..................................................................................................................................ii Index of Tables. ....................................................................................................................vii Acknowledgments ...............................................................................................................xiv Chapter One. Introduction. Dialectal variation and diachronic change: Null and overt subject patterns in Dominican Spanish................................................................................... 1 1.1. Language variation and change in the generative tradition. .................................................................... 8 1.2. Language variation and change in the variationist paradigm. ............................................................... 14 1.3. The present study: Dominican Spanish in the context of language variation, language change and formal grammars. ........................................................................................................................... 18 1.3.1. The nature and limits of dialectal variation.................................................................................... 20 1.3.2. Language change and the Dominican variable pattern of subject expression................................ 40 1.3.3. Formal grammars and variable systems. ........................................................................................ 42 1.4. Organization........................................................................................................................................... 44 Chapter Two. Theoretical Background: The Null Subject Parameter.................................. 46 2.