Discourse and Syntax in Linguistic Change: Decline of Postverbal Topical Subjects in Serbo-Croat

The extensive discussion of the principles of word order change in the last decades has resulted in a number of proposals on how to deal with the mechanisms and the motivation for this kind of diachronic development (see e.g. Lightfoot 1999 for an overview). The proposed solutions range from the allegedly universal principle of harmonic branching (Vennemann 1975) and adaptation to human parsing capacities (Aitchinson 1979, Hawkins 1990, 1994) to switches from one parameter setting to another (e.g. Lightfoot 1979, Kroch 1989). What seems to be common to all the different approaches to word order change is that they take two finite states of grammar as their starting points (the initial state X and the final state Y) and try to account for the stage between X and Y as a transitional state in which speakers can freely decide between at least two different grammatical choices, due either to the existence of more than one grammar in the internal language of the speakers (Kroch 1989, Pintzuk & Taylor 2006), or to the optionality of derivations within one grammar (Wurff 1997). The present paper deals with a word order change that cannot be attributed to syntactic processes and is therefore impossible to phrase in terms of competing grammatical choices. Postverbal topical subjects (PTS), i.e. subjects with topical interpretation placed to the right of the verb, have been attested throughout the history of Serbo-Croat (SC)1 and