July 2023, Daniel Shields

My book on Aquinas’ First Way was released this past Monday. It has been forthcoming for over two years, and some interesting contributions to the conversation have appeared between the time that the book was accepted for publication and the day it was finally published (such as Oberle’s article discussed in an earlier post.) In particular Joseph Schmid and Daniel Linford have written an interesting book Existential Inertia and Classical Theistic Proofs. Most of the book is not directly relevant to my interpretation of Aquinas’ proof, since I deny that the thesis of divine conservation has anything to do with Aquinas’ unmoved mover proof–unlike, say Edward Feser or Gaven Kerr. I believe in divine conservation, but cannot yet see how to prove it philosophically. (I have some hope that I will grasp the reason for it eventually; it took me 15 years to see why there must be a real distinction between essence and existence in mundane beings, but it is now clear to me.) In previous articles that I have read Schmid (and Oppy) raise reasonable and significant objections in favor of existential inertia.

The first chapter after the introduction of Schmid and Linford’s book is relevant as it deals more directly with the First Way, although they disavow any purely historical claims about Aquinas. They are trying to respond to contemporary Thomistic interpretations of the First Way. Schmid and Linford have raised a number of serious and reasonable objections to the First Way, objections very similar to ones I raised in my own book to the First Way as commonly interpreted.

Schmid and Linford argue that there is nothing in the logic of the First Way that rules out the possibility that different (essentially ordered) causal chains end with different first movers. Nor does the logic of the argument rule out the possibility that the unmoved mover that terminates any given causal chain is moved or movable in other respects irrelevant to its ability to initiate the causal chain in question. Finally, there is nothing in the logic of the argument that rules out the possibility that the unmoved mover terminating a given causal chain is unmoved in the relevant respect but yet not unmovable in that respect. The only thing that the logic of the argument shows is that for any given motion, there must be some mover that possesses the necessary actuality to cause the motion of itself, and not in a purely derived/instrumental way. All of this I myself have claimed in my book Nature and Nature’s God.

How, then, does the First Way conclude to God, as its last sentence indicates it does? There is a basic difference between the way Aquinas thinks about proving God’s existence and the way contemporary philosophers of religion do. Aquinas contrasts on this score with Scotus, who is more like our contemporaries. Scotus does not think that God’s existence has been proved until the existence of a unique, infinite being who is the first efficient cause, most eminent being, and ultimate final cause has been proved. For this reason his proof for God’s existence is very long. Aquinas, by contrast, does not think that very much is implied in the mere word “God”/”god”. The ancient Romans called the emperor a god, and the planets, and in some cases even the elements. God is a name for whatever rules the universe, in the sense of determining what goes on in it. By proving that there are one or more first movers, Aquinas proves that someone or some persons, or even something or things rules the universe. So the First Way has to do very little to prove the existence of God or gods. Aquinas’ strategy, by contrast to Scotus and our contemporaries, is to prove the existence of God in a very minimal sense, and then to progressively determine more and more about the attributes of that being that is called God, until He looks very much like the God that Christians worship.

But Aquinas’ claim that “this all call God” is made further understandable by the cosmological context in which he was writing. In the medieval understanding, motion here on earth was crucially dependent on the motion of the heavenly bodies. The heavenly bodies, in turn, must be moved by something, either a soul or a completely immaterial being. Those souls or immaterial being or beings would be the most obvious candidates for the first, unmoved movers of any motion here on earth. No one would have hesitated in the ancient world to call them gods. Aquinas knows that the logic of the First Way does not itself show that such souls or immaterial planet movers exist, only that one or more unmoved movers exists. So he does not draw any stronger conclusion than his logic warrants. But whatever is in fact a truly unmoved, first mover would be a kind of god, so the argument does show that one or more gods exists. It will turn out, given subsequent argument, that there is only one truly unmoved mover, and that He is completely immaterial. So the general conclusion of the First Way is never undercut, only progressively determined.

The First Way, in its basic structure, is based on Aristotle’s argument in Physics VII. Aquinas also provides an argument with the same structure in the Summa Contra Gentiles (what Kretzmann called G1). But in the latter work he also provides another motion proof (G2) that is based in its structure on Physics VIII. In his commentary on Aristotle’s Physics, Aquinas states twice that the argument in Physics VII shows that there is an unmoved mover, whereas the argument in Physics VIII shows what sort of being an unmoved mover is. We don’t get anything resembling what contemporary philosophers of religion think of as God (as opposed to the sort of thing a pagan might call a god) out of the First Way by itself. It is, rather, the first step in a longer argument. It is extended by the Third Way, or by the parallel argument G2. I explore both of these latter arguments in my book, but especially G2.

The Third Way and G2 turn the argument towards the possibility of an infinite accidentally ordered causal series and a beginningless universe. There it is argued that without an eternal, necessary being to sustain it, there cannot be an infinite accidentally ordered causal series. The conclusion, made explicit in G2 in the Summa Contra Gentiles, is that if the universe had a beginning, then an immaterial eternal God must exist to start it, and if the universe has no beginning, then an immaterial eternal God must exist to sustain it in motion. Otherwise it would come to rest (in modern terms, it would reach a condition of thermodynamic equilibrium) within a finite time. If the universe has no beginning, then an infinite time has already elapsed and the universe would be at rest already, if no God were sustaining it (the world would already be in a state of heat death.) This proves that God exists. It does not prove that the universe has a beginning.

Other authors should certainly continue to defend their interpretations of Aquinas’ argument. But it looks to me that my book is exactly what is needed to respond to Schmid and Linford’s criticisms.

Month: July 2023

New Podcast

Schmid and Linford on Aquinas’ First Way

Podcast Interview on Nature and Nature’s God

Nature and Nature’s God on Sale