Copernicus and Aquinas on Moving Day

Copernicus and Aquinas on Moving Day September 2, 2015

Duck pond, Morro Bay
Duck pond, Morro Bay

Recently I got the following comment from Sophia Sadek on one of my Aquinas posts.

The beloved of Aquinas is the prime mover of Aristotle. Ever since the days of Copernicus, it has been known that such an entity is neither necessary nor sufficient. Someday, the fans of Aquinas will wake up and realize the error of their ways.

I don’t usually respond to these; I’m never sure whether Sophia regards this as the prelude to a real discussion or whether she’s just trolling me, and gosh, life is short.  But she’s made this particular claim more than once, and I thought I’d address it.  (To be clear, the “beloved” in the above quote refers to God in context.)

To the extent that there’s a shadow of an argument here I take it to be this:

1. The God of Aquinas is the Prime Mover of Aristotle.

2. It was shown in the days of Copernicus that Aristotle’s Prime Mover is neither necessary nor sufficient (for what?) and hence doesn’t exist.

3. Therefore the God of Aquinas is neither necessary nor sufficient and doesn’t exist.

4. One day those of us who are fans of Aquinas will realize how wrong he was.

I’ll take these one at time.

The God of Aquinas is the Prime Mover of Aristotle.  It is true that Thomas’ proofs for the existence of God derive from Aristotle’s proof for the existence of the Prime Mover.  However, Aristotle understood the cosmos to be eternal; his Prime Mover was the ultimate cause of all motion and change in the cosmos, but was in no sense the creator of the Cosmos.  Thomas, by contrast, shows that God is not only the ultimate cause of all change, but the creator and the ultimate source of all being.  God certainly is the Prime Mover in some sense, but is rather different than what Aristotle understood by that term.

It was shown in the days of Copernicus that Aristotle’s Prime Mover is neither necessary nor sufficient and hence doesn’t exist.  Sophia doesn’t tell us who showed that the Prime Mover is neither necessary nor sufficient, nor how they showed it, nor just what it is that the Prime Mover is neither necessary nor sufficient for.  I understand her as follows.

According to Aristotle, the Prime Mover was directly responsible for the motion of the “heavenly bodies,” the stars and planets, which were thought to be of a different order of matter than things here on earth.  In particular, the planets were thought to be perfect spheres, eternally unchanging except in location.  The idea that the stuff up there is physically identical to and obeys the same laws as the stuff down here is relatively modern, and dates back to the invention of the telescope and the discovery of mountains on the moon.  This happened more or less around the time of Copernicus, and I presume that this is what Sophia is alluding to.

Where to start?  First, Thomas doubtless accepted Aristotle’s account of astronomy, at least so far as he could consistent with Catholic orthodoxy.  However, though he might refer to Aristotle’s account of planetary motion while illustrating some principle,it would only be an illustration, not a premise of an argument.  In short, the discovery that planetary motion is more complex than Aristotle realized casts no doubt on Thomas’ conclusions.

Second, it doesn’t even cast doubt on the existence of the Prime Mover.  The Prime Mover, remember, is the ultimate cause of change of motion, not necessarily the direct cause.  Thomas, were he aware of modern physics, would say that the planets move according to the Law of Gravity because it is the nature of physical bodies to so move; and the nature of physical bodies flows from their being; and their being they ultimately have from God, the Prime Mover, without whom nothing would be.

It is true that modern astronomy need not invoke the Prime Mover to explain planetary and celestial motion in terms of classical and relativistic physics; but the richness of physics reflects the richness of the God-given nature of things and is a cause for adoration rather than rejection of God.  And then, the existence of things and of the laws of nature both remain to be explained.

In short, you don’t need God to do physics; and God as Prime Mover is an unsatisfactory explanation for the physicist.  That’s fine; physics has a narrower bailiwick than metaphysics and theology.  But you can’t stretch from “you don’t need God to do physics” to “God doesn’t exist” or “God is irrelevant”.  It simply doesn’t follow.

Therefore the God of Aquinas is neither necessary nor sufficient and hence doesn’t exist.  I trust I’ve already dealt with this.

One day those of us who are fans of Aquinas will realize how wrong he was.  I’m still waiting.

____
Photo credit: William H. Duquette


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