Loss is the ontological primitive that defines the boundaries of the moral field: any subject capable of irreversible loss belongs to this field, regardless of whether it bears obligations or is their object. This paper does not attempt a complete metaethical foundation. The more modest aim is to show that loss is the structurally prior grounding — one that does not collapse under pressure from alternatives. The central defect of existing criteria — sentience, rationality, autonomy — is a grounding failure: they identify morally relevant properties without explaining why those properties generate reasons at all. The loss criterion provides that explanation and is defended through a structural priority argument, not as a logically necessary claim. Any alternative grounding either denies normativity altogether or reintroduces loss implicitly. The transition from normative evaluability to moral considerability proceeds through a minimal bridge of practical reasons. A normatively organised system cannot be exhaustively captured by purely causal description — a refutation of this claim would require a system whose behaviour involves no reference to goal states at all. The paper positions the is-ought transition as an inter-level transformation rather than a reduction. Moral membership in the field is not procedurally empty: qualifying systems receive default integrity status, placing the burden of justification on whoever would degrade their enabling conditions. The aggregation algorithm includes an absolute lexical shield: complete destruction of enabling conditions cannot be justified by performance gains.
Volodymyr Hlynskyi (Mon,) studied this question.