ueit said:
No.
You misunderstood my position. What I'm saying is that:
1. QM is a very good statistical theory.
2. Being statistical, it fails to predict exactly some experimental results, like the point on the screen where a particle would be detected.
3. It is the duty of science to look for a theory that can account for the above experimental results. Bohmian interpretation might or might not provide a framework for developing such a theory.
Some deny 3. saying that there is no need to assume a cause behind those experimental results. Such view is, IMO, unscientific.
In conclusion, it is good science to work on the theory of thermodynamics. It is not good science to posit that there is no cause behind the motion of a molecule in a gas and there is no reason to look for such a cause because thermodynamics makes good predictions.
In the case of QM, many arguments are put forward to elevate such nonsense to the status of good science (Heisenberg uncertainty, EPR experiments, delayed choice experiments etc.). It is the merit of Bohm to clearly show their failure.
Some points.
I.) A "statistical description" i.e. a probabilistic language is better, not worse than the alternative. We can still indicate certain knowledge of an outcome e.g. [X will occur with 100% probability, Y will occur with 0% probability.] But we can also express those intermediate degrees of knowledge in between. Thus utilizing a statistical language is an expansion of possible physical statements about what we may know about nature rather than a limit.
II.) Science has no duty per se. Science is an epistemological discipline (that of belief based on repeatable empirical test) and it is the duty of the scientist qua scientist to abide by that discipline. The canard about the Moon ceasing to exist when not observed is a total misconception of this principle. The statement about the non-reality of the moon is just as invalid as the statement of its existence. Baring an empirically verified means of prediction the duty-bound scientist would simply state his ignorance of the moon's state of existence between observations.
With this in mind the duty-bound scientist should formulate theories in an operational language and avoid expressing opinions about what cannot be observed. This can be most difficult when those opinions are implicitly integrated into the formal language he uses. One such case is the use of the language of classical states when the effect of observing said states is an open question. (Another is the use of implicit absolute time in discussing relativistic phenomena such as traveling twins.)
II.a) Point (I.) then brings up the question as to whether an accurate physical theory, expressed within a probabilistic language, is possible in which all statements about the empirical behavior of a system can be simultaneously predicted with probabilities of the 100% vs 0% variety. Call this classical determinism or classical completeness. It comes to the same thing when one is attempting to extrapolate future phenomena from past experience (the main purpose of science).
If so then Bell's inequality cannot possibly be violated. Bell's inequality begins by asserting that a physical system has a physical state representable by the selection of one point in a set of possible states. Then all true probabilistic statements about the system must form an additive measure on the set of states. This because each outcome results from the measurement applied to the system in some specific state and hence the probability of that outcome is fixed and must add to the probabilities of that outcome given alternative states.
Since empirically we have observed Bell inequality violation then Classical determinism is disproved and QM is still a viable theory. It is not per se a question of locality. Note that by allowing FTL causal effect in QM you also allow future-to-past effects (assuming Einstein's theory is close to correct) which in turn allows any past observation to be changed in the future. You loose classical determinism anyway and also loose any sense of reality as it is.
III.) Quantum mechanics is causally deterministic: When you ask the question:
Can any specific outcome be positively determined? The answer is yes in QM. Set up a specific observable and there is a prior measurement which will tell you with certainty which value will be observed. Even in classical mechanics one implicitly assumes a prior measurement must be made before one can know with certainty the outcome of a later observation. This is true for any choice of outcome provided one understands that the choice of prior measurement must depend on the choice of outcome to be predicted. However QM does not assume that intermediate measurements fail to invalidate this predictability e.g. QM recognizes that observation = interaction.
IV.) It is the concept of the classical "state of the system" which implicitly assumes that all possible measurements may be made simultaneously. Quantum Mechanics relaxes this a priori assumption and allows that the non-commutativity of observables be determined empirically instead of dictated by "religious tradition". One must at the same time reject the concept of state based reality as a non-contingent absolute. Our construction of an ontological reality is that of building a model in our heads wherein phenomena there correspond to empirical phenomena. In transcending the classical description we must put aside the use of ontological models and stick to a wholly phenomenological language of observables and events. This is as hard and counter-intuitive as letting go of absolute time in Special Relativity, if not more difficult. But it is necessary to understanding QM whether you agree with it or not.
V.) The indeterminism of quantum mechanics comes from the logical incompatibility of the sequences of assertions in the relevant experiment.
E.g. that a photon is polarized vertically is logically incompatible with it being left-hand circular polarized. One is not quite asserting both A and Not A but one is making two positive assertions which cannot both be absolutely true.
It is the richer language of QM which provides for more possible inconsistent pairs of assertions than simply "A and not A".
It is the very deterministic nature of quantum mechanics which equates (e.g. for a free photon) that an earlier plane polarization measurement is equivalent to a later one and thus an earlier assertion about plane of polarization is incompatible with a deterministic assertion about a later circular polarization measurement. The only way to reconcile the incompatibility in what we assert must happen with what we
may observe in some cases, is to expand our logical language to include probabilities.
One is in QM able to make sets of assertions which are partially incompatible and thus the answers are partially unpredictable. We can nonetheless say more using QM, namely,
* Which observations separated over time
are compatible,
and also
* How close two observations are to being compatible in the form of the correlation probabilities.
Regards,
James Baugh
It seems reasonable to want to have "objective physical reality". Altough this didn't convince me of Bohmian interpretation. I think it is actually good thing that we have philosophical problems conserning quantum theory, because as long as a theory is not trying to tell too clearly what reality is, there is a good chance it is not completely wrong.
