Recently I’ve been rereading Etienne Gilson’s brilliant Being and Some Philosophers. The book is difficult to get these days, but if you’re interested in understanding the basic questions of metaphysics, I can think of few better books to read. Not only is Gilson’s book exceedingly clear, but it is tightly argued and nicely explores the problems of metaphysics that have haunted various philosophers from Parmenides to present throughout the history of philosophy. Gilson is at pains to argue that 1) part of the reason metaphysics has developed as it has is that the term “being” has, in fact, two significations, depending on whether it is treated as a noun, “being”, or a verb, “to be”. Under the interpretation of being as a noun, philosophers are drawn to articulating being and reality in terms of an answer to the question “what is being?”, which, in turn, leads us to ignore being as existence, conceiving it instead in terms of a structure of abstract possibility. By contrast, if being is understood as a verb, the focus is on existence or actuality. 2) Gilson is at pains to show that because existence or being in the sense of “to be” cannot be represented conceptually (recall Kant’s thesis that “being is not a real predicate”), philosophers have tended to ignore the signification of being as “to be”, thereby being led ineluctably to ignore existence altogether. And finally, 3) he is at pains to argue that emphasis on being as a noun leads philosophers in the direction of idealism and correlationism, concluding that being and thought are identical to one another as conceptuality is identical in both instances.

I won’t detail Gilson’s arguments and analysis here– which are both compelling and impressive –but simply draw attention to a passage that appears as Gilson begins to articulate what existence might be. Speaking in the context of Aristotle’s metaphysics, Gilson writes,

The question is to know what there is, in an individual subject, that makes it to be a being. In our sensible experience, which is the only one we have, the most striking indication we have that a certain substance is there is the operations it carries and the changes which it causes. Everywhere there is action, there is an acting thing, so that we first detect substances by what they do. Let us call “nature” any substance conceived as the intrinsic principle of its own operations. All true substances are natures: they move, they change, they act. And this leads us to a second characteristic of substances. In order thus to act, each of them must first of all be a subsisting energy, that is, an act. If we follow Aristotle thus far, we are entering with him a world entirely different from that of Plato: a concretely real and wholly dynamic world, in which being no longer is selfhood, but energy and efficacy. Hence the twofold meaning of the word “act,” which the medieval disciples of Aristotle will be careful to distinguish: first, the act which is the thing itself or which the thing itself is (actus primus); secondly, any particular action exercised by that thing (actus secundus). Now, if you take together all the secondary acts which a given thing performs, you will find that they constitute the very reality of the thing. A thing is all that it does to itself as well as to others. In such a philosophy, “to be” becomes an active word, which, before anything else, signifies the exercising of an act, whether it be the very act of “being,” or that of “being-white,” or any other one of the same sort. (43 – 44)

Here, with wonderful clarity and brevity, Gilson sums up what a thing is. As I have argued elsewhere, to be a thing is to be an act. And this in two senses. On the one hand, the endurance of any entity is not a fixed given, but is an activity on the part of that thing. The existence of a thing only continues and endures through activity. On the other hand, any quality that an object happens to manifest is an act on the part of an object. Sometimes these qualities will arise from activities internal to the thing, while at other times these qualities will be how the thing responds to being acted upon by other objects.

In both cases, the core of existence lies in activity. Existence as activity enjoys both an epistemological and ontological priority. Epistemologically, it is only through the acts of a thing that we can ever come to know the being of a thing. Ontologically it is only through the acts of a thing that a thing endures. In both cases, however, it cannot be said that objects are static or unchanging things. To be is to act and to act is to move and change.