There has been a vogue during recent decades for the formulation of theoretical models in linguistics. These are sometimes suggested on the basis of data in a very limited set of languages, but are then put forth as general accounts of how all human languages operate. When unexpected data from new languages come to notice there can be a number of reactions: ignore it; reinterpret the data so that it fits the theory; revise the theory so that it does explain the data; acknowledge that the theory cannot explain the data and as a consequence abandon it.

In this short Appendix I shall comment on some of the ways in which some theoretical models have approached ergativity. My treatment is partial and selective; a full discussion of this topic would require a book in itself.

Foley and Van Valin's (1984) Role and Reference Grammar (RRG) is one of the few theoretical models to have been formulated with full knowledge of a range of ergative phenomena. Their discussion of syntactic ergativity, pivots, passives and antipassives is informed and useful. My one reservation is that they do not always make a sufficiently clear distinction between syntax and semantics, sometimes talking about syntactic operations applying to semantic categories (I prefer to specify that syntactic operations apply to syntactic categories and then to discuss the semantic correlates of both the categories and the operations.) Lexical Functional Grammar (LFG) has also paid some attention to the various kinds of ergativity; see, for instance Kroeger (1991a, b) for an LFG treatment of ergativity in Tagalog.