The Structural Origin and Uniqueness of Planck's Constant

This work constructs an intrinsic notion of structural action without relying on physical models, dynamical laws, Hilbert spaces, or quantization assumptions. Structural admissibility under intrinsic second variation enforces a nonzero lower bound Rmin that cannot be subdivided further. Minimal structural action is therefore a requirement of the structure itself, not an empirical observation. The lower bound is unique, representation independent, and stable across all realizations. No probabilistic or microscopic framework is needed. When represented externally, this invariant appears as the constant h. Quantization is thus the external expression of structural minimality rather than its cause.