Cross-Substrate Experiential Continuity Is Observationally Underdetermined: An Independent Recovery of HORIZON Ω from the Mind-Uploading Problem

Proposals for whole-brain emulation and mind uploading commonly treat the preservation of psychological organization, autobiographical memory, or functional dynamics as relevant criteria for determining whether a person survives transfer to a non-biological substrate. This paper identifies a prior epistemic problem that remains unresolved even under an idealized scenario in which technological limitations are removed. We introduce Experiential Continuity Underdetermination (ECU): informational preservation, psychological continuity, subsequent algorithmic dynamics, and even the possible presence of subjective experience at the destination do not independently discriminate between continuation of the same first-person experiential center and emergence of a new experiential trajectory possessing the informational organization of the source. A non-destructive cross-substrate branching experiment makes this underdetermination explicit. Competing experiential-continuity hypotheses can remain compatible with the same autobiographical, behavioral, functional, and first-person reports. Destruction of the biological branch adds no observation of the alleged transition. ECU entails neither that subjective experience is transferable nor that it is non-transferable. Its result is epistemic rather than ontological: under the specified observational architecture, the scientifically warranted answer is “we do not know.” This analysis independently recovers HORIZON Ω, an epistemic architecture previously developed within HibriMind through analyses of cosmological observability, biological death, and structural limits of empirical inquiry. The present derivation provides independent conceptual convergence from the problem of cross-substrate experiential continuity.