@Eamon: "I wonder what a *genuine* stochastic process *would* look like if not the ones I mentioned. In other words, what possible observational state of affairs would, for you, serve as evidence for genuine indeterminism?"
Good question. I think I would be willing to accept indeterminism despite my gut feeling that it is a mistake, if accepting indeterminism answered more questions than it raised. The prima facie reason for accepting indeterminism is the examples you cited (radioactive decay, etc.), but that interpretation has the following problem.
- Pretty much everybody accepts the reality of superposition, which is in effect Many-Worlds.
- Then, in order to explain the fact that our "thread of consciousness" sees only one discrete outcome, the Copenhagen interpretation posits a wavefunction collapse -essentially, all superpositions instantaneously "die," except the one containing my "thread of consciousness."
- But this collapse is the ONLY known phenomenon in physics that is inherently random/acausal, along with a bunch of other weird properties like non-locality, non-CPT-symmetry, faster-than-light influence...
- And then we get to the crux of the matter: what is this queer collapse theory trying to explain in the first place?
- Answer: why our "thread of consciousness" sees only one outcome, which outcome is apparently not predictable in principle.
- So the question becomes: what happens if we drop our intuitive idea of a single unique "thread of consciousness?"
- Answer: there is nothing left to explain. All branches of the wavefunction remember their own history, and to all of them it prima facie appears that their "thread" made it while the others didn't.
Summary: quantum randomness/collapse "explains" why our "thread of consciousness" sees only one outcome, but this is explained equally well by no collapse and no randomness. Quantum randomness does ZERO explanatory work (although at first intuitive glance, it seems to). -- Ian Pollock [link]