I think this excerpt describes the situation succinctly:
"... But the most tangled area in present physical science
is surely the standard old 1927 vintage quantum theory, where the conceptual problems of the
Copenhagen interpretation" refuse to go away, but are brought up for renewed discussion by every
new generation of physicists much to the puzzlement, we suspect, of the older generation who
thought these problems were all solved . Starting with the debates between Bohr and Einstein
over sixty years ago, different ways of looking at quantum theory persist in making some see deep
mysteries and contradictions in need of resolution, while others insist that there is no difficulty.
How can scientists of unquestioned competence be in sharp disagreement about such things? It
must be that we have different unstated premises hidden assumptions in the back of our minds. If
so, then until we bring out into the open just what those premises are, there would be no possibility
of resolving the issue.
Defenders of the Copenhagen interpretation have displayed a supreme self confidence in the
correctness of their position, but this has not enabled them to give the rest of us any rational
explanations of why there is no difficulty. Richard Feynman, while defending the QM formalism
on grounds of its practical success, at least had the honesty to admit: Nobody knows how it can
be that way."
While we doubters have not shown so much self confidence, nevertheless for all these years it
has seemed obvious to me for the same reasons that it did to Einstein and Schrodinger that the
Copenhagen interpretation is a mass of contradictions and irrationality and that, while theoretical
physics can of course continue to make progress in the mathematical details and computational
techniques, there is no hope of any further progress in our basic understanding of Nature until this
conceptual mess is cleared up.
Because this position seems to arouse fierce controversy, let me stress our motivation: if quan-
tum theory were not successful pragmatically, we would have no interest in its interpretation. It is
precisely because of the enormous success of the QM mathematical formalism that it becomes cru-
cially important to learn what that mathematics means. To find a rational physical interpretation
of the QM formalism ought to be considered the top priority research problem of theoretical physics;
until this is accomplished, all other theoretical results can only be provisional and temporary.
...
The failure of quantum theorists to distinguish in calculations between several quite different
meanings of `probability', between expectation values and actual values, makes us do things that
don't need to be done; and to fail to do things that do need to be done. We fail to distinguish
in our verbiage between prediction and measurement. For example, the famous vague phrases:
`It is impossible to
specify . . . '; or `It is impossible to
define . . . ' can be interpreted equally well
as statements about prediction or statements about measurement. Thus the demonstrably correct
statement that the present formalism cannot
predict something becomes perverted into the logically
unjustified and almost certainly false claim that the experimentalist cannot
measure it!
We routinely commit the Mind Projection Fallacy: supposing that creations of our own imag-
ination are real properties of Nature, or that our own ignorance signifies some indecision on the
part of Nature. It is then impossible to agree on the proper place of information in physics. This
muddying up of the distinction between reality and our knowledge of reality is carried to the point
where we find some otherwise rational physicists, on the basis of the Bell inequality experiments,
asserting the objective reality of probabilities, while denying the objective reality of atoms! These
sloppy habits of language have tricked us into mystical, pre scientific standards of logic, and leave
the meaning of any QM result ambiguous. Yet from decades of trial and error we have managed
to learn how to calculate with enough art and tact so that we come out with the right numbers!
"
From, Jaynes, E. T., 1990, `Probability in Quantum Theory,' (200Kb) in Complexity, Entropy, and the Physics of Information, W. H. Zurek (ed.), Addison-Wesley, Redwood City, CA, p. 381
http://bayes.wustl.edu/etj/articles/prob.in.qm.ps.gz
