Hi reilly,
I don't think there's anything wrong with QM (except its potential problem with GR maybe). It certainly is odd! But I don't mind nature to be odd. I don't think there's anything wrong with a probabilistic theory either.
However, I do have a problem with the "orthodox" views on quantum theory (although, I often said this, the standard, orthodox view is by far the best to LEARN quantum theory). My problem with the orthodox view does not reside in oddness, or the fact that it is probabilistic or whatever ; it resides essentially in the fact that I have to switch descriptions between "myself", "apparatus" and "microscopic" things. Now, I know the whole story about how you should not extrapolate your daily experience to microscopic or whatever extravagant situations, but that's not the point. The fundamentalist reductionist in me requires that *everything* should be eaten with the same sauce. That might be an odd way or not, but I cannot accept that one should treat certain things in nature fundamentally differently than others. Everything should be equal for the law. No matter what strange law.
And *this* is what goes wrong with the orthodox view (and which inspires me to consider at first sight crazy ideas such as MWI): the fact that one sets apart certain phenomena wrt to others. The fact that my voltmeter should be described in a *fundamentally* different language than an electron. I can accept that a voltmeter is a system which is quite different than an electron, but, at the bottom, both should be fundamentally be described in the same way. It might be *practical* to use certain *approximations* in certain cases. But we're not talking about approximations here. We're talking about incompatible descriptions. If it's a wave function, then a wavefunction for everybody. If it is a classical description, then a classical description for everybody. But not, one thing described in *this* formalism, and another thing described in *that* formalism - unless one can show that "that" formalism is a good approximation for "this" formalism in some peculiar cases - which is NOT the case with the relationship quantum-classical in the orthodox view.
I have difficulties defining "measurement" as something different than "interaction", and I have difficulties defining a "measurement apparatus" as something different than "a physical system". Especially when you study the physics of measurement apparatus!
Now, I agree that this is a purely reductionist worry. If you are a holder of the view that "every level of complexity its own theory" and that the "underlying layer has nothing to say about the theory of the next layer", then there's no difficulty in saying that some things are governed by quantum theory, and other things are governed by classical physics.
But I'm a reductionist, and as such, I require a serious theory to be applicable - at least in principle - to everything within its scope. And as the scope of quantum theory is supposed to encompass everything (quantum theory is not known to be *an approximation* to a better theory as far as I know), then its fundamental description should apply to everything. Myself and my voltmeter included.
This has always been the case: until we knew better, when we had classical physics, it was to be applied to everything, our bodies and measurement apparatus included. Thermodynamics is supposed to apply as well to the "system" as to the apparatus and our bodies.
This should be the case with quantum theory too, and this is contradicted by the orthodox approach to quantum theory, where there is a FUNDAMENTAL difference between the lab apparatus (setting up the state and measuring the state) - which is classical - and the "system under study" which is quantum mechanical.
So again, I have no difficulties with QM per se. It is a highly successful theory. And I have no difficulties with the orthodox view *as an algorithm*. It's a perfectly good way to use quantum theory.
But I have a difficulty with the "metaphysical" picture it tries to create, and I prefer another one, namely the MWI view - because I find that a much more coherent (although admittedly very strange) picture for the reductionist in me.
With MWI-QM I have _certainly_ no difficulties (except trying to explain to people that it is not totally absurd

)... apart from the still apparent incompatibility with GR.
reilly said:
As I have indicated time-after-time I am no fan of alternative approaches to QM. I've been very critical in some cases, as only a retired physics professor can be; sometimes my civility has gone out the door. So , enough. What I propose is a series of questions that, I hope, will stimulate discussion on the efficacy, or lack thereof, of QM.
1. Is QM odd because nature is odd?
2. Does the measurement problem show up in classical systems?
3. What's wrong with a probabilistic theory?
4. Why should we be able to understand Nature in "classical terms" when we go past our normal spheres of perception?
5. Why focus so much on the two slit experimet, at the expense of other phenomena?
6. How can anyone who does not have at least a few years of experience with QM, after school, be a legitimate critic of QM?
7. What's to complain about QM's extraordinary and manifold agreement with Nature?
So, there they are.
Regards,
Reilly Atkinson