This is the third and (hopefully) final post concerning the famous Prime Mover argument for the existence of God. In the first post I set forth the argument and claimed that it established the existence of a “being of Pure Act.” In the second post I responded to some common objections, and also explained why the being of Pure Act is “God,” in that the being of Pure Act must be one, immaterial, timeless, omnipotent, and immutable. I also claimed that it is somewhat irrelevant whether or not the Prime Mover argument alone is sufficient to establish that this being of Pure Act is personal. If such a being exists, who is purely actual, immaterial, timeless, omnipotent, and immutable, that is at least enough to prove false non theistic world views such as atheism and naturalism.
But besides this, I also made the comment that it is possible to show that the being of Pure Act is personal, although it is admittedly a bit less clear than with other attributes. In this final post, then, I’d like to accomplish the following: 1) show that the being of Pure Act is indeed personal, and 2) respond to more in depth, complicated objections to the argument.
The first argument used to show that the being of Pure Act is “personal” claims that all immaterial beings must be personal. In order to understand this claim, we first need to understand a bit of the underlying metaphysics. For Aristotle and Aquinas, all objects have a “form,” or an essence/nature, that which makes the object what it is. All material objects are “hylomorphic,” which just means that they are composites of form and matter, much like, as I discussed in the previous post, all material objects are also composites of act and potency. So, for example, a tree just is the form/essence/nature of a tree instantiated in the particular particles of matter which make up that tree.
Now, as should be clear, all material objects can only possibly have one form at any given moment in time. How could a tree possibly have the form of some other object such as, say, a crocodile, at the same time it has the form of the tree? For an object to change forms just is for the object to change to some other object. If I were to break down a chair and take the wood to make a table, the matter which makes up the chair would lose the form of a chair, and gain or become instantiated with the new form of a table.
But now consider the human mind. For Plato, “forms” actually exist on their own, independently of any instantiation of such forms in matter. In fact, for Plato, material instantiations of forms are less real than the forms themselves, mere shadows. For Aristotle, however, and then for Aquinas, forms are real only either in the objects in which they exist, or as abstractions from those objects in some mind which “grasps” that abstract idea of the form. So the form of, say, a kangaroo, doesn’t exist in some vague “world of forms” independently of the actual world; rather, the form of kangaroo only exists in real, actual kangaroos, and in any mind which thinks about/contemplates/understands kangaroos. When I conceive of a triangle, I am “grasping” the form of a triangle. The form, in a sense, exists, or is instantiated in, my mind. This means that the human mind cannot be a material object, for to be a material object is to only be capable of ever instantiating one form at a time, whereas the human mind quite obviously instantiates many forms, the forms of whatever it is capable of thinking/conceiving of (this last point gets into philosophy of mind, which will be a subject of a future post).
This seems to indicate that any immaterial object, by virtue of not being hylomorphic and thus not having the restraints of matter, would be capable of instantiating, theoretically, an infinite amount of forms. Since the being of Pure Act is necessarily immaterial, and is indeed the “most fundamental” immaterial being in that it actualizes all other potencies for existence, it would seem that, just like the human mind, the being of Pure Act must be “personal” in the sense of having the ability to “conceive of” different forms.
But, in addition to this, there is actually another, clearer way to show that the being of Pure Act is personal, although it too rests on an understanding of underlying metaphysical principles. For Scholastic philosophers, the Principle of Proportionate Causality entails that an effect of a cause must be proportionate to that cause. In the words of philosopher Edward Feser, “whatever is in the effect must in some sense be contained in the cause as well…a cause cannot give to its effect what it does not have to give” (Feser, The Last Superstition). As an example, imagine you come across a fire in the middle of a forest. You would rightly conclude that this fire had been caused to come about in some way, and that it did not just randomly pop into existence without any cause; but there are several different ways in which it could have come about. One way is that a different, already existent fire could have caused this fire to exist, either by say, a spreading wildfire, or someone carrying a torch who used that torch to ignite a pile of sticks. In this case, the cause would be said to contain the effect “formally.” Another way, however, is that someone came along and used a match to start the fire. In this case, though the cause of the fire does not actually contain fire itself, it does have the power to create fire. Thus, the cause contains the effect “eminently.” If the cause did not contain the effect in one of these ways, the effect would be impossible, and the fire would not exist.
Now, when we are considering the cause of things in the world, and in particular when we are considering the cause of human beings and human personhood, the principle of proportionate causality requires that our cause have our attributes either formally or eminently. Our attributes just are different powers or potentialities that we have due to our nature as human beings, and these attributes include our “personhood.” Now, if our attributes are just potentialities that we have, and if every potentiality must ultimately be made actual by the being of Pure Act, then the being of Pure Act is ultimately the “cause” of our attributes. This indicates that the being of Pure Act must also share our attributes, at least analogically.
No doubt a good deal of confusion will arise at this claim. After all, certain humans have attributes that surely we wouldn’t even want to say that God has: such as being evil, or being physically defective, or even just something trivial, such as smelling bad. In addition, if the being of Pure Act is necessarily immaterial, as we have shown, how could it be said to contain the material attributes that humans have, such as being short or tall, having skin, etc. Well, as said above, it is not the case that the being of Pure Act must actually contain all these physical attributes formally, but rather only that he must contain these attributes eminently; that is to say, that even if the being of Pure Act does not actually possess all of the attributes which humans do, he must at least have the power to produce such attributes. In the case of attributes such as moral deficiency, this is what is called a “negative” feature, or a “privation.” Moral evil is not an actual attribute in its own right; rather, it is the lack, or absence, or deficiency of an actual, positive attribute, namely moral uprightness (if you want to know why this is, just ask in the comments below and I’ll explain). In the case of attributes which only exist due to our physical, material nature, the being of Pure Act could only be said to contain these in the sense of having the power to create matter and material beings. Humans have other attributes, however, which are not material, such as morality and personhood. These the being of Pure Act could be said to contain formally; that is, not just having the power to create them, but actually possessing the same attributes, albeit analogically. In this way we can show that the being of Pure Act must possess a moral nature as well as personhood (let it be known that the idea of “personhood” is extremely complex and debated. Here, I am taking personhood to mean what Aquinas meant by it, that is, having intellect and will. This topic will be discussed further in a later post).
So finally we have established the existence of one being of Pure Act who is immaterial, immutable, timeless/eternal, omnipotent, and personal; and this being we can rightly, finally, call God.
But now let’s backtrack a little bit. For the most part, the objections to the prime mover argument that I’ve examined so far have dealt with the conclusion of the argument, that a being of Pure Act exists, and these objections I’ve looked at so far have been some of the most popular/common objections to the argument. I’d now like to look at a few, much more complicated, in depth objections. The first one again concerns the being of Pure Act. This objection states that the very idea of an unmoved mover is incoherent. Next, I’ll look at objections having to do with quantum mechanics. These last objections will be aimed not at the being of Pure Act, but rather the basic metaphysical principles themselves.
The first sort of objection claims that an “unmoved mover” is a logically incoherent idea in itself, on par with a “married bachelor,” even if not quite so blatantly inconsistent. After all, in our experience, everything which “moves” something else must itself be moved. A baseball bat can’t swing and hit a baseball unless it is swung by a person. This is, in fact, one of the main premises of the argument to begin with; that whatever is moved must be moved by another being already in act. The point is that no objects in our experience have an inherent power to move themselves or other objects, and yet objects are moved, thus the need for some being which does have the inherent power to move other objects. Baseball bats don’t swing themselves, brooms don’t stand up by themselves and magically sweep the floor; unless, of course, we’re in Disney’s Fantasia. But even in Fantasia, the brooms weren’t actually sweeping by themselves, they had been enchanted to do so by a magician. Even in our fantasies we cannot escape this intuitive metaphysical principle.
So how does the the unmoved mover actually move? The issue is that the premise states that “a potency can only be raised to act by another which is already in act.” But a being of Pure Act has no potencies able to be actualized. In our experience, everything that is moved, is moved by something which is itself moved, and etc. The Prime Mover argument was originally created not as a proof for God as Aquinas used it, but rather as just Aristotle’s attempt to explain all motion that we perceive. A being of Pure Act must exist to explain this motion. So is it possible for a being to move other objects without itself being moved, even though we don’t perceive such a being in our experience of motion? Emphatically, it is not only possible, it is necessary. Otherwise, there would be no such motion. We haven’t perceived such a being just because that being is the source and cause of all motion that we do perceive.
“But wait,” you might ask, “if motion is a potency raised to act, then wouldn’t the being of Pure Act have a potency if it changes from not moving to moving?” In other words, in order for the being of Pure Act to move anything, wouldn’t it have to go from a state of not causing motion, to a state of causing motion? And wouldn’t this change of states be itself a case of motion that needs explaining? The problem is that such a question assumes a temporal framework, whereas, as we have seen, the being of Pure Act is necessarily timeless. In our experience, all motion does exist within time. When I swing a baseball bat to hit a baseball, the motion exists in a temporal sequence. The bat goes from not swinging, to swinging, over a period of time. Also, this swinging happens relative to spatial position, because it is made of matter. For the bat to swing is just for the bat to change its spatial location. But the being of Pure Act is outside of time, space, and matter, and thus such frameworks just don’t apply. The being of Pure Act never goes from a state of not causing something, to a state of causing something, because such change of states is a temporal sequence. Rather, the being of Pure Act is outside of time, causing motion within time.
Take, for example, the beginning of the physical universe. Assuming that standard Big Bang models are correct (which is a totally separate, irrelevant issue), our universe had a beginning a finite amount of time ago. The way some people conceptualize the creation of the universe is that God had just existed for eternity past, and then, all of the sudden, bam! he created the universe; thus God was not creating for an eternity past, and then he started creating, which means he “changed” from not creating to creating. But again, this conceptualization just doesn’t work for a being that is outside time. It’s just meaningless to say that God “started” creating, or even to say that God has “always been” creating, because such concepts are intrinsically temporal. God can cause and affect motion that happens within time, and such motion does require an actual mover; but God himself exists outside of time as a purely actual being, and thus he himself never changes or undergoes motion. It would be like saying that in order for God to be the ultimate cause of a baseball bat swinging, God himself would have to move spatially, from one location to another. But God is immaterial and thus non-spatial, and its just nonsensical to say that he moves “from one location to another.” The argument says that all motion is potency raised to act, and that all potency can only be actualized by another already in act. But the argument nowhere states that a “mover” must itself be moved; it just so happens that all “movers” in our experience are secondary movers which themselves undergo motion and require external movers, and this series must terminate in one, unmoved mover, who is a primary rather than a secondary mover. Nothing has the power to move in itself except for this being of Pure Act, and all other beings derive their motion from this being alone.
To take an example that might work better for another of Aquinas’s Five Ways, but nonetheless fits here, think of the relationship between the moon and the sun. The moon is our second brightest source of light here on earth. But the moon does not actually possess any light in itself; it does not have the power to shine on its own. Rather, the moon reflects light from the sun, which does have the power in itself to give off light. Now, imagine a world where the moon didn’t directly reflect the sun’s light, but instead reflected the light from another moon. And this second moon, in turn, reflected the light from a third moon, and so on. Imagine that the only light that ever reached this world was from a series of thousands of moons, each reflecting the light from another moon. Even if we could not directly see the sun from this world, we would still know that there must be a sun, because moons, by their very nature, do not have the power to give off their own light. There must be a source of all the light. People from this world might wonder, “how is it possible for the sun to give off light without itself reflecting light from another source? All the sources of light in our experience only reflect light from other sources?” In the same way, we might wonder how a being could exist that moves other objects without itself being moved. We may not know exactly “how” this being does so, but we do know that such a being must exist, because all objects that we perceive are like moons; they are only secondary movers, which don’t have the power to move on their own, but only derive their motion from other moving objects. The Prime Mover is, in effect, the sun; the source of all motion.
The next, and final, objection, however, challenges this notion that all objects in our experience are secondary movers and can only be moved by other beings. In effect, it challenges the premise that “a potency can only be raised to act by another that is already in act.” If you recall, in my first post I provided several examples to support this premise: the changing of leaves, the playing of a piano, an animal walking, etc. In all of these examples there is an essentially ordered causal series in which every instance of motion is caused by another object already in act. But the objection is raised that the discoveries of quantum mechanics show that this premise is faulty. After all, doesn’t quantum mechanics show that at the subatomic level, changes occur randomly, without any external cause?
There are several ways of going about answering this objection. The first is to point out the difference between physics and metaphysics. Many who argue that discoveries of physics, such as quantum mechanics, undermine metaphysical principles, do so with at least an implicit assumption of scientism. Scientism is the belief that only science can give us real knowledge about the world, which is blatantly and obviously false (for many, many reasons, one of which being simply that scientism itself is a philosophical belief, not a scientific discovery/demonstration, thus undermining itself). I hope to address scientism in a future post, but until then, I will direct you to an article by Edward Feser, which can be read here (this online article is a shorter, altered version of a similar chapter in his book Scholastic Metaphysics). As that article, and many others, show, metaphysics is actually prior to and more fundamental than science, if for no other reason than that science itself rests on metaphysical assumptions which it cannot itself validate. This is all to say that metaphysical principles must be analyzed/countered metaphysically, not physically. The scientific method itself rests on the assumption (albeit implicitly, and often denied by scientists) that metaphysical causation is real; if physics ever was to “discover” or “demonstrate” that metaphysical causation is not real, physics would have succeeded in undermining itself (just think, if there were no actual causal relation between our knowledge and external reality, the scientific method would crumble, and all scientific findings would be completely meaningless).
In other words, in order for the scientific method to even work, it presupposes the metaphysical principle of causality, which includes within it the act/potency distinction. Remember from my first post about the Prime Mover argument that Aristotle came up with the act/potency principles as a way to explain change, which was a heavily debated philosophical question at his time. On one side, you had those who completely denied the existence of change. On the other side, you had those who completely denied the existence of everything but change, who insisted that stability and consistency are illusions, that everything is constantly changing (never mind the fact that if everything is “constantly” changing, then at least one thing, namely change, is never changing, thus rendering this view self defeating). Then along came Aristotle, who argued that change is real, but it is not the only real thing. He did this by proposing the act/potency principles, that change is the actualization of a potency by something already actual.
Now, as I tried to make clear in my first post, the act/potency principles are just obviously true, despite the fact that they are ignored by most scientists/philosophers today. That change is the actualization of a potency by something already actual is just common sense. Imagine that you have a lamp in the middle of an empty room. The lamp is the only light source in the room, but right now the lamp is turned off. At the moment, the lamp is actually dark. But it has the potential to give off light, due to its essence/nature as a lamp. No one would deny this, even if they think the point is uninteresting or just semantics. Now, if you go into the room and light the lamp, the lamp’s potential to give off light has been made actual. It used to be actually dark, now it is actually light. How did it do this? Because even when it was actually dark, it had the potential to be light, and that potential has been actualized by something else already actual (namely, the actual person lighting the lamp by an actual flame, or, if it is an electrical lamp, an actual person flipping the switch which activates the actual electrical conduction system). Change is just incoherent if the act/potency principles are false; there is no other way to make sense of it. And since change is obviously a real feature of the world (although, of course, not the only real feature), it is incoherent to deny the act/potency principle. It is metaphysically established, and it cannot be uprooted by the discoveries of physical sciences, even if such discoveries, such as quantum mechanics, are seemingly strange, and raise interesting questions of interpretation. Indeed, no one is really sure as of yet how exactly to interpret many of the implications of quantum mechanics, and so, if nothing else, it is at least premature to claim that these implications “prove false” classical logic or other metaphysical principles (in truth, it is not just premature, it is also impossible).
Let’s use an example from quantum mechanics, such as the radioactive decay of an unstable atom. According to an article on physics.org (an excellent source, I know), “Radioactive decay occurs in unstable atomic nuclei – that is, ones that don’t have enough binding energy to hold the nucleus together due to an excess of either protons or neutrons.” The atom is said to “decay” when the nucleus loses particles of energy, emitting radiation in the process. Notice the language which the physics.org article makes use of: the particle “escapes from the nucleus of the parent atom…by quantum mechanical processes and is repelled further from it by electromagnetism.” Even if this language is just used as a semantic means to present the concepts of radioactive decay, it is still telling that we seem unable to make sense of phenomena–even phenomena which is apparently supposed to undermine causation–without inherently causal terminology. Remember in my first post the example of leaves changing color in fall. This is obviously on a much larger scale than an individual atom, but similar aspects are at play. The leaves of the tree change color due to lack of sunlight and colder temps, which cause the leaves to cease their production of chlorophyll. The lack of sunlight is “actual,” which causes the potential for losing chlorophyll to also become actual. In a similar way, we can think of the “lack of binding energy” as an actual cause, which actualizes the potential for radioactive decay, and the electromagnetic force as another actual cause, which actualizes the potential for particles to be repelled from the nucleus. And so on.
If this is the case, what is it exactly about radioactive decay and other quantum events which lead people to claim that such discoveries demonstrate that the act/potency premises are false? It is that such quantum events are “probabilistic,” rather than deterministic. That is, there is no deterministic way to predict when the unstable atom will decay. It seems to happen “randomly” or “spontaneously,” without any external factors determining the event. But even this is not a challenge to the act/potency premises.
Think again of my lamp example. When the lamp is dark, it has the potential to be light. Why does it have this potential? It has it by virtue of being what it is, namely a lamp. Because it has its specific form/essence/nature, which includes all its relevant features, such as say an electrical conduction system, it has the ability to be either light or dark. If it did not have the form/essence/nature that it does, it would not have these potentials. After all, if I were to attempt to take a flame and light water on fire, I would not be very successful. Because the nature of water (on its own, under normal circumstances) just does not have the potential to catch fire and give off light. Thus the potencies an object has are due to its nature.
The same is true for atoms, and electrons, and protons, and all other material objects, including all subatomic particles. An unstable atom, due to its form/essence/nature as an unstable atom, has the potential to decay. If it did not have this potential, it would never decay. Now, for most modern scientists and philosophers, the notion of causation consists only of efficient causation, or the “agent” which actually does the causing. So when I swing a baseball bat, my arm swinging the bat is the efficient cause. For Aristotle, Aquinas, and the scholastic philosophers, however, there are four types of causes: 1) Material Cause, 2) Formal Cause, 3) Efficient Cause, and 4) Final Cause. To go into much depth on all four of these and their implications would require much more space in an already over length article, so suffice it to say that any four of these causes could be that which actualizes a potency, and indeed most often they all work together to do so. Now, an unstable atom, due to its essence (or its formal cause), is directed towards, or tends towards decaying (which is its final cause), as an outflow of its very nature. Its nature just is to decay at some probabilistic point in time, and so its nature can be said to be the “cause” of its decay. The fact that such decay happens at a random, “spontaneous” point in time does not mean that it happens uncaused, its cause may just not be a deterministic one. It’s formal and final causes actualize its potencies to decay. Now matter, on its own, has the potential to be instantiated with any form. So an unstable atom is an object whose potential to exist as an unstable atom must have been actualized. And thus our essentially ordered causal series continues, taking us right back to the being of Pure Act, whom we have already determined is God.
Now, I realize this argument may take some time and thought to fully sink in. It certainly did so for me. After all, on an extremely simplistic level, the argument essentially claims that if change exists, God must exist. It’s a foreign and strange idea. Things change all the time, we see and experience change everyday. Is it really possible that all such change must trace back to God? But when all of the deeper, metaphysical principles are laid out, it becomes clear that this ancient argument not only makes sense, its actually an absolute proof for the existence of God. Now it doesn’t establish other aspects about God, such as that God is a trinity, or that God has ever acted in history, etc. But there are other arguments for those other issues. What matters is that there is indeed at least one argument that takes us, by pure reason alone, to the existence of God. Two of the greatest philosophers in the history of the world, Aristotle and Aquinas, both agreed.
I know this article is already much too long, and many may find it boring and repetitive. But I take the time and care to delve into and explain such metaphysical matters because this argument, and these ideas, have much significance for me personally. The argument from motion was one of the final nails in the coffin of my unbelief; it really convinced me, in a time of confusion and despair, that at bottom there is something Real, and something knowably so. And so it is fitting to end this series of posts on the article with a lengthy quote from one of my favorite writers, G. K. Chesterton, from his book on Aquinas. Chesterton was one of the greatest thinkers of the last century, and he had, according to one writer, a “preponderance of image over linear argument” (Steven Shroeder, from the Introduction of the Barnes & Noble Library of Essential Reading version of Chesterton’s Heretics). I have presented the Prime Mover argument basically as a linear, logical argument. But Chesterton had a way with words; he knew how to strike an idea not just into the mind, but deeper, into the heart. Here is how we described the argument from motion:
“Long before [a child] knows that grass is grass, or self is self, he knows that something is something. Perhaps it would be best to say very emphatically…”There is an Is.” That is as much monkish credulity as St. Thomas asks of us at the start. Very few unbelievers start by asking us to believe so little. And yet, upon this sharp pinpoint of reality, he rears by long logical processes that have never really been successfully overthrown, the whole cosmic system of Christendom…”
“…Aquinas has confirmed that our first sense of fact is a fact; and he cannot go back on it without falsehood. But when we come to look at the fact or facts, as we know them, we observe that they have a rather queer character; which has made many moderns grow strangely and restlessly sceptical about them. For instance, they are largely in a state of change, from being one thing to being another; or their qualities are relative to other things; or they appear to move incessantly; or they appear to vanish entirely. At this point, as I say, many sages lose hold of the first principle of reality [that something exists], which they would concede at first; and fall back on saying that there is nothing except change; or nothing except comparison; or nothing except flux; or in effect that there is nothing at all. Aquinas turns the whole argument the other way, keeping in line with his first realisation of reality. There is no doubt about the being of being, even if it does sometimes look like becoming; that is because what we see is not the fullness of being; or (to continue a sort of colloquial slang) we never see being being as much as it can. Ice is melted into cold water and cold water is heated into hot water; it cannot be all three at once. But this does not make water unreal or even relative; it only means that its being is limited to being one thing at a time. But the fullness of being is everything that it can be; and without it the lesser or approximate forms of being cannot be explained as anything; unless they are explained away as nothing…”
“…Most thinkers, on realising the apparent mutability of being, have really forgotten their own realisation of the being, and believed only in the mutability. They cannot even say that a thing changes into another thing; for them there is no instant in the process at which it is a thing at all. It is only a change. It would be more logical to call it nothing changing into nothing, than to say (on these principles) that there ever was or will be a moment when the thing is itself. St. Thomas maintains that the ordinary thing at any moment is something; but it is not everything that it could be. There is a fullness of being, in which it could be everything that it can be. Thus, while most sages come at last to nothing but naked change, he comes to the ultimate thing that is unchangeable, because it is all the other things at once. While they describe a change which is really a change in nothing, he describes a changelessness which includes the changes of everything. Things change because they are not complete; but their reality can only be explained as part of something that is complete. It is God.
“Historically, at least, it was round this sharp and crooked corner that all the sophists have followed each other while the great Schoolman went up the high road of experience and expansion; to the beholding of cities, to the building of cities. They all failed at this early stage because, in the words of the old game, they took away the number they first thought of. The recognition of something, of a thing or things, is the first act of the intellect. But because the examination of a thing shows it is not a fixed or final thing, they inferred that there is nothing fixed or final. Thus, in various ways, they all began to see a thing as something thinner than a thing; a wave; a weakness; an abstract instability. St. Thomas, to use the same rude figure, saw a thing that was thicker than a thing that was even more solid than the solid but secondary facts he had started by admitting as facts. Since we know them to be real, any elusive or bewildering element in their reality cannot really be unreality; and must be merely their relation to the real reality. A hundred human philosophies, ranging over the earth from Nominalism to Nirvana and Maya, from formless evolutionism to mindless quietism, all come from this first break in the Thomist chain; the notion that, because what we see does not satisfy us or explain itself, it is not even what we see. That cosmos is a contradiction in terms and strangles itself; but Thomism cuts itself free. The defect we see, in what is, is simply that it is not all that is. God is more actual even than Man; more actual even than Matter; for God with all His powers at every instant is immortally in action.” (Chesterton, Saint Thomas Aquinas).
In other words, real things change because they are not the most real thing. The branches sway in the wind, but they must all trace their way back down to the one, ancient, immovable trunk, ever standing amidst the fray, ever rooted in the solid ground, solid, unshakeable, unmovable but not at rest. For it is the trunk which holds up the branches, which sustains them; and it is God in whom are rooted all things, the entire cosmos. It is God who sustains all things in being, it is God who is the fullness of all being, who is being itself.
(This is hopefully my final post on the Prime Mover argument. The Prime Mover argument is the First of Aquinas’s famous Five Ways. I plan to do a similar series of posts on each of the Five Ways. Until then, please offer comments and suggestions below!)
As with the last two posts, I must again acknowledge that for the vast majority of this post I am greatly indebted to the works of philosopher Edward Feser, who has opened my eyes on so much. While this article is in my own words, and includes my own thoughts and analyses, the central ideas come from the writings of Feser. These include his books (The Last Superstition, Aquinas, Scholastic Metaphysics) as well as his online blog.
I would also like to acknowledge this post at Rocket Philosophy blog: http://rocketphilosophy.blogspot.com/2014/05/is-there-knowledge-in-god.html
For more information about the relation between quantum mechanics and metaphysics, here is a post on Feser’s blog: http://edwardfeser.blogspot.com/2014/12/causality-and-radioactive-decay.html
In particular, here are the sources which were quoted in the article above, in the order in which the quotations appear:
Feser, Ed. The Last Superstition: A Refutation of the New Atheism. South Bend: St. Augustine’s Press, 2008. ebook.
“What is Radioactivity?” Physics.org. n.p. n.d. Web. 19 May 2016.<http://www.physics.org/article-questions.asp?id=71>.
Schroeder, Steven. Introduction. Heretics. By G. K. Chesterton. 1905. New York: Barnes & Noble, 2007. Print.
Chesterton, G. K. Saint Thomas Aquinas. 1933. New York: Image Books, 2014. Print.