The European Commission has claimed that 'Solidarity is part of how European society works...'. But how are we to understand solidarity, and what are its implications to Government policy? This book addresses the question of what solidarity might mean today and its relevance to the purposesof the European Union and the way it functions. Is solidarity just a slogan or can it have meaningful legal and policy content? This book brings together contributions from leading scholars in law, politics and sociology to discuss an idea that is coming under fresh scrutiny at a time when the EU'sdirection following the implementation of the Lisbon Treaty is hotly debated. The book engages with both the content and limitations of solidarity as a concept in political and legal debate, and its application to specific fields such as migration, education and pensions policies.The book provides a thoughtful and provocative analysis of the power and potential of solidarity, applying a sceptical and rigorous assessment of the conditions necessary for it to make a difference to the European political and legal space at a time when traditional manifestations of nationalsolidarity (e.g. in health care) are perceived to be under threat from EU market liberalization policies. A number of contributions consider whether an EU concept of solidarity is possible and how that might affect the balance between market and social priorities for the Union's future.If the EU is to be more than just a market, promoting solidarity as a value and a principle has a key role. This rich collection of essays explores how solidarity might fulfil its status as a core value for the Union.