God As the Ultimate Cause

Why is there something, rather than nothing at all?  How is it that this “something,” both in its arrangement and unfolding, manifests order and thus intelligibility?  These questions take us to the heart of what Aquinas’ so-called “five ways” seek to address.  Such questions, however, do not meet with an immediately exhaustive answer at the conclusion of Aquinas’ first way.  Were this the case, Aquinas’ subsequent proofs would lose something of their power; they would represent a mere transposition of the same melody into four additional keys, seemingly for the sake of reaffirmation or variety.  Admittedly, having multiple means by which to establish God’s existence can be salutary in its own way, since not everyone finds each of Aquinas’ proofs to be equally compelling.  Still, thinking of the five ways as so many instruments by which to secure the same outcome underappreciates what Aquinas is up to in this text.  We thereby risk overlooking what the other four ways might teach us.

Even Aquinas’ own words can potentially mislead, since—as he repeatedly affirms—his arguments seek to demonstrate “only” that God exists, and not who or what God is.  Given the relative modesty of the goal, the payoff of each proof would appear to be identical.  Still, careful attention to the five ways reveals that the expression “that God exists” admits of further nuance.  For Aquinas also repeatedly affirms that we know God through his effects and that the nature of these effects casts light upon their cause—in accordance with Rom. 1:20, we know and name God through his creation.  It stands to reason that an attention to different kinds of effects can alter and enhance our knowledge of the source that ultimately explains these effects.  Accordingly, in considering various respects in which the natural world depends on God, the five ways correspondingly consider various respects in which God is at work in causing the cosmos.  In this way, each argument provides an opportunity to deepen our understanding of what we mean by both “God” and “creation.”

With this in mind, we are better disposed to appreciate how the five ways might represent not a scattershot of theistic proofs, but an intentional sequencing of arguments whereby Aquinas draws us more deeply into the mystery of the world’s dependency on God.  Expressed in simple terms, he begins by establishing the need for divine influence and subsequently radicalizes this influence so as to show that the world depends on God in the most significant way possible, for its very existence, from which all order, unfolding, and perfection follow.Thomas begins by establishing the need for divine influence and subsequently radicalizes this influence so as to show that the world depends on God in the most significant way possible, for its very existence. Share on X In this context, while standing on its own two feet, the second way serves as something of a bridge between the first and third way.  Taken as a whole, the second way will gently compel us to think in more abstract terms so that we can better appreciate how nature points to God, as something created points to its Creator.

While each of the five ways begins with a consideration of the natural order, as disclosed to our senses, the second way takes its departure from the “order of efficient causes” (ordinem causarum efficientium).  This is not to say that it attends to a distinct subset of natural things; rather, it attends to the natural world from a distinctive vantage point, according to distinct principles, or under a distinct formal aspect, i.e., according to the notion of efficient causality.  What, then, is an “efficient cause”?  While the term itself is scholastic, it clearly aims to express one of Aristotle’s “four causes,” discussed (among other places) in his Physics and Metaphysics.  Alongside his inclusion of the material cause, the formal, and the final, Aristotle identifies this particular cause, the so-called “efficient cause,” as “the primary source of change” (Physics II.3).  He offers various illustrations of what he means by such a cause:  the parent with respect to the offspring, the counselor with respect to those receiving direction, or more generally what makes or changes with respect to what is made or changed.  In each of these cases, the efficient cause would be the primary, relevant source of change upon which an effect depends for its realization.  Put simply and prepositionally, an efficient cause acts as that “from which” a change comes about.

Not Chaos but Order: Efficient Cause in Nature

So Aquinas begins the second way by reminding us that we observe efficient causality at work within a world of sensible things.  We witness, e.g., animals producing offspring (generation), the sun darkening the flesh (alteration), bees transporting pollen (locomotion), food gradually bringing about growth (quantitative change), etc.  These forms of efficient causality, considered on a larger scale, constitute an “order.”  What we confront in nature is not chaotic and inexplicable interaction but an intelligible network in which effects are subordinated to their causes.  Such intelligibility results from the conditions that define causality:  efficient causes act because they possess a distinctive causal power, and (at least within nature) their effects follow by virtue of some relevant potency or possibility on the side of what comes to be.  Thus, due to its agency, the efficient cause brings to actuality what previously existed only in potency.  Nature’s very susceptibility to scientific and philosophical inquiry is secured by this proportionate relationship between effects of a certain kind and their commensurate, explanatory causes.  The order of efficient causes underwrites rationality.

We recognize, perhaps with little explicit reflection, that an effect requires a cause and that, by extension, an effect requires a cause distinct from itself.  An effect cannot cause itself.  That we have never observed an effect that causes itself is not just a matter of happenstance, something that we might experience but heretofore have not; rather, through rational insight into our sense experience, we recognize self-causality to be impossible.  A cause enjoys a priority with respect to its effect, since it imparts something that would otherwise be absent without its influence; if an effect were to cause itself, “it would be prior to itself,” such that it would impart to itself what it in fact lacks.  Since the result cannot simultaneously be its own cause, strict self-causation is not simply unobserved but metaphysically incoherent.  (Of course, lest there be confusion, nothing prevents a single substance from being a “self-cause” in a qualified way, e.g., as a doctor might heal himself, but this putative self-causality always assumes composition or duality, such that the doctor’s knowledge helps to restore his health; in such a case, the proper effect—the restored health—does not cause itself.)

Dominoes and Cellos: What kind of causality are we talking about?

Now, in the concrete order of nature, an effect not only requires a cause distinct from itself, but it generally finds itself enmeshed within a web of causal relationships, such that it relates to a multitude of distinct causes.  A single being may be subject to multiple causes acting in parallel with one another, as a plant’s growth might benefit from both water and light, even if each of these causes makes its own proper and distinctive contribution.  Furthermore, a single effect might be subject to multiple causes acting by way of a “nested” relationship, with these causes being more proximate to, or more remote from, the effect.  An example that perhaps readily springs to mind is that of cascading dominos, where the falling of the final domino depends not only on the contact of the immediately prior domino, but in some sense on all prior dominos in the series; similarly, we might consider a musical piece issuing from members of an orchestra, who themselves are playing under the direction of a conductor, or further still we could consider sounds emanating from a single cello, itself instrumentally subordinated to the cellist.

It is essential to recognize, however, that while these last three examples illustrate ordered or nested causality, the kind of subordination in question varies.  Notably, the subordination at work in the first example, that of the whole series of dominoes, is arrayed across time and so applies in a qualified manner.  When we say that the falling of the final domino “depends on” the “prior” falling of the first, the dependency and priority both refer us to the past.  As the final domino falls, it does so under the direct influence of the most proximate domino. Whereas the first, most remote, domino has ceased to exercise its causality in an active manner.  Accordingly, the dependency expressed across the whole series represents an aggregate of many, more localized causal interactions, occurring sequentially across time.  This case can be fruitfully contrasted with the example of the orchestra or the cellist.  In the latter case, the cellist does not first act upon the cello such that the cello in turn emits sound in a temporally subsequent act.  Instead, there is a concurrence of activity, such that the music is presently and actually subordinated, not only to the instrument, but also to the musician.  Were the cellist to stop playing, the instrument would also cease to produce sound—whereas, by contrast, dominoes might continue to fall while the first domino in the series lies inert.  What we have in the case of the cellist is not mere ordering but, more precisely, an “essentially ordered” series (see, e.g., ST I.46.2 ad 7), a series in which the ultimate effect is subordinated to causes that presently and simultaneously exercise their power. As we’ll see, this kind of ordering figures prominently in Aquinas’ demonstration.

Causes all the way down: Can there be an infinite regress?

Having acknowledged a natural order of causes and having established that a thing cannot be the efficient cause of itself, a fundamental question lies before us.  What ultimately grounds the order of efficient causality that we observe in nature?  Evidently, the phenomena that lie before us depend upon causes, but how far does this chain of dependency extend?  Two basic options lie before us:  the causal series terminates and so has a finite number of members, or the causal chain is unbounded and so extends ad infinitum.  Aquinas argues against the latter possibility so as to establish that the order of efficient causes rests upon an ultimate cause, namely God.

While texts outside of the five ways make this more apparent, Aquinas’s investigation into the order of causes is meant to be “synchronic” in nature, rather than “diachronic.”  That is, he examines relationships of cause and effect that hold at any particular moment in time; his concern is not the causal history of the cosmos.  For effects do not simply depend on the past (in a “horizontal” manner), but also (“vertically”) on other causal influences in the present; in fact, effects depend more directly on present or concurrent factors, since the past as such does not actually exist.  Thus, insofar as Aquinas attends to actual causal subordination at any given moment—most conspicuously, the present—he has in mind the subordination found in an “essentially ordered” series.

Evidently, any essentially order series must have an effect and a cause.  Between this effect and cause could exist a number of intermediaries, beings that exist both downstream of the first cause and upstream of the effect and thereby transmit the efficacy of the first cause.  It would be difficult to enumerate every present causal condition that makes possible even a relatively mundane activity, such as lifting one’s mug of coffee while reading the latest edition of Credo.  Still, for Aquinas, this much must be true as a matter of principle:  the number of intermediary conditions must be finite, and so these conditions must be subordinated to a first, ultimate cause.For Aquinas, this much must be true as a matter of principle: the number of intermediary conditions must be finite, and so these conditions must be subordinated to a first, ultimate cause. Share on X For him, admission of an infinite number of relevant causal factors would entail, logically enough, an elimination of any first or ultimate cause, since the series would never terminate.  More controversially, he further concludes that such a series would actually undermine itself, since the elimination of the first would entail the annulment of its causal power.  Were the series infinite, the effect would never realize itself.

Aquinas’ denial of an infinite regress—central to the first, second, and third way—is easily misunderstood, in no small part because Aquinas’ argument is so terse that it practically functions as an allusion to justification provided elsewhere (see, e.g., Summa Contra Gentiles I.13).  Some clarifications help us understand why Aquinas isn’t straightforwardly begging the question.  First, Aquinas isn’t rejecting, simply out of hand, any and all kinds of infinity.  Somewhat remarkably, he thinks that philosophical reasoning, apart from revelation, cannot conclusively demonstrate whether the world was created at a first temporal moment or exists as an eternal effect of God; the latter case would ostensibly introduce an infinite series of cause and effect relationships, stretched across time, but this is not the infinity Aquinas is at pains to deny.  Instead, Aquinas denies the possibility of an infinite, essentially ordered series:  a single, active subordination comprised of infinite members, rather than an infinite number of distinct subordinations.  For him, an effect cannot be realized if it depends on an infinite number of concurrent layers of causality.

Why, however, does this follow?  Yes, “to take away the cause is to take away the effect” (ST I.2.3 corp.), but how is taking away a first cause by way of an infinite series violating this axiom?  Doesn’t an infinite series multiply causes, entailing that every effect anywhere in the series has a preceding cause?  According to Aquinas, such a multiplication of causes neuters causality inasmuch as this apparently quantitative difference between the finite and infinite proves also to be qualitative.  For in eliminating a “first cause,” such an infinite series doesn’t dispense with a merely numerical “first” but with the very causal power that only such a “first” can provide.  In the absence of the first cause, we are left, not with a string of causes but with a string of putative intermediaries with no causal power to mediate.  By way of analogy, a video projector might cast an image on a screen, and it might do so via the mediation of a mirror, or even by way of a series of mirrors.  Once this series becomes infinite, however, we aren’t simply lengthening the series but fundamentally altering its character, since each and every member is now only a mirror, an intermediary.  Mere mediation remains, “all the way up and down,” but with nothing to mediate and no final effect; rather than the image being transferred without end, the image is never projected and is never received.  This is why, in removing a first cause by way of infinite regress, “there will be no ultimate, nor any intermediate cause” (ST I.2.3 corp.).

God as the Uncaused-Cause

We are left with the conclusion that any observed effect of efficient causality finds itself, in the present moment, essentially ordered to a necessarily finite number of causes.  Why must we further conclude that such a series leads all the way to God?  While we might subordinate a musical performance to a musician or a conductor, or an image to a projector, or the growth of a plant to the sun, each of these causes is “first” in an only qualified sense.  The conductor might be first “in the order of the performance,” but he or she is clearly caused in other respects and so is subordinated to other environmental factors; the sun might principally explain the effects of solar energy on earth, but the sun’s activity is sustained by other cosmic conditions.  Thus, the causality of the conductor and that of the sun are first only in a relative sense, as each finds itself subordinated in other respects to some still more universal network of causes.  Whatever underlying or overarching causal conditions happen to constitute this network, we avoid an incoherent regress to infinity only by acknowledging an unqualified first cause.  Such a cause would be altogether uncaused and so lack the susceptibility to be acted upon in any respect.  Otherwise, such a being could be beholden to something else, and so have a merely intermediary status.  Thus, while specifying all intervening causal factors may remain an open-ended, empirical matter, philosophical reflection demands that the total order of efficient causes find its repose somewhere, and specifically in a wholly uncaused cause.

A few words might be said in closing regarding why this first cause should receive the designation of “God.”  According to Aquinas’ understanding of nature, all accidental modes of being (qualities, quantities, etc.) inhere in and depend upon substances.  In the end, any substance within nature will have the potency to be acted upon in some respect and so cannot be ultimate.  If the cosmic order depends on a first cause that cannot be acted upon, this cause must be immaterial and so transcend the order of nature.  Such a lack of potency entails both a fullness of actuality and a lack of limitation, though Aquinas explores divine infinity elsewhere.  Aquinas presumes, reasonably enough, that such a “transcendent first cause of the cosmos” would merit the name “God,” even though the five ways hardly exhaust how a Christian might conceive of God.

Further reflection might compel us to insist that natural beings are efficiently caused, most fundamentally, with respect to their very act of existence. The second way suggests, beyond the first way, that God is not simply a mover but a maker. Share on X Correspondingly, God’s efficient causality turns out to be an act of creation, whereby God uniquely and directly imparts existence to each creature.  (See On Being and Essence IV, where Aquinas argues for God as the efficient cause of creaturely existence.) In the context of the second way, Aquinas skims the surface of this more metaphysical treatment. The second way suggests, beyond the first way, that God is not simply a mover but a maker. The character of this making and the depth of creaturely dependency becomes clearer in light of the third way.

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