The 19th-century European notion of the one people-one language nation as the ideal state has been a very pervasive influence in spite of the fact that most countries in the world today are multilingual, that is they contain ethnic groups in contact and not infrequently in competition. Such thinking has held implications for the setting of language policies, from hanging a wooden clog around the neck of a child heard speaking Occitan in Southern France to the considerable budgeting in Ireland for the promotion of Irish. In this book, Paulston presents an analytical framework for explaining and predicting the language behaviour of social groups as such behaviour relates to linguistic policies for minority groups. She argues that a number of factors must be considered in the understanding and establishment of language policies for minority groups: (1) if language planning is to be successful, it must consider the social context of language problems, (2) the linguistic consequences for social groups in contact will vary depending on the focus of social mobilization, i.e. ethnicity or nationalism, and (3) a major problem in the accurate prediction of such linguistic consequences lies in identifying the salient factors which contribute to language maintenance or shift, i.e. answering the question “under what conditions?”. Part I outlines and discusses the analytical framework, beginning with a general consideration of language problems and language policies and of the social factors which contribute to language maintenance and shift. The author continues to discuss four distinct types of social mobilization, which under certain specified social conditions result in different linguistic consequences: ethnicity, ethnic movements, ethnic nationalism, and geographic nationalism. The argument is that such an understanding is vital to helpful educational policies and successful language planning in general. Part II contrasts and compares a number of case studies for clarification of their diverse courses of mother tongue maintenance. It particularly seeks to illustrate the type of social mobilization discussed in Part I and to understand the social conditions which influence and alter the effects of the type of social mobilization.