One who is sent is related to the One who sends. That would only point out that the Son proceeds from the Father, which could mean at least three different things (see above: to be God, to be man, or to be in man). “Mission” also identifies the terminus point in time. For that reason, a mission can only be temporal, and we should only use it to refer to the temporal event.
Or you could talk about it another way: You could say that a mission does reach all the way back and include the eternal procession, but it adds to it a temporal effect. When a divine person shows up on this end of having been sent to us, he still has the same exact relation that he always had to the One from whom he proceeds. And that relation is exclusively eternal; there is nothing temporal about that relation itself. What is temporal is the new terminus point (human nature) annexed to the relation by grace (the incarnation). So you could call the incarnate Son’s mission a “twofold procession,” a procession that is both temporal and eternal. But that is not because it has a twofold relation to its principle, but because it has a twofold terminus point: One in time, the other in eternity. If the Son had a twofold relation to his principle, we would end up with two different sons. But there is only one Son of God: He is who he is, in eternity and in time. The Son is always “from the Father” in exactly the same way of “being from:” in a sonly or filial way. But he ends up in God as his eternal terminus point, and ends up in humanity as his second, added terminus point.