Reply To: Why Bohmian theory?

Richard Healey

I don’t want to permanently and irrevocably give up on the goal of describing the world as accurately and completely as possible. But I think that goal is at least (probably) humanly unachievable, and possibly even incoherent, since it presupposes that there is some set of concepts rich enough to permit such a complete description. Pragmatism is not incompatible with the realist program: but it is flexible enough to make room for alternative programs. Its central insight is that concepts are intellectual tools for coping with the world, and that we can create concepts and use them in a variety of ways in pursuit of our goals. One way of doing this is to create theories that posit beables: if the theory works, you can hope the beables exist. That, I take it, is the Bohmian program. But the problem with that program is that even if the theory is empirically adequate the existence of the beables remains a hope—it is not supported by the evidence. Quantum theory does not posit beables: instead, it offers advice on what descriptive claims to make about magnitudes and entities supplied by other theories. We have good reason to accept quantum theory because that advice proves to be good, empirically. If your goal is an accurate and complete description of the world, then quantum theory won’t meet it: if your goal is predictive and explanatory success, then quantum theory does meet it. I take science to have the latter goal. I don’t see the Bohmian program making progress toward either goal, since I don’t think the evidence supports Bohmian theories. But (speaking personally) I’d love to see some other theory that is supported by the evidence and that does provide a rich description or representation of the physical world. And I don’t rule out the possibility that further developments in the Bohmian program could lead to such a theory, though I wouldn’t put money on it!

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