Hi Laurence,
It's good to see you back, and I think you have the makings of another winner here, in your understated style.
Like you, I accept the ERH as true [with the proviso that it is the existence of the external reality that is independent of us, not its local evolution.]
You discuss 'abstract entity' and 'mathematical structure'. Without repeating your arguments, I agree that the premise does not connect to the conclusion.
Whereas you argue about time as part of the external physical world, and thus, by MUH, belonging to mathematical structure, I think a similar argument can be made for gravity. And certainly, your example of time and consciousness being unexplainable as mathematical structure is convincing. To argue the opposite would seem to impose a duty to demonstrate such a mathematical structure. You discuss neuroscience, AI, etc, and ask does the model experience temporal flow. Specifically, you state:
"Either the passage of time is an objective feature of reality, independent of human consciousness, or the passage of time is a product of consciousness."
I will not try to summarize your arguments but I would like to augment them. So I would also state:
"Either the experience of gravity is an objective feature of reality, independent of human consciousness, or gravity is a product of human consciousness."
Another essay stated "Logic implying the physical means precisely that: the physical is implied! An ERH before a MUH must lead astray."
As I stand in my walk-in shower, shampooing my head and moving around with my eyes closed, I am guided by gravity, not visual impressions, not by logic, and the fact that my physical neurons operate logically does not contradict the physical reality of gravity that is at work. There are no abstractions employed here, nor any implications.
If, instead, my neurons operate logically to solve a calculus problem, or even to address metaphysical problems, the neurons are physical, their operation may lead to abstractions, but the abstractions, i.e., the 'implications' are always secondary, and this encompasses the Mathematical Universe.
In short, the abstract structure of the Mathematical Universe derives from physical reality, not the reverse. And the gravity I experience with my eyes closed is not derived from any abstraction or mathematical structure.
Just as you suggest "we should be cautious about accepting any theory which requires us to believe that temporal flow is an illusion produced by consciousness" I suggest the same for gravity.
Your next question is "what differentiates the mathematical structure for physical existence from all these other mathematical structures which seem to have no physical application?" Your analysis of this is masterful.
Let me change the subject; still another essay states:
"Arguments can be no better than their premises allow."
In my essay I discuss Bell's premise of precession in a constant field, which, since constant fields produce no [Stern-Gerlach] results, leads to a contradiction. From this contradiction he proceeds to conclude that there is no local causality, and that no local model can reproduce the quantum mechanical correlations.
I investigate the physics of the non-constant field which does not lead to an inherent contradiction, and I construct a local model that does produce the quantum correlation, unless it is prevented doing so by imposition of Bell's constraints.
This causes me to analyze the reasons why Bell imposes constraints, and this leads to new conclusions. I invite you to read my essay and I hope you will comment on it.
My best regards,
Edwin Eugene Klingman