That language structure is fairly resistant to change in situations of language contact has been widely held among students of linguistics for a long time, presumably rooted in Ferdinand de Saussure's distinction between “internal” and “external” linguistics. In this tradition, Edward Sapir managed to persuade a generation of American linguists that there were no really convincing cases of profound morphological influence by diffusion (Danchev 1988: 38; 1989). While it was conceded that certain parts of language, such as phonology and the lexicon, tend to be affected by pressure from other languages, grammar was considered to be immune to major restructuring. More recent studies have shown that this view is incorrect. As some of these studies have demonstrated, essentially any part of language structure can be transferred from one language to another (see especially Thomason & Kaufman 1988: 14; Harris & Campbell 1995: 149–50; Aikhenvald 2002: 11–13). In fact, there is substantial evidence to support this general claim; still, it would seem that such an “anything-goes hypothesis,” as Matras (1998a: 282) refers to it, is in need of modification: There is at least one domain of language use and language structure where a significant constraint on linguistic transfer from one language to another can be observed, namely the domain of grammatical meanings and structures.

The main purpose of this book is to demonstrate that the transfer of grammatical meanings and structures across languages is regular, and that it is shaped by universal processes of grammatical change.