Hi Edwin,
Some important points raised here, that I expect will occur to others, so I'l spend a bit of time picking them apart.
When I say " it isn't clear whether there really *is* anything in the world being represented" I mean that it isn't clear that there is a 'counterpart' object in reality (independent from theory and mind and anything like it). We think of watches as giving us a representation of "time out there", but of course it is only "time-relative-to-a-human-chosen-standard". There is no clock in reality that the Casio and Rolex are both measuring. I am saying something similar applies to our scientific theories, and to questions about the digital/analog nature of reality. An analog watch's being successful in various ways does not imply that there is something in the world that exactly shares it's properties. Likewise, even if we ended up with some successful discrete theoretical system to represent the world, we could not infer a matching 'entity in the world' (that could be seen from a God's-Eye view, as they say). "Representation", "Information", "Reality", "Physical" are all very slippery concepts (weasel words, but we don't have better ones): there is no way to evade metaphysics here! Though you charge me with metaphysics, I would say your stance is in fact far more metaphysical since you are saying precisely that we can "go beyond" what the physical theory tells us (namely the results of measurements). Indeed, in any case, part of what I was saying in this paper was that this *is* a highly metaphysical question, not something to be settled by physics.
The bus example is just a version of Dr Johnson kicking a stone in a bid to refute idealism. I'm defending a form idealism here, but of a very restricted kind. I'm not denying the existence of an 'external world' or anything of that sort. I am denying that there is anything like a Gods-eye view of reality that physical theories can map like cartographers. Rather, like real cartographers, all sorts of approximation schemes must ALWAYS be employed.
I was careful to define "physical universe" to be the framework that physical theories aim to describe. Of course, both Newton's system and quantum theory are examples of fairly comprehensive physical universes. They are also very much in conflict. Inasmuch as they agree (at certain scales) they agree on the relational structure that is preserved at those scales - not on what they have to say about, e.g., the nature of energy, force, matter, etc... The equations of physical theories do not tell you about what particular objects will do, they tell you about relationships between quantities.
You might respond: but QM is *better* than Newton's system, since it covers more ground and deals with empirical problems (it maps more terrain)! So it does. But the system that results is nonetheless radically underdetermined. There are lots of ways of interpreting QM, many in direct conflict. But none of them conflict with respect to the relational structure: the answers it gives to our experimental questions (where an experiment will always involve a correlation/coincidence of quantities/objects). Further, there is still massive selection going on in what questions we choose to ask.
Also: I do not defend Wheeler's position. 'It' does not come from 'bit', it comes from 'us', though it does only in the sense of Eddington's selective subjectivism: it's a highly filtered IT! Eddington has a nice metaphor about just this point. He imagines the scientist to be like a fisherman with a net with quite large holes. The fisherman only ever catches fish over 5cm. Look, he say, ALL fish are over 5cm! Depends on the net of course (where net = theory). We also get the relationship between quantum theory and Newtonian physics from this. If we increase or decrease our net to 5cm holes (change the scales) then we will agree on what there is. Likewise, theories can agree at certain scales, but the scale was a result of selecting particular energies. But there are lots of possible nets, and we never know if we have included them all.
I do not think my thesis is in the least bit mystical by the way. I was careful to use the phrase "International system", and this could, with sufficient ingenuity, be made by future humans, or could be entirely distinct from humans. If it has radically distinct faculties for sensing and gathering data (or a radically different environment), then you can bet that the theories that result will be of a very different kind to ours, though could be just as successful in their own way. We are surely adapted for pattern finding and unifying things together into classes? Those that didn't act in this way would not do very well in a rapidly changing,
Lastly: METAPHYSICS IS NOT THE SAME THING AS MYSTICISM!
What everyone is doing, when they are engaging in the interpretation of physics, is metaphysics. Why? Because physics isn't able to settle these matters. Why not? Because all of the different interpretations make the same predictions (which, I might add, amount to experimental results/ measurements). Why? Because if they didn't they could be ruled out (or in) on grounds of empirical inadequacy.
Best,
Dean