Dear Cristi,
I must say I'm baffled that you can be so daring and so level-headed at the same time. Also, your writing style is serves you very well. For example, "Zoom-dependent reality... On the same canvas there are multiple paintings, each of them visible at different scales." Altogether this is excellent work, though you deal with so many interesting topics that I sometimes found it hard to follow the through-line.
I'll respond only to a couple of points. First, I don't like this MUH business, and I don't think the objections you mention get to the heart of the issue. I have no problem with the logical sense of "exists," but it's clearly distinct from the physical sense. Any mathematical structure, and in particular any useful equation in physics, can represent an infinite number of particular cases, only some of which are physically instantiated in any particular part of spacetime. Even if we assume the universe is infinite and contains all possible cases somewhere, a mathematical structure can be "isomorphic" to it only in a very partial and limited sense, that abstracts from every local viewpoint.
So your quotation from Hawking seems to me on target. The whole value of mathematics is that it abstracts from particular cases to articulate general principles. Yet isn't the existence of distinct instances at particular times and places a basic feature of the physical world? What do our equations refer to, if not to the dynamic relationships between these instances?
Well, in quantum mechanics the equations don't refer to determinate cases, only to the structure of probabilities. But this only strengthens my point - the equations don't give us a world we can actually observe. The statistical patterns are very important, but also importantly different from the measured values that appear on each occasion.
It's true that our physical universe doesn't "exist with necessity." Neither do you and I, of course; in fact 100 years ago it was incalculably unlikely that we would ever come to exist. Nonetheless, we have the history we have, going back to what looks like the Beginning. And the example of evolutionary biology shows beyond a doubt that there are ways of making sense of this history, in great depth, that don't need to invoke mathematical necessity.
In my current essay I've tried to show how quantum measurement can be treated as a form of natural selection, different from but analogous to the way selection operates in biological reproduction and human communication. This develops the thought you mention in passing, that if "the universe has a purpose, then the purpose seems to be that of behaving according to its own physical laws."
Of course quantum dynamics is not strictly "purposeful" any more than biological evolution is. But it's an interesting question how the universe comes to be able to "obey" laws that are only computable in the simplest cases, or how it "knows how to build atoms," etc. I try to show that these questions can in principle be addressed in physics, just as they can be in biology. That means that consistency is not our "only hope to understand the laws and the metalaws." I hope you'll eventually find time to give me feedback on this argument, which also happens to address the difficulty of defining subjective consciousness.
As to that, I agree with you that "whenever we try to define it, we do it in objective terms, which makes it trivial and irrelevant." Quite so - the "hard problem" exists only because we want to treat consciousness as an objectively existing property of certain complex systems, whereas quite evidently it's something that only exists subjectively, from one's own point of view. Unfortunately, our intellectual tradition doesn't do very well with integrating viewpoints into the physical world, though you'd think QM and relativity would have pushed us to do better.
My sense is that we conflate "having a particular point of view on the world" - which is something we can reasonably ascribe to atoms, or anything else that's localized in space and time - with the kind of reflective self-awareness we humans have. The point I make in my essay is that the latter is essentially a communicative relationship with ourselves, that we evolve early on in life as we learn to communicate with others. Again, natural selection is at work here, though operating in ways quite different from Darwinian biology. If we're talking about the "consciousness" of bees or horses, biology gives us everything we need, but the same is not true of us humans. Our brains are essentially the same biological hardware that our primate ancestors used, but the software we run on our brains is unique, and evolves differently.
Sorry for the length of these comments - though it's your fault, for handling so many basic questions in such interesting ways.
Thanks - Conrad
