Reply To: Why Bohmian theory?


Hi Richard, I read your post several times trying to understand your point of view, but I’m still just not sure what you mean to be saying. Can you, for lack of a better phrase, dumb it down for me a bit? It sounds like you’re saying that, according to “observer-free quantum theory”, the ontology (i.e., the stuff that really exists physically according to the theory) includes settings of switches and knobs, and currents, and presumably a lot of other macroscopic things/properties described in classical terms. Whereas wave functions (meaning, presumably, the typically microscopic things like individual electrons or atoms whose states are, in QM, described by a wave function) are not part of the ontology. Am I at least close to right so far?

What I don’t get is how this kind of picture isn’t just drowning in the sorts of problems Bell identified by noting that ordinary qm is “unprofessionally vague and ambiguous”, i.e., part of what’s usually called the measurement problem. Is there some clean, unambiguous way of saying exactly what, according to the theory, is real? It seems like you mean to say that big, macroscopic, classical things (whose reality nobody (sane) ever doubted) are real. But where, exactly, is the boundary as we move along the continuum from big/macro to little/micro? To me, as long as you can’t specify *sharply* what the theory says is real, I can’t really take it seriously as a candidate fundamental theory. And then this same feeling applies as well to the dynamics, which, it seems to me, inherits and amplifies whatever vagueness/ambiguity there is about ontology: if you only say something like “big/macro things are real, but little/micro things described by wave functions aren’t real”, and there are some equations for how the big/macro stuff behaves, and some other equation for how wave functions behave, and maybe some other equations to describe how big/macro stuff interacts with wave functions, etc., you can’t possibly give sharp unambiguous rules about which equations apply in which situations, until/unless you’ve got some unambiguous way to decide which kind of thing (or non-thing) you’ve *got* — when, say, what you’ve got is something mesoscopic. And then of course there is the general worry about what in the world it could mean to say that big/macro things are real, but the smaller and smaller pieces that they are made of cease to exist at some sufficient level of smallness.

But really I’m just expressing my concerns with “ordinary QM”. My sense is that, while your view has some kind of overlap with that, you mean for it to be somehow different and immune to these sorts of concerns. Can you help me understand better what your view is and why you think it’s immune to such concerns?

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