The Nature of ψ: Epistemic and Ontic Views of the Wave Function

Abstract

The dilemma concerning the meaning of the wave function is perhaps one of the most controversial and overlooked in contemporary physics. There is widespread disagreement in the scientific community as to whether the wave function should be viewed as a representative of a real physical object or whether it corresponds to a state of incomplete knowledge about the underlying system, such as a probability density. These views are respectively called ψ-ontic and ψ-epistemic. This article aims to give a clear insight into the problem and features of both views. After some clarifying preliminaries, I will give an overview of how the question was perceived and interpreted by the pioneers of quantum theory, such as Bohr and Einstein, and then move on to more modern days with the likes of Bell, Kochen, and Specker. Then I will focus on the contemporary literature and try to give a comprehensive account of the pros and cons of each view. Finally, I will discuss some of the questions that the question of the wave function raises for us, such as our relationship to reality.