With Marc Artiga at the ECAP12 from 24 to 28 August 2026 in Madrid

Proper functions are used to explain why some hearts malfunction, why some neural states misrepresent, and why certain psychological and physiological conditions are considered disorders. We treat the question „What is it for something to have a specific proper function?“ as a real-kind question. We argue that proper functions — the proper function to Φ — constitute etiological natural kinds. From the explanatory roles proper functions play in philosophical and scientific projects, we extract three hallmarks: selectivity, normativity, and an existence-link. We then propose a minimal, reinforcement-based etiological core that satisfies these hallmarks. Building on this core, we identify a space of recurrent „modules“ concerning temporal profile, depth of iteration, competition, reproduction, and service embedding that sharpen selectivity and strengthen the normative and explanatory profile without altering the underlying kind. This framework unifies disparate etiological accounts, clarifies counterintuitive cases, and provides tools for adapting function concepts to different explanatory projects.