This book examines the nature of human language and the ideology of linguistic legitimacy - the common set of beliefs about language differences that leads to the rejection of some language varieties and the valorization of others. It investigates a broad range of case studies of languages and dialects which have for various reasons been considered 'low-status' including: African American English, Spanglish, American Sign Language, Yiddish, Esperanto and other constructed languages, indigenous languages in post-colonial neo- European societies, and Afrikaans and related language issues in South Africa. Further, it discusses the implications of the ideology of linguistic legitimacy for the teaching and learning of foreign languages