3.4 What Has Aquinas Achieved in the Natural Theology Offered in SCG 1,13?
3.4 What Has Aquinas Achieved in the Natural Theology Offered in SCG 1,13?
Aquinas evidently thinks that his arguments for “God exists” in SCG 1,13 are good demonstrative ones. But has he succeeded in doing this? My view is that this is not an easy question to answer since some of the arguments contain stages that are difficult to understand.
Consider the very last argument. What is Aquinas thinking of when he says what I report as (1) in it? Perhaps he means that parts of machines would not work together were they not set up and maintained by a mechanic of some kind. But it is not obvious that he means this since he does not provide examples to back up what he says in (1). Nor does he give examples to illustrate what he says in (2). Perhaps (2) is just drawing attention to the fact that things that interact with each other in the world are law-governed in some way. But then one wonders why any law-governed process should be thought to imply the existence of intelligent agency. If Aquinas thinks that it does, he does not explain why.
Again, consider the argument concerning degrees of truth. What does Aquinas mean when saying that one thing can be more true than another? In this connection he refers to Aristotle’s Metaphysics IV, but he does not explain or justify what he takes Aristotle exactly to be driving at. This leaves us somewhat in the dark when it comes to understanding what Aquinas takes himself to be saying in the argument from degrees of truth.33
Yet again, what kinds of motion does Aquinas have in mind in the SCG 1,13 arguments based on motion? As I have noted, Aquinas has a general view of motus as being a progression from potentiality to actuality, and he sometimes explicitly draws on this general view in SCG 1,13. Sometimes, however, he seems to be focusing only on local motion and taking himself to be able to draw a significant theological conclusion simply from it. So does he think that local motion is especially able to lead us to the conclusion that God exists? If he does, he does not say so, which leaves me, at any rate, wondering how the SCG 1,13 arguments based on motion hang together in Aquinas’s mind.
You may think that the arguments should just be considered and evaluated individually. Still, I suspect that Aquinas is of the view that there is something binding them together, and I do not see what he takes this to be unless it is the idea that motion always involves a progression from potentiality to actuality. Perhaps that, indeed, is what is running through all the arguments from motion in SCG 1,13. But then why do we have so many different arguments from motion in SCG 1,13?
It could be that Aquinas wants to pay attention to distinct arguments that he believes to be offered by Aristotle, considered as an especially famous philosopher. Even if that is so, however, the SCG arguments from motion amount to a difficult set of texts to interpret and evaluate considered as a whole, and the difficulty is compounded if one bears in mind that, as I have noted, what Aristotle meant by the word “God” seems to be significantly different from what Aquinas means by “God.” I am sure that Aquinas was himself aware of this fact and that he is interested in Aristotle on God only because he thinks that there is some overlap between what he thinks about God and what he took Aristotle to think about what he refers to as God.34 Yet there is still a general puzzle here, and in SCG 1,13 Aquinas does not go out of his way to explain how it is to be dealt with, which leads us to another question when it comes to understanding the arguments for God in SCG 1,13: why does Aquinas think that this chapter’s largely Aristotelian-inspired arguments should be thought to show that it is God that exists?
This question arises because when he goes on to talk about God later in the SCG, and when he talks about God in other works, Aquinas obviously takes God to be much more than what he claims God to be in the arguments of SCG 1,13. Aquinas believes that God is omnipotent and omniscient, but neither omnipotence nor omniscience feature explicitly in SCG 1,13. Again, Aquinas thinks of God as the creator of all things while denying that for God to create something is for God to bring about a change in it. He thinks that for God to make something to be, to create it, is not to modify it since it does not exist unless God makes it to be. Yet the notion of existing by virtue of God does not explicitly feature in SCG 1,13’s arguments for “God exists.” So why does Aquinas think that they successfully argue that God exists? On the basis of what look like teeth marks, I might reasonably conclude that there is a rodent loose in my home; but I should not conclude there is a mouse around, as opposed, say, to a squirrel or a guinea pig. So what leads Aquinas to identify what he takes himself to be arguing to exist in SCG 1,13 with God? And is he entitled to do so?
When it comes to the second question here, my answer is yes because of what I take to be the correct answer to the first question. If Aquinas thought that in SCG 1,13 he had said all that can be said about God on the basis of reason, he would have stopped writing the SCG having completed 1,13, just as he would have stopped writing his Summa Theologiae having written Summa Theologiae 1a,2, which contains arguments for God’s existence, some of which seem at least superficially similar to what we find in SCG 1,13.
In SCG 1,13 Aquinas purports to have shown that God exists since: (1) there is an unmoved and immovable mover that is not composed of bodily parts; (2) there is an uncaused efficient or agent cause; (3) there is something supremely true and most in being; and (4) something governs the world as a whole. In Summa Theologiae 1a,2,3, Aquinas takes himself to have shown that God exists since he takes himself to have shown (1) that there is some “first cause of change not itself changed by anything,” (2) that there is a first efficient cause, (3) that there is something intrinsically necessary that accounts for there being anything contingent and anything necessary that is created,35 (4) that there is something that “causes in all other things their being, their goodness, and whatever other perfection they have,” and (5) that there is something “with intelligence who directs all natural things to ends.”36 Following up on SCG 1,13 and Summa Theologiae 1a,2, however, Aquinas says a great deal more about God than he does in these texts. The reason why he is happy with them as they stand, considered as containing arguments for the existence of God, is that he is working with certain nominal definitions of “God” that he assumes would be accepted by orthodox Christians.
Aquinas regularly distinguishes between nominal definitions and real ones. He thinks of a nominal definition as capturing what something might be thought to be, whether it exists or not, without reporting all that it is essentially should it happen to exist. Correspondingly, he thinks of a real definition as what we end up with as we examine something that does exist and arrive at a serious grasp of what it is, what makes it tick, how it differs from other existing things, what its origins are, and so on. So Aquinas would say that, for example, I can happily define “cat” nominally as “something with ears and whiskers,” and that I can nominally define “wizard” as “someone able to cast spells,” even if there are no wizards.37 He would also say that a real definition of something is what we might, hopefully, end up with having carefully examined the thing in question, this, for Aquinas, having to be something spatiotemporal. As I have noted, however, Aquinas denies that one can construct a demonstration propter quid for the truth of “God exists” since he thinks that we cannot know what God is. So the arguments for “God exists” in SCG 1,13 are working from nominal definitions of “God.” But are they working from definitions of “God” that allow Aquinas to conclude that he has argued well for “God exists”?
I think that they are since Aquinas has reason for supposing that he and his thirteenth-century readers, not to mention his twenty-first-century readers, could hardly deny that when Christians, Jews, and Muslims speak of God they at least mean what Aquinas refers to as God in SCG 1,13. What Christian, Jew, or Muslim would deny that, for example, God accounts for there being movement in the world? Again, do not Christianity, Judaism, and Islam clearly proclaim that God is one who acts providentially in the universe and that God is the first cause lying behind all other causes? Not all Christians, Jews, and Muslims have taken God to be “immovable,” as Aquinas puts it. Many people who claim to believe in God would say that God undergoes change. On the other hand, however, there is a long theological tradition according to which God is wholly immutable. That God is this is taught, for example, by the Fourth Council of Constantinople (869–870), the Fourth Lateran Council (1215), and the First Vatican Council (1869–1870). In short, Aquinas’s nominal definitions of God in SCG 1,13 make sense in the light of some long-standing beliefs concerning God. It might be said that the nominal definitions now in question can be faulted since God is more than they take God to be and since Aquinas cannot claim to have demonstrated that God exists unless he has successfully shown that God is all that those who believe in him take him to be. But that view erroneously supposes that one cannot demonstrate that X exists unless one has demonstrated that X is all that it actually is. One might, for example, demonstrate that speech heard on a radio channel derives from a human being while also being unable to demonstrate that it derives from someone who is right-handed, an orphan, or a lover of ferrets. That Aquinas recognizes this fact is shown by the way in which he follows up on SCG 1,13 by arguing for the truth of various statements about God that he does not seek to demonstrate in that chapter.
3.4.2 Aquinas on Motion in SCG 1,13
What, though, of the arguments concerning God and motion in SCG 1,13? Are these open to challenge? It has been argued that they are. I cannot here even hope to document and comment on all the criticisms that have been leveled against them, but here are some of the major ones to be found in recent philosophical literature:
1. Aquinas assumes that something in motion has to be moved. But there is no problem in assuming that something in motion is just moving with nothing accounting for its movement.38
2. In SCG 1,13 Aquinas writes in ignorance of Newton’s first law of motion, according to which a body will continue to move in a straight line unless interfered with.39
3. We have no good reason to suppose that there cannot be an endless or infinite series of things moving and being moved. Why suppose that there has to be an absolutely first mover in a series of things moving and being moved?40
4. “If something can be made F by an agent which is merely potentially F, there seems no reason why something should not actualize its own potentiality to F-ness.”41
5. Even if “Whatever is moved is moved by something else” is a true proposition, it does not follow that God exists since there might be many unmoved movers. Yet those who believe in God insist that there is but one God.
How effective are these objections when it comes to what Aquinas argues in SCG 1,13? Let me say something about each of them in order.
1. The first objection uncritically accepts that the movement of a thing should be taken as a brute fact not calling for explanation. But why should we take the movement of something as brute in this sense? After all, we do not generally presume that instances of movement are self-explicable. We assume, for example, that if my cat is vomiting, then something is causing him to do so. We make assumptions like this continually, and it would be hard to understand someone who did not, someone who, confronted by movement, simply said “Well, there it is; nothing more to be said.” You may think that our demand for causal explanations of motion simply reflects an unreasoned prejudice on our part. But if “reasonable” means anything, then it surely describes the raising of causal questions concerning motion. Can we, for example, make sense of someone asserting that airplanes fly just because they do, or that dogs bark just because they do, or that grass grows just because it does? In any case, Aquinas does offer a reason for supposing that what he calls movement or real change has to be something that requires explanation in terms of something other than a thing moved or in motion. This lies in his claim that something undergoing change is acquiring what it does not actually have since change or motion is the movement from being potentially F to becoming actually F. Aquinas thinks that nothing can give itself what it does not have, that the movement of X from being potentially F to becoming actually F is not explicable in terms of X in its state of being potentially F. Aquinas thinks this because he takes it that some new state of X comes about as X proceeds from being actually G to becoming actually F, and he is surely right to think this. In that case, however, what X is while being actually G cannot account for X coming to be actually F. There is a difference coming about here that is just not explicable by merely reporting what is there before the difference comes about. The F-ness of X when acquired by X does not exist when X is actually G and only potentially F. So why should we not ask “How come the existence of the F-ness of X?” If “X is F” were true of logical necessity, this question, which I take to be a causal one, would not arise, any more than it does when it comes to propositions like “All triangles have three sides.” But if X’s F-ness does not have to exist as a matter of logical truth, then it might never have existed, which seems to raise the question “What accounts for it existing?” This question can hardly be adequately answered by describing X in its non-F state and leaving the matter there. If nothing else, the existence of X’s F-ness at one time raises the question “Why does it exist at that time and not at another time?”
2. Newton’s first law of motion does seem to tell against what Aquinas argues in SCG 1,13. That is because it conjures up the picture of there being something unmoved that goes through local motion without acceleration, reduction of speed, or change of direction, something moving along in an idealized frictionless plane, as it were. Aquinas seems to hold that if X moves “primarily” from position A to position B, it must be moved by something else. Newton’s first law of motion, however, appears, while invoking the notion of inertia, to countenance exceptions to this rule. Recognizing this fact, some philosophers have suggested that we should take SCG 1,13 as defeated by Newton when it comes to local motion but should note that it can be defended with respect to motus considered only as change of quantity and quality.42 Yet, perhaps, this concession is premature. For one thing, Aquinas did not believe that everything undergoing motion has to be moved by something as it undergoes its motion. As John Wippel notes, Aquinas’s account of motion “does not imply that a distinct moving cause must be constantly conjoined with a body which it moves naturally.”43 Again, even Newton never believed that something beginning to move locally lacks a cause of its moving. Nor did he think that variations in a thing’s local motion lack a cause, or that there is no cause for there being local motion at all. He argued that, hypothetically speaking, something could remain in a state of unvarying motion without any physical object causing it to do so. But he did not cite examples of things remaining in such a state, which is unsurprising since things undergoing local motion do not actually exist as unaffected by other things in the world. As Edward Feser observes: “At every moment in which an object is moving through space, and not merely at its initial acquisition of momentum, its motion is being affected in a way that requires explanation in terms of something outside it. But in that case, even with respect to the explanation of local motion, the principle of inertia seems practically moot.”44 Along with Feser, I would add that Newtonian inertial motion is commonly taken to be a “state” as opposed to a process, which raises the question “Is it an example of what Aquinas would have taken to be motus?” When he talks about motion in SCG 1,13, Aquinas is focusing on genuine alteration of some kind, not an abiding “state,” which, I suspect, he would have taken to be a case of stasis or lack of motion. On the other hand, Newton’s uniform rectilinear motion seems to be a constant state rather than an instance of change.
3. We would, of course, beg the question if we argued that there is a first unmoved mover since there is a series of secondary movers that can be thought of as its agents. That is because any “first” and “secondary” distinction seems to presume that there is a first to be distinguished from a secondary. But there is nothing wrong in arguing that, given a series of secondary (as opposed to unmoved) movers, that series has to depend on what is not secondary and is unmoved insofar as it accounts for the movement of the movers that it moves. Think again about the books held up by my hand. All of them fall to the ground if I take my hand away from them. But book A can be thought of as supported by book B, and book C by book D, and so on. Here we have a series of causes of the kind that Aquinas would have described as per se, a series in which something being such and such owes this not just to some temporal predecessor in a causal chain but to something whose causal power runs through the chain in such a way as to make the members of the chain do what they do or be what they are. And it seems hard to see how such a chain can exist if there is not something outside it, if there is no cause that is not part of the chain considered as containing members that equally depend on a cause. A cause whose causality runs through its effects, as I am when holding books in the palm of my hand and moving them from left to right and back, does not, of course, have to be immutable. After all, I am not immutable. But that does not mean that we should doubt that in any causal series per se, there has to be a first cause.
4. The fourth of the above arguments against Aquinas is simply not engaging with what he says. As I have noted, it is not Aquinas’s view that, for example, only what is red can bring it about that something is red. What he thinks is that only something with the ability to bring it about that something is red can account for something becoming red.
5. The virtue of the fifth of the above arguments lies in the fact that in SCG 1,13 Aquinas does not offer a demonstration to the effect that there is but one unmoved mover. Yet that virtue also undermines the argument as an objection to SCG 1,13 since it amounts only to an account of what Aquinas does not argue in that text, and an account of what Aquinas does not argue can hardly be held to be a refutation of him. I mean that if, for example, I argue that my cat is hungry, but do not argue that it is black and white in color, my argument for my cat being hungry is not to be impugned with reference to my not arguing that it is black and white. By the same token, if Aquinas argues for there being an unmoved mover, but does not explain why there is only one such mover, he is not to be impugned for not arguing that there is only one unmoved mover since he is not concerned to argue for this conclusion. As I will show, however, Aquinas proceeds in the SCG to single out the question of God being one (i.e., nonmultipliable) so as to deal with it directly. The fact that he does not do this in SCG 1,13 is nothing against him even though it might provoke impatience in a person who wants Aquinas to start talking about the oneness of God before he is ready to do so.
There is doubtless a great deal more to be said about the arguments of SCG 1,13. But I hope that I have now said enough about them to get you thinking for yourself concerning them. Before I move on to other matters, however, I would like to make two points to round off this chapter. The first concerns Aquinas’s conception of efficient causation in general. The second concerns the extent to which SCG 1,13 can be read as concerned not just with motion but with the topics of existence and nonexistence.
3.4.3 Aquinas on Efficient Causation
As I have explained, in SCG 1,13 Aquinas moves to his various conclusions with an eye on what he would have called “efficient” or “agent” causation. Yet I should note that what Aquinas means by “efficient” or “agent” cause is not what some philosophers mean by “cause.” More precisely, there have been influential accounts of causality that are at odds with what Aquinas has in mind when talking about efficient or agent causes. To be even more precise, there is David Hume’s theory of causation.
Hume argues that causal statements like “X was caused to move by B” are not necessarily true in the way that, say, “Any bachelor is unmarried” is necessarily true. We assume, says Hume, that such and such was the cause of whatever because we are accustomed to associate events of type A with events of type B. But, he thinks, a cause and its effect are distinct, and we can conceive of there being what we are pleased to call an effect without it having any cause at all.45 According to Hume, therefore, we can even conceive of something beginning to exist without a cause, implying that from what we take to be an effect we cannot demonstrate that it has a cause (an efficient cause, in Aquinas’s language). On this view causal reasoning derives its force from habit, from our previous experience of connecting what we call effects to what we call causes. It is not to be grounded in reason.
If Hume is right here, then Aquinas is wrong to argue as he does in SCG 1,13. For Aquinas there claims to be demonstrating the existence of a certain cause. Aquinas thinks that efficient causal agents have powers that produce effects, while Hume separates cause and effect so as to allow for there being no necessity when it comes to what we take to be an effect having a cause. So, if Hume’s approach to causation is right, then there is something amiss with SCG 1,13.
The virtues of Aquinas’s largely Aristotelian view of efficient causation, and the virtues of Hume’s very different approach, have been much discussed by philosophers. This is not the place for me to try to pursue them in detail, but I do think it worth observing that Aquinas, unlike Hume, intimately relates effects to causes and, therefore, does not end up with some of Hume’s skeptical conclusions concerning reasoning from effect to cause. That is because Aquinas thinks that “what the agent does is what the patient undergoes” and that “action and passion are not two changes, but one and the same change, called action in so far as it is caused by an agent, and passion in so far as it takes place in a patient.”46
The idea here is that something can only be said to be the cause of some event as the event is occurring by virtue of its cause. Hence, for example, on Aquinas’s account I am the cause of my bed getting made only as my bed is actually getting made by me, or I am teaching you only insofar as you are learning by virtue of me. On this account, cause and effect are not separable in the way that Hume seems to think. Aquinas allows that there can be effects that come about without causes in the natural world, for he believes that God can work miracles (a topic Aquinas turns to in SCG 3). Aquinas also believes that there can be chance events that lack a single cause while also falling under God’s will.47 In general, though, Aquinas regards efficient causation as always involving both cause and effect, and he does so because he takes an efficient or agent cause to be something exerting its power in or on something else. Hume would say that we form the concept of a cause as we note the constant conjunction of various kinds of events. Aquinas, however, would say that we form the notion of efficient causation as we seek to explain changes in terms of agents able to bring them about. This approach to causation would seem to be more at work in the way we typically think about causes and effects than is the approach associated with Hume, but I leave it to you to consider whether it is a viable one and superior to what Hume advances. That there is matter for debate here seems evident, which, perhaps, at least indicates that the causal reasoning of SCG 1 should not be dismissed as obviously archaic or unsound in principle.
3.4.4 Existence and Nonexistence in SCG 1,13
As I have emphasized, the bulk of SCG 1,13 is taken up with arguing for the truth of “God exists” with reference to motion. This, however, might seem surprising since in many of his writings Aquinas speaks of God as accounting for things simply existing. It is a presiding view of Aquinas that God brings it about that everything other than God exists from moment to moment only because God is causing it to do so, and this is a view that features quite a lot in the SCG later than SCG 1,13. Yet is the notion of God as a cause of the being of things entirely absent from SCG 1,13? I do not think that it is, and that is because of SCG 1,13’s use of the principle that something coming to be actually F having previously been only potentially F has to be accounted for in terms of something actual bringing about actuality from potentiality.
For Aquinas, being actually thus and so involves being in some way. For him, something actually F is something that exists as that which is actually F. Aquinas does not think that there are nonexisting actual things. So, when attributing something’s being moved by God to God as first mover, he is implicitly saying that God accounts for things existing in some way. To be sure, Aquinas does not in SCG 1,13 speak of God as, for example, making things to exist from nothing, which is what Aquinas takes God to do given that God is the creator of all things. We have to wait until SCG 3 for Aquinas to tackle the notion of God as creator head on. Yet even in SCG 1,13 we find Aquinas talking about God bringing something about while not being potentially this, that, or the other. The unmoved mover of SCG 1,13 has to be something in which there is no possibility of a transition from potentiality to actuality, meaning that it is something in which no change can occur, and something not lacking what it might have but does not. If one reads through the SCG and through other works by Aquinas, however, one will be left in no doubt that Aquinas takes only God, the creator of all things, to be fully actual in this sense because he thinks that potentiality always requires to be actualized by what lacks potentiality in some way. Yet this thought concerning actuality and potentiality is very much in evidence in SCG 1,13, not only in its arguments from motion but also in its argument for a first efficient cause. So the notion of God as being what accounts for what exists, while potentially nonexistent, is definitely lurking around in SCG 1,13 even if it is not spelled out. As Edward Feser says: “If motion is just the reduction of potency to act, then since the existence of a thing no less than its activity involves (in everything other than that which is pure act) the reduction of potency to act, any explanation of motion must account for the existence of things and not just for their activities.”48 I take it that Feser is suggesting that something that actually exists, but does not have to exist, is potentially nonexistent, and that its sheer existence depends on it being actualized by what cannot not-exist. And, of course, Aquinas thinks of God as not able not to exist.
Yet how does Aquinas develop his thinking about God’s nature as he continues with the SCG? In the next chapter I shall begin to note how he does so while he concentrates on what we cannot take God to be. You may wonder why Aquinas should embark on a discussion of God’s nature in the SCG by talking about what God is not. As I will show, he has his reasons.