OK, yes, let’s wrap up. I appreciate your comments and they actually help me understand your view better. But I guess I would have to summarize by saying two things. One, you’re making a big fuss (as Dustin already pointed out) about the kinds of things (like schematic treatments of pointers and associated implied decoherence assumptions) that…[Read more]

Reinhard, Could you elaborate on your statement that (even) position is not “directly observable” in BM? I don’t think you’re right, but then I’m not entirely sure what you mean. I would say that position is directly observable in BM in the sense that it is possible, according to the theory, to find out the actual position of some particle at…[Read more]

Hi Ken. I think I agree with your description of the situation and the problem and even your statement of what the solution must be:

“Nevertheless, for consistency’s sake, it must be true that some internal interactions are treated as boundary constraints, of one subsystem on the other. That’s the only possible conclusion: effective bou…[Read more]

Since the issue of a retro-causal qtwo came up, I thought this might be a good place to mention Rod Sutherland’s model. I’m not at all convinced by a number of the claims that he’s made with that, but I still find his model interesting, in the sense that it provides a simple example of a retrocausal qtwo. Just have two universal wave functions,…[Read more]

Responses to the excellent responses you all gave to my previous post…

Dustin: I think I agree with everything you wrote about measurement being special in some thermodynamic sense, this being bound up with our sense of agency and macro-causality, etc. Obviously this is tricky stuff and nobody would claim to have a solid grasp on how it all…[Read more]

I just wanted to highlight two ironies that I found in catching up with this thread.

1. Re: the “surreal trajectories”, I find it somewhat amusing that people who basically think it’s impossible to say anything coherent about what’s really going on physically at the microscale, are nevertheless quite certain that (in certain cases) what BM says…[Read more]

Bob, can you give a simple concrete example of the kind of thing you have in mind when you say that BM sometimes “gives the wrong answers” and/or fails to make correct predictions for certain (two-time) correlations? I’m pretty sure you are forgetting that what we actually have direct access to, empirically, are “pointer positions” and such…[Read more]

Thanks Daniel — Yes, I saw (and read with interest!) your earlier comments above. It seemed (from what you wrote in #2791) that you were still thinking of the argument as really strongly suggesting (if not quite rigorously proving) that there is retro-causation, but then also reconsidering this. I didn’t really have anything to say in response…[Read more]

Hi Dustin — I finally got around to reading through the new version of your paper. I again found it very clear and very thought-provoking. Here are some questions and half-baked thoughts, in no particular order:

(1) Now I understand better why there was a little bit of confusion/disagreement in our earlier comments (above) about whether your…[Read more]

Ah, sorry! Thanks for clarifying. But in any case, I still think there is some unacknowledged assumption in your argument that makes you think you’ve established retro-causation, when in fact faster-than-light (but perfectly forward-causal) influences (such as in orthodox QM with a preferred frame over which collapse occurs, or in Bohmian…[Read more]

“I certainly don’t consider … exceeding the speed of light.” I think that is the problem. The setup/scenario in question here is exactly the sort wherein Bell showed — making a few other assumptions (like that the future cannot influence the past, that experimenters’ choices about what to measure can be considered “free” in the relevant s…[Read more]

Hi Dustin — First, I don’t think you’re “interfering” at all. I’ve found all of your comments to be extremely illuminating and on-point! Second, I know the kind of Vaidman/Gisin argument you’re referring to, and (not surprisingly) I agree with you that it’s really no argument at all if you’re willing to just take BM seriously. And I do see why…[Read more]

Hmmm. I guess I thought the first few sentences constituted a kind of argument for why “the existence of [whatever] remains a hope — it is not supported by the evidence”. That is, I thought what you were saying was: supposing the Bohmian trajectories (etc.) to exist may allow me to account for what I observe, but this doesn’t imply that those…[Read more]

Hi Reinhard, Re: “gravitationally and electrodynamically invisible”, I think I understand what you meant, but I still think you are misunderstanding (or maybe it would be better to say misapplying) Bohm’s theory here. It really is, I remain convinced, just what I said in my comments in response to Richard: you insist on thinking of Bohm’s…[Read more]

Thanks Lev, it is so refreshing to get clear and simple answers to these kinds of questions! I continue to have concerns about the view you’re advocating, and would love to continue probing you about them if you’re game, but I just wanted to say that it’s nice to get straightforward answers!

So, can you tell me about how you think of the wave…[Read more]