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Aquinas’ Way to God: Arguing Essence and Existence

May 11, 2020


Originating in various form among those intellectually herculean Greek philosophers (Plato and Aristotle), being promulgated by many prominent and mega-minded theologians throughout the monotheistic traditions (Maimonides: Jewish; Averroes: Muslim), and coming to a height (or so I believe) through the high-octane, motor-breathed metaphysics of St. Thomas Aquinas, arguments for the existence of God are possessed of a rather distinguished pedigree.

Speaking personally, coming to proper understanding of the metaphysical proofs for God’s existence is what restored my severely diminished childhood sense of wonder (and belief), and caused me to eventually reconsider religion wholesale. Ultimately, philosophy is what thrust me into the cushiony bosom of the Catholic Church, after (ironically enough) reading the Old Atheists and existentialists in early high school plunged me into the revolting depths of atheistic materialism for nearly a decade, an account I recently shared on EWTN’s The Journey Home.

And so I have something of a sappy sentimentality regarding theistic philosophy, seeing the real, positive difference such clear-headed thinking can make in the life of a comparatively open-minded skeptic. But such arguments do more than just convert people; they deepen our understanding of God and of God’s relation to the world. They can, in fact, help us to love God more by coming to know him better.

My contention is simply this: because philosophical arguments for God serve multiple, useful purposes, they ought to be of (at least some) familiarity for every practicing Catholic, as both a source of edification in one’s faith commitment and a raw, intellectual exercise of value.

For starters, then, I’ll offer a contemporary (and condensed) version of the frequently assumed master argument of St. Thomas Aquinas for the existence of God, which I believe best encapsulates his metaphysics of participation. This is not, it should be mentioned, one of St. Thomas’s famous Five Ways, found in the Summa theologiae (Bishop Barron provides an excellent overview of the First Way here). Rather, the argument “from essence and existence” originates from his De Ente et Essentia (On Being and Essence), which has been brilliantly exegeted by many contemporary philosophers, particularly Dr. Gaven Kerr in a book that shares the same title as this article. (To be clear: I’m borrowing from Dr. Kerr, and not the other way around.)

On Being and Essence

The “what” of something is called its essence, whereas the “is” of something—specifically, the fact of it being present (and therefore, active) in reality—is called its existence, and famously it has been argued by philosophers, including and especially St. Thomas, of there being (among things common to experience and particularly among things whose essence is finite and limited) a real, metaphysical distinction between its essence and its existence. So, while essence and existence may be inseparable, and you cannot have one without the other, still they remain truly distinct.

There are many reasons to accept the real, metaphysical distinction between essence and existence, particularly among limited and/or finite instances of being. (Note: Limited and/or finite instance of being = anything which exists in this specific way, and/or with those specific powers/abilities, and/or in that specific time, place, etc. One could say, in other words, of limited and/or finite beings how they exist “only to this degree,” “only in this way,” “only to this or that perfection,” etc. For example, a roast beef sandwich. Also, electrons).

The first and most obvious bit of evidence in support of the so-called “real distinction” is simply the immediate and radical contingency of any limited and/or finite being. Certain things enter existence and eventually expire from it. Lions, atoms, roast beef sandwiches—none of these beings exist necessarily. Otherwise, such beings would never have not been or could never not be. But among these types of things, there was a time when none existed, and perhaps a time will come when none of them exist again. So, their contingency—the fact they exist, but don’t have to exist, or could have existed otherwise—points to a real distinction between their essence and existence; for if they existed in virtue of what they are, they would not be contingent but necessary.

In other words, the “what-ness” of this or that finite, limited being doesn’t determine its inclusion into reality. Their existence does not “flow” from their essence, and to suggest otherwise would be viciously circular.

The second reason to accept the real, metaphysical distinction between essence and existence is because we can understand the essence of something without understanding whether such an essence is really “already, out there.” Imagine describing the essence of lions, pterodactyls, and unicorns to an overly sheltered person. You then ask this person to describe which of these beings exists now, which existed in the past, and which has never existed. But from a mere essential description a person cannot know which of these has existed or does exist. So, knowing the essence of a finite, limited instance of being does not entail that such a finite, limited instance of being exists—hence, more support for the real, metaphysical distinction between essence and existence.

But even more, to say of a lion that no such being exists is not to misconceive what a lion is but only to hazard a mistaken assumption regarding the actual world. However, to say of a lion that such a being is a bird is to misconceive what a lion is, which increases support for the notion that essence and existence are truly distinct in finite realities, since if they were not truly distinct, then to say of a lion that no such being exists would be to misconceive what that creature is (like saying a lion is a bird), but no misconception is happening on this account. Only a mistake pertaining to the existence—but not the essence—of lions, etc.

Lastly, to say a limited, finite mode of being exists in virtue of what it is—for example, to say that Pat Flynn exists simply because he is Pat Flynn—would seem to commit us to the arresting absurdity that everything which exists in a finite, limited mode would exist as Pat Flynn. Alternatively, if something existed simply because that something were (or is), say, an electron, then everything which existed would be an electron, since to exist = to be an electron. But things exist which aren’t electrons (protons, anti-electrons, etc), so this cannot be the case. Existence is a prerequisite for electrons; but not the other way around. And so it is for any other finite and/or limited instance of being.

Therefore, among finite, limited acts of being, there must be a real distinction between what that thing is and the fact that it is; and so any finite, limited act of being must have the act of existence conjoined (or continually added to) its essence to exist. (This notion fits snuggly with the contingency of finite, limited modes of being; of such things being in need of a cause.) But now we’ve reached a philosophical riddle, because now every finite, limited mode of being—that is, among things whose essence and existence are really distinct—well, such things are in need of a cause of their existence which is external to them. Something that not only brought such things into existence but keeps them in existence. So, what is that thing?

The nature of this series of causes is hierarchical (or per se) and cannot proceed to infinity. There cannot, in other words, be an endless, backwards (or downwards, or upwards, etc.) line of limited, finite beings in need of a cause, since without a primary, uncaused act of existence to initiate and sustain the entire series, no finite, limited mode of being could ever have come into existence.

For example: If Thing A requires a cause (not just in the past, but here and now) and is caused by Thing B, which also requires a cause, and is caused by Thing C, which also requires a cause (etc., ad infinitum), then we are always “1+ cause of existence out” from Thing A ever coming into existence. (The infinite, in other words = the unachievable; and yet something—specifically, the being of some efficient cause—has been achieved.) But Thing A has come into existence, and so the explanatory buck cannot regress infinitely.

But the only way to terminate such a series is to settle at some being that exists in virtue of what it is; whose essence just is existence as such, full stop; who is not “a being” but “Being Itself”—more specifically, Being which not only does not have a cause, but could not in principle have a cause, because this Being just is the self-subsistent and unrestricted (read: unlimited/infinite) act of existence as such.

Furthermore, whatever this self-subsistent act of being is, it cannot exist in a limited or finite mode. It must be free of any/all restrictions, limiting essences, or boundaries on being, because then it would be in need of a cause or external series of fulfilled conditions to explain it. It would need something that imparts existence to it, which determines it to exist as that particular, limiting essence or mode of being, and not another. Therefore, God is qualitatively unlimited and possessed of no arbitrary limits or boundaries on existence as such, perfect in his self-subsistent act of Being, which he freely donates to everything else in existence, and is able to bring about all possibilities in being (God is therefore omnipotent), and is wholly good (there are no privations in God, or perfection yet attained—again, no limits).

To put it another way: limited instances of being have causes. And because we cannot explain X (the existence of limits) in terms of X (further) limits, we must conclude on the existence of something which is completely—and qualitatively—unlimited. That exists as the fullness of actuality itself, the plentitude of pure existence as such, with no restrictions, limits, or boundaries on what it is, what is knows, or what it can do.

Lastly, God is one and only one, since there cannot be more than one qualitatively infinite and perfect act of existence, since there would be no way to differentiate between two qualitatively perfect and infinite acts of existence without one lacking something the other possessed. But then we would no longer talking about two qualitatively perfect and infinite acts of existence, would we?

So there is one and only one perfect and qualitatively infinite God who imparts existence to everything else that exists, not only as such beings come into existence but as they are sustained in existence. Because of this, nothing can have “existential inertia”—that is, existence on its own accord or without the concurrent assistance of God’s ongoing, creative act. God, then, is the one (and only one) who is keeping things real.

P.S.—For a more in-depth discussion of this Thomistic argument, I recently spoke with Dr. Gaven Kerr on my podcast here.