The Risk-Bearing Subject of AI-Related Existential Risk to Humanity: From Species Survival to the Realization of Subjecthood under Conditions of Human Civilization

This paper is a work of conceptual engineering on the risk-bearing subject of AI-related existential risk to humanity. It also has significance for social epistemology, philosophy of technology, and AI risk governance. Existing discussions usually understand “humanity” as the biological species *Homo sapiens*, and accordingly define the risk in terms of species extinction, permanent incapacitation, or future deprivation. This paper preserves the baseline status of that framework, but proposes a paradigm extension: while the risk-bearing subject remains humanity as an embodied species, the possible modes of existential harm to that subject should be extended from destruction or permanent incapacitation at the single level of biological survival to the irreversible or difficult-to-reverse weakening of the foundational conditions under which humanity realizes subjecthood within civilization. The central question of this paper is: when we say that AI may threaten “humanity,” what exactly is the “humanity” at risk? The paper distinguishes two basic layers of possible harm to humanity as the risk-bearing subject: the biological-survival layer and the civilizational-conditions layer. The former concerns the survival of humanity as an embodied species; the latter concerns humanity’s capacity, within an intergenerational common world, to know what is true, form judgment, bear responsibility, participate in institutions, and create meaning. Within the civilizational-conditions layer, the paper further identifies the category-calibration mechanism: the mechanism through which foundational categories such as truth, evidence, responsibility, subjecthood, value, and meaning are clarified, maintained, and revised. The philosophical kernel is not an independent entity, but the category-calibration mechanism internal to civilizational conditions that maintains the operability of foundational categories. AI may weaken humans’ substantive participation in the functional systems of civilization, or destabilize the calibration of foundational categories, through **deprivation by substitution** or **mediated reconfiguration**. The expanded definition proposed in this paper is as follows: AI-related existential risk to humanity refers to the risk, arising from the development, deployment, integration, or loss of control of AI systems, that AI may irreversibly destroy the human species; or render humanity permanently incapacitated, or otherwise permanently foreclose humanity’s future; or undermine—irreversibly or in ways that are difficult to reverse—the foundational conditions under which humanity, as an embodied species, realizes its subjecthood within civilization. Within this definition, risks to the realization of human subjecthood at the civilizational-conditions layer are constrained by **four thresholds**: they must act upon foundational civilizational conditions, possess cross-domain diffusion capacity, be capable of causing irreversible or difficult-to-reverse structural damage, and cause the first three forms of damage to converge into overall damage to humanity’s capacity as a future-oriented subject. What this paper provides is not a complete risk taxonomy, nor a technical control scheme or policy checklist, but an **ontological coordinate system** needed at the level of risk identification in AI safety, AI risk analysis, and AI governance. Before discussing specific risk types, governance pathways, or technical solutions, we must first clarify the risk-bearing subject called “humanity” and the possible modes of harm to it.