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Quantum mechanical foundations are usually phrased in terms of measurement. I believe this is the main cause why these foundations remain shaky after almost 100 years of a good mathematical basis. Classical mechanics never had any reference to measurement in its foundations, and hence it was always clear what the terms meant on a theoretical level. It should be like that in any foundations that deserve this name.
For measurement is an exceedingly complex process that cannot be taken as unexplained primitive, vague to the point of meaninglessness when used in foundational arguments. In the present foundations of quantum mechanics it looks as if there were a miraculous process that creates measurement results when an experimenter sets up a corresponding setting. No wonder that the traditional interpretations of quantum mechanics are similarly miraculous in one or more respect!
In reality (i.e., in actual practice) measurement results are nothing miraculous at all but appear as the result of complex physical activities. Thus whatever can be said about measurement must be based on a description and analysis of these activities. This makes measurement an area of statistical mechanics that cannot be discussed without having already the whole theoretical set-up of a background theory that defines what the objects measured are and what the items mean that go into the description of a protocol for how valid measurements are created by those (people or automata) who take measurements.
The proper theoretical description and analysis of these measurement activities is the real measurement problem, and it is an unsolved problem both in classical mechanics and in quantum mechanics, and for very similar reasons. Without progress in solving these problems there is little hope of clarifying even the meaning of the present foundational discussions.
For measurement is an exceedingly complex process that cannot be taken as unexplained primitive, vague to the point of meaninglessness when used in foundational arguments. In the present foundations of quantum mechanics it looks as if there were a miraculous process that creates measurement results when an experimenter sets up a corresponding setting. No wonder that the traditional interpretations of quantum mechanics are similarly miraculous in one or more respect!
In reality (i.e., in actual practice) measurement results are nothing miraculous at all but appear as the result of complex physical activities. Thus whatever can be said about measurement must be based on a description and analysis of these activities. This makes measurement an area of statistical mechanics that cannot be discussed without having already the whole theoretical set-up of a background theory that defines what the objects measured are and what the items mean that go into the description of a protocol for how valid measurements are created by those (people or automata) who take measurements.
The proper theoretical description and analysis of these measurement activities is the real measurement problem, and it is an unsolved problem both in classical mechanics and in quantum mechanics, and for very similar reasons. Without progress in solving these problems there is little hope of clarifying even the meaning of the present foundational discussions.