It might be a problem for predicate logic. But that already presumes the existence of definite particulars as part of its axiomatisation. That is what the principle of identity is about. Starting off with that as the assumption already granted. — apokrisis

That's not quite true. The law of identity does not assume the existence of particulars, the existence of particulars follows from the application of the law of identity to the sense world. The thing identified by the law of identity is not necessarily particular, but when we apply that law to the sense world, we can identify things which are separate and distinct from each other, individuals, which move in different directions, etc.. So we conclude that there are particulars, and proceed to identify these particulars. It may be the case that all things are somehow really united as one, "the universe", and our senses are unreliable in showing us particulars.

But if it were the case that all things were united as one, "the universe" this would falsify relativity theories because it would mean that there is an absolute frame of reference. So the ontology you argue is faulty no matter how reality turns out to be. If relativity theories are ontologically true, then there is necessarily particulars, individual things which are related in relativity theories. Therefore we need to apply the law of identity and identify these particular things. And if we fail in our capacity to identify the particulars, and proceed toward the conclusion that there really are no particulars, then we must dismiss relativity theories which theorize about the relations of individuals, as necessarily false, and proceed to apply the law of identity toward the one whole "the universe" such that we can derive the absolute frame of reference..

Should ontology limit itself to that kind of atomistic or nominalistic reasoning? Why would you think so? — apokrisis

I agree that we should not limit ourselves to any unnecessary assumptions. But identity is necessary for any logic to proceed, and logic is necessary for understanding. If our believed premises force us to conclude that there are no real particulars, then we are forced to identify the entire universe as one whole. When this is the case, we can no longer support relativity theories as ontological principles.

"accepting that quantum "weirdness" is bound up in the structural fact that you can't ask a particle about two contrary properties, like position and momentum, in the same act of measurement. "
But this is a consequence of an unknown ontology: all of the interpretations of QM are consistent with the measurement, so you can't know which is true. I just think we need to be explicit about what we can know, and what we can't know. I emphasize the unknown and say this implies we should be agnostic about those points.

The thing identified by the law of identity is not necessarily particular, but when we apply that law to the sense world, — Metaphysician Undercover

OK. But I am talking physicalism. There is no room for a Platonic world where forms exist as universals. Universality would be what emerges from the inevitability of certain overarching structures ... the structures that can bring stable formal constraint to material uncertainty, per the OP.

But if it were the case that all things were united as one, "the universe" this would falsify relativity theories because it would mean that there is an absolute frame of reference. — Metaphysician Undercover

No. It just says spacetime ain't absolute. And we already know that. The container is shaped by its contents. So the next step for physical theory has to be one that includes energy and gravity into the fundamental level description.

Structural realism says that the absoluteness, the unity, is to be found in that relation, somehow.
Spacetime doesn't have some inherent fixed order. That organisation emerges in reciprocal fashion from a relation that exists between energy density and spacetime curvature. So it is about the absoluteness of the three fundamental Planck constants, and the essentially dimensionless web of relations they then weave.

But identity is necessary for any logic to proceed — Metaphysician Undercover

Even if this were the case, the issue would be how do you produce that identity - the particularity that is what it is to be individuated in a physicalist realm of spacetime and energy? If you are concerned with ontology, you can't simply just claim identity as a brute fact of existence. And so OSR - piggybacking on condensed matter physics - can offer a theory of how identity can arise as localised acts of individuation.

I emphasize the unknown and say this implies we should be agnostic about those points. — Relativist

Fine. Be as agnostic as you like. Meanwhile the field of quantum interpretation moves on. The current trend towards quantum information approaches make admirable sense to me.

OK. But I am talking physicalism. There is no room for a Platonic world where forms exist as universals. Universality would be what emerges from the inevitability of certain overarching structures ... the structures that can bring stable formal constraint to material uncertainty, per the OP. — apokrisis

Clearly you are the one making unnecessary assumptions. In ontology we must start with an open mind about existence. You accused me of starting from the assumption that the thing identified is a particular. When I said not necessarily, you claim we must start from a pnysicalist assumption. and not allow the existence of Platonic universals.

You have a glaring problem. You will not start from the assumption that the thing identified is a particular. And your physicalist bias prevents you from allowing universals to be real, and identifiable. This leaves you nothing to identify, so you cannot even begin to apply the law of identity. Without the capacity to identify anything, you have no basis for applying any logic.

No. It just says spacetime ain't absolute. And we already know that. The container is shaped by its contents. So the next step for physical theory has to be one that includes energy and gravity into the fundamental level description. — apokrisis

Where do you derive principles like contents and containers? And there is no necessity that a container be shaped by its contents. That's illogical, as the container shapes the contents and reciprocation is not necessary.

Structural realism says that the absoluteness, the unity, is to be found in that relation, somehow.
Spacetime doesn't have some inherent fixed order. That organisation emerges in reciprocal fashion from a relation that exists between energy density and spacetime curvature. So it is about the absoluteness of the three fundamental Planck constants, and the essentially dimensionless web of relations they then weave. — apokrisis

Perhaps the unity is to be found in the relation, but you cannot proceed with unnecessary assumptions that it is so necessarily. There is no logic to the claim that the container is shaped by the contents. We have many examples in our lives where the container contains rigidly, without being shaped by the contents. Reciprocation is completely uncalled for at this point, and should not be introduced until a proper separation through a thorough analysis is established.

The principles of physics do not suffice for an ontological analysis. You already employ a synthesis of space and time in "spacetime", and this concept must be deconstructed to determine whether it is ontologically acceptable.

Even if this were the case, the issue would be how do you produce that identity - the particularity that is what it is to be individuated in a physicalist realm of spacetime and energy? If you are concerned with ontology, you can't simply just claim identity as a brute fact of existence. And so OSR - piggybacking on condensed matter physics - can offer a theory of how identity can arise as localised acts of individuation. — apokrisis

See, you are insisting on a "physicalist realm" as your starting point. But this is cannot be produced as a starting point, because we are starting as human beings, attempting to understand. We cannot get ourselves out of that perspective, being a human being, therefore we must start with that assumption, what is true, and undeniable, that we have a specific perspective which is within a human body and is conditioned by the constitution of that human body. From this perspective, we attempt to identify things because this helps us to understand them and communicate about them, which helps us to obtain different perspectives and understand even better.

Without identity we have no hope of understanding anything. So it's not the case that identity is a "brute fact of existence", it's a brute fact of understanding. If you posit a realm where there is no identity, and claim that OSR's intent is to take us into this realm, then OSR is just giving us meaningless nonsense, where there is no understanding and no possibility of understanding.

”Materialists think that all of Reality consists of the physical world.” — Michael Ossipoff
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Structuralists would take an expanded view of physicalism - one in which information becomes part of the picture. A context or history is the information that bears down to constrain the possibilities of what might happen at some locale.

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Yes, it’s very fashionable to bring "information" into philosophy. And don’t forget entropy.
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So it is Wheeler's "it from bit". Materialism believes that substantial, already in-formed, matter sits at the bottom of physical existence. An informational or constraints-based ontology flips it around so that the material is whatever is left as a concrete possibility after a context has restricted its variety.

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See above.
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”It recognizes that there’s no reason to believe that experience isn’t the fundamental reality of the describable world.” — Michael Ossipoff
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If your idealism rejects physicalism,…

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Is there an Idealism that doesn’t? They’re mutually-contrary by definition.
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…then you won't have any interest in OSR as a species of physicalism.

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That’s right.
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(But, by the way, Ontic Structural Realism (such as Tegmark’s MUH) isn’t a species of Materialism.)
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As I say, I don't take idealism seriously. It's a joke.

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Thank you for repeating your unsupported personal opinion.
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And It has nothing to do with the OP. So it is off topic.

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What a funny thing to say. No, it has everything to do with the OP. In fact, the Ontic Structural Subjective Idealism that I propose directly addresses the issue that the OP’s subject-line asks about.
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Michael Ossipoff