Abstract

This paper develops friction as an epistemic structural concept for stability under finite conditions. Friction is not understood as a mere disturbance or as technical energy loss due to rubbing, but as a boundary signal: it indicates where stabilization under load is only possible with disproportionately increasing costs, or where stabilization loses its load-bearing capacity. Starting from an analytic distinction between the subjective, intersubjective, and functional-empirical domains, the paper works out a unified functional logic of friction. Friction makes boundaries visible, translates load into cost profiles, and generates selection effects over time between competing stabilization patterns. Boundaries are understood strictly functionally, not as ontological barriers, but as markers of the limited load-bearing capacity of concrete models, routines, or institutions. Friction thus functions as a diagnostic instrument for validity under load: it enables early detection of overstretching, externalization, and blocked revision, without generating ontological or normative ultimate claims. The paper develops a typology of forms of friction and derives friction competence as a principle of design and diagnosis for epistemic, social, and technical systems. Friction therefore appears not as the opposite of order, but as its functional condition.