Existence and Action
The word “action” has both a narrow and a wide interpretation: in the narrow sense it means human (or animal) intentional action (OED “the process of doing something to achieve an aim”); in the wide sense it includes actions of inanimate objects (OED “the effect or influence of something such as a chemical”). Most simply an action is a “thing done”, where the agent can be a psychological creature or a physical object. In this latter sense we find such phrases as, “action at a distance”, “for every action there is an equal and opposite reaction”, “the action of acid on a substance”, “the principle of least action”, “chemical action and reaction”, “action potentials”, and so on. Clearly the concept of action can be applied quite broadly and without solecism.
A comprehensive metaphysics should find a place for this broad notion. Not only are there physical objects, physical properties, and physical events (as well as psychological); there are also physical actions. Physical objects do things, as well as being a certain way. Matter acts as well as is. One can envisage a metaphysics in which action, both physical and mental, is given pride of place—not merely events but actions proper. We already have “process metaphysics” (contrast “substance metaphysics”) and there are some who would jettison the ontology of objects for one of events; well, we could have “action metaphysics”, or at least a metaphysics that includes actions as a fundamental general category. For some reason philosophers have tended to view matter as passive, in contrast to mind, but a more active view of it is certainly possible. This metaphysics would explore the nature of physical action, relate it to intentional action, and ask which interactions (nota bene) involve action. For example, it might be wondered whether all action is action on something and thus relational, or whether the concept of energy is integral to the concept of action, or whether causation is a type of action in the broad sense. Are there basic physical actions, how are physical actions individuated, is acting-on a transitive relation? One can imagine a whole philosophical industry devoted to “action metaphysics”.
Delicious as that subject may be, I am concerned here with a more specific question. Be warned that it is, or will seem to be, a very odd question, possibly even a meaningless question. It is this: Is existence an action? Is existence a thing done? Is “exists” a verb of action? When something exists, is that an action performed by the thing? To be sure, it is not an intentional action, but is it an action in the broad sense just adumbrated? And the answer I propose to give (deep breath!) is that existence is an action: not simply that existing things act, let it be noted, but their existence is itself a type of action. We may speak of “the act of existence” and not merely of “the fact of existence”.  Existence is not just an attribute; it is an active attribute. Why might anyone think such a thing?
The first point to note is that “exists” is a verb not a noun or adjective: thus it connotes activity—like “swims”, “lives”, “breathes”, etc. It is not like “red” or “male” or “tall”, which do not connote activity but simply property-hood. The second point to note is the etymology of the word “exists”: it comes from a Latin word meaning, “stand forth, come forth, arise”. These are action verbs, suggesting the onset of bodily presence or salience—as when an object looms up out of the fog boldly advertising its existence. Thus there is linguistic evidence for the active nature of existence, though such evidence is obviously far from conclusive. How might we bolster it?
First consider non-existence. Non-existence is no kind of action. It is not a thing done. It is an omission, a thing not done. Non-existence is like non-swimming: an absence of action. It takes no effort not to exist, nothing positive or creative. A non-existent thing does not need to do anything in order not to exist. Contrast the creation of an existent thing: that requires action, production. When a thing comes to exist an action is performed—something is brought actively into being. This is obviously true for human (and divine) artifacts, but it is also true of objects created by “acts of nature”—such as planets, volcanoes, animals, and selves. The act of creation is the act of converting non-existence into existence. The big bang was an act that created the entire physical universe. Who or what performed this act? According to some, it was an intentional agent; but we can also credit acts to nature itself—natural acts. Objects act, but nature also acts, through its objects. We may as well say that the universe acts when actions are performed within its precincts, though it does so via its several parts—just as we say that a human being acts, though only in virtue of certain of his or her parts. In any case, creation is active: but what about preservation? Once a thing comes to exist does its activity cease? Does it continue to exist without any further activity? No: it must constantly ward off the forces of destruction. This is obvious for organisms–hence the “survival of the fittest”, i.e. the continued existence of the organisms best capable of resisting destruction. But it is also true for inanimate objects; they too are subject to all sorts of destructive forces—weather, corrosion, collision, fire, decay, and entropy. Nothing is forever. Existence is one long battle against antithetical forces. Maybe the whole physical universe will one day vanish in a puff of smoke (“the big puff”). Things only continue in existence because they have destruction-resistant properties such as rigidity, impenetrability, and cohesion. If they didn’t, they would perish in short order.
So we can say that objects act (operate) in such a way as to lead to their continued existence: they play an active role in their preservation (mainly by reaction). They don’t disintegrate at the first breath of air. Existence is active destruction-resistance. If you imagine history greatly speeded up, this fact would be more evident: you would see all the forces acting on the object over time from inception to destruction, and its dogged resistance against the onslaught. Consider a tree branch that survives being made into a piece of furniture, as well as all manner of bangs and scrapes, finally succumbing to fire: the branch would appear to be engaged in a frantic struggle against inimical forces. If things had no resistance to destruction, they would be gone as soon as they arrived; they persist only because they have properties that keep them in existence. But all this talk is action talk: objects actively preserve themselves—their very existence depends upon it. Some objects intentionally preserve themselves, but all objects naturally preserve themselves—it isn’t just a happy accident that things persist. The act of existence is an act of self-defense: the object must react to what it interacts with in such a way that it emerges intact–if dented, bent, scorched, or bloodied. Existence is an act because extinction is a threat. Nature acts on an object and it acts back. Our concept of existence is thus the concept of a positive achievement. To exist is to withstand the effects of time—to prevail against the agents of annihilation. That is no mean achievement, and it deserves the name of action. Existence is a feat–hence an act. 
Here is a potential counterexample: numbers. Numbers exist, but where are the forces of destruction they have defeated? Numbers have no need to ward off destruction, so what acts do they perform to ensure their continued existence? They exist blissfully without effort (they are not an endangered species). But aren’t numbers the exception that proves the rule? For numbers are precisely things for which the concept of existence has been disputed: numbers don’t really exist—not like tables and chairs, animals and stars. They are not active at all and so cannot exist in the verb-like sense—there is no activity in them (but there is activity in every natural thing). Numbers are, we can say, but they do not exist—so it has often been thought. If we are to apply the word “exists” to them, it must be in a second-class or metaphorical sense. This feeling is explained by the present theory of existence: numbers don’t act; they simply are. They don’t act on each other or on the physical world; their “existence” is a foregone conclusion not a positive achievement (note that they are also not created by any act). Numbers are beyond action, so beyond existence in its primitive sense. Existence in the natural world takes place against a background of non-existence—the nothingness before, the threat of nothingness during, and the nothingness after–but numbers don’t emerge from, are threatened by, or collapse into non-existence. The “language game” of existence-talk doesn’t apply to them. So they confirm, rather than confute, the account of the concept of existence suggested here. 
It has often been remarked that existence is not like other properties—not just another property alongside shape, color, weight, etc. This is sometimes thought to favor the second-order (quantifier) theory of existence and disfavor the first-order (predicate) theory, but the action theory has another explanation: existence is an act not a state (characteristic, feature, attribute). Being red or square or a man is not an action (hence these properties are ascribed by adjectives or nouns), but existing is an action and hence is expressed by a verb. Existence involves the action of self-preservation, and that is very different from other properties. From a metaphysical point of view, existence is sui generis: it is an act (a thing done)—not a quality or trait. Existing is something an object does, while being red or square or a man is something that an object is. Existence is a very unusual property—indeed, a very unusual act. 
 I came across the phrase “act of existence” in Nabokov’s King, Queen, Knave (1928), p. 202, and it set me thinking. It struck me as both surprising and apt (very Nabokovian). I could also cite Hamlet’s “To be or not to be” which hints at the idea of existence as action: it seems to mean, “Should I carry on being or should I put an end to being?” The question gains power by representing existence as a kind of decision—a revocable act, a project that could be abandoned.
 We can imagine a world in which objects are powerless against the prevailing destructive forces, perishing as soon as they arrive on the scene; they just don’t have a nature that permits them to persist—a mere gust of wind will consign them to oblivion. In such a world there would be little use for the concept of existence.
 There is a lot to be said about existence in mathematics that I have not gone into (especially the use of the so-called existential quantifier); my point is just that it is not clear that the case of numbers refutes the action theory of existence because it is such a special case.
 It should be noted that categories such as “property” and “act” are highly general and in danger of blurring distinctions. There is so much variety within these categories, accompanied by a compulsion to seize on paradigms. I call existence a “property” and an “act” and immediately risk misguided assimilations; what I am really doing is drawing attention to similarities. I have put the point ploddingly by saying simply that existence is an act; I could say more cautiously that it is act-like or act-ish.