Here are some of the difficulties in making sense of the Fifth Way:
 
1. The gap problem seems especially severe. The only conclusion that seems to follow is that every unintelligent natural substance has an intelligent cause. This could be a large number of finite intelligences.

2. No good reason is given for the crucial inference from natural teleology to intelligence. What’s the middle term supposed to be? Given the relatively deflationary understanding of final causation that Aristotle and Aquinas share, there doesn’t seem to be any definitional connection between something’s acting for an end and its being directed by an intelligence to that end.

3. What’s the relationship supposed to be between the Fifth Way and the other four? Are we supposed to be relying on the conclusions of the other ways? If so, how? Is it intended to add intelligence only to the characteristics of a first cause, or is it also supposed to provide some reason to suppose that there is just one first cause?
 
Starting with 3, my guess is that the Fifth Way is supposed to provide us with information about the first cause (or causes) whose existence has been established in the first four ways. This is suggested by the Reply to the second objection in this article (STh I.q2.a3). If so, this helps with the gap problem. The Fifth Way is not intended to stand on its own but to extend the arguments of the preceding Ways.
 
In SCG I.44, in which Aquinas argues for God’s intelligence, there is a passage that closely parallels the fifth way (paragraph 7). In paragraphs 4 and 6 of that article, Thomas infers God’s intelligence from the intelligence of some of His creatures. In particular, in paragraph 6, Thomas appeals to the same thesis that is the conclusion of the Fourth Way, namely, that God possesses all perfections possessed by any existing thing. He asserts that intelligence is a perfection, and consequently God must be intelligent, given the existence of intelligent creatures. We could think of the Fifth Way as simply plugging a loophole. Suppose that a critic objects to the claim that intelligence is truly a perfection, as opposed to a mere by-product of the interaction of natural bodies). The Fifth Way could provide independent support for the intelligence of any First Cause.
 
Alternatively, we could interpret the Fifth Way as an a fortiori argument: if even unintelligent finite substances need an intelligent cause, how much more so must the cause of an intelligent finite substance be intelligent? The Reply to the second objection does allude to the fact that human intelligences need an intelligent cause, since they are changeable, finite, and contingent.
 
Let’s turn to the middle term problem (problem #2 above). The parallel passage in SCG I.44, paragraph 7 provides the key. “Again, that which tends determinately to some end either has set (praestituit) itself that end or the end has been set for it by another.” This is a kind of PSR or principle of causality, and it doesn’t mention intelligence at all (whether absent in the effect or present in the cause). Applying this principle in the way modeled by the first four ways yields the conclusion that there must be some agent that sets its own end. This interpretation has the advantage of bringing the Fifth Way in line with the first three Ways.
 
How is it possible for a substance to set its own end? Prima facie this is impossible, since anything a substance does (including ‘setting’ or ‘preastituting’ something) is explainable as directed to that substance’s end. The only solution to this problem would involve something’s having the Good itself as its end, ‘setting’ itself toward that end simply by grasping the good as good. Only this could eliminate the element of arbitrariness in the constitution of the First Cause’s end. Moreover, this good that is grasped must be identical to the substance itself, or else it would be being moved by something else and so wouldn’t be a first cause in the order of final causation. Thus, a First Cause must be Goodness itself, grasping itself as good in an act of self-understanding.
 
The Fifth Way, therefore, explains why the First Cause couldn’t be an unintelligent thing, possessing some end “by nature.” Why couldn’t a First Cause be its own end, acting for the sake of itself naturally but unintelligently? How could such an unintelligent first cause cause something else? It would have to be naturally directed toward causing such an effect, and the fact that it is so directed would be arbitrary and beg for a further explanation. Such unintelligent direction toward an end would be a brute fact and therefore incompatible with the First Cause’s being necessary in and through itself. There would be an element of contingency or in-principle explainability about the First Cause’s so acting. Such a First Cause wouldn’t be in principle uncausable, since we could imagine something else causing it to be directed toward creating the actual creature.
 
In contrast, if the First Cause is intelligent, then it can create things simply because they are good (by way of participating in God’s goodness). No unexplained contingency enters into the process, except for the contingency of rational free choice. The contingency of rational free choice is compatible with a strong principle of causality or PSR, since each rational choice can be adequately explained in terms of necessary facts (i.e., the intrinsic value of the action taken).
 
We can appeal to a principle stated in Thomas’s Commentary on Physics II.8. “But because they [unintelligent creatures] always act in the same way it is clear that they do not act by intellect but by nature. The artisan judges the form of the thing built and can vary it.” Both intelligent and unintelligent agents are determined to act as they do by their ends, but unintelligent agents always purse these ends in the same way, while intelligent agents can purse the same end in different ways, since an intelligent agent can grasp intellectually which actions are and which are not effective means for the end, and the intelligent agent can choose any of the many effective means (if there are many such).
 
A first cause that causes other things to exist (i.e., a first cause that acts as a creator) must be intelligent, since it must act in more than one way in pursuit of its end. Every such first cause effectively pursues its end simply be existing in a state of perfection. To create is to pursue that end in at least one additional way. To create multiple creatures because each of them is good in some way is to exercise intelligent choice in still further way.
 
One might question whether it is true that each unintelligent agent must pursue its end in a single way. Why couldn’t it have many ways of doing so, with the actual way or ways being selected not by intelligent choice but by random chance? If that were to be the case, then there would have to be some objective probability of the first cause’s causing any particular creature. We could then ask why the objective probability has the value it does. This would require some further cause to “set” this objective probability to its actual value. Only a rational and perfectly free agent can be a genuinely uncaused agent, since it can choose its own actions in light of its knowledge of the value of the chosen actions, where both the knowledge and the value are necessary in themselves.
 

Does God have a Will?
Summa Theologiae I, Q19, a1, and SCG I.72
 
For Thomas, this pretty easy. Everything that has intellect also has will. Every substance is striving in some sense to perfect its own nature. If a substance is intellectual, then it moves towards its own perfection with understanding. But to move with understanding is precisely to move voluntarily, by the exercise of will. This will be especially true of God, since He understands Himself perfectly.
 
However, there is a problem: God is unmovable, immutable. So, He cannot be said to move toward His own perfection. He is essentially His own perfection. But when a substance rests in its own perfection, that perfection remains its natural end. And when an intellectual substance rests in its own perfection, that resting is resting with understanding, which is by definition the state of delight. So, God perpetually delights in His own perfection. But delight is a function of the will, so God has a will.
 
In the SCG, Thomas also points out (in paragraph 8), that God, as first agent, is supremely free. Nothing can move Him or make Him do anything. To act with free will is essential to being free, so God must have a will.
 
Does God will other things than Himself?
 
Summa Theologiae I, Q19, a2, and SCG I.75
 
So, God will His own perfection, and so He wills Himself. Does He also will other things? Given that God is essentially in a state of perfection, which is also a state of perfect happiness in which His will is at rest, is there any room for Him to will anything else? He has no needs or deficiencies to fill. He can’t be any happier than He would be if He willed nothing but Himself. No additional object of the will can add to His happiness, if ‘adding’ implies a kind of increase. (Objection 3)
 
In addition, if God willed more than His own essence, then His will would be divisible. Or, at the very least, His act of willing would be complex. But God is simple. (Objections 1 and 4)
 
Moreover, if He did will something else, it seems that the value of that other thing could be said to “move” His will by attraction. But God is immovable. (Objection 2)
 
In response, Thomas appeals to the self-dispersive nature of goodness. Good things (including especially good people) have a natural tendency to spread that goodness to others, even if doing so doesn’t add to their own happiness. To good to others is a sufficient reason in itself for acting. Since God is maximally good, this dispersive nature is especially true of Him.
 
Thomas makes the point in a slightly different way in SCG, paragraphs 3 and 4. We’ve established that God loves Himself. Whatever loves itself also loves to some degree the things that resemble. Every actual thing resembles God to some degree, so God naturally loves all actual things.
 
God wills Himself as the sole proper and immediate object of His will, but He wills other things insofar as their existence is a fitting effect of His perfect goodness. Just as He understands all possible things by understanding His own essence, so He wills all actual things by willing His own perfection. There is a single act of will in God, just as there is a single act of understanding. And these two acts are the same act.
 
In response to objection 2, Thomas argues that God is “moved” only by His own goodness, and so His immovability is not compromised.
God doesn’t will things in order to add to His happiness. He wills them simply because and insofar as it is good that they exist.
 
Thomas explains in SCG I.77 why God’s willing multiple objects is compatible with His absolute simplicity. God wills multiple things only insofar as they are included (“comprehended”) in His goodness, just as He knows multiple things by knowing Himself in His infinite power. In paragraph 5, Thomas argues that the multiplicity of objects of will is less of a threat to divine simplicity than multiple objects of understanding were, since the will acts for the sake of the goodness that is in the object, not for some value existing in itself. Hence, there is no obstacle to a simple will’s willing multiple objects

​Summa Theologiae I, Q14 Of God’s Knowledge
Article 1: Whether there is knowledge in God
 
Thomas relies heavily on the fact of God’s immateriality to prove that He is intelligent, i.e., a being with knowledge and understanding. In effect, he argues that any immaterial substance must be intelligent, because it is matter that it is the sole obstacle to intelligence. Remove matter, and you remove that obstacle.
 
One might criticize St. Thomas on the ground that he is confusing a necessary with a sufficient condition. Suppose that we grant that no material substance can be intelligent, because material substances can have only one substantial form, and they cannot have contrary accidents, while an intelligent being must be able to contain substantial forms other than its own, and must be capable of understanding (and, therefore, of containing) contrary accidents. But, from the premise No material thing is intelligent, it does not follow that Every immaterial thing is intelligent. An immaterial thing has one of the necessary conditions of intelligence (immateriality), but does it follow that it has a sufficient condition?
 
Thomas could argue that we do not know of any immaterial substances except for intelligent ones (angels, and the separated human soul). Perhaps we can’t even conceive of any such things. Nonetheless, it might be that such things are possible, even actual, lying beyond the bounds of our own understanding.
 
Of course, in God’s case, we know more than just that He is immaterial. We also know that He has the power to cause the existence of every possible kind of creature. Perhaps Thomas could argue that an immaterial substance can have an active power (like the power to cause things’ existence) only through the capacity for understanding and will. The forms of all possible creatures must pre-exist somehow in God, by virtue of the principle of proportionality. They cannot exist in God “naturally,” in the sense that God could actualize each of the forms in His own person, since many of the forms are mutually incompatible. Nothing can be black and white, or a blue whale and a daffodil. So, they must exist in God in some kind of “intentional” (non-natural way). And we could plausibly define understanding as simply being a thing that contains forms intentionally.
 
But what about unintelligent, material substances that have active powers? Take, for example, the sun’s power of heating the surface of the earth. As we saw in the Fifth Way, Thomas argues that such active powers cannot exist in unintelligent bodies except instrumentally, by virtue of existing primarily in some intelligent maker or user of the unintelligent thing. So, perhaps we could define understanding in this way:
 

• Substance x understands form F if and only if F exists in x intentionally and intrinsically (not by virtue of x’s being an instrument of some other substance).

 
And we could define ‘intentional’ existence of a form in a substance thus:
 

• Form F exists intentionally in substance x if and only F exists in x in some mode M such that it does not follow with metaphysical necessity that:  if some form G exists in some substance y in mode M, then G can be predicated truthfully of y.

 
Given these definitions, we can prove that God understands every form that could possibly exist naturally in any substance. Note that this argument relies heavily on God’s unity, as well as on His status as the necessary first cause of everything else. This helps to explain why Thomas postpones the discussion of God’s intelligence to this late point.
 
It’s also worth noting that Thomas does not appeal here to the Fifth Way at all. That suggests to me that he thought that this argument was stronger or more rigorous than the proof in the Fifth Way.
 
Summa Contra Gentiles I, Chapter 44 That God is Intelligent
 
In the SCG, Thomas offers six supplementary arguments. First, in paragraph 2, he appeals to the Aristotelian argument for God as Prime Mover. This argument seems to assume that the first Mobile thing is a self-mover, like the intelligent celestial spheres of Aristotle’s cosmology.
 
He offers an alternative version of this argument in paragraph 3, one that doesn’t rely on this outdated assumption. The Prime Mover must be responsible for all possible changes. This requires that the First Mover moves things through (per) some universal form, a form in a universal mode. This seems very similar to the interpretation I gave of the argument in the Summa Theologiae, an argument from a universal set of active powers to an understanding that is universal in scope.
 
In paragraph 4, Thomas argues that an intelligent being can never be the mere instrument of an unintelligent one. All intelligent creatures are mere instruments of God, so God must be intelligent. The first premise doesn’t seem obviously true to me. Couldn’t the sun heat the air around me by heating me? In response, Thomas could point out that it is my body, and not my soul, that is being instrumentalized in that case. The principle of proportionality might require that if God is the per se cause of changes in intellects, then He must be intellectual Himself.
 
Paragraph 5 is the appeal to God’s immateriality that I discussed above.
 
In paragraph 6, Thomas appeals to God’s containing all perfections. Assuming that intelligence is a perfection and not reducible to a set of merely physical and chemical powers, then God must be intelligent.
 
Paragraph 7 brings forward a version of the Fifth Way. At this stage he considers the argument worth mentioning, but he doesn’t put it forward as the first, much less the only, argument for God’s intelligence.
 
Paragraph 8 involves another appeal to God’s perfection. Thomas argues that when forms exist naturally in particular things, then they are imperfect. Thomas might have even more plausibly said that such forms are ‘finite’, since they are limited, either by matter or (in the case of angels) by some finite essence that distinguishes them from other agents. A form can exist in a perfect (and infinite) being only by existing in its intellect, as an object of understanding. All forms must exist in God, since otherwise He would be incapable of being the first cause of their natural instantiation. So, God must have the forms in His understanding.

By delaying this issue until Question 11 in the First Part of Summa Theologiae (and chapter 42 in the SCG, I), Thomas is indicating that it is easier to prove that there is at least one God than it is to prove that there is no more than one. It is also important to realize that the ‘one’ that we appeal to in proving God’s unity is not the number 1, but the concept of oneness that is convertible with being. God is supremely one precisely because He is supremely a being. We don’t count gods in the same way that we can count apples or doors. As we shall see, the nature of God excludes the very possibility of there being two or more gods. At the same time, since the oneness involved is not that of the numerical one, Thomas is leaving open the door for God’s being, in some sense, a plurality or multitude. This will help in working through both the problem of God’s ideas  and the Trinity.
 
In Summa Theologiae I, Q11, article 1, Thomas explains that the focal meaning of ‘one’ in ‘there is one God’ is that of being undivided. God is supremely indivisible, and this follows from His simplicity. Thomas argues that if oneness were not convertible with being, an infinite regress would result. If oneness is not equivalent to being, then it would have to be something that is added to being. But then we can ask what makes this addition one addition, and an infinite regress follows.
 
But what about multitudes, like crowds of people? If they exist, they must also be one. And, indeed, a crowd is one crowd. But how can something be both one and many? Isn’t that inconsistent? Thomas anticipates here an answer given much later by the German logician Gottlob Frege. A multitude is one in one way, and many in another. It is, for example, one crowd but many people. Thomas elaborates this point in article 2, again distinguishing between one as the principle of number and one as convertible with being. We can ask for the number of a crowd, and this question must appeal to some way of dividing the crowd—into families, or individuals, or human cells.  At the same time, a crowd must be, like anything that exists, in some more basic sense one thing. Some more recent metaphysicians, following the work of American logician George Boolos, have suggested that multitudes can exist without being one thing at all. Very large proper classes, like the class of all sets, for example, seems to be a real multitude that is not in any sense one thing. If this is right, it could create some difficulty for some of Thomas’s proofs (in article 3) for God’s oneness. Or, it might simply point to the fact that the oneness of God is consistent with His comprising a kind of multiplicity, so long as these things are not parts or attributes of God.
 
In objection 4, Thomas addresses the problem of the definition of one as undivided. Being undivided is a negative notion, signifying the absence of division. But being is perfectly positive. So, how can being be convertible with oneness? Thomas replies that division is prior to one only in the order of our understanding. Ontologically, being undivided is prior to being divided. It’s just that we are first aware of composite things before we are aware of their simple parts.
 
In article 3, Thomas offers three arguments for the oneness of God. The first argument appeals to God’s simplicity. God is made to be God by His divine nature, and that divine nature also makes Him exist as a particular being. For there to be two gods, there would have to be two divine natures, each of the same species. But for two natures to exist with the same species, there would have to be something responsible for making each distinct from the other. So, for example, two men can be two by virtue of being combined with two packets of prime matter. Two packets of prime matter have no actual nature of their own, and so they can be fundamentally or primitively distinct. The divine nature is an actual nature (it is maximally actual), and so two divine natures cannot be fundamentally distinct. Since God is identical to His own nature, there cannot be two instances of the divine nature, just as there cannot be two instances of a single angelic species.
 
In the second argument, Thomas appeals to God’s infinity. (This is a new argument, not present in the SCG.) In fact, he appeals to the infinity of God’s perfection, by which he means that nothing can be superior to God in perfection. Suppose that there were two such maximally perfect beings. In this argument, Thomas concedes (for the sake of argument) that there could be two distinct species of god. If there were two such species, something would have to differentiate them. One would have to have something that the other did not have. But this means that one would have to have some form of perfection that was lacking in the other. But God has all perfections. So, in fact, this argument actually appeals to God’s perfection, rather than His infinity.
 
Third, Thomas appeals to the apparent unity of the world. This is one of the relatively few cases in which Thomas appeals to some form of the Fifth Way—pointing to God as the cause of the world’s systematic harmony, the fact that the active and passive powers of the world’s created substances fit together in order to make a stable, scientifically intelligible universe. Thomas gives a more detailed version of this argument in Summa Contra Gentiles 1.42, paragraph 7.
 
In Summa Contra Gentiles 1.42, paragraph 5, Thomas also appeals to some details of Aristotle’s natural philosophy, especially the assumption that the movement of the heavenly spheres are regular and continuous. It’s not clear to me whether any of this can be salvaged, given the falsity of Aristotle’s astronomy.
 
In paragraph 8, Thomas argues that if there were two gods, at least one would have to be composite. But no composite being could be necessary through itself (as established in the Third Way). It’s not obvious here why one of the gods would have to be composite, but the two arguments that Thomas gives in the Summa Theologiae support this premise: either the two gods would belong to the same species, in which case each would have to have a part that individuates it from the other, or they would belong to two species, in which case each would have to add some differentia to their common genus.
 
Paragraphs 9-11 contain another interesting argument that appeals to God’s necessity of being. This argument involves a complex dilemma: if there were two necessary beings (each necessary per se), then either (1) the two differ by something required for the completion of the necessity of being, or (2) not.
 

• Assuming (2). (Paragraph 9) If not, then they are different by something accidental. This accident must have a cause (since all accidental additions must be caused), which is either (a) the essence of the necessary thing, or (b) some external thing. We can rule out (a), since both necessary beings would have the same accident, if it is a proper accident determined by their common essence. If (b), then the existence of two necessary beings depends on the action of this third thing. But then the existence of each thing would also depend on the third thing, and so neither could be necessary in itself.
•  
• Assuming (1). (Paragraph 10) That which differentiates the two necessary beings would be either (a) something included in the common nature of necessary being, or (b) something that differentiates the two natures into two species. Case (a) is impossible because in that case, the factor will be present in both necessary beings. In case (b), the common nature must be made actual by each of the two differentiae, in which case, each necessary being would derive its existence from something else. Hence, the two things cannot be necessary in themselves, nor could each be simple and identical to its own act of existence. This complex argument seems to be mirrored in the first two arguments in the Summa Theologiae. The SCG helps us to see that these are really two parts of a single argument, based on a dilemma (either one species of god or two).

 
Paragraph 12 involves a very simple argument, based on the thesis that God is identical to His nature and to His act of existence. If there were two gods, then each god would have the same divine nature. But this divine nature would then have to be identical to two distinct acts of existence. But nothing can be identical to two distinct things.
 
Paragraphs 13 and 14 contain another complex argument.
 

1. If x is a per se necessary being, then x’s necessary being belongs to x insofar as it is x. That is, the necessity of x is grounded by x’s being x.
2. Suppose there were two per se necessary beings, x and y. Then x’s being x would also consist in x’s not being y, since if x and y are distinct, x’s being x depends on its not being y.
3. Consequently, x’s necessity would belong to it insofar as x is distinct from y.
4. This means that x’s necessity depends on the existence of y.
5. Consequently, x’s necessity would not be per se. Contradiction
6. So, there cannot be two per se necessary beings.

 
Thomas defends premise 1 in paragraph 14. If x’s necessary being depends only on x, then x’s necessary being must belong to x insofar as it is x.
 
In paragraph 18, Thomas appeals to the fact that God is supreme being. Since being is convertible with oneness, God must be supremely one, and so undivided. This applies equally well to the divine nature.
 
Thomas also appeals in paragraph 20 to the superiority of monarchy as the form of government. Since God is the perfect governor of the universe, God must be one.

In the Summa Theologiae Q4, a1, Thomas gives just one simple argument for concluding that God is perfect: namely, the fact that imperfection always implies some lack of actuality, and God is actuality in its absolute fullness. His reply to objection 3 is also noteworthy. Objection 3 observes that ‘existence’ seems radically imperfect, since things can exist no matter how far they are from perfection. Since God’s nature is simple, unqualified existence, He would have to be the most imperfect thing of all.
 
In the Reply, Thomas rejects this greatest common factor conception of ‘existence’. It is true that the formula ‘X exists’ can be true, no matter how minimal X’s grip on existence may be. (Thomas calls this the ‘formal principle of existence’, by which he seems to mean its logical or semantical role.) However, Thomas urges us to focus instead on the metaphysical role that is played by acts of existence (actus essendi). It is the act of existence that gives each thing whatever degree of being it has. The act is limited by the nature or essence of the thing, not vice versa. Acts of existence are the source of reality and actuality. Hence, God, as the supreme act of existence, must contain eminently every possible degree of being, so that He can give to each individual act of being all the actuality it needs to do its work, given its associated essence.
 
In article 2, Thomas argues that God possesses all the perfections had by creatures. This is the crucial point at which we depart from purely negative theology. He gives two arguments: one from God’s place as First Cause, and the other from God’s essence being His pure existence. First, since God is the cause of all the perfections in any creature (not only in the actual world, but also in any alternative possibility), God must possess in an eminent form each of those perfections. This is an appeal to the principle of proportionate causality which we’ve seen repeatedly since the First Way. As Thomas explains, the fact that the sun is the cause of heat does not entail that the sun is formally hot. But it does entail that it contains heat eminently—that it has some attribute that is, by virtue of its greater nobility of being, capable of making other things formally hot. Similarly, God is the cause of all heat, but He is not himself formally hot. How, then, is He eminently hot? He is so, as we shall see, by being an Intellect, knowing the form of heat as one of His possible creations. This is the same sense in which an architect is eminently a house.
 
So far, we have not really moved very far from a negative theology, since to say that God is eminently F is really to say little more than that He is the cause of F-ness. The second argument is, I think, the more fruitful. God’s existence is unlimited by any distinct form or essence. He is thereby a case of pure, unqualified existence. For the moment, let’s define a perfection as a property that doesn’t explicitly entail that its bearer is not God (not the First Cause, not identical to its own act of existence). So, for example, being finite, being created, having a nature, having passive potentiality—none of these would count as perfections, since they all entail explicitly that their bearer is not the First Cause. In contrast, being powerful, loving, knowing things—none of these explicitly rule out being God.
 
Say that F is such a perfection. If God lacked the possibility of being F, then being itself would lack this possibility. If F were not absolutely impossible, and if F does not explicitly rule out being God, then it would have to be possible for God to be F. There could be then no explanation of the impossibility of God’s being F: F itself does not rule this out, and God has no nature but existence, so if His nature rules it out, there must be a fundamental incompatibility between existing and being F. So, God must be possibly F.
 
But God lacks all passive potentiality. Hence, it is impossible for God to be merely potentially F. If He can be F, He must actually be F. Consequently, God must possess every perfection.
 
The basic premise of this second argument is that impossibility must have some explanation. If F and G are both purely positive, then there could be no logical inconsistency between them. Hence, is must be possible for F and G to be combined. Existence as such is purely positive. Hence, existence can be combined with any purely positive property. Since God’s nature is nothing but existence, it must be possible for God to have any purely positive property. Since God is a being of pure actuality, He must have in actuality every purely positive property.
 
We saw, when considering the Third Way, that Thomas seemed to assume that the possible existence of something that doesn’t actually exist needs to have an explanation. There is some prima facie tension between that principle and the principle relied on here. Suppose that there is no explanation for the possible existence of p, and no explanation for the impossibility of p. Is p then possible or not? The Third Way would say No, and the argument from perfection would say Yes. But p can’t be both possible and impossible.
 
The two principles can be reconciled in the following way. The Third Way appeals to the Nihil ex Nihilo principle:
 
(NEN) If x does not actually exist, then x’s existence is possible only if there is something that actually exists with the actual power to cause x to exist.
 
The second perfection argument depends on the principle that logically consistent combination is always possible:
 
(LCC) It is impossible to combine two properties only if there is some logical inconsistency between their essential internal structure or definition.
 
Are the two principles consistent? Consider some x that does not actually exist. Now consider two properties: actually existing, and being x. These are clearly not logically inconsistent in their internal structure or definition. So, by LCC, it must be possible to combine them. This means that x’s existence is possible. By NEN, it follows that something has the power to cause x to exist. But this is true: God exists and has this power. What’s interesting is that these two principles by themselves seem to entail that in every possible world, something exists with the power to cause the existence of anything that doesn’t exist in that world. This isn’t quite a proof of God’s existence, but it’s close. This does suggest that many atheists will find either NEN or LCC implausible. One could mitigate this problem by restricting LCC in such a way that it doesn’t apply to properties like being x (some particular thing). We might limit LCC to potentially general properties, properties that could in principle be instantiated by more than one thing. Then the atheist could consistently accept both principles.