Nationalism is a dominating force in contemporary politics, but political philosophers have been markedly reluctant to discuss, let alone endorse, nationalist ideas. In this book, David Miller defends the principle of nationality. He argues that national identities are valid sources of personal identity; that we are justified in recognizing special obligations to our co-nationals; that nations have good grounds for wanting to be politically self-determining; but that recognizing the claims of nationality does not entail suppressing other sources of personal identity, such as ethnicity. Finally, he considers the claim that national identities are dissolving in the late twentieth century. This timely and provocative book offers the most compelling defense to date of nationality from a radical perspective.