The orthodox Copenhagen interpretation that I have been describing up to now is based on a sharp separation between the physical system, governed by the rules of quantum mechanics, and the apparatus used to study it, which is described classically, that is, according to the prequantum rules of physics. Our mythical particle may have a wave function with both here and there values, but, when it is observed, it somehow becomes definitely here or there, in a manner that is essentially unpredictable, except with regard to probabilities. But this difference of treatment between the system being
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