Kun Yuan

This paper develops an ontological and conceptual-engineering framework for understanding AI-related human existential risk. As AI systems become more capable, more general-purpose, more agentic, and more deeply embedded in human knowledge production, institutional processes, judgment formation, and technological development, AI risk can no longer be understood merely as a problem of model performance, product safety, or engineering governance. In frontier technical contexts, AI is increasingly used to assist code generation, model evaluation, research automation, and the development of AI systems themselves. In public-ethical contexts, AI is also increasingly understood as posing categorical challenges to human dignity, responsibility, freedom, the common good, and the self-understanding of human societies. These developments reopen the question of human existential risk. Yet in many discussions of AI risk, a more basic question remains insufficiently clarified: when we say that AI may pose an existential risk to humanity, what exactly is the “humanity” that is at risk? This paper argues that AI-related human existential risk should not be assessed solely in terms of whether *Homo sapiens*, as a biological species, is physically destroyed, permanently disempowered, or deprived of its future. Human beings certainly exist as a biological species, but humanity also exists as a civilizational subject: an intergenerational common world constituted by language, knowledge, institutions, responsibility, truth, agency, value, and meaning. If AI does not directly destroy the human species, but irreversibly weakens the basic conditions under which humanity can continue to exist as a civilizational subject, then this form of risk should also be included within an expanded understanding of AI-related human existential risk. To develop this claim, this paper distinguishes three nested layers: the human species as the biological substrate of civilization; human civilization as the intergenerational common operating environment formed by the species; and philosophy as the reflective kernel through which civilization defines and revises its foundational categories. The human species provides the biological substrate of civilization. Human civilization enables the species to become a collective subject capable of knowledge, judgment, responsibility, transmission, and meaning-making. The philosophical kernel supplies foundational categories—such as truth, evidence, responsibility, agency, value, and meaning—that are presupposed by civilizational systems such as science, law, politics, education, economy, culture, and the arts. This paper uses a functional hardware–kernel–distribution analogy to clarify the relation among these layers. The human species may be compared to hardware; philosophy to a kernel; and human civilization to a distribution or complete operating environment running on a biological substrate and structured by a philosophical kernel. The analogy is neither literal nor historical. Its purpose is to illuminate the layered structure of human existence: hardware may remain intact while the system fails to operate well; a distribution may still boot while the kernel is damaged; the application layer may continue to flourish while foundational categories deteriorate. It concludes by proposing an expanded definition: AI-related human existential risk arises not only when AI threatens the biological survival of humanity, but also when AI irreversibly weakens the civilizational conditions under which humanity can continue to exist as a subject of truth, responsibility, agency, and meaning. This definition does not attempt to classify all AI-driven social change as existential risk. Rather, it provides a conceptual basis for further analysis of the major dimensions of human existential risk in the age of AI and AGI.