Why is this a cut? If you study a particular system you can ignore the rest of the universe or use an approximate description of some other systems if that is good enough. It would be a cut only if you say that all of the rest cannot be in principle described by quantum mechanics and you need at some point a classical system.

Here's another Bub story from our dinner on Wed related to the book. Adam is bemoaning the fact that so many physicists don't bother to articulate their ontological assumptions concerning QM, indeed some even deny having them altogether! After arguing against this attitude, Adam says physics students should at least be shown various interpretative options for QM.

At dinner, I told Jeff I hadn't seen any real progress in the debate over QM interpretations since I began work in the field in 1994. We get new experiments, some of which are even motivated by a particular interpretation, but then everyone brings out their favorite interpretation and explains the experimental result to their own satisfaction. The people I first met in foundations of physics (FoP) in 1994 are still today arguing for what are basically their same interpretations from 1994. Jeff said he sees FoP splitting along two lines -- the old line of hackneyed interpretative debate and a new line exploring the deeper mathematical underpinnings of quantum theory, e.g., as with quantum information theory. He thinks the future of FoP lies in this new line.

That's because all interpretations make the same predictions for all experimental results; they have to, since they all use the same (or equivalent) mathematical machinery.

To make progress, someone needs to come up with a new theory--different mathematical machinery that makes the same predictions for experiments that have already been done, but makes different ones for some experiment that hasn't yet been done. If the new theory also rules out some subset of interpretations of current QM, then running the new experiment might help, if it confirms the new theory (and therefore contradicts current QM).

As a physicist involved in this program, I agree completely. I started working on an interpretation of QM so I could have an ontology for all of physics. In other words, I want an ontology that is just as good for GR as it is for QM. I knew that such an ontology would change the way we view reality and consequently lead to new physics, e.g., when we changed from geocentricism to heliocentricism. And that's what excited me about FoP. But, I found many participants didn't even care if their interpretation was compatible with physics other than QM. I can't tell you how many talks I've given with Silberstein (philosopher of physics) where he told me we had to restrict our talk to applications in QM because that's all the audience was interested in. Given that restriction, I fail to see the advantage of any interpretation over any other. Indeed, my adynamical interpretation of QM is unnecessarily deviant from intuition if all it's good for is interpreting QM. The reason I'm so pleased with it is precisely because I can use it to understand all of physics, even resolving controversies in classical physics, e.g., paradoxes of CTCs, dark matter, dark energy, horizon problem, etc. Sorry to prattle on, this is a pet peeve of mine :-)