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. This essay examines whether physics actually delivers that closure. It does not. Classical mechanics provided deterministic closure — given initial conditions and laws, every subsequent state is fixed. But quantum theory replaced this with something structurally different: statistical closure with outcome-level openness. The Born rule specifies which outcomes are possible and with what probability; it is silent on which specific outcome actualizes. This outcome-selection degree of freedom is not a gap in current knowledge — it is a structural feature of the formalism. The essay then examines the interpretive history: the founders of quantum mechanics immediately recognized that consciousness and measurement could not be cleanly separated — the first and most parsimonious interpretation. What followed — many-worlds, decoherence-as-solution, hidden variables, objective collapse — were alternatives designed to remove consciousness from the picture, each introducing greater ontological cost than the interpretation it replaced. The same asymmetric methodological restraint this project diagnoses in consciousness studies operates within the foundations of physics itself. Keywords: causal closure · quantum mechanics · measurement problem · Born rule · wave function · consciousness · interpretive history · von Neumann · quantum indeterminacy Part of the Return to Consciousness research program — 26 philosophical essays exploring consciousness-first metaphysics. Full project: https://brunoton.github.io/return-to-consciousness/