What the Philosophical Interpretation of Quantum Theory Can Accomplish

Abstract

I argue that philosophical reflection can contribute to a better understanding of physical theories by performing conceptual clarification, epistemological analysis and ontological exploration. I begin by reconstructing early ontological interpretations of quantum theory, i.e., by explaining Copenhagen instrumentalism and the shift toward a quantum realism. I turn to entanglement, whose chief philosophical challenge is to understand which deeper property of nature it reveals. The trouble is that the EPR-correlations it gives rise to are not produced by common causation. Conceptual analysis shows that this failure is due to the violation of separability in quantum theory. In entangled states, it is the composite state that is primary since it cannot be neatly divided into two states that unambiguously pertain to the partial systems. As a result, total states are not produced by an interaction among the parts. This feature can be interpreted in ontological terms as suggesting a holist picture of nature. Another question of philosophical import concerns the quantum measurement problem and the contribution decoherence makes to its solution. The conceptual point is what, precisely, this problem amounts to and what we require considering it settled. The issue that divides the philosophical factions is whether a solution needs to show that superpositions are actually destroyed or whether it suffices to demonstrate that superpositions become unobservable.