Chap. 9: God’s Existence
CHAP. 9: GOD’S EXISTENCE
AS A CHRISTIAN, AQUINAS BELIEVED in the existence of God because God has revealed it in his Word (Gen. 1:1). He also believes that God has revealed himself in his world (Rom. 1:19-20). Consequently, Aquinas holds that it is possible to know God from his creation. But contrary to popular perception, Aquinas spent very little time on proofs for God's existence. In his massive Summa theologiae he treats the question only briefly.1
The Arguments for God's Existence
Aquinas offers five arguments for God's existence. Forms of all of them were used by his predecessors. There is little unique about them, except perhaps the metaphysical system involved. Many of them were utilized by Plato and Aristotle. All of them were used by Maimonides and other medieval theists before Aquinas.
The Argument from Motion
This argument is listed first because it is apparent to the senses that things are moving. The argument can be stated as follows:
1. Things change (motion being the most apparent form of change).
2. Whatever changes has the potential for change.
3. But no potential can actualize itself.
4. And there cannot be an endless series of actualizers.
5. Therefore, there is a First Actualizer.
In support of the fourth premise, Aquinas notes that an infinite series is impossible because subsequent movers move only when they are moved by the First Mover. In fact, there cannot be any intermediate efficient causes between the First Cause and the effect, only instrumental ones. The First Mover is moved by no other; and this First Mover is God.
The Argument from Efficient Causality
Aquinas's second argument for God is from an efficient cause. Aristotle argued only to God as a Final (purposing) Cause. Others, like Plato, saw God as a Formal Cause. But Aquinas believes that everything that exists needs an efficient cause. The argument can be summarized as follows:
1. There is an order of efficient causes in the world.
2. But nothing can be the cause of its own being.
3. And no series of efficient causes can cause their own being.
4. Therefore, there must be a First Efficient Cause.
Aquinas supports the second premise by arguing that if something were its own efficient cause, then it would be prior to itself, which is impossible. An infinite series is impossible because if there is no First Cause among efficient causes, there will be no ultimate, or even intermediate, cause. Therefore, a First Efficient Cause (God) is necessary.
The Argument from Contingent Beings
The third argument is from what Aquinas calls "possible beings." By this he means beings of which it is possible that they not exist. Possible beings are contrasted with a Necessary Being which, by nature, has no possibility of nonexistence. The argument from contingent beings can be summarized as follows:
1. Some things exist but can not exist (i.e., possible beings).
2. And something has always existed.
3. But possible beings do not ground themselves.
4. Therefore, there must be a Necessary Being.
In support of the first premise, Aquinas observes that whatever comes to be and ceases to be cannot be a Necessary Being. For a Necessary Being must necessarily be. Only a contingent being can not be. The second premise implies the self-evident principle that nothing cannot cause something. Hence, if there were ever a state of total nothingness, then there would always be nothing, since nothing cannot give rise to something. Since something now is, then something must always have been. Further, the only thing that can ground a contingent being is a Necessary Being. For if at one time nothing was in existence, it would have been impossible for anything to have begun to exist. And if this were true, even now there would be nothing in existence, because that which does not exist begins to exist only through something already existing. And the something that always existed must be a Necessary Being, not another contingent being. Therefore, there must be a Necessary Being as the cause of all contingent (possible) beings.
The Argument from Gradation of Perfection
The argument from gradation of perfection is in one respect the most distinct.2 Although Aquinas is Aristotelian in his philosophy, this argument seems very "Platonic." It is based on the premise that there are degrees of perfection among finite things, some being more perfect than others. Like the other arguments, however, it is one from effect to cause, since Aquinas insists that the Highest is always the cause of the lower. The argument can be summarized as follows:
1. Some things are more or less perfect.
2. More or less perfection can be known only by comparison with what is most perfect.
3. But the maximum of a kind is the cause of the rest of that kind.
4. Therefore, there must be a Most Perfect Cause.
The second premise is based on the obvious truth that we cannot know that something falls short of the standard unless that standard is known. The third premise is explained by noting that all good things are good only because they participate in what is Good. So what has goodness in one degree or another has it only because it shares in what is Goodness by its very nature. From this Aquinas concludes that there must be something that is the cause of being, goodness, and every other perfection—God.
The Argument from Design
The final argument Aquinas offers is from what he calls "the governance of the world." Unlike the first three, which are basically cosmological-type arguments from efficient causality,2 this is a teleological argument. Unlike William Paley's teleological argument from a watch to its efficient cause (a watchmaker), this one is an argument from final causality. It can be summarized as follows:
1. Every agent—even a natural agent—acts for an end.
2. Nov what acts for an end manifests intelligence.
3. But natural agents have no intelligence of their own.
4. Therefore, they are directed to their end by some Intelligence.
The first premise is simply the self-evident principle of teleology or finality (see Chap. 6). That even natural things act for an end is evident from their acting always, or nearly always, in the same way, in order to obtain the best results. But, in support of the third premise, whatever lacks knowledge cannot move toward an end, unless it is directed by some being endowed with knowledge and intelligence. Therefore, some intelligent being exists by whom all natural things are directed to their end—God.
The Basic Metaphysical Proof for God
Many Thomistic scholars believe that behind the five proofs for God, especially the first three or four, is one basic argument that can be found in Aquinas's tiny but influential work, On Being and Essence.
The Statement of the Metaphysical Argument
Whatever belongs to a thing is caused either by the principles of its own nature or else by something extrinsic to it. For example, risibility (the ability to laugh) is caused by rationality, since only rational beings have the ability to perceive the incongruous, which is the essence of humor. On the other hand, the sun is the cause of light in the air, since the sun is outside of our atmosphere.
But being cannot cause itself; a thing cannot bring itself into existence. A self-caused being is impossible.
Therefore, every being whose essence is not to exist must be caused by another. That is, every being whose essence is distinct from its existence is caused by another. For if it is not of its very essence to exist, then it could not exist. But whatever exists but could not exist does not account for its own existence. It needs another to ground its existence.
Every being caused by another is dependent on that which is not caused by another but exists in and of itself. Such a being is by definition a being that cannot not exist, that is, a Necessary Being. Therefore, a Necessary Being exists as the cause of every other being that exists but need not exist.
A Restatement of the Metaphysical Argument
Since Aquinas understands God in terms of Pure Act and all creatures as compositions of actuality and potentiality (i.e., act and potency), his argument can be restated as follows:
1. Changing beings exist.
2. All changing beings are composed of act and potency.
3. No potency can actualize itself.
4. Only Pure Act can actualize being.
5. So, all finite beings are actualized by Pure Act.
The first premise is evident to Aquinas. Change is an undeniable fact of finite existence. But anything that changes passes from potentiality to actuality. We both observe change in others and experience it in ourselves. Change is undeniable. Although Aquinas did not have occasion to address the point, he would have agreed that anyone who denies change changes in the very process of that denial. For to claim that everything has always been changeless overlooks the fact that there was a change in the one making that very claim. This is obvious from the fact that there was a change in consciousness from before making the claim to after making the claim.
Any being that is truly and eternally changeless would not have a change in its consciousness. It could never come to know anything; rather, it must always know what it knows. Likewise, anyone who changes in knowledge, as we undeniably do, cannot be changeless. Only an omniscient being never changes in what he knows. Hence, it follows that all who come to know, as we unquestionably do, are changing beings.
The second premise is evident from the very definition of change. Change means to pass from a state of potentiality with regard to the change to a state of actually having it. Rocks, for example, have no potential to learn the Pythagorean theorem. Hence, no rocks actually know it. Metal has the potential to be made into a cooking pan but jello as such does not. When metal is made into a pan then this potential has been actualized.
Likewise, a being that changes must have the potential for that change. Otherwise, it could not have had that change actualized. For example, if a being can come into existence or pass out of existence, then it must be composed in its very being of actuality and potentiality. It must have actuality, since it actually exists. And it must possess potentiality, since it has the potential in its being to come into or go out of existence. Therefore, its very being must be composed of actuality and potentiality.
This leads to the third premise. No potentiality for being can actualize itself. The mere potentiality to be something cannot account for why it is that. The possibility of existence does not explain why something actually exists. So potentialities cannot actualize themselves. Only something that is actual can actualize. If a potential to exist has been actualized, then it has passed from a state of potentiality to a state of actuality. It went from not being to being. But nonbeing cannot produce being. Nothing cannot produce something. Only something can produce something. Thus, any potential for existence must be actualized by something that already exists. Only actuality (act) can actualize.
This leads us to the fourth premise. Only Pure Act can actualize being. Not every act can actualize the act of being in something. Only Pure Actuality (Act) can actualize a potentiality to exist. For everything composed of actuality and potentiality has its potentiality actualized. But it cannot actualize its own potentiality. Thus, there must be some Pure Actuality that is never being actualized but is simply and eternal in act. This Pure Act and this alone can actualize the existence of something else. It alone is a Necessary Being; everything else is contingent. Pure Act alone is a Must-Be; all else may or may not be. But whatever can be and is, exists only because what is and cannot not be caused it to exist. Only Existence can cause something to exist. Nonexistence does not cause existence. The potential to be cannot actualize itself. Therefore, what is Actual, and has no potential not to be, is the cause of what is actual but has the potential not to be.
It is noteworthy that in this form of the argument for God's existence there is no need to refute the possibility of an infinite regress. For the very first and only Being that causes any other being to exist must be Pure Actuality. Only a being with no potentiality to exist can cause the existence of another. If it’s being is caused, then it cannot cause the being of another. For if it is dependent for its own being, how can it cause the being of another? Whatever is dependent for its own being must depend immediately on a being that is not dependent for its being, namely, an Independent Being. Therefore, there cannot be even one intermediate link between the being that is being caused and the Cause of its being, to say nothing of an infinite number of links.
The conclusion, then, is that all finite beings—however many there may be—are actualized by the one Pure Actuality that exists. Everything composed of actuality and potentiality is actualized by what is not composed of act and potency but is Pure Act. Every finite being is caused by the one being that is not finite, that is, the Infinite Being. All contingent beings are caused by the Noncontingent Being, namely, a Necessary Being. Also every changing being is caused by the Unchanging Being. And every temporal being is caused by the Eternal. That is, every characteristic of finite being points to a corresponding negative characteristic of its Infinite Cause. Since Pure Act has no potency, it cannot change. It cannot be in time, be dependent, be composed, or anything else that involves a potentiality to be actualized. From this Aquinas develops the so-called negative attributes of God, that is, the transcendent nature of God from which we must negate all finite, limiting aspects.
What, then, can we know positively about God? If Pure Act has no potency, then in what sense can we know about it from its effects? If it differs from its effects in that it has no potentiality, then how is it similar? Aquinas answers that Act communicates act. Pure Act resembles its effects in that they too are actual. They are not mere potentials, but a composition of actuality and potentiality. So Act is different from what it causes in that it has no potency but is similar in actuality. For Pure Act cannot produce another Pure Act. The Creator cannot create another Creator. If something is created, then it cannot be the Untreated Creator. A Necessary Being cannot make another Necessary Being. Likewise, a Necessary Being cannot not exist, but a being that is created can not exist. Hence, a being that comes to be cannot be the Being that cannot come to be but necessarily is. Since this is the case, then the only kind of being a Necessary Being can make is a contingent being. The only kind of being Pure Act can make is one with act and potency. Therefore, the creature must differ from the Creator in that the creature has potency; but the creature must be similar to its Creator in that it has actuality. This fact is the basis for the real analogy between creature and Creator (see Chap. 11).
Objections to Aquinas's Arguments for God
Most of the traditional objections to Aquinas's basic argument for God's existence widely miss the mark and none is telling. Consider the following typical arguments, mostly stemming from Hume and Kant, all of which Aquinas could easily have answered.3
Finite Beings Need Only Finite Causes
This objection fails because every finite being or effect is limited, and every limited being is presently caused by some Being. Thus there must be a Cause that is not limited but that is the Unlimited Limiter of every limited thing that exists. The First Cause cannot be finite or limited because if it were limited (i.e., caused), then it would need a cause beyond it to ground its limited existence. For every limited being is caused. But Pure Act of existence as such is unlimited. If there is a limited existence, then something must be limiting it. And the Actuality that provides the limits for everything else that is actualized must itself be unlimited in its existence. The First Cause must be uncaused, and an Uncaused Cause cannot be a limited cause. It must be the Unlimited or Infinite Cause of everything else.
The Concept of a Necessary Being Has No Meaning
Terms like "necessary" and "infinite" are derived from their relationship to what is dependent upon them. Their meaning is, in fact, twofold. First, such terms are negative. God is neither limited nor contingent. We know what these limitations mean from experience. So, by contrast, we know that God does not have any of these limitations. A negative term, however, does not denote a negative attribute. It is not the affirmation of nothing; rather, it is the negation of all contingency and limitation in the First Cause. The positive content of what God is derives from the causal principle. He is Actuality because he causes all actuality. He is Being since he is the Cause of all being. As the Cause of all being his Being cannot be caused. As the ground of all contingent being, he must be a Necessary (non-contingent) Being.
There Is No Way to Prove the Principle of Causality
This criticism is based on Hume's epistemological atomism—the idea that all empirical impressions are entirely loose and separate. Hume believes that there is no empirical way to establish a necessary causal connection for sensible experience. But Aquinas's cosmological argument is not based merely on empirical observation but on metaphysical necessity. Hume himself does not deny that things have a cause for their existence: "I never asserted so absurd a proposition as that anything might arise without a cause."4 Indeed, it would be ontologically absurd to suppose that something could arise from nothing. The principle of causality used by Aquinas is that every limited being has a cause for its existence. This principle is not based in any mere conceptional or definitional necessity but in the fundamental reality that nonexistence cannot cause existence.
The need for a cause of existence is rooted in the nature of finite, changing beings as composed of existence (act) and essence (potency). Existence as such is unlimited; all limited existence is being limited by something distinct from existence itself (this limiting factor will be called essence); whatever is being limited is being caused (for to be limited in being is to be caused to be in a certain finite way; a limited existence is a caused existence); therefore, all limited beings are caused beings. Stated another way, all limited beings are composed beings; they are composed of existence and essence—an essence that limits the kind of existence they can have. Likewise, an Unlimited Being is an uncomposed Being (i.e., a Simple Being). Such a Being has no limiting essence as such. Its essence is identical with its unlimited existence. The need for causality, then, is derived from an analysis of what finite being is. Upon examination, finite being is seen to be caused being, and caused being must have a cause of its being.
Theistic Arguments Are Not Persuasive
Whether anyone is convinced by this argument will depend on several factors. First, granting the soundness of the argument, persuasiveness will depend in part on one's understanding of this argument. Further, once the mind understands the argument, it is a matter of the will whether one assents to it. No one is ever forced to believe in God simply because the mind understands that there is a God. There may be personal factors beyond the analysis here that lead a person to remain uncommitted to God. Theistic arguments do not automatically convert. On the other hand, persons of good will who understand the argument ought to accept it as true.5
An Infinite Series of Causes Is Possible
As already noted, the very First Cause of any contingent being must be a Necessary Being. There cannot be even one intermediate causal link between the Creator and his creatures. The very First efficient Cause outside of beings whose existence is not being actualized must be the Actualizer of being. At best, any intermediates would have to be mere instrumental causes through which, not by which, the efficient causality is being exercised.
Furthermore, an infinite series of simultaneous and existentially dependent causes is not possible. There must be a here-and-now ground for a simultaneous series of causes, none of which would otherwise have a ground for its existence. An ungrounded infinite regress is tantamount to affirming that the existence in the series arises from nonexistence, since no cause in the series has a real ground for its existence. Or, if one cause in the series grounds the existence of the others, then it must be a First Cause (and hence the series is not infinite). Otherwise it turns out to be a cause that causes its own existence (which is impossible), while it is causing the existence of everything else in the series.
Confusion sometimes arises because mathematical (abstract) infinite series are mistaken for metaphysical (actual) infinite series. An actual infinite series of real finite beings is impossible. For in such a series it is always possible to add one more. But since one more than infinite is impossible, it follows that such a series must always be finite.
The Cosmological Argument Depends on the Invalid Ontological Argument
This Kantian criticism is not applicable to the argument of Aquinas. Aquinas begins with existence, not with pure thought. The first premise is that "Something exists," not Anselm's ontological idea of "that than which nothing greater can be conceived."
Furthermore, Aquinas's argument proceeds with ontologically grounded principles and not with mere rationally inescapable thought. It is based on the metaphysical truth that "nothing cannot cause something" rather than the rational assertion that "everything must have a sufficient reason."
Finally, Aquinas's cosmological argument concludes with a real Ground of all finite being as opposed to only a logically Necessary Being. That is, it ends with Pure Actuality as the cause of existence for all limited existence, as opposed to a Being that logically cannot be. This cosmological argument does not begin with a priori rational principles, and at no point does it borrow from the purely conceptual to complete its task. In other words, it is not based on the invalid ontological argument.
Necessity Does Not Apply to Existence, But Only to Concepts
This objection is self-defeating. For either the statement "Necessity does not apply to existence" is itself a statement about existence, or else it is not. If it is a statement about existence, it is self-defeating, for it claims to be both necessary and about reality while maintaining that no necessary statements can be made about reality. On the other hand, if it is merely a meta-statement, or statement about statements (and not really a statement about reality), then it is uninformative about which kind of statements may or may not be made about reality. In brief, the only way to deny the possibility of existentially necessary statements is to make (or imply) one in the very denial, which is self-falsifying.
The Cosmological Argument Leads to Metaphysical Contradictions
Kant offers several alleged contradictions or antinomies that he thinks result from applying cosmological argumentation to reality. At least three of these antinomies apply to Aquinas's cosmological argument.
THE ANTINOMY ABOUT TIME
If we assume that time applies to reality, then the world is both temporal and eternal. Thesis: The world must have begun in time or else an infinity of moments has elapsed before it began, and this is impossible (an infinity of moments can never be completed). Antithesis: The world could not have begun in time, for this implies that there was a time before time began, and this is contradictory.
In response to the first antinomy, Aquinas would note that Kant's view of time is incorrect. Time is not a continuum of successive moments that exist without beginning or end. Thus, creation did not begin in time that was already there; creation is the beginning of time. The only thing "prior" to time is eternity, and eternity is prior in a causal but not temporal way.
Further, Kant's objection overlooks the possibility of an eternal creation, which theoretical possibility Aquinas upholds, although he believes the world began from divine revelation.6 In any event, Kant's objection does not affect the argument based on a here-and-now cause of existence. For this type of cosmological argument is not dependent on a specific view about the origin of creation but only its present conservation in existence. The finite world demands a cause right now, regardless of whether it began in time or is eternal.
THE ANTINOMY OF CAUSALITY
It must be true that the world both has a First Cause and does not have a First Cause. Thesis: Not every cause has a cause or else a series of causes would not begin to cause as they in fact do. Antithesis: A series of causes cannot have a beginning, since everything demands a cause. Hence, the series must go on infinitely.
This antinomy has already been addressed. The antithesis is incorrect in stating that every cause needs a cause. According to Aquinas's principle of causality, only finite things need causes. Thus the Cause of finite being is not finite. Only finite causes need a cause; the First Uncaused Cause needs no cause, because it is not finite.
THE ANTINOMY ABOUT CONTINGENCY
Kant insists that everything must be both contingent and not contingent, if we assume that these concepts apply to reality. Thesis: Not everything is contingent or else there would be no condition for contingency. In other words, the dependent must be depending on something that is not dependent. Antithesis: Everything must be contingent, for necessity applies only to concepts and not to things.
Aquinas would reject Kant's antithesis. For, as noted, there is no way to deny that necessity can apply to reality without making a necessary statement about reality. Only an ontological disproof could possibly establish Kant's point. And ontological disproofs are self-defeating. Further, the cosmological argument has already concluded that something necessarily exists. The validity of this argument is the refutation of Kant's contention that necessity does not apply to existence.
The Conclusion Does Not Prove a Theistic God
How can the conclusion of Aquinas's cosmological argument be identified with a theistic God any more than with polytheistic gods, a panentheistic God, a pantheistic God, or even the atheist's material universe? Any of these could be the "Uncaused Cause" of the cosmological argument. A Thomistic answer to this question will relate to each of these alternatives in turn.
First, the Uncaused Cause is not many polytheistic gods. There cannot be more than one unlimited existence as such; more than the Most is not possible. The central premise of Thomism is that Act as such is unlimited and unique. Only act as co-joined with potency is limited. In order to differ, one being would have to lack some characteristic that the other one had. But any being that lacked some characteristic of existence would not be an unlimited perfect existence. In other words, two infinite beings cannot differ in their potentiality, since they have no potentiality; they are pure actuality. And they cannot differ in their actuality, since actuality as such does not differ from actuality as such. Hence, they must be identical. There is only one Unlimited Cause of all limited existence.
Second, the Uncaused Cause cannot be identical with the material universe. As ordinarily conceived, the material universe is a limited, spatiotemporal system. It is subject to the Second Law of Thermodynamics and is running down. But an Uncaused Cause is unlimited. Further, since space and time imply limitations to a here-and-now kind of existence and God is not limited, then God cannot be identical to the space-time world. God is in the temporal world as its very ground of continuing existence, but he is not of the world in that it is limited and he is not.
If, in response, we claim that the whole of the material universe is not temporal and limited as are the parts, this would only demonstrate what Aquinas asserts. For his conclusion is that there exists beyond the contingent world of limited spatio-temporality a "whole" reality that is eternal, unlimited, and necessary. In other words, there is a God beyond the limited, changing world of experience. It is a substitute for God that admits there is a "whole" reality that is "more" than the experienced part of reality and that has all the essential metaphysical attributes of the theistic God.
Third, the Uncaused Cause is not identical with the God of panentheism. Dipolar theism or process theology affirms that God has two poles: an actual pole (which is identified with the changing temporal world) and a potential pole (which is eternal and unchanging). Such a conception of God must be rejected for the following reasons. The conclusion of the cosmological argument demonstrates the need for a God of Pure Actuality with no potentiality (pole) at all. Further, God cannot be subject to limitations, composition, or spatio-temporality, since he is unlimited in his Being. Moreover, God cannot have poles or aspects, since he is absolutely simple (i.e., uncomposed) with no duality at all. He is a simple and unlimited existence as such, with no limited pole. A partly limited unlimited existence is a contradiction. In addition, God cannot be subject to change. For anything that changes must be composed of actuality and potentiality for change. Change is a passing from potentiality to actuality, from what can be to what actually becomes. But since existence as such has no potentiality, it follows that it cannot change. If something changes, it proves thereby that it was not pure actuality but possessed some potentiality for the change it underwent. A pure and unlimited actuality cannot change.
The God of panentheism or process theology is a confusion of the world process with the God who grounds that process. God is in the process as the unchanging basis for change, but God is not of the process. God is the Cause of all finite, changing existence, but he is beyond all finitude and change. God changes relationally (by entering into changing relationships with the world), but he does not change essentially. When a person moves from one side of a pillar to the other, there is a real change in relationship, but there is no change in the pillar.
Fourth, the Uncaused Cause is not the God of pantheism. Pantheism affirms that an Unlimited and Necessary Being exists, but denies the reality of limited and finite beings. For Aquinas change is a fundamental, undeniable part of finite existence. Pantheism is contrary to our experience of change in the world. It affirms that all change, including that in our own minds and consciousness, is unreal. It would mean that no river really moves, no tree grows, and no person actually ages. If there is any real change, there must really be changing beings distinct from God, for God is an unchanging Being.
There Is No Need for a Here-and-Now Cause of Existence
Unlike other cosmological arguments based on a beginning of the universe or contingent being, Aquinas's argument is not dependent on a past but a present Cause of being. This gives rise to the objection that there is no need for a present cause of being. There are two aspects to objections of this kind. Some contend that it is not meaningful to speak of simultaneous cause-effect relations; effects generally follow causes temporally. Others simply say that there is no need to insist that the world needs a conserving cause; an originating cause, if anything, would be sufficient.
First of all, simultaneous causality does make sense. There is no contradiction in saying that an effect is being effected at the very instant it is being caused. This is clearly the case with the relation between the premises (cause) and the conclusion (effect) of a syllogism. Cause and effect are simultaneous, for the instant we take away the premise(s), at that very instant the conclusion does not follow.
Likewise, the causal relation between my face and the image in the mirror is simultaneous. What clouds the understanding of the simultaneity of causality is the confusion of an effect with an aftereffect. For example, when I throw a ball, it continues to move even after I am no longer throwing it. A clock continues to run after I wind it. In each of these and like examples, the aftereffect is directly and simultaneously effected by some cause. The force of inertia keeps the ball moving; the forces of tension and reaction keep the mechanism of the clock moving. If any of these forces would go out of existence, at that very instant the aftereffect would stop dead. If inertia ceased the very instant after the ball left my hand, the ball would instantly stop in midair. Likewise, the clock would stop ticking the instant the physical laws affect it were not operative. Every so-called aftereffect is really an effect of some simultaneous cause. In like manner, there are no existential aftereffects. Whatever is being caused to exist right now must have something causing it to exist right now.
A basic distinction will help illustrate the point. The artist is not the cause of the being of a painting, but only the cause of the becoming (or coming to be) of the painting. The painting continues to be after the artist stops painting it. In like manner, a father does not cause the being of his son but only the son's becoming, for when a father dies his son continues to live.
Now it is necessary that finite beings have a cause not only of their becoming but also of their here-and-now being. For at every moment of their existence they are dependent for their existence on another. They never cease to be limited, finite, contingent beings. And as such they demand a cause for their existence, for every finite being is caused. Hence it does not matter whether we are referring to John Doe at moment one of his existence or at moment two or moment three. He is still existing, that is, he still has a received existence, that is, he is still receiving his existence from something beyond him. Changing the moment of his dependent existence does not make him a nondependent existent. Perhaps some of the problem would be removed if we did not talk of existence (as though it were a whole package received at once) but of existing (which is a moment-by-moment process). Maybe the word "being" is even more misleading in this regard. No one receives the whole of his being at once, nor even the next instant of it. Each creature has a present "be-ing." Existence comes only a moment at a time. But at each moment of a dependent be-ing there must be some Independent Be-ing on which that be-ing is depending for that moment of being. In this respect, the distinction between the Latin esse (to be) and ens (being, thing) is helpful. God is Pure Esse and our present esse is dependent on him. Pure Existence must existentialize our potentiality for existence; otherwise we would not exist. God as Pure Actuality is actualizing everything that is actual and not merely potential. Hence, it is the present actuality of all that is actual that demands a causal ground.
The Act-Potency or Contingent-Necessity Models Are Arbitrarily Imposed on Experience
This objection states that it is only because we have modeled reality as contingent or composed of actuality and potentiality that we are forced to conclude that there is a Necessary Being or Pure Actuality. This, proponents insist, is an arbitrary and loaded way to view reality, which can be conceived in other ways.7
In response, Aquinas would point out that the contingency-necessity model is not arbitrary but logically exhaustive. Either only Necessary Being exists, or else there is a contingent being(s) as well as a Necessary Being. But there cannot be merely contingent being(s). For contingent beings do not account for their own existence, since they are but might not be.
To put it another way, either everything is one pure undifferentiated Actuality or something else also exists. But there cannot be two Pure Acts, since act as such is unlimited and unique. There cannot be two Ultimates or two Infinite Beings. So whatever else exists must be a combination of actuality and potentiality. But since no potentiality can actualize itself, then whatever composed beings there are must be actualized by Pure Actuality.
For Aquinas there is no need to prove something exists. That is self-evident, undeniable. And the proof that something that exists is contingent or composed of an actuality and a potentiality not to be is that beings change. Change is a passing from a state of potentiality to actuality. And since nothing can actualize its own potentiality, then there must be an Unactualized Actualizer of every other thing that is actual.
The Cosmological Argument Commits Modal Fallacies
Modal logic is based on the distinction between what is possible and what is necessary. This form of reasoning has developed its own list of fallacies. Alvin Plantinga argues that it does not follow from the fact that it is possible for all the parts of my car to break down at one time or another that it is necessary that at one time all the parts will break down.8 Thus, although all contingent beings possibly do not exist, they do not necessarily not exist at one time and thus need no universal cause of existence. Of course, Plantinga is correct in this assertion and thereby throws some formulations of the argument from contingency into doubt. But his objection does not apply to Aquinas's argument, since it is not concerned with showing that all things that could not exist need a single cause to produce their existence, but that all things that do exist (although possibly could not exist) need a cause for their present existence, both individually and in toto.
A second possible charge of committing a modal fallacy would be to say that it is illegitimate to infer from the fact that the world necessarily needs a being as First Cause that the world needs a Necessary Being as First Cause. Again, as it is stated, that charge would be correct, but our cosmological argument does not make that inference. God is not considered a Necessary Being because the argument necessarily demonstrates his being. He is called Necessary Being because ontologically he cannot not be. We learn of his Necessary Being not from the rigor of our premises, but because existentially a First Cause must be a Necessary Being.
The mistake of many theists, especially since Leibniz, is to cast the cosmological argument in a context of logical necessity based on the principle of sufficient reason. This ultimately leads to contradictions and an invalidation of the argument. In contrast to this procedure, Aquinas uses the principle of existential causality to infer the existence of an Unlimited Cause or Actualizer of all existence.9 Thus, his conclusion is not rationally inescapable, but actually undeniable. In brief, if any contingent being exists, then a Necessary Being exists; if any being with the potentiality not to exist does exist, then a Being with no potentiality not to exist must exist.
Volumes have been written on Aquinas's arguments for God's existence. Aquinas himself devoted only two pages of his great Summa to them. Nonetheless, there is a profundity in their simplicity that still captivates the minds of great thinkers. Behind his famous "Five Ways" is one less famous metaphysical proof that has withstood the assaults of critics down through the centuries. Beginning with the undeniable fact that some changing finite being exists, Aquinas argues convincingly that there must be an Infinite, Eternal, unchanging Cause of this finite being. For if something comes to be, then Something must always have been. Nothing cannot cause something, so something must always have been. This proof of an eternal Necessary Cause of all contingent being still stands as a monument among rational arguments for God's existence.