The following consists of an attempt to postulate “ontology” as a science in itself—included in, but not synonymous with, metaphysics—realized upon reflection of the full meaning of being or existence in the thought of St. Thomas Aquinas. Traditionally, as per Aristotle, we call metaphysics the science of being qua being—e.g., as opposed to “being as objects subject to change” as in physics, or “being as number” as in mathematics, or “being as good” as in ethics. The meta- prefix translates as roughly beyond or after; thus metaphysics is beyond that science of objects subject to motion or change, namely physics. Permanent being, immaterial, infinite, and unchanging being—such are the themes of metaphysics. Still the first difficulty of metaphysics resides in the question of definition: what is being? is it a property? is it in potency, or in act, with respect to formality? One of the most ancient answers—the one adopted by Aristotle and continuing down through the Middle Ages—is that being means essence, coextensive with form, not in potency (as matter) but in act; not a property or accident, but the very nature or substantial definition of the object under consideration. Essence is identity, quiddity, whatness, that-which-it-is to be this being and not that.
Although the number of essences in reality must be finite, yet with respect to our minds it seems that essences could multiply indefinitely. Multitudinous essences must not—unless we remain content to let the multiplication go on infinitely, which is clearly untenable, since it would contradict our obvious ability to comprehend them—comprise the ultimate with respect to being. An essence or form will unify a conglomeration of material objects into a single quiddity presented to our comprehension; but essence, strictly speaking, only verily indicates a particular essence—a species—a particular definition to classify a multitude of objects or things sharing a common form. In other words, the science of being qua being cannot terminate in essence, since every essence ultimately means the essence “of” some thing(s), i.e., the being of some thing, and not being sheerly as ‘be’-ing. Take, for example, an everyday item, like a penny. A penny, as an essential form, is not being, otherwise, in order to be, all things would have to be pennies; nor, for the same reason, may its material form, copper. Finally, we cannot find pure being in agency nor purpose, or everything would have to contribute to, in this example, the making and spending of currency, in order to be. This metaphor (however feeble) illustrates that being as such must transcend mere things and essences; indeed, it must contain these, for they indubitably are, but we cannot find their ultimate ground in essentiality or quiddity without ending in a maze of unintelligibility. We require some unifying principle, related to essence but not bound by it, in order to constitute the true science of being qua being.
The fact, then, as St. Thomas puts it, stands thus, that “to exist is other than the essence or quiddity” (On Being and Essence; emphasis added). In the same passage, St. Thomas cites the examples of a phoenix and a man. Since “every essence or quiddity can be understood without its existence being understood”—i.e., one can understand a phoenix or a man, regardless of their existence in reality—then clearly “to exist is other than the essence or quiddity. Unless of course there is something whose quiddity is its very existence” (emphases added). What, then, is the difference between “being” and “being a being”?
Although a fine English term, for its part, “being” can easily fall away from the philosophical elegance of Analogy into the logical hells of Equivocation and Univocity. If we speak of being univocally, it has only one meaning—that all existing things are really in fact just one thing—which contradicts the variety of experience. Yet if we speak of being equivocally, it has just as many indeterminate number of meanings as indeterminate number of existing entities, and, more than likely—as we would have had no sense of mediate inference—we should never have raised the question of the meaning of being in the first place. Analogical predication, however, avoids the former pitfalls by recognizing that we, and what we perceive, are, but not all in the same sense, and in various degrees and perfections and kinds. To the extent, for instance, that all objects A possess properties x, y, z, then they stand identifiable as A-objects. But if A is A and is not not-A, how should we perceive it in the same field of experience in which objects B, C, D, etc., present themselves? They all have their proper accidents and proper relationships, but they all differ, and sometimes form no symbiosis at all. Still, we can identify all of them as being. In St. Thomas’s Latin, we would use two terms for which English has but one term, namely “being.” To carry over the appropriate distinctions into English, therefore: Being qua essence (or nature, or whatness/quiddity), we should call ens, while being qua ‘be’-ing, we should call esse, the present active infinitive verb “to be.” Ens is that which habens esse, that which has ‘be’-ing. For our purposes, we may render esse into English as act-of-being, or act-of-existing, or, even more simply, as existence. We shall speak, then, of Essence as “what a thing is,” and of Existence as “that a thing is.”
Regarding the latter, if existence means that a thing is, we deal, again, with what in grammar we call an active infinitive. Existence is an act, amenable to all different forms, shapes, sizes; intentions, intuitions, imaginations; minerality, animality, divinity. The only contrary of being-in-act is, in fact, not being-in-act—in fact, nothing. Thus, the common principle in which every entity must “participate” is esse itself, the act of being and of not not-being. Yet how does essence, or whatness or quiddity, fit in to this all-encompassing scheme of existence? St. Thomas says that “essence means that through which and in which the thing has existence.” Essence is the receptacle of Existence. Returning to Thomas’s example, that of the man and the phoenix: although both may be imaginary and/or conceptual beings, we know that one of them may exist in reality while the other (so far as we know) only exists in the imagination. Certainly a real man has existence and an imaginary phoenix does not, although they both have a meaning, i.e., an essence. But what distinguishes a real man from an imaginary man? A crucial point for understanding this existential doctrine is that a real man, even if in every way like an imagined man—perhaps, to the imager, having the same accidents, or even the same identity, as a real friend or acquaintance (e.g., Plato knows the real Socrates, but has an imaginary Socrates that he debates with in his solitude)—distinguishes himself from said imaginary man precisely by his act of being. The real man habens esse, and the imaginary man does not.
But this being, this act, although it is one, is not so absolutely, otherwise to exist would be the same as to be a particular thing; we would fall back into the problem of univocity. If, say, a tree possesses esse, it actually, actively, exists—but it does not comprise the totality of existing, else in order to exist, everything would have to be a tree, and in particular, would have to be the exact tree under our present consideration. Our tree, then, must (1) possess its essence, must be, in fact, “a tree”; and (2) possess a designated act-of-being, by which it participates in being per se, but precisely to the degree proper to being-a-tree; furthermore, precisely to the degree proper to being this tree and not some other.
Now if, as Thomas says, there exists “something whose quiddity is its very existence,” i.e., a Being in which no difference, no distinction, arises between what it is and that it is—a single absolute, pure Being, unlimited by essence, whose very essence it is in fact to exist—then we have an explanation for why any given substance is not existence-as-such, and an explanation for beings more or less perfect, i.e., gradations of being, and how contingent beings may come to be and pass away without corrupting the ultimate fiber of the universe. This Being is the referent for the aforementioned notion of “participation.” This distinct and fundamental Act of Being is synonymous with God, for this Act must be originary and not pre-exist itself. Each specific being—whether angel, animal, vegetable, or mineral—is a finite participation in the Original Being, just so far its essence allows. Given, as noted above, the potential infinitude of divisions of essences or forms in the world, we must presume that all of these natures, with their correspondent properties, pre-existed in the Original Being, at least in some sense; certainly there cannot be an absolute correspondence, otherwise the manifold forms would be the Original Being, which, because of their radical contingency, is clearly not the case. We now have a fresher, more distinctive meaning to the term essence qua definition: each and every essence literally defines, finitely limits, delineates, every being-in-act, such that each only achieves being in the kind and degree proper to it alone. This objective distinction between essence and existence amounts to what the late great professor of metaphysics W. Norris Clarke called “irreducible co-principles”; we could never discover, in principle, an objective being which does not possess both an act-of-being—which makes it stand out from nothingness—and a limiting essence—which makes it to be this being and not that. Ontological definition sets limits to an actual being so that it does not, as it were, burst out into that totality of all being which God alone possesses by virtue of His ‘is’-ness.
It is important to note, as well, that esse is not subject to definition, for one cannot form of it a conception. Esse, rather, is an act, “the act of all acts, and therefore must be understood as act and not as a static definable object” (G. Phelan in Clarke, Person and Being). This “dynamic impulse” of esse makes of each being a “self-communicating” agent, “actually present, as standing out from nothingness, but [also] actively present to other beings. . . .” (Clarke, P&B). If we deny that being is active, then that would mean that it is not active, i.e., not ‘be’-ing—in a word, non-existent. In Thomas’s own words—
It follows upon the superabundance proper to perfection as such that the perfection which something has it can communicate to another. Communication follows upon the very intelligibility (ratio) of actuality. Hence every form is of itself communicable.
(Aquinas in Clarke, P&B)
It is not merely accidental that each being communicates by being in act, for communication is being-in-act’s consummate purpose. Each being is, as it were, so as to say to every other being, “Yes, I am.”
Thus does this very specific aspect of metaphysics—this science of esse—call for a particular designation, not outside the realm of, but still not synonymous with, “metaphysics.” Following St. Thomas’s cue, we may refer to Exodus 3:14, when the God of Israel tells Moses that His name is “YHWH,” “Ehyeh-Asher-Ehyeh,” “I am That (Who) I am.” God identifies Himself as Being Itself (ipsum esse)—pure, originary, uncorrupted—indeed whose very “essence” is simply To Exist.
In Greek, the ōn- prefix, whence comes our word “ontology,” is the present participle of eimí, which means “I am.” It seems appropriate, then, to designate this very uniquely Thomistic rendering of metaphysics as Ontology. Granted that “metaphysics” and “ontology” frequently find themselves used interchangeably, it furthermore seems appropriate, in light of what has been said, to include in metaphysics all of what would have been called “physics” by Aristotle, in addition to what we already call “metaphysics,” and to reserve the term “ontology” to designate this technical Thomistic conception of being as presentive and active existence. If metaphysics is the pinnacle of philosophy generally, then ontology is the pinnacle of metaphysics specially—the final step before sacred theology. This is an especially useful delineation for Thomistic studies since Thomas’s view of being is arguably the most decisive and unique step taken by any philosopher since Classical Athens; it deserves whatever demarcations it can find to make fully apparent its distinctiveness (just as, for example, the likes of Husserl and Heidegger incorporated such rich terminologies so as to make their peculiarities of thought at once identifiable). Once incorporated into one’s own thought, the Thomistic ontology proves out as a doctrine of unfathomable fruitfulness, although it remains overlooked due to the general modern tendency to ignore medieval philosophy and, even when not overlooked, to misunderstand St. Thomas Aquinas.
Certainly every human person can say “I am,” and say so without error. We say we exist and speak thus truly. But we do not exist absolutely. Recalling the real man versus the imaginary man, essence and existence in finite beings are not identical. Limited by our quiddity, we say “I am John,” or “I am Mary,” or “I am Peter,” and have a range of potentialities and properties relative to these specific differences. We know we do not exist absolutely, else we would not know of a time before we existed, nor would we ever cease to exist. The fact of our contingency does not escape us; still, we cannot have come from nothing, for nothing can. Hence if the Necessary Being did not exist in principle and in fact, the world we perceive, and our consciousness of it and ourselves, would have come from non-being, or at least from non-necessary being (which itself would rely on another for its being). Whatever exists through itself can never have not existed, and must be the Source whence all “existents” or entities come. Vainly does the infidel demand “proof for the existence of” that for which existence is the proof. Appropriately, then, we refer to God as Creator; for even on our microcosmic scale, we note that being begets more being—through art as well as through self-communicative active presence. Thus for the Supreme Being, self-communicativeness is to the absolute degree, and all that that Supreme Being has to communicate of itself is precisely being. In the words of the Angelic Doctor, “to create belongs to God by reason of his being [esse], which is his essence [essentia]” (Summa Theologiae I.45.6). If to be terminates in self-communication, and God is being par excellence, then that God, by His own act of self-communication, communicates being to the fullest—that is to say, He creates.