Subject-auxiliary inversion: A natural category

This article argues that subject auxiliary inversion in English (SAI) provides an example of a syntactic generalization that is strongly motivated by a family of closely related functions. Recognition of the functional properties of each subconstruction associated with SAI allows us to predict many seemingly arbitrary properties of SAI: e.g., its (partial) restriction to appear in main clauses, the fact that the inversion only involves the first auxiliary, and the fact that its use in comparatives is more limited. The dominant feature of SAI, being nonpositive, is also argued to motivate the syntactic form of SAI. It is suggested that attention to the rich data inherent in language and to findings in categorization research simultaneously serves to reinforce and benefit our understanding of both language and categorization more generally.