The ontological status of the quantum wavefunction remains one of the most debated questions in quantum theory. While epistemic interpretations regard the wavefunction as a reflection of our knowledge or beliefs, ontic interpretations treat it as a real physical object. In this paper, we argue that epistemic approaches struggle to explain the universality and precision of the uncertainty principle, a core feature of quantum mechanics. By contrast, treating the wave-function as ontic allows a consistent and natural derivation of quantum uncertainty from the mathematical structure of Hilbert space. We examine key interpretations on both sides and highlight why the epistemic view falls short in addressing constraints that appear to be intrinsic to nature.
The ontological status of the quantum wavefunction remains one of the most debated questions in quantum theory. While epistemic interpretations regard the wavefunction as a reflection of our knowledge or beliefs, ontic interpretations treat it as a real physical object. In this paper, we argue that epistemic approaches struggle to explain the universality and precision of the uncertainty principle, a core feature of quantum mechanics. By contrast, treating the wave-function as ontic allows a consistent and natural derivation of quantum uncertainty from the mathematical structure of Hilbert space. We examine key interpretations on both sides and highlight why the epistemic view falls short in addressing constraints that appear to be intrinsic to nature.
The meaning of the wave function has been a hot topic of debate since the early days of quantum mechanics. Recent years have witnessed a growing interest in this long-standing question. Is the wave function ontic, directly representing a state of reality, or epistemic, merely representing a state of (incomplete) knowledge, or something else? If the wave function is not ontic, then what, if any, is the underlying state of reality? If the wave function is indeed ontic, then exactly what physical state does it represent? In this book, I aim to make sense of the wave function in quantum mechanics and find the ontological content of the theory. The book can be divided into three parts. The first part addresses the question of the nature of the wave function (Chapters 1-5). After giving a comprehensive and critical review of the competing views of the wave function, I present a new argument for the ontic view in terms of protective measurements. In addition, I also analyze the origin of the wave function by deriving the free Schroedinger equation. The second part analyzes the ontological meaning of the wave function (Chapters 6, 7). I propose a new ontological interpretation of the wave function in terms of random discontinuous motion of particles, and give two main arguments supporting this interpretation. The third part investigates whether the suggested quantum ontology is complete in accounting for our definite experience and whether it needs to be revised in the relativistic domain (Chapters 8, 9).
Abstract The ontological models framework distinguishes ψ-ontic from ψ-epistemic wave-functions. It is, in general, quite straightforward to categorize the wave-function of a certain quantum theory. Nevertheless, there has been a debate about the ontological status of the wave-function in the statistical interpretation of quantum mechanics: is it ψ-epistemic and incomplete or ψ-ontic and complete? I will argue that the wave-function in this interpretation is best regarded as ψ-ontic and incomplete.
In discussion of the interpretation of quantum mechanics the terms ‘ontic’ and ‘epistemic’ are often used in the sense of pertaining to what exists, and pertaining to cognition or knowledge respectively. The terms are also often associated with the formal definitions given by Harrigan and Spekkens for the wavefunction in quantum mechanics to be �ψ-ontic or �ψ-epistemic in the context of the ontological models framework. The formal definitions are contradictories, so that the wavefunction can be either ψ�-epistemic or ψ �-ontic but not both. However, we argue, nothing about the informal ideas of epistemic and ontic interpretations rules out wavefunctions representing both reality and knowledge. The implications of the Pusey–Barrett–Rudolph theorem and many other issues may be rethought in the light of our analysis.
This study examines the epistemological implications of competinginterpretations of quantum states, focusing on the distinction between epistemicand ontological accounts of the wave function (Harrigan & Spekkens, 2010).Rather than treating interpretative disputes as purely metaphysical, this studyanalyses the extent to which quantum theory constrains, enables or underminesclaims to knowledge about physical reality (van Fraassen, 2008). By situatingthe epistemic–ontological debate within broader discussions of realism,objectivity and scientific explanation, this study argues that quantum theorynecessitates a reconceptualisation of epistemic access to reality (O’Neill,1997). Particular attention is given to the roles of uncertainty, contextuality andobserver-dependence in shaping the epistemic limits of quantum physics (Bohr,1935). The article concludes by proposing a moderate epistemic realism thatpreserves empirical objectivity while acknowledging principled limits onontological transparency (Healey, 2017).
Abstract In discussion of the interpretation of quantum mechanics the terms ‘ontic’ and ‘epistemic’ are often used in the sense of pertaining to what exists, and pertaining to cognition or knowledge respectively. The terms are also often associated with the formal definitions given by Harrigan and Spekkens for the wavefunction in quantum mechanics to be ψ ψ -ontic or ψ ψ -epistemic in the context of the ontological models framework. The formal definitions are contradictories, so that the wavefunction can be either ψ ψ -epistemic or ψ ψ -ontic but not both. However, we argue, nothing about the informal ideas of epistemic and ontic interpretations rules out wavefunctions representing both reality and knowledge. The implications of the Pusey–Barrett–Rudolph theorem and many other issues may be rethought in the light of our analysis.
The physical states of matter and fields are represented in the quantum theory with complex valued wavefunctions, or more generally by quantum states in an abstract linear vector space. Determining the physical nature of wavefunctions remains an open problem that is at the very core of quantum mechanics, About a decade ago, Pusey, Barret and Rudolf (PBR) claimed to prove an ontologically real status of wavefunctions by ruling out ψ -epistemic models. The result was obtained by associating wavefunctions to hypothetical distributions of notional physical states, and by examining whether some physical states were associated with more than one wavefunction, a criterion they chose for defining a wavefunction as ‘epistemic’. I show that the starting assumption in the PBR argument, of associating a wavefunction with a distribution of physical states, is flawed and contradictory to the linear structure of quantum mechanics coupled with its quadratic Born’s rule. Since none of the axioms or calculations of observable statistical results in the standard quantum theory depends on specifying the physical nature of a ψ -function, the considerations in the PBR paper, involving a standard process of the preparation and projective measurements of quantum states, cannot address the ontological status of the wavefunctions in space and time.