Empirical Adequacy Should Not Constitute a Defence of the Proximate-Ultimate Distinction

Ernst Mayr’s distinction between proximate and ultimate causes has been under sustained critique from advocates of the Extended Evolutionary Synthesis, who hold that it is poorly suited to reciprocal and developmental causes of evolutionary change. I argue that this debate has stalled in recent years because two distinct issues have been run together. The semantic issue concerns the empirical adequacy of the proximate-ultimate distinction; the stance issue concerns its wider explanatory and methodological implications. I settle the semantic issue in Mayr’s favour by way of a doctrine that evolutionary extenders have largely overlooked: proximate bias. Supplemented by a substrate-neutral transmission-fidelity criterion for ultimate causation and a time-indexing procedure for causal loops, the distinction survives niche construction, constructive development, epigenetic inheritance and developmental bias. I then argue that this verdict is no defence of the proximate-ultimate distinction. Empirical adequacy and explanatory value are orthogonal: a framework may individuate biological causes correctly and remain poorly suited to the explanatory work at hand. The semantic victory I supply is worth conceding precisely because it moves the wider debate forward.