Mass, Inertia, and Wave–Particle Duality Are Not Fundamental

This paper argues that mass, inertia, and wave–particle duality need not be fundamental axioms of physics. Within a strictly causal, protocol-locked IR framework, we show that whenever a measured force-like readout depends on an internally relaxing mode with finite response time, an acceleration-proportional term emerges generically in the low-frequency expansion. The corresponding inertial coefficient is identified as a response parameter proportional to the relaxation time, not as an intrinsic property of particles. Bounded saturation of the relaxation time prevents divergence and ensures stability without introducing microscopic cutoffs or new ontology. Within the same response calculus, wave- and particle-like behaviors are reinterpreted as distinct dynamical regimes controlled by the single dimensionless parameter ωτ, eliminating the need for a fundamental duality. The framework introduces no new fields, particles, or scales, and is formulated with explicit calibration gates and falsifiable kill conditions.