Physicists Maintain Deep Divide Over Wave Function's Reality Status

A significant schism continues within theoretical physics and philosophy of science regarding the fundamental nature of the quantum wave function. This academic dispute, which saw active discussion around 2025 and 2026 in conceptual physics circles, centers on whether the wave function provides an objective description of physical reality or serves solely as a practical mathematical construct for calculation. This ongoing debate fundamentally shapes the modern understanding of physical reality, aligning with broader naturalistic views that seek to anchor the world image firmly in scientific findings.

Quantitative data underscores the depth of this division. Survey results from 2025 indicated a near split among surveyed physicists: approximately 36% asserted that the wave function represents a genuine physical entity, while a larger segment, 47%, categorized it as a tool for computation. Key figures articulating these contrasting positions include physicist Sean Carroll, who champions wave function realism, and philosophers Raoni Arroyo and Jonas R. Becker Arenhart, who present counterarguments. The debate probes whether a successful scientific theory necessitates ontological truth or if its mathematical components can be considered real objects in their own right.

Sean Carroll adheres to ontic realism, maintaining that the wave function itself describes reality as a fundamental constituent of the universe. This perspective aligns with interpretations such as the Many-Worlds Interpretation, originated by Hugh Everett III, which posits that all potential outcomes described by the wave function materialize. In contrast, Arroyo and Arenhart contend that the arguments supporting wave function realism are fundamentally confused, demonstrating only the function's theoretical utility rather than its objective reality. Their work, including a paper forthcoming in Foundations of Physics in July 2025, examines wave function realism as a case study in scientific realism, arguing that realism based purely on pragmatic, non-truth-conductive grounds creates tensions with broader scientific realism.

The conceptual framework for this discussion is informed by historical developments, including the implications of the Pusey-Barrett-Rudolph (PBR) theorem from 2012. The PBR theorem, cited by some as the most important theorem in quantum foundations since Bell's theorem, rules out certain psi-epistemic hidden-variable models, suggesting that pure quantum states must be "ontic," meaning they correspond directly to states of reality, not just incomplete knowledge. This theorem uses operational assumptions like preparation independence and multipartite entangling measurements to establish that the quantum state cannot be interpreted as mere statistical knowledge.

Despite the PBR theorem's implications favoring an ontic view, the philosophical divide remains robust. For instance, some interpretations, like Relational Quantum Mechanics (RQM), circumvent the theorem by not being strongly realist theories, interpreting the wave function as a computational device encoding observer-specific information. Carroll's realism, where reality is a ray in Hilbert space, contrasts with other realist views, such as Alyssa Ney's, which places the wave function as a physical wave in a higher-dimensional configuration space. The persistent disagreement highlights the enduring gap between quantum theory's mathematical predictive success and the lack of consensus on its ultimate ontological interpretation, a mystery that continues to drive foundational physics research, as evidenced by discussions at events like the 2025 Conference for Physical & Mathematical Ontology in Munich, Germany.