Defining Boundary Knowledge Without Ontology: Tier-8 Limits and Admissibility in the Paton System

Scientific frameworks routinely encounter boundaries that resist internal description, including singularities, horizons, undecidable regimes, and scale limits. These regions are often treated either as incomplete ontology or as prompts for speculative extension. This paper argues for a disciplined alternative: boundary regions may require precise definition without descriptive content. Within the Paton System, Tier-8 represents such a limiting condition. It is not an ontological layer, but a formally defined stopping boundary inferred from breakdown behaviour, curvature dominance, and constraint saturation. The contribution is methodological rather than physical: it establishes boundary knowledge as negative, limiting, and admissibility-governed. The framework preserves continuity, prevents speculative overreach, and formalises a principled stopping rule fully compatible with existing scientific theories.