Abstract

Extended entities have boundaries of two different sorts: those that do, and those that do not correspond to physical discontinuities. Call the first sort (coastlines, the surface of your nose) bona fide boundaries; and the second (the boundary of Montana, the boundary separating your upper from your lower torso) fiat boundaries. Fiat boundaries are found especially in the geographic realm, but are involved wherever language carves out portions of reality in ways which do not reflect physical discontinuities. These ideas are applied to the treatment of cognitive categorization, of the semantics of vagueness, of Quine’s indeterminacy thesis, and of standard ontological problems such as Tibbles’ tail.