Reply To: Quantum causal models, faithfulness and retrocausality (onl. 7/16 @ 11pm UTC+10)

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Mark Stuckey

Hi Pete,

If you don’t see the connection between my footnote and faithfulness, it’s likely because I don’t properly understand faithfulness and there is no such connection. I was thinking faithfulness implies no ad hoc causal mechanisms, such as fine-tuned future boundary conditions. A time-like causal link that isn’t directed constitutes fine tuning. That’s what I was thinking, but I’m clearly confused 🙂

Concerning your comments directed at the footnote per se, I agree that an adynamical explanation in 4D doesn’t preclude a corresponding 3D time-evolved explanation in general. However, in the case of EPRB correlations, it’s not time-evolved but retro-time-evolved explanation that is invoked to “save the appearances” (of dynamism). Given the co-reality of the present and future required to render retrocausal explanation in, for example, TI and TSVF, one must invoke “pseudo-time” processes to create a dynamical story. Where is this process taking place? If you rather have a “global constraint” (Huw’s language and ours) that explains the distribution of the 4D ontological entities in the BW (e.g., TI’s completed transactions), then the “pseudo-time” process is certainly superfluous from a physics standpoint. That is, the desire for dynamical explanation based on our dynamical perspective, when that dynamical explanation requires extraneous mechanisms relative to an empirically equivalent adynamical explanation, is superfluous. As Ken points out in his essay, and you acknowledge in your post, the desire for dynamical explanation is based on our biased dynamical perspective. Nature doesn’t seem to care about our biases, e.g., our Earth-bound perspective clearly indicates Earth is the center of the universe and our low-velocity perspective clearly indicates that velocities add without limit. I haven’t seen TI or TSVF mention a corresponding “global constraint,” but RBW provides one (c.f., the RBW and the TSVF explanations of the Danan et al. experiment starting on p 131, section 2, of ).

That’s not to say one can’t construct a robust time-evolved counterpart to RBW, I think PTI might be exactly that. And, you do actually gain something explanatory in PTI that you don’t have in RBW, so its additional mechanisms aren’t superfluous, i.e., PTI contains a robust model of Now (experience of a preferred present moment). Some (most?) physicists argue that physics needn’t bother attempting to model Now, but I think the lack of a robust Now in the BW creates a serious objection to BW that is arguably justified, as I posted in the General Block Universe Discussion.

I’ll stop prattling on and let you respond 🙂

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