This book introduces readers to the concepts of political philosophy. It starts by explaining why the subject is important and how it tackles basic ethical questions such as 'how should we live together in society?' It looks at political authority, the reasons why we need politics at all, the limitations of politics, and whether there are areas of life that shouldn't be governed by politics. It explores the connections between political authority and justice, a constant theme in political philosophy, and the ways in which social justice can be used to regulate rather than destroy a market economy. David Miller discusses why nations are the natural units of government and whether the rise of multiculturalism and transnational co-operation will change this: will we ever see the formation of a world government?