Wiltsche Shows Glick's Perspectival Realism Cannot Ground QBist Born Rule Without Brute Facts

Wiltsche examines Glick's attempt to reconcile QBism's agent-centered probabilities with scientific realism. Glick locates objectivity in shared normative constraints across perspectives yet finds no mind-independent state of affairs that binds every agent simultaneously. This forces him to treat the Born rule's universality as brute. The critique reveals that any realism debate centered solely on represented content cannot accommodate a formalism that explicitly denies representation of a mind-independent domain.

Phenomenology supplies the missing ground by reframing the quantum state as an agent's curvature of a horizon rather than a defective description. Horizons are conditions for any world to appear, not positions within it. The Born rule then expresses invariant lawfulness across all such curvatures. This move preserves QBism's rejection of third-person ontology while explaining why probabilities remain objective for every agent.

The analysis connects to earlier QBist work by Fuchs and Mermin on personalist probabilities and to broader debates on scientific realism after Bell and EPR. It also highlights why purely epistemic or information-theoretic interpretations struggle with normativity without additional structure. Future engagement with Merleau-Ponty or Husserl on embodied perspective could strengthen the phenomenological alternative.

Empirical tests remain distant, but the framework predicts that agent-dependent measurement contexts will continue to show Born-rule statistics without requiring hidden variables or collapse mechanisms.