Dear Karl,
You write
---"It is the unknowable closed universe as a whole which evolves deterministically. "---
Though all things inside of it certainly evolve with respect to each other, if the universe creates itself out of nothing, so the total of everything, including space and time remains nil, then it doesn't exist as a whole. If particles create themselves out of each other, like zero's splitting into positive and negative numbers (energies), then the total of all these numbers in the universe remains zero. Unlike numbers, particles alternate their charge or energy sign at a frequency equal to the 'number', the energy of the particle. Now if the sum of all these numbers stays zero as conservation principles require, then there is no 'excess' charge which can be involved in an observation reaction from outside the universe: all charge is tied up in the exchange between particles inside of it, so the universe has a zero 'net charge'. This is why I insist that the sum remains nil: to keep aware of the fact that particles power each other's existence, that 'to be' is a verb and not a noun, a passive state. It is this continuous exchange which knits spacetime together, which makes particle force each other to obey the laws, the rules of behavior, the frequencies to oscillate at etc., they themselves have installed or are the product of, laws which must be obeyed if they are to belong to the same universe, if they are to exist to each other. The universe, then, only exists to inside observers and objects which are physically part of it, so it makes no sense to ask how much energy it contains, how old and large it is. A statement like "The mass of the Universe is 1.8x10^54 kg. The radius of the Universe is 0.95x10^26 meter" doesn't make any sense if there's nothing outside the universe with respect to which these quantities matter, have a physical reality to. Whether the universe exists as a whole or not isn't so much a philosophical question: it is of crucial importance to physics if we want to understand nature. By insisting that inside particles exist, have a reality even if they wouldn't interact at all, as if but for practical reasons they are observable from outside the universe, we distort their properties beyond recognition, so they become incomprehensible. By insisting that their charge is either positive or negative, no matter what happens, that their mass is a property, a quantity which is constant, independent from interactions, we create a theory in which forces and interaction energies become infinite at infinitesimal distances. We can avoid this unsolvable problem by accepting the idea that in a self-creating universe any property must be as much the product as the source of particle interactions. As the same holds for the force between them, forces between particles cannot be either attractive or repulsive. Though the charge of particles then cannot be either positive or negative, that doesn't mean that the Maxwell laws don't apply. Of course they do: it is only our 19th century notion of what charge is which urgently needs revision, which must be translated in the non-causal language of quantum mechanics. Since according to our present, simplistic ideas particles either attract or repulse so the strength of the force between them solely depends on their distance, the question arose as to how protons can fit in atomic nuclei despite their huge electric repulsion. Though this repulsion is said to be 10^38 times stronger than gravity between them, as a force never can exceed (or be smaller) than the counter force it is able to evoke, it evidently cannot be greater than the opposition to it the particles offer, to their inertia. If we apply Einstein's equivalence principle and call every influence which brings the inertia of an object to expression as a counterforce 'gravity', then there's only gravity. To distinguish it from the weak force pulling Newton's apple, I've called the continuous energy exchange between particles which powers their inertia 'strong gravity'. So there also is no need for the strong nuclear force (see UPDATE 1 - STRONG FORCE, 4 Feb, at my thread), for string theory nor Higgs bosons.
---"It is the unknowable closed universe as a whole which evolves deterministically."---
Though everything continuously changes inside the universe, it does not evolve as a whole, so doesn't make sense to speak about 'unknowable' as this presumes that it has particular properties as a whole, which for practical reasons we cannot unveil. As to "deterministically", the only rule the universe follows is that the grand total of everything inside of it remains nil, so it cannot, as a whole, be ascribed a state which evolves, let alone in a 'deterministic' manner. It can only have properties, evolve as a whole if there's a clock outside of it, a clock which directs the pace of inside events, but is not itself affected by whatever happens inside of it, which is a religious view on the universe.
---"the "bird's view," the theoretical omniscient-observer view of the entire universe, is a perspective to which we observers are not and cannot be privileged."---
This again presupposes that the universe as a whole has some particular properties, as if it is embedded in something larger and interacting with it, implying the universe to be an object which passively has been created by some outside intervention.
---"Unobserved or isolated pockets [..] such as [..] individual quanta in a symmetrical double-slit experiment, are closed systems which can be demonstrated to evolve deterministically according to the Schrödinger equation"---
Again, you assume that the content of a system can completely be isolated from any outside influence, which is impossible, as a perfect isolation also would cut off gravity from acting on the quanta. Though the continuous energy exchange by means of which particles preserve and express their properties, keep existing, remain part of the same universe is unobservable, that doesn't mean that we may ignore it. Because macroscopic, classical objects indeed don't seem to display any activity to keep existing, that doesn't mean that quantum objects also are 'dead' things. A fundamental, quantum particle cannot be distinguished from its function, at the same time being the product as well as the source of its interactions. It is their continuous energy exchange which informs (the particles of) a light source about (the spatial distribution of the particles of) the 2-split setup so the source 'knows' where to send photons. This is why no energy is liberated where identical photons 'annihilate' and why the source looses no energy either. Informed about the setup, the source simply doesn't send photons in these directions. So instead of saying that particles "evolve deterministically according to the Schrödinger equation", we can as well say that the Schrödinger equation 'works' because of this exchange. It is this continuous two-way traffic, this alternating flow of energy between them why particles are wave phenomena in the first place, the frequency of the exchange equal to the energy they have according to each other.
---"that the closed universe as a whole behaves according to the same rules as individual isolated quanta."---
Though a universe certainly can be defined as the entirety of objects following the same rules of behavior, laws of physics, outside of it there's nothing with respect to which it can have properties, act in this way or the other.
---"we are forced to describe the interaction of subsystems. The question is then, what is the origin and fundamental nature of this partitioning?"---
If I may replace 'subsystems' with 'particles', then my answer to this question is that the 'subsystems' as they create one another, try out, design each other in such a manner that they can keep existing to each other, that is, 'partition' themselves off each other, at the same time maintaining a physical communication (energy exchange) to be able to remain part of each other's universe. So whereas you seem to accept that the 'subsystems' have some more or less accidental properties they've been provided with at their creation, as if they've passively been created by some outside intervention, to me these properties are as much the source, the cause as the product, the effect of their 'partitioning'. As to professor Hawking's tale, as I argue in my essay, the Big Bang only happened to physics, with all its devastating effects, not in nature. I wonder why nobody cares that his hypothesis doesn't even offer a glimmer of a beginning of an explanation as to the origin of all matter and energy, which suddenly popped up out of nothing, a finite quantity which -despite observations proving this to be untrue- is supposed to remain the same ever after. Who/What determined that particular quantity? Can we really have a beginning if there's nothing with respect to which it can have a beginning? Sure, if a virtual particle pops up together with its counterpart, then these particles see, create and exist to each other at the same time, so they certainly can have a beginning and end. However, the universe as a whole has no such counterpart with respect to which to exist, so we shouldn't treat it as an ordinary object and stubbornly insist that it has a beginning. It is because we regard energy and mass as absolute quantities that we come up with nonsensical assertions about the energy content of the universe, that we regard particles to be only the source of their interactions. Indeed, they would be if they passively have been created by some outside intervention, if we believe in the Big Bang tale. As cannot explain the observed homogeneity and isotropy in the universe, it needs other flawed ideas, like the cosmic inflation, a hypothesis which likewise cannot predict nor prove the rate of inflation, but is set at that value as to yield the desired result. It also offers no mechanism as how the universe may know when to start, what rate to assume and when to stop. As to the 2.8 ° K cosmic background radiation, Hoyle et al. offer an alternative explanation, see Further astrophysical quantities expected in a quasi-steady state Universe, Astron. Astrophys. 289, 729-739 (1994), p 732. This is not to say that we live in Hoyle's steady state universe: like the bigbang universe, it regards the universe as an ordinary object so cannot explain the creation of energy either. The result of all this nonsense is that physics has become entrapped in a vicious circle of delusions, one misconception breeding the other, so a drastic conversion is needed.
Regards, Anton