Abstract

Verifiable physical theories can deal only with reproducible phenomena. To the extent that some objectively real aspects of quantum phenomena are inherently not reproducible, to that extent quantum theory cannot be expected to provide a complete description of reality. Einstein, Podolsky, and Rosen argued, however, that quantum mechanics does not even provide a complete description of reproducible reality. But their reasoning fails to distinguish between the “predictability” and the “predictedness” of a physical quantity. It is shown that in quantum mechanics, as in classical mechanics, predictability is not affected by a nondisturbing measurement, only predictedness is affected. Since Einstein, Podolsky, and Rosen define the (reproducible) reality of a quantity on the basis of its predictability, we find that the quantum mechanical description of this reproducible reality is unaffected by nondisturbing measurements and does not need to be considered incomplete