Numerous difficulties arising in connection with developing an ontology for linguistic entities can be thought of as manifestations of a more general problem, aptly characterized by David Lewis (1975) as a tension between two conflicting conceptions of language. On the one hand, our best theories model languages as abstract semantic systems—roughly, functions assigning meanings to expressions. On the other hand, we think of languages as contingent and changing social constructs—both grounded in, and grounding, various social relations and institutions of human (...) beings. There are various ways in which these conceptions appear to be in conflict. For instance, if languages are set-theoretical entities—as our best logical and linguistic theories would have it—how do we account for the fact that they change? Or that they could have been different in various respects? And how do we provide principled and noncircular conditions for set-membership, when there appears to be nothing in common to all tokens of the same expression other than belonging to the same type? This paper aims to develop an ontology of linguistic entities—specifically, of languages and linguistic communities—that can resolve these apparent tensions. (shrink)