The Limit and Its Ground. QBism, Scientific Realism, and the Born Rule
Abstract
QBists insist that theirs is a realist position while denying that the quantum formalism represents a mind-independent world. The insistence is hard to place. The realism debate is throughout a dispute about represented content, so a theory that denies standing in the representation relation appears not to take up a position within that debate at all. This paper examines the most developed attempt to make good on the QBist claim--David Glick's perspectival normative realism--and argues that it fails instructively. Glick seeks the ground of the Born rule's objectivity among states of affairs and construes an agent's perspective as a location within an already-constituted world; finding no state of affairs fit to bind every agent at once, he must book the ground as brute. Phenomenology supplies the third thing his picture lacks. A horizon is not a position within the world but the condition under which a world is given. Read as an agent's weighting--her curvature--of such a horizon, the quantum state is neither a defective description nor a brute posit, and the Born rule articulates the invariant lawfulness by which any sense confers a curvature at all.
Related
- Ontology without states: PBR as an argument for dynamics-first realism
- Violation of Bell-type Inequality in the Hanbury Brown-Twiss (HBT) Toy-Model: Quantum Correlations beyond Local-Realism
- Passive realism in the presence of open system dynamics
- Bell's go theorem: regaining local causality with a new notion of realism
- The exact price of local realism in CHSH experiments: a measurement-dependence-detection trade-off surface, a moiré phase-locking mechanism that saturates it, and an unmeasured fringe in the fourfold coincidence sum
BibTeX
@misc{wiltsche2026limit,
title = {{The Limit and Its Ground. QBism, Scientific Realism, and the Born Rule}},
author = {Harald A Wiltsche},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.22159},
eprint = {2609.22159},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.22159},
}
RIS
TY - UNPB
TI - The Limit and Its Ground. QBism, Scientific Realism, and the Born Rule
AU - Harald A Wiltsche
PY - 2026
DA - 2026/09/01
PB - arXiv
DO - 10.48550/arxiv.2609.22159
UR - https://arxiv.org/abs/2609.22159
AB - QBists insist that theirs is a realist position while denying that the quantum formalism represents a mind-independent world. The insistence is hard to place. The realism debate is throughout a dispute about represented content, so a theory that denies standing in the representation relation appears not to take up a position within that debate at all. This paper examines the most developed attempt to make good on the QBist claim--David Glick's perspectival normative realism--and argues that it fails instructively. Glick seeks the ground of the Born rule's objectivity among states of affairs and construes an agent's perspective as a location within an already-constituted world; finding no state of affairs fit to bind every agent at once, he must book the ground as brute. Phenomenology supplies the third thing his picture lacks. A horizon is not a position within the world but the condition under which a world is given. Read as an agent's weighting--her curvature--of such a horizon, the quantum state is neither a defective description nor a brute posit, and the Born rule articulates the invariant lawfulness by which any sense confers a curvature at all.
ER -