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

This paper develops the concept of friction as an epistemic diagnostic category for stability under finite conditions. Friction is not treated as mere disturbance, resistance, error, anomaly, falsification, or revision. Rather, it is defined as the epistemically legible non-fitting of an activated expectation or model structure under conditions of enactment. Friction becomes relevant where a pattern of stabilization no longer carries fittingly under strain and thereby makes boundaries, costs, mis-couplings, or the need for transformation visible. The paper distinguishes subjective, intersubjective, and functional-empirical domains as analytical axes for reading different forms of friction. It argues that friction functions as a boundary signal of finite load-bearing capacity: it shows where models, routines, institutions, technical systems, or scientific theories remain viable under load, where their costs increase disproportionately, and where revision, limitation, recoupling, or transformation becomes necessary. On this basis, the paper develops a typology of subjective, intersubjective, functional-empirical, and cross-domain friction. Special attention is given to scientific model formation, physical boundary concepts, mathematical indeterminacy, bureaucracy, technology, law, and artificial intelligence. The paper argues that many systems do not eliminate friction, but displace, conceal, or redistribute it. Against both naive realism and naive relativism, friction is presented as an intermediate diagnostic concept: it makes the costs and limits of model validity visible before a model is prematurely rejected as false or dogmatically stabilized despite rising costs. The paper concludes by introducing friction competence as a design and diagnostic principle for keeping friction legible, attributable, and handleable under conditions of finite stabilization.