Negation is a central feature of language and cognition, interacting with all areas of grammar as well as with the philosophy of language. Whereas there is a cross-linguistic uniformity in logical and semantic aspects of negation, there is a diversity of syntactic and morphological forms and rules. This asymmetry in function and form poses problems for syntactic and universal grammar theory and for the study of the interface between syntax and discourse. It is particularly evident in negative polarityDSwords and phrases which can appear only in negative sentences. The exploration of negation and negative polarity phenomena and their implications for linguistic theory are the main themes of this book.