The Structural Necessity of Valuation: Why Biological Explanation Requires More Than Selection

Biological explanations successfully describe how living systems persist, reproduce, and adapt under energetic cost, yet they routinely defer or bracket the question of why such costly persistence occurs rather than collapse into equilibrium. This paper isolates the minimal structural requirements any coherent answer to this explanatory target must satisfy. We argue that explanations of persistence-under-cost necessarily presuppose two structural primitives: valuation, understood as an internal discriminative orientation toward maintaining non-equilibrium states, and contingency, understood as a genuine possibility space in which alternative outcomes are admissible. Valuation is empirically visible only where work is paid against entropic gradients; contingency is required to render preference non-trivial. Removing either primitive collapses explanation into tautology or vacuity. We further propose a dual-aspect account in which these primitives admit two explanatory registers. In the exterior register, valuation and contingency appear as selection, error correction, and stochastic variation; in the interior register, they correspond to experienced valuation and freedom. These registers are structurally isomorphic but explanatorily non-redundant. On this view, natural selection functions as a filter rather than a driver, externalizing but not replacing valuation. The contribution of the paper is not a new mechanistic model, but a constraint claim: any adequate biological explanation of persistence, reproduction, or sacrifice under cost must implicitly or explicitly contain valuation and contingency. This reframes debates about teleology, agency, and reduction by identifying the structural conditions of intelligibility for biological “why” explanations.