Last week I linked to my paper “The Medieval Principle of Motion and the Modern Principle of Inertia,” which appears in Volume 10 of the Proceedings of the Society for Medieval Logic and Metaphysics. The paper addresses the familiar claim that Newton’s law of inertia has undermined the argument of Aquinas’s First Way, which rests on the principle that whatever is in motion is moved by another -- or, to state it more precisely, the principle that any actualized potency is actualized by something already actual. I argue that when Newton’s principle and Aquinas’s are properly understood, it is clear that the objection has no force and that those who raise it have not even managed to explain exactly what the conflict between Newton and Aquinas is supposed to be.
The first half of the paper is devoted to developing five reasons why the appearance of conflict here is illusory. In summary they are:
1. There would be no formal contradiction between the principles even if we took them to be using “motion” in the same sense.
2. In fact they are not using “motion” in the same sense, so that the objection rests on an equivocation.
3. That Newtonian inertial motion is commonly said to be a “state” which can be altered only by an external force in fact implicitly affirms, rather than conflicts with, Aquinas’s principle rightly understood.
4. Contrary to a common erroneous assumption, Aristotle and Aquinas do not hold that natural motions require a conjoined mover, which puts them much closer to Newton than is commonly realized.
5. Since Newton’s principle is intended to address a question of physics while Aquinas’s is intended to address a question of the philosophy of nature, the two principles rightly understood are not even addressing the same issues in the first place.
In the second half of the paper I examine, without endorsing, several ways of construing the relationship between the two principles, depending on whether:
1. We construe inertial motion as involving a genuine actualization of potency,
2. We construe inertial motion as stasis in the sense of not involving any genuine actualization of potency, or
3. We construe not only inertial motion, but physical events in general, as not involving any genuine actualization of potency.
I note several objections that might be raised against various alternative ways of construing the relationship of Newton’s principle to Aquinas’s on each of these interpretations. The reason I do not argue for or even endorse any particular interpretation is that it simply does not matter which one we adopt for purposes of evaluating the First Way. For none of the interpretations eliminate, or in principle could coherently eliminate, the actualization of potency; at most they merely shift it around like the pea in a shell game. And as long as there is some actualization of potency somewhere in reality, we have what is needed to get a First Way-style argument off the ground.
Now, my longtime readers might expect, as I certainly would have, that atheist physicist Robert Oerter, a smart and usually serious guy with whom I have previously had some very useful and friendly exchanges (here, here, and here), would have something of interest to say in response to the paper if he bothered to comment on it at all. If so, then they would be as surprised and disappointed as I was when I read this post which criticizes it. Prof. Oerter completely ignores the first half of the paper -- that is to say, he completely ignores the paper’s main arguments -- and he ignores almost all of the second half too. Instead he sums up the paper for his readers as follows:
Newton says that an object that is completely isolated, so that it has no external influences on it, will continue to move. Aquinas denies this.
So how does Feser resolve the conflict? Easy! The object in uniform motion is moved along by....
(wait for it)
Yes, angels are necessary to keep a moving object moving. I'm not making this up, he really says it…
End quote. Oerter then proceeds to ridicule this thesis he’s attributed to me, saying, among other things:
And how many angels are needed for this heavenly guidance? If an asteroid is being guided by an angel, and suffers an impact that splits it in two, does the angel recruit another angel to guide the second piece? Or can the first angel handle both pieces? What if the asteroid gets shattered into smaller and smaller fragments? Maybe each elementary particle has its own angel? How many angels are needed to guide a fragment the size of a pin? (And do they dance?)
Once again we see the Sophisticated Theologian in action. When the world doesn't work the way you want it to, just invent some invisible, undetectable beings to fill the gap.
End quote. Now those who read through my paper very quickly or only read the first half of it might have no idea what Oerter is talking about. They will no doubt find themselves as shocked as I was to learn that the aim of my paper was to argue that angels move asteroids around. But to afford Oerter the minimal fairness he has not afforded me, it is true that he has not spun his attribution out of whole cloth. For you will find, nine pages into my paper, a single paragraph wherein I do discuss (though I do not endorse) the idea that angelic substances are the cause of inertial motion. What Oerter has done is to rip this brief discussion out of context and insinuate that I endorse the thesis in question, that I think the thesis is needed in order to reconcile Aquinas and Newton, and that putting this thesis forward was the main point of the paper.
In fact, none of these things is true. In fact I do not think that angels are the cause of inertial motion, I do notthink that any appeal to angels is needed in order to reconcile Newton and Aquinas (one reason being that there’s no conflict between them in the first place), and the very idea of an angelic cause of inertial motion is discussed only very briefly in passing. All I was saying in that passage is that IF one regards inertial motion as genuinely involving the actualization of potency and IF we reject the thesis that the external physical initiator of motion is sufficient to account for inertial motion and IF we also reject the impetus theory and IF we also reject the idea that the Unmoved Mover directly causes inertial motion, THEN the notion of intelligent or angelic substances might provide a model for a cause of inertial motion. But I never endorsed every or even any of the options in this decision tree.
On top of that, Oerter offers no serious objection to the thesis in question, but merely ridicules it as an arbitrary “angel of the gaps” pseudo-explanation. But it is not that at all. Though I do not myself accept the thesis, it is not a silly one but makes perfect sense IF one moves down the decision tree in the way described above and IF one also understands what an angel is in the thought of an Aristotelian like Aquinas. (Needless to say, the idea has nothing whatsoever to do with wings, golden hair, white robes and the other stuff of children’s books. The relevant point is rather that an angel is something which, since it is not a composite of matter and form, has no inherent tendency toward corruption -- and is thus, unlike material substances, which do have a tendency toward corruption, a candidate for a cause of indefinite motion. If you don’t like the word “angel,” call it X.)
In fact all Oerter is doing is tossing some red meat to the New Atheist mob, who are sure to get some cheap giggles at the word "angel" without bothering to understand exactly what a writer like Aquinas means by it, or to read an article which Oerter has implied is nothing more than an absurd attempt to apply Highway to Heavento serious questions in physics. No doubt the meme “Feser claims that asteroids are moved around by angels!” will soon be regularly thrown out in comboxes as something “everyone knows.” Hope you’re proud of yourself Prof. Oerter.