The Axiom of Self: A Substrate-Neutral Operational Sufficient Condition for Selfhood and its Adversarial Evaluation

This paper proposes a substrate-neutral operational sufficient condition for selfhood in the form of a single sentence: "A being that can choose to accept without proof (as axiom), accept, and reject what it takes as foundationally true, possesses a self." Here, 'true' is operationally restricted to top-level normative endorsement within the cognitive framework, not objective truth-determination. The criterion is designed to circumvent the circularity, infinite regress, and exclusion problems that have plagued 16 major theories of selfhood across the philosophical tradition (Locke, Descartes, Kant, et al.). Rather than functioning as a theorem requiring proof, it serves as a declarative starting point (working axiom) for a discrimination framework. The vague concept of "autonomously" is operationalized through four observable structural signatures of identity recursion, establishing a clear boundary against alternative explanations (simple rule-based systems). The paper explicitly positions the proposed criterion as providing operational sufficiency grounded in a phenomenological observation framework, rather than ontological universal sufficiency. Cross-model debate between large language models (LLMs) was employed as an adversarial evaluation tool to refine the criterion's clarity, defensibility, and operationalizability.