The Cardinality of Experience Is Underdetermined by the Quantum State: A Constructive Case for a Consciousness-Primitive Interpretation

Quantum mechanics and the metaphysics of consciousness are usually pursued apart; this paper joins them with a result and an interpretation. The result: the number of unified subjects of experience — the cardinality of experience — is not fixed by anything operationally accessible to a localized perspective in a no-collapse setting; we exhibit this computationally and state it precisely. The significance of the result lies less in the underdetermination itself than in what follows from it: the decombination problem (the standard objection to cosmopsychism) and Everett's how-many-minds problem are the same underdetermination seen from opposite sides, meaning the dialectical cost is shared, not a special liability of consciousness-first views. The non-determination isolates the minimal posit every no-collapse interpretation must add. Taking that posit as ground yields a structural cosmopsychism on which a universal subject's self-relational structure is the Hilbert-space structure. Advaita Vedānta supplies illuminating labels for moves the view defines independently.