What do we mean by language? A pluralist map for the language sciences

The word language names several distinct objects across the language sciences: capacity, idiolect, communicative practice, population convention, named sociohistorical object, and formal system. Pluralist accounts (especially Santana's distinction among psychological, social, and abstract ontologies) show why monism fails but don't say when a proposed sense licenses inference or when evidence about one sense can travel to another. This paper adds a homeostatic property cluster (HPC) discipline: a sense earns realist standing where its properties are stabilized by identifiable mechanisms and project for a field's purposes; where the mechanisms diverge, the shared label doesn't license transfer. The map distinguishes three categories proper (population convention, named sociohistorical object, abstract formal system) from three neighbourhoods of substantively coupled constituent categories (capacity, idiolect, communicative practice). The payoff is diagnostic. The Casten / Pinker exchange over genomic evidence for spoken-language ability shows how developmental verbal-performance evidence gets read as evidence about a uniquely human language faculty; similar slippages arise when census recognition is read as convention, formal models as cognitive architecture, or analyst diagnostics as the object. The umbrella label remains useful for coordination, but the load-bearing scientific units are the categories and neighbourhoods, not the umbrella.