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My book Nature and Nature’s God is on sale until the end of the year. If you order from the CUA Press website and use the discount code CREL23 you will receive 35% off and free domestic shipping.

Last week Alex Pruss, Rob Koons, and Ed Houser graciously joined me for a panel discussion of my book Nature and Nature’s God. I enjoyed everyone’s comments and objections, and found the event productive. What follows is the precis I delivered to start the discussion.

In my book Nature and Nature’s God I try to do two things: to set the historical record straight about Aquinas’ unmoved mover argument, and to defend a contemporary version of the argument in light of the developments of empirical science. Over the course of two decades I have felt that most presentations of Aquinas’ First Way have read much into the argument that just isn’t in Aquinas’ texts, and at the same time have drawn too much conclusion out of too little argumentation. Although St. Thomas certainly isn’t infallible, he was a brilliant man, and I take him seriously enough to think that understanding him on his own terms is worth my time.

My project on Aquinas’ First Way began when I learned something interesting about his philosophy of nature from Fr. Weisheipl, namely, that on his view heavy bodies fall of their own accord, with nothing impelling them downwards. I knew that Aquinas builds his First Way around the premise that everything in motion is moved by something else, which I thought meant that everything in motion must be currently impelled by some mover. If that mover was in motion, it too was currently impelled by some other mover, until one gets to an unmoved mover that impels them all: God. I found the argument, understood this way, unconvincing. But now it was obvious that this account of the First Way did not square with Aquinas’ own understanding of natural motion. Perhaps a much more interesting unmoved mover argument was hiding underneath a conventional interpretive cover.

Through a careful reading of Aquinas’ more elaborate presentation of the case for an unmoved mover in the Summa contra Gentiles, as well as books seven and eight of Aristotle’s Physics and Aquinas’ commentary on those books, an exciting physical as opposed to metaphysical argument for God’s existence emerged. Aquinas’ argument is clearly rooted in Aristotle’s, but Aristotle’s argument is quite foreign to us. We are used to cosmological arguments that first try to prove that the universe has a beginning, and then that God must exist to get it started. But Aristotle begins his whole argument by attempting to prove that the universe cannot possibly have a beginning. That proposition then becomes the key premise on which his entire argument for God’s existence is based: only an infinite power could cause a motion of infinite duration, and no physical being can have infinite power. Thus an immaterial being exists.

Aristotle’s argument proved troublesome for Jewish, Christian, and Muslim Aristotelians. It is a central tenet of traditional western monotheism that the universe had a beginning in time, a moment of creation. But the culminating piece of Aristotle’s philosophical corpus was built around a denial of this point of religious doctrine. Moses Maimonides solved the problem, and Aquinas adopts his solution in the Summa contra Gentiles. Aristotle’s proof is placed inside a disjunctive wrapper: although we can’t prove that the universe has a beginning, clearly it either did or it didn’t. If it did, then since nothing brings itself into being God must exist to get the universe started. If it didn’t have a beginning, then it has been in motion for an infinite duration, and then Aristotle’s argument applies: God must exist to sustain the universe forever in motion.

But why must a motion of infinite duration be sustained by an immaterial mover? Motion can either flow from a thing’s nature, or be imposed by an external agent. In Aquinas’ view motion that flows from a thing’s nature is directed, as to an end, to the thing’s natural place and condition. When the body reaches its natural place it naturally comes to rest and does not undergo any further motion unless acted on by an external agent. Hence natural motion is of finite duration. But external agents can only act insofar as they are moved or energized by the motion of a heavenly body. Otherwise the would-be agent and would-be patient simply undergo motion to their natural conditions and rest in equilibrium with each other. Only a voluntary, rational agent can continue to move other things in a cycle indefinitely, and such an agent, if physical, will be of finite power and wear down over time.

According to St. Thomas, all things on earth would move towards their natural place, rest there, cease to act on one another, and remain forever motionless if it were not for the fact that the cyclical motions of the heavenly bodies continued to affect terrestrial things and change them out of their natural conditions, stirring the pot so to speak. But the motions of the heavenly bodies cannot themselves flow from the nature of the heavenly bodies, since such motion is cyclical and does not head towards a natural place of rest. Thus the heavenly bodies themselves are moved by one or more immaterial agents. Since their motions are choreographed to maintain the natural cycles and teleological harmony here on earth, they must ultimately be directed by one single, overarching immaterial being who is directed by no other. This is God.

But if this is Aquinas’ argument, of what interest is it to us? We surely do not believe in the harmony of the spheres, celestial influences, or angels moving planets around. We also believe in inertia, indefinite “natural” motion that never comes to rest, and the conservation of energy as a physical law. Yet a closer look at modern physics reveals that Aquinas’ proof, in its essentials, is just as valid as ever. Allow me to explain.

Isaac Newton, the father of modern physics, stated that “The force of inertia is a passive principle by which bodies persist in their motion or rest. . . . By this principle alone there never could have been any motion in the world. Some other principle was necessary for putting bodies into motion; and now [that] they are in motion, some other principle is necessary for conserving the motion. . . . By reason of the tenacity of fluids, and attrition of their parts, and the weakness of elasticity in solids, motion is much more apt to be lost than got, and is always upon the decay.” No collision is perfectly elastic, and so bodies rebound with less total motion than they had before. Also, the viscosity of fluids and the friction of surfaces diminishes the motion of bodies moving through them or over them.

But the first law of thermodynamics states that no physical process can increase or decrease the amount of energy in a closed system. The energy of motion (“kinetic energy”) lost in collisions and through friction is converted to the energy of heat. Heat, in turn, can be converted back into kinetic energy by various processes, for example in steam locomotives. It might seem, then, that Aquinas’ argument cannot work: no immaterial mover is needed to sustain motion in the universe forever; the energy conservation law guarantees perpetual motion.

Yet scientists are agreed that a perpetual motion machine cannot exist. Why? Because the first law of thermodynamics is complemented by the second law of thermodynamics, according to which the energy in a closed system can only decrease in its availability, and never increase. “Entropy” is a measure of the degree to which energy has become unavailable to do work, and thus the second law is often expressed thus: the entropy of a closed system can only increase, and never decrease. As energy goes through various changes, it tends to find its way into the form of heat, and thermal energy can only be converted back into other forms of energy if it exists in two bodies at different temperatures. But heat tends to flow directly from a hotter body to a cooler body without doing any work, and thus more and more of a system’s energy tends to get locked away into the unusable form of thermal energy at equilibrium. In a sense Aquinas was right: all bodies head towards the natural condition of equilibrium, and once they reach it they never change again unless acted on by an external agent.

Rudolf Clausius, the pioneer of thermodynamics who coined the term entropy, applied the two laws of thermodynamics to the universe at large and expressed them thus: “1. The energy of the universe is constant. 2. The entropy of the universe tends to a maximum.” Modern physics and cosmology conclude that the universe must inevitably head towards the equilibrium condition known as the “heat death,” in which all energy is dissipated about the universe at even temperature, and nothing interesting ever happens again.

All bodies radiate their energy away in the form of photons; they shine at a frequency proportional to their temperature. This is why night-vision goggles work. But many of these photons inevitably escape into space where they undergo a cosmological redshift as the universe expands. As each photon’s frequency drops, the amount of energy it can deliver upon impact with a body diminishes. Thus energy is spread thinner and thinner throughout space, entropy rises, and the universe gets ever closer to the heat death.

If the universe had no beginning and had already existed for an infinite time, it would already have reached heat death. The fact that it has not indicates that the universe had a beginning a finite duration in the past. Alternatively—and this is where Aquinas’ argument differs from that the kalam argument—the universe has existed forever but God has either continuously or periodically converted some of its high-entropy, unavailable energy back into usable energy. In that way it could still exist out of equilibrium as it does today, without having a beginning in time.

Thus Aquinas’ unmoved mover argument is still valid, and serves as a welcome, more accessible addition to his other arguments, particularly to the argument based on the act of existence in De Ente et Essentia. The De Ente argument is a powerful one, but very subtle and not very accessible to the empirically minded. Aquinas’ more physical unmoved mover argument is a good first step for such people.

John DeRosa at the Classical Theism podcast graciously interviewed me about my book on Aquinas’ First Way, Nature and Nature’s God. It just went up yesterday. Check it out.

My article “Infinite Regress and the Hume-Edwards-Ockham Ojbection: A Thomistic Analysis” just appeared in the Proceedings of the American Catholic Philosophical Association. Here is the abstract:

One of the standard objections against the impossibility of infinite regress is associated with David Hume and Paul Edwards, but originates with William Ockham. They claim that in an infinite regress every member of the series is explained, and nothing is unexplained. Every member is explained by the one before it, and the series as a whole is nothing over and above its members, and so needs no cause of its own. Utilizing the well-known Thomistic distinction between essentially ordered and accidentally ordered causal series, I show that the Hume-Edwards-Ockham objection fails to touch Aquinas’s argument against the impossibility of infinite regress in an essentially ordered series. However, Aquinas also argues that accidentally ordered causal series can only regress infinitely if supported by an everlasting essential cause. The Hume-Edwards-Ockham objection does raise a question about this thesis, but I show how St. Thomas can reply to it convincingly.

Of note is that I respond in the endnotes to recent arguments in favor of infinite regress by Thomas Oberle.

My article in defense of classical theism against Schmid’s providential collapse objection has been published online here. A pre-publication manuscript version is available on my “Writings” page.

The International Journal for Philosophy of Religion just accepted my article “Simply Providential: A Thomistic Response to Schmid’s Providential Collapse Argument against Classical Theism.” In the article I advance an alternative to the standard “extrinsic predication” defense of classical theism from modal collapse. That defense works against modal collapse but leaves the doctrine of divine simplicity open to the charge of “providential collapse,” as Schmid has argued. On the extrinsic predication view the creation that obtains determines what it is that God can truly be said to will, rather than the other way around as ought to be the case. I argue that the extrinsic predication thesis is true of God’s “transeunt” actions such as creating this universe, but it is not true of God’s “immanent” actions such as willing or intending this universe to exist. The predication “God wills this creature to exist” is true in virtue of God’s relation to the creature, rather than in virtue of the creature itself. God, with no differences in Himself, can relate himself differently to possible creatures, thereby freely determining which will exist and which will not. Although Aquinas calls such relations of God to creatures “relations of reason,” the relations of willing and knowing these creatures is not, according to Aquinas, a relation invented by our reason reflecting on God and creatures. Rather, they are relations established by God’s reason. Such relations would exist even if no rational creatures existed.

Here is the abstract:

Classical theism is often said to suffer from the problem of modal collapse: if God is necessary and simple then all of his effects (creatures) are also necessary. Classical theists often turn to extrinsic predication in response: God’s simple and necessary act is compatible with any number of possible effects or no effects, and is only said to be an act of creating in virtue of the existence of the universe itself. Leftow and Schmid criticize this solution for leading to “providential collapse”: God would not have control over which creation obtains if all his intrinsic features are compatible with any possible universe. Thomistic classical theism avoids both modal collapse and providential collapse by utilizing the metaphysics of relations. With no differences within his simple essence/act, God can relate himself differently to his possible effects, willing some and not willing others. These relations determine whether or not the effects will exist. Thomistic classical theism’s version of divine simplicity is not incompatible with God having a multiplicity of relations, for the three divine persons are distinct relations within God. Divine simplicity is only incompatible with a multiplicity of absolute items within God. Furthermore, not all differences of relation are grounded in the different absolute characteristics of their relata. Rather, sometimes differences of relation themselves ground differences in the absolute characteristics of their relata. God’s divine act is thus said to be an act of willing this creation rather than that in virtue of his chosen relation to possible creatures, rather than in virtue of the creatures themselves.

At November’s American Catholic Philosophical Association conference in Houston there will be a panel discussion of my book, Nature and Nature’s God. Participating will be myself, Rob Koons, Alex Pruss, and Ed Houser. If you are attending the conference, please join us.

In my book I argue for a new, non-metaphysical interpretation of Aquinas’ first way and his other unmoved mover arguments. The arguments are natural philosophical ones. Understanding and defending the arguments require rolling up one’s sleeves and getting into issues of medieval cosmology and modern physics.

Until quite recently I have tended to use “concept” as a synonym for Aquinas’ terms “intelligible form” and “intelligible species” in the intellect. Aquinas does not use the Latin conceptus as a synonym for intelligible forms as far as I’m aware, but to students and non-experts in medieval philosophy “intelligible form” sounds too foreign. “Concept” seemed like an acceptable, familiar alternative.

But I have been reading Aquinas’ Treatise on the Trinity in the Summa and there he does use conceptus as a term, saying that “the mind’s interior concept/conceived thing (conceptus) is called a word (verbum).” (ST I, q. 34, a. 1, c. See also I, q. 27, a. 1.) As the Word of God, the Second Person of the Trinity originates from/is conceived by/is spoken interiorly by the Father. And a word/concept is distinguished from an intelligible species (I, q. 34, a. 1, ad 2.) An intelligible species is not posterior by nature to the act of understanding. But the concept/word is; it proceeds from the intellect. Hence a concept is to be distinguished from an intelligible form.

This distinction helps to solve a problem with Aquinas’ and Aristotle’s epistemology. Both of them hold that we come to understand something when the very same substantial form that exists in the natural substances of our experience comes to inform our intellect as well. It exists in the intellect not as a “natural form” but as an “intelligible form,” which has “intentional existence” rather than “natural existence.” The form of dog, for instance, takes on a new mode of existing when it informs our intellect; rather than making our intellect a dog, as the form does in its natural existence, it instead makes our intellect to know the essence of dog. Aquinas does not mean that there is a representative in our mind standing in for the essence of dog; rather the essence of dog itself is there, in an intentional mode of existence. Hence there is no problem in Aquinas’ theory of trying to bridge the gap between the mind and the external world by verifying how much the representation in our mind is like the dog-essence out there in Fido. This would be impossible since we would have no independent access to the essence out there to verify the similarity/lack of similarity in the representation. According to Aquinas, the form in our intellect is the very same form as that in Fido, Rex, Chester, and Rover, and so there can be no question of similarity/lack of it.

This understanding, if plausible, solves the “content fallacy” objection to Aquinas’ argument for the immateriality of the intellect. For it is not that the mind has something that represents an immaterial, universal essence. In that case, the content/thing represented could be immaterial while the representation and its subject (the intellect) could be material. Rather, to know the universal and hence immaterial essence, the mind must itself be informed by an immaterial, universal essence. And such an immaterial universal cannot exist in matter. Thus the intellect is itself immaterial. (The form of dog, say, is the form of particular material things, and hence exists in matter in its natural existence; but in its intentional existence it becomes immaterial and thus universal in its scope, no longer restricted to a particular instance of its kind.)

But Aquinas’ and Aristotle’s position here can seem implausible. For how can we say that we have the very same form in our intellect as exists in the world outside when we find that we can misapprehend the essences of things, and we need to revise and reconstruct our concepts of them? As a friend said to me recently, Aquinas thought that fire was an elemental body, and that turned out to be wrong. Surely Aquinas had enough experience of fire to possess the kind of phantasm from which the intelligible form of fire could be abstracted.

But here is where I think the distinction between an intelligible form and a concept becomes quite helpful. (I wish Aquinas himself brought what he said in his discussion of the Trinity about words/concepts into his epistemological texts. Perhaps he did somewhere and I’m not aware of it.) Our concepts are things that we construct; they originate from our intellect once it is informed by intelligible species. These concepts express to oneself, interiorly, what one knows. The concepts, not the intelligible species, are the things we are readily conscious of. Intelligible species are things by which we know the essences of physical things, but we do not have any ready cognitive access to the intelligible species themselves. On the other hand, the concepts we conceive in our minds are readily accessible to us.

But just as one can express oneself poorly to other people, so too the concepts one forms can express to oneself one’s intelligible forms poorly. We can misconstruct our concepts, and they can be in need of reconstruction. Most people, however, once they have formed their concepts, cannot think outside those concepts and have a hard time understanding other ways of looking at things. One of the things that philosophy is good at is teaching a person how to get behind his concepts and grasp other conceptual frameworks (think Kuhnian paradigm shifts; compare MacIntyre also.) Once one does this, one can then evaluate which conceptual framework more accurately captures reality. This involves comparison to one’s experience, but because sense-experience does not itself present essences or universals, to evaluate competing conceptual frameworks one needs more than a comparison to sense-experience. One must compare the conceptual frameworks in question to the intelligible forms that one has sub-consciously within one. Do the concepts one has been using accurately capture what one knows about reality? If not, what concepts might capture them better? Aquinas’ concept of fire was in need of revision, even if he possessed the intelligible form of fire in his intellect. Precisely because one has these intelligible forms in one’s intellect, the process of choosing between competing conceptual frameworks (e.g., Kantianism and Aristotelianism) is not a hopeless task. It is possible to see which set of purported concepts and principles is more true.

But unlike our concepts, the Word of God expresses God and His knowledge perfectly. The one Word eternally expresses God Himself and everything. Praised be the Blessed Trinity!

There is a second podcast about my book available, this one a quicker listen than the previous one. You can find it here:

https://wyomingcatholiccollege.podbean.com/e/nature-and-nature-s-god-with-dr-daniel-shields/

While you are at it, check out these other two podcasts, unrelated to the book:

A Philosopher reads St. Thomas:

https://wyomingcatholiccollege.podbean.com/e/a-philosopher-reads-st-thomas-aquinas-with-dr-daniel-shields/

Augustine’s Confessions:

https://wyomingcatholiccollege.podbean.com/e/augustine-s-confessions-with-dr-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.