What Physics Actually Closes: Causal Closure, Quantum Indeterminacy, and the Interpretive Asymmetry

Abstract: Physicalism's most common implicit defense against consciousness-first frameworks is the appeal to causal closure: if every physical event has a sufficient physical cause, there is no work for consciousness to do. Does physics deliver that closure? It does not. Classical mechanics provided deterministic closure; quantum theory replaced it with statistical constraint and outcome-level openness. Probability distributions are fixed, but which outcome actualizes is not — a feature of the textbook package of unitary evolution, Born rule, and projection postulate, which contains no outcome-selecting variable. Every reading that restores determination either replaces the projection postulate with a dynamics or removes definite outcomes, at a cost the package does not impose. The openness is two-layered: for which observable is measured, and when — von Neumann's Process 1 — the package supplies no rule at all, and whether anything in physics fixes that choice is itself the interpretive question. The founders agreed that the formalism alone does not produce definite outcomes; von Neumann and Wigner proposed that consciousness terminates the measurement chain. That reading has two forms: a finite-observer form, in which one mind's consciousness triggers collapse, and a ground form, in which consciousness is what there is and selection is the ground's in every event. The essay prices both against the rivals in their strongest versions, and shows that the finite-observer form was set aside on one cost weighed as fatal while its rivals' comparable costs were weighed as research problems — on grounds the physics does not supply. Keywords: causal closure · quantum mechanics · measurement problem · Born rule · Bell's theorem · wave function · consciousness · interpretive history · von Neumann · quantum indeterminacy · quantum Zeno effect Part of the Return to Consciousness research program — 30 philosophical essays exploring consciousness-first metaphysics. Full project: https://returntoconsciousness.org/