Entropy Resistance as a Physical Criterion for Life: A Thermodynamic Framework

Life has traditionally been characterized through biochemical hallmarks—metabolism, heredity, evolution—but none of these mechanisms provide a substrate-independent physical boundary. We propose a criterion for living systems based on a single thermodynamic scalar: entropy resistance. A system is alive precisely when it sustains a strictly positive entropy resistance rate on an operationally defined boundary: R(t) ≡− dSsys(t)/dt >0. We derive this criterion from non-equilibrium thermodynamics, connecting it to the entropy balance˙ Ssys = σ−JS, where σ≥0 is irreversible entropy production and JS is entropy flux. Using fluctuation theorems and the Jarzynski equality, we show that sustained R > 0 requires external work input, consistent with Landauer’s principle. The criterion addresses classical edge cases (viruses, dormancy, autocatalysis), distinguishes active regulation from passive dissipation, and provides a falsifiable, substrate-independent detection protocol for astrobiology. We acknowledge coarse-graining dependence as a fundamental limitation—entropy resistance is observer-dependent through the choice of state-space partition—and propose maximum mutual information as a guiding principle for observable selection, while recognizing that practical implementations remain an open problem. The framework complements rather than replaces existing definitions, providing a necessary thermodynamic condition for sustained active organization.