This important new work explores the key linguistic issues of syntactic theory, comparative syntax, and the study of language acquisition. Written by Luigi Rizzi, one of the discipline's leading authorities, some of the essays collected here have already been profoundly influential in their field. Others are published here for the first time, and present important new directions for linguistic research. the theory of principles and parameters, with special reference to the properties and functioning of the pronominal systems the theory of locality the detailed study of syntactic configurations, leading to a refined cartography of structural positions the theory-conscious comparative study of language acquisition and language development This book represents an essential text for any linguist with a particular interest in syntax and language acquistion.