"The mass movement of people across the globe constitutes a major feature of world politics today." "Whatever the cause of the movement, the governments of western states see this 'torrent of people in flight' as a serious threat to their stability. The scale of this migration indicates a need for a radical re-thinking of both political theory and practice, for the sake of political, social and economic justice." "This book argues that there is at present a serious gap between the legal and social practices of immigration and naturalisation in liberal democratic states and any theoretical justification for such practices that can be made within the tradition of liberal political philosophy. How can liberal states develop institutions of democratic citizenship and at the same time justifiably exclude 'outsiders' from participating in those institutions? The book examines various responses to this contradiction within the liberal tradition, and finds none of them satisfactory - there are no consistently liberal justifications for immigration control and this has serious implications for both practice and theory." In seeking an answer to the question 'what can morally justify the exclusive membership practices of modern states?' Phillip Cole offers the first comprehensive overview of various positions within political philosophy on immigration. His original text provides a radical critique of these positions and will be of interest to students of Political Philosophy, International Relations, Social Policy and Law.