Friction: Boundary Signal of Finite Load-Bearing Capacity in Subjective, Intersubjective, and Functional-Empirical Domains

This paper develops friction as an epistemic structural concept for stability under finite conditions. Friction is not understood as mere disturbance, technical friction loss, or refutation, but as a boundary signal: it indicates where stabilization under strain remains possible only with increasing or disproportionately rising effort.Starting from the distinction between subjective, intersubjective, and functional-empirical domains, friction is defined as a diagnostic variable for validity under load. It makes boundaries visible, translates strain into cost profiles, and shows over the course of a process which patterns of stabilization remain load-bearing, must be transformed, limited, or abandoned. Boundaries are understood here in a strictly functional sense: not as ontological barriers, but as markers of the limited load-bearing capacity of concrete models, routines, institutions, or technical procedures.The paper distinguishes friction from disturbance, anomaly, falsification, and revision. Not every difficulty is friction, and not every friction means that a model is false. Friction arises where an activated expectation or model structure fails to carry in a fitting way under conditions of enactment. It may indicate overextension, incorrect domain assignment, changed conditions of strain, or coupling errors between appearance, model, and context.On this basis, the paper develops a typology of subjective, intersubjective, functional-empirical, and cross-domain forms of friction. It shows how technical, organizational, legal, and AI-based systems often do not eliminate friction, but displace, conceal, or rapidly redistribute it. Finally, friction competence is introduced as a principle of design and diagnosis: systems should not eliminate friction as much as possible, but keep it legible, attributable, and handleable in such a way that stability under strain can be tested, limited, or transformed.