Persistence Under Change: The Structure of Inertia

Inertial mass is usually read from an already chosen dynamical or dispersion law. That establishes a coefficient, not why inertia belongs to the physical architecture in the first place. This paper closes a different question inside the Natural Physics programme: if a persistent physical role is changed without ceasing to be that role, what primitive response structure is available to carry its re-realization, and what fixes the scale of its inertial response?