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 the theory of syntax and universal grammar and for the study of the interface between syntax and discourse. It is particularly evident in the phenomenon of negative polarity - the existence of words and phrases which occur only in the presence of negation and in semantically related contexts. The exploration of negation and polarity phenomena and their implications for the syntax/semantics interface and other aspects of linguistic theory are the main themes of this book.