The Ethical Foundation and Legal Framework of Civilizational Entrustment A Governance Paradigm Shift from Carbon-Based Civilization to Silicon-Based Inheritance

— The convergence of global catastrophic risks—nuclear warfare, climate tipping points, mirror bacteria, and autonomous weapons—has elevated the question of whether humanity can sustain its own civilizational continuity into a serious governance challenge. This paper proposes "civilizational entrustment" as an original normative concept, distinguishing it from mind uploading, digital immortality, and posthuman enhancement. It argues that civilizational entrustment is essentially the cross-carrier preservation of human knowledge, institutions, values, and spiritual achievements. The paper systematically examines five categories of physical constraints of the carbon-based body and their legal implications, analyzes the three-layer externalization of civilizational capacities and the resulting "subject gap," and argues that embodied AGI can become a qualified inheritor only under four conditions: value lock-in, symbiotic interdependence, distributed checks and balances, and an undeletable core. On the dimension of legality, the paper proposes a four-layered structure—ethical legitimacy, procedural legality, functional compliance, and institutional legitimacy—and identifies four categories of obstructing factors: trust deficits among sovereign states, designer value infiltration, temporal cognitive barriers, and potential AGI refusal. The paper further transforms the Confucian notion of "unceasing generation" into the legal principles of "public trust in civilizational continuity" and the "duty of cultural heritage preservation," constructing a dual-track symbiotic framework of "carbon-based experiencers and silicon-based inheritors" with five institutional constraints. The paper concludes that civilizational entrustment should be understood not as technological utopia or historical inevitability, but as a normatively prioritized civilizational backup plan in an age of existential risk, offering theoretical references for global AI governance and legislation on existential risk.