Some abstruse philosophizing.
I have not thought about metaphysics in quite a while, but have been thinking about it a bit of late after having read an essay entitled "What Are Entities?" by Dave Jilk in the latest issue of the Journal of Ayn Rand Studies (note: most of this journal entry won't make sense unless you've read that essay). It strikes me that the Randian metaphysics is seriously underdeveloped. This is not necessarily a bad thing, because there may not be much point to metaphysics. But I do note the fact. For example, Rand in IOE talks about existents, but not as much about entities. In Dave's essay, he talks about "physical existents", which narrows the range of inquiry quite a bit.
Rand's "existent" seems to refer to anything that exists, or any aspect thereof. In our language, it feels natural to talk about objects (things with independent existence in some sense -- whether animals, plants, physical products of human effort, or non-living things). We also talk about what I think of as undifferentiated matter: earth, air, water, fire; but it's not as natural for us to talk about these as objects or separate existents, which is why dividing them into bounded entities feels artificial (this cubic foot of ocean, that square inch of earth). Sometimes undifferentiated matter has rough but fairly stable boundaries: a lake, a river, a mountain, a valley. Sometimes the existence of undifferentiated matter is ephemeral: a forest fire, a flood. In modern times we have become more sophisticated in these matters, so that we talk not of "air" but of particular gases. But that is a more recent overlay onto (or extension of) earlier concepts, and, I think, not necessary for understanding the human conceptual faculty.
What is the epistemological point of formulating the concept "entity", and from what lower-level concepts is that concept abstracted? As I mentioned, it feels artificial to talk about "this square inch of earth" as an "entity" -- though in a sophisticated modern context, we do talk about things like "this acre of earth", "this city block", or (perhaps at an archeological dig) "this square meter of earth". Those are legal or scientific entities in some sense and are used in specialized contexts, but I don't think they are truly entities. Perhaps I'm not being sophisticated enough, though.
Aristotle held that the prototypical things are living things. This makes sense to me historically (indeed, the animists felt that each "thing" was animated by a spirit -- mountains, trees, etc.). I tend to agree with Aristotle, in the sense that I think tables and chairs are not good examples of entities, since human beings had the concept of entity before they invented tables, chairs, or perhaps even stone tools (pure speculation, naturally).
Some matter takes the form of "entities" or "objects" -- things with boundaries (or sharp gradients, if you prefer). Most matter does not. Thus I see no reason to say that "all of existence consists of entities" (nor would that make much sense); in Dave's terms, it doesn't even make sense to say that "all of existence consists of existents", since where one intentionally locates the boundaries is up to the measurer.
Dave says that "clearly, entities are intrinsically differentiated from the background by their characteristics and gradients"; I'm not quite sure how to square this with Dave's statements that "the whole is a unity, without intrinsically isolated parts" and "we can impose an intentional partition of this unity that helps us to understand its behavior, but the partition is not intrinsic". This seems to involve a distinction between differentiation and isolation, both of which are metaphorical, I think. But more on that in a minute.
I sense that the concept of "background" could use explication here. Are not the concepts of background and foreground epistemologically privileged in some sense? To say that an entity is intrinsically differentiated from its background veers perilously close to saying that an entity is naturally separate, which seems at odds with Dave's underlying view that the totality of existence is a unity, whereas any given entity is only a portion, part, or piece of that unity, which is separated from the unity in thought (though based on some features of the entity, or for some human purpose).
Much of our language is metaphorical, especially in philosophy. Dave uses four terms that involve metaphors:
"Separate" means fundamentally "set apart", "cut off", "a part divided off from a whole".
"Isolated" means, literally, "of the nature of an island".
"Independent" means "not contingent upon anything else", "hanging on its own".
"Differentiated" means "unlike something else".
So, speaking metaphorically, Dave's thesis seems to be that "no entity is an island": every so-called entity is a part chopped off from the whole in human thought for human purposes, but is in fact a "peninsula" that maintains multiple connections to the rest of existence (in part because there are no hard-and-fast boundaries, only gradients). However, Dave also say that an entity (or perhaps only certain kinds of entities?) is intrinsically differentiated from the background ( = the rest of existence?) because its characteristics and gradients cause it to be unlike the background or the rest of existence in some respects (which respects are intrinsic, i.e., the characteristics and gradients are features of the existent, not imposed by the human mind).
I sense at least two dimensions along which we can measure things here:
"Distinguishability" -- the extent to which something is or can be seen as unlike or different from other things (the background, the rest of existence)
"Objectness" -- the extent to which something is or can be seen as a separate, independent, individual "thing"
It seems best to keep these separate, as it were. Perhaps the first is epistemological and the second is the metaphysical? Something can be distinguishable without being an object; for example, day is unlike night and is distinguished as such, but neither is a thing or object. Two products created on an assembly line are separate and independent things, but may be indistinguishable for almost all purposes.
This distinction has implications for Dave's "argument from gradients". The fact that a gradient between an existent and the background is not sharp, or that there is no perfectly defined border between two existents, does not mean that we cannot easily and properly make a differentiation; e.g., the phenomena of dawn and dusk do not invalidate the differentiation between day and night. Yet day and night are not objects or entities, I would say.
Again, we return to the question of "what is an entity?", or, in other terms, "what are the aspects of reality that give rise to the concept of 'entity'?" -- or even "what are the needs of human cognition that require us to abstract, from lower-level concepts such as 'animal' and 'plant', the concept of 'entity'?"
I don't yet see why it is desirable to abstract the concept of 'entity'. What needs does it address, what problems does it solve, what purposes does it enable us to achieve, what knowledge does it enable us to gain?
Rand (IOE, p. 6) says that the concept of 'entity' is the first stage in the development of the (implicit) concept of 'existent'. If that is so, why spend so much time on what is only a booster rocket toward escape from the perceptual level into the fully conceptual level of the concept of 'unit'?