memes

This is just an identity paradox, which the literature is full of them, and I find Plato's solution way less convincing than the holistic solutions presented by people like Engels and Bohm.

The holistic solution is to argue that "identity" really doesn't exist. There was never a "river" to begin with. Reality is just not actually divided up into autonomous objects. As Bohm argued, autonomous objects are human inventions. We create them because talking about reality as a whole, all at once, is not physically possible with our finite brains. We have to break it up into chunks to talk about it, and it is a mistake to confuse those chunks for reality, as if reality really contains autonomous objects moving around within it.

This was something Engels also cautioned against, outright rejecting identity for a simple reason. Imagine you say that this particular tree is represented by the variable A. Well, the moment you have said the tree is A, the tree has already changed a bit, it's not what it was before, so it is now ¬A. If you say both A and ¬A are the same, that's logically inconsistent. If you say the tree at the instantaneously later time should be considered a different variable B, then you no longer have a single "tree" but an infinite number of distinct objects, which contradicts with the notion of there being a single tree.

Indeed, he points to many other problems, such as the fact that you cannot meaningfully draw a concrete border for where the tree begins in space and where it ends, and where it begins in time (when it was "born") and when it ends (when it dies). If you zoom in closely enough, the border between the "tree" and everything else becomes fuzzy and ill-defined, and its transition from a seed to a tree, and from a tree back to the earth, also is a gradual process without a well-defined boundary. Engels thus concludes that for formal logic to make sense at all, we intentionally have to ignore the real complexity of the world. If we say the tree is A, for example, we have to first ignore the flow of time and treat it completely static, and we have to not zoom in too closely so that we don't notice the issue with ill-defined borders, so on and so forth.

The conclusion is, again, that objects don't really exist. There is no "tree" or "river" that is a well-defined, static and unchanging object like the variables in formal logic, A or B or X or Z. This is where your Plato point breaks down. You replace the ill-defined river with another definition including an ill-defined "shape of the landscape," which is also changing all the time just as much as the river does, with no singular and consistent "shape of the landscape," and its very precise shape is impossible to rigorously define even at a single time instant.

Although, the philosopher Jocelyn Benoist, who does take a similar approach, disagrees with the framing of saying that "objects don't exist," because a philosophy that just says no thing exists can be linguistically confusing, so there should be some meaningful way to refer to the existence of real objects.

He makes a distinction between abstract objects, which do not exist in reality and are only a human construct part of our language, and real objects, which is when the linguistic symbol is employed in a Wittgensteinian language game, and thus is imbued with a context.

For example, Benoist would say that, if you are talking about a river in the abstract, it does not refer to anything real. But the word "river" serves as a socially constructed norm that can be used to judge reality to be something, and thus can be employed in a social setting. If I see a river and point to it, and say, "look at that river over there," the river is now not just an abstract symbol, but it is a symbol pointing to something in a real world context, where people can really observe its glistening surface, dip their toes in it and feel its cold water, etc.

It's meaningful to talk about real objects only if we are implicitly or explicitly imbuing that object (as a symbol) with a real-world context (where the symbol is employed to identify something in real-world experience) through the social practice of identification, which is the purpose of objects, to serve as a norm by which to judge reality by. The real object is thus the object + the context in which it is employed.