Prior Information and the Development of New Ideas: The Copenhagen Family of Theories

Abstract

In classical physics, mechanical systems are thought of as fully determined entities in two prominent senses. First, they always have sharply defined values of position, momentum, and all the so-called dynamical properties (angular momentum, energy, etc.). Second, the evolution of the values in question follows a deterministic law. According to classical mechanics, therefore, a measurement of a dynamical property on a system o yields a value which one can attribute to a retroactively, at least in principle. None of this is clearly the case in quantum mechanics [QM], a theory in which the standard dynamical properties split into incompatible subsets. For example, simultaneous specification of position and momentum is not straightforward in QM. On the most influential interpretation of the theory among practicing physicists, the so-called “Copenhagen Interpretation” [CI], this incompatibility is of an ontological character and rooted in the quantum world. Within the framework of CI, all physical entities are subject to some degree of property-indeterminateness, ontological entanglement, and objective chance, all of which traits are completely alien to the traditional conception of physical objects. Refusing to regard the mentioned oddities as shortcomings of the theory, defenders of CI maintain that QM provides a complete description of mechanical systems, and that the measurement process plays an active role in the very generation of property values(i.e., measurement fails to to reflect prior reality).