Background
Before we turn to consider Feser's proof, I need to say something about the perspective from which I approach it. In his ‘Introduction’, Feser writes:
A long line of thinkers from the beginnings of Western thought down to the present day . . . have affirmed that God's existence can be rationally demonstrated by purely philosophical arguments. The aim of this book is to show that they were right. . . . The real debate is not between atheism and theism. (15)
Feser says here, quite clearly, that his five proofs remove atheists from the field of play. They are simply not part of ‘the real debate’.
One question that emerges immediately is this: does he thinks that any one of his five proofs suffices to remove atheists from the field of play, or does he rather think that it is only the five proofs together that do this? I think that it must be the former. Each argument is intended to be valid; each argument has the same conclusion. We could put them together to form a single argument intended to be valid by disjoining the premise sets. But there is nothing that speaks in favour of this supposition: were this what he intended, Feser surely would have said so.
Another question that then emerges is this: how could it be that a proof suffices to remove atheists from the field of play? What properties is Feser attributing to his proof when he makes this claim? I take it that what he has in mind is that his proofs show that it is irrational for anyone to deny the conclusion of the argument: it is irrational for anyone to deny that God exists. That is why atheists are removed from the field of play. This interpretation is plausibly confirmed by Feser's talk of ‘rational demonstration’ (my italics).
How might a proof show that someone is irrational? The obvious answer is this: if an argument with premises P1, . . ., Pn and conclusion C is valid, then anyone who believes all of P1, . . ., Pn and ~C has an inconsistent set of beliefs. But it is not rational to hold inconsistent beliefs. Of course, if this is how the proof is supposed to work, then its working depends crucially on its targets believing all of P1, . . .., Pn and ~C. A less obvious answer is this: if, in a valid argument with premises P1, . . ., Pn and conclusion C, none of the premises can be rationally rejected, then anyone who rejects the conclusion C is shown to be irrational, for the conclusion C is a logical consequence of a set of claims none of which can be rationally rejected. Of course, if this is how the proof is supposed to work, then its working depends crucially on its being the case that none of its premises can be rationally rejected.
I take it to be obvious that Feser knows that there are atheists who reject his premises. The two premises that I shall be considering in my subsequent discussion are claims that I think are false. If Feser thinks that I am removed from the field of play because I accept all of the premises of his argument and yet reject its conclusion, then he is just mistaken: I do not accept all of the premises. So, I think, Feser is proposing that his proof removes atheists from the field of play because none of the premises in his proof can be rationally rejected.
How should you respond to the claim that it is irrational for you to believe given propositions that you do believe? Perhaps the obvious response is to ask the following question: where does the alleged irrationality lie? Where we disagree about a claim, each of us is bound to think that the belief of the other is false. If we left matters there, we would just be agreeing to disagree. This is the typical state of almost every philosophical disagreement: for any pair of philosophers, there is a very wide range of propositions where each thinks that the other has a false belief, but contemporary philosophers rarely accuse each other of irrationality on that account. If we consider a particular proposition about which we disagree, and then consider other propositions that would support that proposition, we typically find out that we disagree about those as well.
Perhaps the best that you can do, in responding to the charge of irrationality, is just to point to some of the other things that you believe that support your allegedly irrational beliefs. Of course, you do not need to suppose that the relevant beliefs of the other person are irrational, or that you are giving the other person a reason to change their relevant beliefs. The accusation of irrationality is about you; it is not about them. Note, in particular, that, if you set out some of your reasons for rejecting one of the premises that the proponent of a given argument claims cannot be rationally defended, it is utterly hopeless for the proponent of the argument to claim that your response ‘begs the question’ against them. If you believe that p, and someone else believes that not p, neither of you ‘begs the question’ in insisting that things are as you say they are.
Feser's ‘Aristotelian proof’
The formal version of the first stage of Feser's ‘Aristotelian proof’ is as follows:
1. Change is a real feature of the world. (Premise)
2. But change is actualization of potential. (Premise)
3. So actualization of potential is a real feature of the world. (From 1, 2)
4. No potential can be actualized unless something already actual actualizes it. (Premise)
5. So any change is caused by something already actual. (From 2,4)
6. The occurrence of any change C presupposes some thing or substance S which changes. (Premise)
7. The existence of S at any given moment itself presupposes the concurrent actualization of S's potential for existence. (Premise)
8. So any substance S has at any moment some actualizer A of its existence. (From 4, 7)
9. A's own existence at the moment it actualizes S itself presupposes either (a) the concurrent actualization of its own potential for existence or (b) A's being purely actual. (Premise)
10. If A's existence at the moment it actualizes S presupposes the concurrent actualization of its own potential for existence, then there exists a regress of concurrent actualizers that is either infinite or terminates in a purely actual actualizer. (Premise)
11. But such a regress of concurrent actualizers would constitute a hierarchical causal series and such a series cannot regress infinitely. (Premise)
12. So either A itself is a purely actual actualizer or there is a purely actual actualizer which terminates the regress that begins with the actualization of A. (From 9, 10, 11)
13. So the occurrence of C and the existence of S at any given moment presupposes the existence of a purely actual actualizer. (From 6, 7, 12)
14. So there is a purely actual actualizer. (From 13)
There are many things that one might think to say about this proof. Here, I propose to argue merely that Premise 4 and Premise 7 are rationally deniable.
Premise 4
Premise 4 says: no potential can be actualized unless something already actual actualizes it. I do not accept this premise. Here is the beginning of an attempt to explain why.
Yesterday, throughout the entire day, there was a red chair in my room. Pick some time t around noon yesterday. At t, the chair existed, and the chair was red. Moreover, at t, the chair had the potential to exist, and to be red, at t + ε, where ε is some relatively short time interval (say, a millionth of second). Do we need to postulate the existence of some distinct thing that exists through (t, t + ε) that actualizes at t + ε the potential that the chair had at t to both exist and be red at t + ε? I do not think so. Given that, at t, the chair has the potential to exist and to be red at t + ε, all that is required for the realization of this potential is that nothing intervenes to bring it about, either that the chair does not exist, or that the chair is not red, at t + ε. Potentials to remain unchanged do not require distinct actualizers; all they require is the absence of any preventers of the actualization of those potentials. In particular, things that have the potential to go on existing go on existing unless there are preventers – internal or external – that cause those things to cease to exist.
Because potentials to remain unchanged need not require distinct actualizers, there are even cases where potentials to change need not require distinct actualizers. Suppose, for example, that the rate of expansion of the universe is some constant value, R. Suppose that, at t, the universe has the potential to be expanding at rate R at t + ε. All that is required for the realization of this potential is that nothing intervenes to bring it about that the rate of expansion of the universe changes. But suppose that the rate of expansion of the universe does remain constant through (t, t + ε). Consider the volume of the universe; clearly, given that the rate of expansion of the universe remains constant through (t, t + ε), the volume of the universe grows in this period. At t, the universe has the potential to have a larger volume at t + ε than it has at t. But even though this is a real change in the universe, we do not require any distinct thing to actualize this change: it is enough that there is nothing that intervenes to bring it about that the rate of expansion of the universe changes.
In place of the claim that no potential can be actualized unless something already actual actualizes it, I offer the following principle: actualizations of potentials to change that are not explained in terms of actualization of other potentials to remain unchanged have explanations for their actualization in terms of already actualized actualities. (Perhaps, for example, the chair is vaporized by a laser beam; or perhaps the chair is sprayed with green paint; or etc.)
Premise 7
Premise 7 says: the existence of S at any given moment itself presupposes the concurrent actualization of S's potential for existence. I argue that this premise is false. I say that the chair's existence at t + ε is fully explained by the actualization of the potential, possessed by the chair at t, to continue to exist through t + ε, and the absence of anything that intervenes to prevent the realization of this potential.
Suppose that a thing has a potential of some kind at a time t that is realized at a time t + ε. For concreteness, suppose that the thing is F at t and G at t + ε, where it is necessarily the case that nothing is both F and G at a single time. At t, we may suppose, the thing is actually F and not actually G, but also both potentially F at future times and potentially G at future times. At t + ε, we may suppose, the thing is actually G and not actually F, but also both potentially F at future times and potentially G at future times. Should we say that, at t, the thing is potentially F at t; should we say that, at t + ε, the thing is potentially G at t + ε? I think not. Given that the thing is actually F at t, it is not potentially F at t; given that the thing is actually G at t + ε, it is not potentially G at t + ε. A thing that has a given property at a given point in time can have the potential to have an incompatible property at later points in time; but a thing that has a given property at a given point in time does not also have a potential to have that property at the given point in time. So: if S exists at t, then S does not also have the potential to exist at t (though it typically does have the potential to exist at times later than t and it typically had the potential – at some earlier times – to exist at t).
Why do I prefer the view that a thing that has a given property at a given point in time does not also have a potential to have that property at the given point in time? Here are two of my reasons. First, if we suppose that a thing cannot be F at t unless it is also potentially F at t, then we should also suppose that a thing cannot be potentially F at t unless it is also potentially potentially F at t. But it would be intolerably arbitrary to halt this regress after taking the first step; the obviously better move is not to make the first step. Second, it is quite clear that we obtain a leaner, cleaner view if we suppose that potentials to remain unchanged do not require already actual actualizers. If we suppose that potentials to remain unchanged are actualized in the absence of preventers of that actualization, then we can simply do without the postulation of an unactualized actualizer for cases in which potentials to remain unchanged are actualized.
Lest it be thought that there cannot be any such thing as being potentially potentially F at t, here is an example. Clearly one might have potential, within twelve months, to have an understanding of Gödel's incompleteness theorem. Since I eventually acquired an understanding of Gödel's incompleteness theorem, there was a time when I had this potential. However, I did not have this potential when I was two weeks old. Even so, when I was two weeks old, I had the potential to have the potential, within twelve months, to have an understanding of Gödel's completeness theorem. So there is such a thing as being potentially potentially within twelve months possessed of an understanding of Gödel's incompleteness theorem.
Transfer of conserved quantities
Feser's informal presentation of ‘the Aristotelian proof’ invites some responses that may be worth recording. In the rest of this article, I provide some quotations from Feser's informal presentation together with some comments about grounds of disagreement.
The coffee in your cup grows cooler. . . . The coffee has the potential to become cold and after sitting out for a while that potential is made actual. . . . While the coffee is still hot, the coldness of the coffee is not exactly nothing, since it is there potentially in the coffee. . . . But it is still there merely potentially and not actually. . . . Potential coldness can hardly do anything. . . . Only what is actual can do anything. In particular, the potential coldness of the coffee cannot make itself actual. . . . Any mere potential can only be actualized by something that is already actual. (17–19)
It is true that ‘the potential coldness of the coffee cannot make itself actual’: in order for the coffee to cool, there must be a transfer of heat between the coffee and its environment. But the generalization here is not one I accept. It may be true that, where there is change, there is transfer of conserved quantities. But, where there is no change, there need be no transfer of conserved quantities. Yet much realization of potential involves potentials to remain unchanged.
Hierarchical series
Consider, once again, the coffee cup as it sits on your desk. It is, we may suppose, three feet above the floor. Why? Because the desk is holding it up. But what holds up the desk? The floor. The floor, in turn, is held up by the foundation of the house, and the foundation of the house by the earth. . . . The potential of the cup to be three feet off the ground is actualized by the desk, the potential of the desk to hold the cup aloft is actualized by the floor, and so forth. . . . This series is hierarchical; . . . there is a certain dependence of the later members on the earlier ones. The cup has no capacity on its own to be three feet from the ground; it will be there only if something else, such as the desk, holds it up. But the desk in turn has no power on its own to hold the cup there. The desk too would fall to the earth unless the floor held it aloft, and the floor, for that matter, can hold up the desk only because it is itself being held up by the house's foundation, and the foundation by the earth. . . . The sort of ‘first’ cause that a hierarchical series must have is a cause that has the power to produce its effects in a non-derivative and non-instrumental way. (21–23)
Consider the relation ‘. . . is being held up by . . .’. This is a causal relation. Moreover, it is a transitive relation: if a is being held up by b, and b is being held up by c, then a is being held up by c. Finally, if we have a series of things related by this relation, then the series terminates in something that is not being held up. In the example given in the text, the series terminates with the earth: the earth is not being ‘held up’ by anything. Of course, given the context, the ‘holding up’ is relative to the earth; it does not even make sense to suppose that the earth is ‘held up’ relative to itself. But, on a less superficial account, outer layers of the earth are ‘held up’ by inner layers of the earth. The earth is a roughly spherical mass whose shape is maintained under gravitational attraction. Sufficiently small slow-moving things falling in the earth's gravitational field stop falling when they make impact with an appropriate part of the surface of the earth; if, for example, they fall in the ocean, they may sink right to the bottom of the ocean.
Should I suppose that the earth differs from the cup because only the earth ‘has the power to produce its effects in a non-derivative and non-instrumental way’? I do not think so. Imagine the cup floating in interstellar space, and imagine a dust particle falling in the cup's gravitational field. Relative to the cup, the dust particle falls until it comes to rest on the cup. In interstellar space, the cup is not falling relative to anything. But the explanation of why the dust particle falls until it comes to rest on the cup is exactly the same as the explanation of why the cup would fall until it came to rest on the surface of the earth were it not for the presence of the table. There is no difference in the kinds of ‘non-derivative’, ‘non-instrumental’ causal powers of the earth and the cup; the only relevant difference between them is comparative mass. (We can complete the analogy with the original case by supposing that there is already an encrustation of dust on the cup: the newly added dust particle is ‘held up’ by the existing encrustation of dust.)
Realization of potential is mostly linear
This hierarchical sort of series . . . is more fundamental to reality than . . . the linear sort of series. . . . Every series of the linear sort presupposes series of the hierarchical sort. . . . How so? . . . The potential of the coffee to exist here and now is actualized, in part, by the existence of the water, which in turn exists only because a certain potential of the atoms is being actualized, where these atoms themselves exist only because a certain potential of the sub-atomic particles is being actualized. This is a hierarchical series which must have a first member. . . . Since what is being explained is the actualization of a thing's potential for existence, the ‘first’ cause we are talking about is one which can actualize the potential for other things to exist without having to have its own existence actualized by anything. (25–27)
I don't accept this. Given that the coffee exists right now, it does not have a potential to exist right now. However, it does have a potential to exist in the near future; and it had that kind of potential in the near past. But those potentials can be realised simply by the absence of anything that intervenes to prevent their realization. The coffee exists at t because it existed at t-ε and nothing intervened to cause it to cease to exist. There is no kind of hierarchical causal series of the kind that is here taken to be fundamental to the existence of things. Moreover, while there are hierarchical causal series, it is not true that they are more fundamental than linear causal series. Consider, again, the question why the coffee cup is three feet above the surface of the earth at time t. Yes, the coffee cup is sitting on a table which is sitting on a floor which is sitting on a foundation which is sitting on the earth. But there is a linear causal history to all of this. Doubtless, for sufficiently small ε, it is true that, at t−ε, the coffee cup was sitting on the table which was sitting on the floor which was sitting on a foundation which was sitting on the earth, and nothing intervened to change any of this. But, at an earlier time, the coffee cup was placed on the table; and, before that, the table was brought into the room; and before that, the foundations for the building were laid; and before that, the earth formed from the aggregation of interstellar dust. Realization of potentials – whether potentials to change or potentials to remain unchanged – is mostly linear rather than hierarchical.
Feser's ‘Neo-Platonic proof’
The replies that I have made to the first stage of Feser's ‘Aristotelian proof’ have equal force against the first stage of Feser's ‘Neo-Platonic proof’. That proof has, as a key premise, the claim that composition of parts requires a concurrent cause. Given the preceding discussion, it should be clear why I think that this premise is false.
Suppose that C is a composite thing that exists at t. Suppose that C has the potential to exist at t + ε. (At t + ε, C may have some different parts, and some of its parts may be differently arranged.) That C goes on to exist at t + ε – that C's potential, at t, to exist at t + ε, is actualized – may simply be the result of the absence of any intervention to prevent this actualization. (Of course, changes to C's parts and/or the arrangement of C's parts, may require a cause; that depends upon the details of the case.) There is no good reason for me to suppose that composition of parts requires a concurrent cause of the actualization of the potential for there to be that composition of parts.
Suppose instead, we focus on C's existing throughout some time interval (t, t + ε). C's continuing to exist throughout the time interval may well depend upon various ongoing conditions, e.g. the continuing existence of a suitable concentration of oxygen in the earth's atmosphere. But, ultimately, the search for explanations of ongoing conditions bottoms out in things whose ongoing existence is explained in terms of the absence of ongoing intervention. For example, there isn't anything that is changing the concentration of oxygen in the earth's atmosphere in a way that would make a difference to the continuing existence of the thing in question.
Feser's ‘Rationalist proof’
The responses that I have made to Feser's ‘Aristotelian proof’ have some carry-over to Feser's ‘Rationalist proof’, though not in such a way as to provide a complete response to the latter. Feser's ‘Rationalist proof’ has, as a premise, that the claim that an individual contingent thing persists in existence at any moment requires an explanation; and that, since it is contingent, that explanation must lie in some simultaneous cause distinct from it. I think that this premise is false.
As the earlier discussion suggests, I think that there is an explanation why any given individual contingent thing is persisting in existence at any given moment at which it is persisting in existence. However, that explanation need not advert to a cause that is distinct from the thing; and, in particular, that explanation need not advert to a simultaneous cause that is distinct from the thing. That natural reality persists in existence is explained by there being nothing internal or external to natural reality that causes it to cease existing. This explanation does not appeal to a cause distinct from natural reality, still less to a simultaneous cause distinct from natural reality.
While this line of response, if correct, meets the claim that there is a continuing cause of the existence of natural reality, it does not speak at all to the question whether there is an originating cause of the existence of natural reality. Since Feser's ‘Rationalist proof’ also aims to establish that there is an originating cause of natural reality, that proof is not fully addressed by this line of reply. Of course, I think that there are other good replies to that proof; but it is no part of the project of this article to table those replies.
Concluding remark
In this article, I have replied to Feser's ‘Aristotelian proof’; and, as a bonus, I have noted that part of this reply carries over to Feser's ‘Neo-Platonic’ and ‘Rationalist’ ‘proofs’. I have said nothing here about Feser's ‘Augustinian’ and ‘Thomistic’ ‘proofs’; any fuller discussion of the other four ‘proofs’ will need to wait for another occasion.
Appendix
Two referees for the journal worried that, in my discussion to this point, I had not given consideration to how Feser might respond to what I have said. That's a fair point; I hadn't thought about that. Worse, I really don't know what he might say. Fortunately, the referees had some suggestions. So I shall respond to those. Note that I am not endorsing their claim that Feser would respond as they suggest. They offer these responses on his behalf; I reply taking these responses at face value.
1. Premise 4 is accepted by many in the Aristotelian tradition, a tradition with a long history, and therefore deserves more than the cursory objection raised against it.
I agree that I would need to say more if I were trying to persuade Thomists to give up Premise 4. But that's no part of my objective here. My target is the ‘Aristotelian proof’, and Feser's claim that it removes atheism from the field of play. I take it that what I have said about Premise 4 suffices to show that the ‘Aristotelian proof’ does no such thing.
2. In response to the discussion of the red chair, Feser might say that it seems that quantum mechanics shows us that nothing stays wholly the same from moment to moment. Rather, there are changes that are constantly taking place which preserve something in being. It may look to us on the macro level that there is no change, but that's not what is going on at the micro level. These changes are explained in terms of something actual acting on a potential.
I do not think that quantum mechanics is plausibly interpreted as showing us that ‘nothing stays wholly the same from moment to moment’. There is an enormously complex literature on the interpretation of quantum mechanics; and there is an enormously complex sub-literature on relationships between classical macro-domains and quantum micro-domains. These literatures certainly have not converged on the view that we should deny that chairs can continue to exist and retain their colour throughout extended intervals of time. It would be clear over-reach to suppose that those literatures show that it is irrational to reject Premise 4.
3. Feser could apply Aquinas’ hand-stick-stone example to the expansion of the universe and to the case of the red chair. In each case, what we have is some actuality actualizing potentials over a period of time.
I take it that this is a correct account of what Feser believes. On his view, nothing happens without divine conservation [and divine concurrence]. Without God's causal activity, the universe and the red chair simply cease to exist. But that's not my view. And what matters for determining whether my beliefs are irrational is what I think, not what Feser thinks. I judge that the best view – the one that makes the best trade-off between minimizing theoretical commitments and maximizing explanatory breadth and depth – is one that accepts the account of actualization of potentials to remain unchanged that I have sketched above. That view does without God, divine conservation, and divine concurrence; and that view provides an explanation in every case of actualization of a potential. All else being equal, that gives me very good reason to prefer my view to the Thomist view.
4. Feser might respond to the example of the red chair by saying that it begs the question against Premise 4: it assumes that Premise 4 is false rather than showing that it is.
Not at all: we could with no less justice say that Feser's insistence on Premise 4 begs the question against those who agree with what I said about the example of the red chair. But, really, it would be better just to give up on these kinds of allegations about begging questions. You cannot turn a straightforward philosophical disagreement into a demonstration that the other party is irrational – or even merely mistaken – simply by claiming that they beg the question when they insist on sticking to their guns.
5. Feser might respond to the claim that there is a kind of deadlock here by pointing to his further argument that a thing cannot possess ‘existential inertia’ if it is composite or made up of parts, because its continued existence will depend on those parts being combined.
Perhaps it is worth adding a little more to what I said earlier about this. Return to my chair. It has various parts: legs, seat, backing, etc. At any given time, those parts are in a given configuration; at any given time, those parts have the potential to remain in the configuration that they are then in. According to me, so long as nothing intervenes, the potential of the parts to remain in the configuration that they are in at near future times will be realized. Not only does the chair have ‘existential inertia’, its parts have ‘configurational inertia’. Of course, the potential of the parts to remain in the configuration that they are in at near future times will not be realized if something intervenes, e.g. if someone demolishes the chair with an axe.
6. Premise 7 does not say that something can be actually F at t and potentially F at t. Feser explicitly denies that something can be actually F at t and potentially F at t in many of his other works.
Premise 7 says: the existence of S at any given moment itself presupposes the concurrent actualization of S's potential for existence. If we deny that something can be both actually F at t and potentially F at t, then – given Premise 7 – it seems that we are required to suppose that, if the thing is actually F at t, there was some earlier time at which it was potentially F at t. But now suppose that t is the first moment at which the thing exists. Since the thing did not exist at earlier times, it is not true that, at earlier times, it had the potential to exist at t. At those earlier times, there was no ‘it’ to be the bearer of that potential. If the existence of this thing at t requires the concurrent actualization of this thing's potential to exist at t, then it seems to me that we are led to the claim that it has the potential at t. Perhaps, however, Feser thinks that there are non-existent objects and that those non-existent objects have properties, including potentialities. If so, that is just one more point of disagreement between us.
7. Feser's view seems to be that a linear series extends through time and therefore presupposes the existence of things at any specific moment of time. But the existence of a composite thing at a specific moment of time presupposes that its parts are combined at that moment. It is here that Feser thinks hierarchical series come in in a fundamental way.
There are uncontroversial cases of hierarchical causal series. But the uncontroversial cases quickly peter out: there is nothing that the earth is resting upon; there is nothing that is causing the brain processes responsible for my moving my arm. Of course, in these cases, there are relevant linear series: both the earth and my brain processes have linear causal histories. Pending further considerations, it is very plausible to suppose that linear causal series are fundamental. For reasons already given, I do not suppose that we need hierarchical causes to explain the composition of composite objects. Again, for reasons already given, I do not suppose that we need hierarchical causes to explain the existence of objects. Yes, Thomists think that there are these hierarchical causal series that terminate in God; yes, Thomists think that these hierarchical causal series are fundamental. But their so believing hardly impugns the rationality of those who disagree with them.
8. There is much haste in the author's argument and little charity or thought about how Feser might respond. What the author offers is just cheap pot shots against Feser. The author seems to lack awareness of the details of the metaphysical background that Feser is presupposing.
It is true that Feser himself says the following:
[Opponents] misunderstand what classical theists like Aquinas mean when they say that God's existence can be ‘demonstrated’. What is meant is that the conclusion that God exists follows with necessity or deductive validity from premises that are certain where the certainty of the premises can be shown via metaphysical analysis. (308)
Fair enough. Perhaps there are arguments from incontestable premises to Premise 4 and Premise 7. But why should anyone take Feser's word for that? If he has such arguments, why did he not put them up? If the reasons that allegedly remove atheists from the field of play remain ‘secret Thomists’ business’, it should not surprise anyone that atheists continue to play on.
I am grateful to the referees for their suggestions of responses on Feser's behalf. Perhaps there are even better responses to what I have said that I have not considered. If I had been able to think of any, I would have tried to answer them, too.
