Jochen, Thanks for the thoughtful response. I think we are more aligned than may be apparent, and I appreciate your clarification of the problem you are actually trying to address. I only want to clarify that my concern does not rest on an older deterministic picture, nor on quantum indeterminacy as its alternative.
My concern is with a background assumption that matters especially for Everettian universal-wavefunction and super-deterministic pictures: that there is a globally given state whose complete history is fixed. Chaos limits predictability, but it need not challenge that stronger image. That is the image I am trying to question, in part because it affects what we can legitimately infer from generalities, averages, and ensembles. Regarding quantum theory, I want to leave open a speculative possibility. What appears to us as quantum probability may arise partly from the object-oriented form of inquiry. We isolate, reidentify, and compare entities such as electrons across preparations and measurements, then form ensembles and extract stable frequencies. In doing so, we presuppose, or perhaps construct, an effective space of repeatable objects and possible outcomes. If the actual unfolding is singular and non-computable, the resulting probabilities may describe the best regularities available to finite observers making successive approximations, rather than probabilities over a fully given underlying state space. Electrons would remain real as stable operational objects, but their probabilistic behavior would not by itself establish fundamental stochasticity or a globally specifiable space of possibilities beneath the phenomena. I suppose I am wary of moving too quickly from successful ensemble descriptions to claims about the ontology of the singular world. Physics works with electrons, states, probabilities, and averages because they are extraordinarily stable and useful handles. But probability begins by constructing a space of possible outcomes and assigning a measure over it. That is indispensable for inquiry, but it does not by itself decide the ontology. It may be that reality is exhaustively represented by a structured space of possibilities, perhaps even by an Everettian multiplicity. But it may also be that we belong to a singular unfolding whose regularities can only be approached through the possible spaces and ensemble descriptions we construct locally. In that latter case, probability would remain indispensable, not because we stand outside reality surveying an already given range of alternatives, but because finite observers within a singular unfolding need ways to organize incomplete, repeatable, and action-relevant experience. I expect that many on the list could point out where these speculations fail or need sharper formulation. For instance, I see that Marcus has just brought up unitarity. I certainly do not claim authority on these questions. Anyway, I do not mean to further detract from the actual point of your writings, which is concerned with agents doing agent stuff.
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