For decades, linguists have treated code-switching as a -special- language of its own, and devised many constraints accounting for code-switching patterns in various language pairs. This book argues that code-switching is governed by the same constraints as those governing native -pure- languages, and hence code-switching data provide a -window- to our language faculty. Although some other works have already suggested that code-switching and -pure- languages are governed by the same syntactic rules, this book goes a step further and explores the possibility that both are constrained by the same system in terms of syntax, production, and pragmatics."