 How does the anti-realist defend conceptual relativity? One way is by arguing that there can be two complete theories of the world which are descriptively equivalent yet logically incompatible from the realist’s point of view. For example, theories of space-time can be formulated in one of two mathematically equivalent ways: as an ontology of points, with spatiotemporal regions being defined as sets of points; or as an ontology of regions, with points being defined as convergent sets of regions. Such theories are descriptively equivalent since mathematically equivalent and yet are logically incompatible from the realist’s point of view, anti-realists contend [Putnam 1985, 1990].