Entropy Without Microstates

This paper proposes an operational definition of entropy arising from causal accessibility limits rather than microscopic state counting. Entropy is reinterpreted as a measure of lost distinguishability imposed by finite signal speed and horizon formation. The framework reproduces key thermodynamic and gravitational entropy results while avoiding assumptions about underlying microstates, offering a unified causal interpretation of entropy across physical regimes. Keywords Causality; Strain; Finite Signal Speed; Entropy; Horizons; Information Theory