When Vagueness Crystallizes: Functional Stabilization and the Ontology of Ordinary Predicates

Abstract This paper argues that certain vague predicates can undergo a process of functional stabilization, resulting in a form of ontological fixation despite the absence of sharp boundaries. While epistemicism, as defended by Timothy Williamson, maintains that vagueness is compatible with precise but unknowable boundaries, it leaves underexplored how ordinary predicates achieve practical and explanatory stability in scientific and everyday contexts. I propose that some vague terms—particularly those embedded in stable causal structures—become rigidly fixed through functional integration into the physical world. This stabilization is not merely semantic or pragmatic but grounded in structural invariance and causal continuity. Drawing on metaphysical accounts of natural properties associated with David Lewis and related work in structural metaphysics, I argue that vague predicates can, under appropriate conditions, crystallize into ontologically stable categories. The resulting view preserves the central insights of epistemicism while supplementing it with an account of how vague language interfaces with the world’s causal architecture. Vagueness, on this model, is not always constitutive instability; in certain cases, it represents a transitional stage prior to structural fixation.