Bear in mind that I was originally talking about a train journey between two specific destinations. — Janus
Sure. Two stakes were stuck in the ground. And so suddenly the landscape had your chosen metric imposed on it.
For me the very notion of "the reality of mathematical structures" beyond their being abstractions from concrete objects and processes, seems unintelligible. — Janus
Yeah. But what I was arguing is that your notion of material concreteness is itself just a matching abstraction.
So sure, there must be a material aspect to reality. And you are now insisting to me about the reality of that abstracted notion. If the fallacy of misplaced concreteness is a thing, it would have to apply to your claims about however you picture this idea of definite local particulars.
This is why Peirce would grant reality to both the formal and material aspects of nature. As generalisations, they are each "concrete" - or just as concrete as each other in terms of both being essential aspects of the whole.
In a holistic metaphysics, substance is emergent. It becomes localise individuation. But you sound as if you want to treat emergent individuation as the concrete baseline reality of existence. You begin with a world of objects, rather than arrive at that world.
Mathematical "reality" seems to consist far more in possibility than it does in actuality, — Janus
If we wind it back, I wasn't defending some kind of spooky seperate existence of Platonic structure. I was in fact arguing that forms are always instantiated - or would have to be intelligibly instantiable. So the kinds of structures that could exist are the kinds of structures that could dovetail with some kind of logically complementary material principle. They would have to be able to yield substantial being in interaction with that material principle.
This then leads to the question of how to conceive of that material principle in properly generic form. This would lead us towards Peirce's answer - vagueness of Firstness. Or more classically, Apeiron or Chora. Or in some modern physicalist sense, chaos or fluctuation or quantum foam. That is, a potential that is lacking in limits, but capable of being limited.
So essentially my point is that the maths that is powerful and useful when it comes to the metaphysics of possible cosmologies is the kind of maths which has this particular character. It can model the constraint of freedoms, the limitation of uncertainty, the emergence of stable habit or law.
And what is exciting is that maths could model both the formal constraints - by speaking to the necessity of certain such structures - and even the material accidents, the constants of nature that then ground that structure. These constants may turn out to be shapes - like the holes in a topological sphere. As I said, global symmetry-breaking is terminated by reaching local symmetries which it can't erase. That is why you have the particle zoo of the Standard Model. A quark or electron exists as fundamental - a fundamental excitation - because they can't be broken down any further. They put a stop to the symmetry-breaking cascade and now start to ground the construction of some kind of material content in the Universe.
That is what string theory is about. Topological irreducibility. If you curl up a higher dimensional space, you can't in the end get rid of all the kinks. You are left with some countable number of holes that then become the material character grounding the Universe. They are the knots that can't be undone.
So the material principle could be reducible to ontological structuralism - becoming the local kinks that can't in the end be rotated or translated out of existence. Matter would be part of Plato's realm, but exist in it apophatically, as the topological holes or features that can't be erased. The material part of being would be the inverse of the formal part of being.
So it was this organic conception of structure - the "co-arising holism" that physics is uncovering - that I'm contrasting to the mechanical conception of pattern generation which Rovelli is using to produce a landscape of mathematical junk.
Plato was speaking to that dawning metaphysical realisation that the intelligibility of reality is about a division of the substantial into the complementary things of the formal and material principle. Aristotle might have said it much more clearly, but the dim outlines of that emergent hierarchical view can be seen in Plato - as when he talks of The Good as a finality which acts to select certain forms, and the Chora as the need for some kind of material receptacle where structure could be instantiated.
Just consider the Platonic solids. In 2D, polygons can have any number of sides, as long as they have at least three. But in 3D, suddenly that adds a huge global constraint that limits local regularity to just 3x2 possibilities - the self-dual tetrahedron (4 triangular faces), the dual cube and octahedron (swapping faces for vertices), and the dual dodecahedron and icosahedron. So place a limit on dimensionality and only a limited number of perfectly exact resonances can fit that space.
The Platonic solids are examples of how local symmetry can become physically manifest if global symmetry is explicitly broken. And of course this mathematical realisation - this intelligible fact of any possible reality - was then used to give a Platonic account of material atomism. If material fluctuation was in fact bound by formal limitation, then these had to be the shapes that would emerge at the end of the trail. Atoms would be little triangles, and so be fiery, etc. (Of course, a sphere was the other emergent perfect shape - the one that then emerges at the infinite limit of "polygonicity".)
So yes, if maths abstracts and generalises, then of course it is stepping back towards the possible, and away from the actual or substantial.
But there are then two ways of stepping back towards generality. And hylomorphism would be about following both those paths - and being able to see the unity in the fact that they are a pair of reciprocally defined paths. Each is the other's inverse. And so the metaphysical formalisation of the description of the one can apophatically stand as the formalised description of its "other". Yin and Yang. Accident and necessity. Matter and spacetime.
It is that deep structural trick that would see Platonism - as understood charitably - being cashed out by a modern physical "theory of everything". If the material constants can be shown to be the irreducible holes produced at the limit of some process of constraint, some process of symmetry breaking, then reality would "pop out" of an intelligible mathematical description.
Again, this is the big prize that Rovelli himself is pursuing. So all his paper demonstrates is the paucity of a more conventional view of mathematics (and thence reality) as the infinite noodlings of mechanistic pattern generators.
If you want to call that "Platonism", I suppose you could. But Rovelli also wrote a book on Anaximander which showed him to be rather a lightweight on Ancient Greek metaphysics. I would rate him highly for his physical speculations, poorly for his history of philosophy.