In the comment here, John Nerst effectively rejects the existence of parts and wholes:

In my view, there must be a set of fundamental rules that the universe is running on and fundamental entities that doesn’t reduce to something else, and everything else is simply descriptions of the consequences of those rules. There is a difference between them, what we call it isn’t important. I don’t see how one could disagree with that without going into mystical-idealist territory.

The word “simply” in “simply descriptions of the consequences of those rules” has no plausible meaning except that wholes made out of fundamental particles, as distinct from the fundamental particles, do not exist: what really exists are the fundamental particles, and nothing more.

John denies that he means to reject the common sense idea that wholes exist by his statement:

I do mean different things by “humans exist” and “humans exist in the territory”, and you can’t really tell me what I mean against my saying so. I haven’t asserted that humans don’t exist (it depends on the meaning of “exist”).

But it is not my responsibility to give a plausible true meaning to his statements where I have already considered the matter as carefully as I could, and have found none; I do not see what his claim could mean which does not imply that humans do not exist, and I have explained why his claim would have this implication.

In a similar way, others reject the existence of parts. Thus Alexander Pruss remarks:

Parthood is a mysterious relation. It would really simplify our picture of the world if we could get rid of it.

There are two standard ways of doing this. The microscopic mereological nihilist says that only the fundamental “small” bits—particles, fields, etc.—exist, and that there are no complex objects like tables, trees and people that are made of such bits. (Though one could be a microscopic mereological nihilist dualist, and hold that people are simple souls.)

The macroscopic mereological nihilist says that big things like organisms do exist, but their commonly supposed constituents, such as particles, do not exist, except in a manner of speaking. We can talk as if there were electrons in us, but there are no electrons in us. The typical macroscopic mereological nihilist is a Thomist who talks of “virtual existence” of electrons in us.

Pruss basically agrees with the second position, which he expressed by saying at the end of the post, “But I still like macroscopic nihilism more than reductionism.” In other words, it is given that we have to get rid of parts and wholes; the best way to do that, according to Pruss, is to assert the existence of the things that we call wholes, and to deny the existence of the parts.

In effect, John Nerst says that there are no wholes, but there are fundamental things (such as particles) that have the power to act as if they were wholes (such as humans), even though such wholes do not actually exist, and Alexander Pruss says that there are no parts (such as particles), but there are simple unified things (such as humans) which have the power to act as if they had parts (such as particles), even though they do not actually have such parts.

To which we must respond: a pox on both your houses. In accord with common sense, both wholes and parts exist, and the difficulty of understanding the matter is a weakness of human reason, not a deficiency in reality.