Book excerpt: Age structures our social fabric - our institutions, relationships, obligations, and entitlements. There is an age for voting, an age for working, and an age when one is expected (and sometimes required) to retire. Each stage of life also brings with it specific forms of social risks andvulnerabilities. Consequently, numerous and multidimensional inequalities arise between age groups. How should we respond to these inequalities? Are they akin to gender or racial disparities? Or is there something distinctive about age that mitigates the need for concern?Justice Across Ages answers these questions and proposes a theory of justice between age groups and co-existing generations. Written at the intersection of philosophy and public policy, the book explores the principles that should guide a fair distribution of goods like jobs, healthcare, income, andpolitical power among people at different stages of their life. It draws upon a range of cases to develop normative tools that help distinguish objectionable inequalities from acceptable ones and explores a variety of policy remedies.Like many political philosophers have, it may be tempting to assume that, since people experience the social position of different age groups throughout their lives, all that matters is that persons are equal over their complete lives. This book shows that we should resist this view and makes theproposition that many diachronically 'equal' arrangements are in fact unjustly unequal. In particular, we should view with suspicion many widely tolerated forms of age-based social hierarchies, such as the infantilization of young adults and older citizens, the political marginalization of teenagersand young adults, the exploitation of young workers through precarious contracts and unpaid internships, and the spatial segregation of elderly persons. If we ever are to live in a society that treats its members as equals, we need to pay attention to how age membership can alter our socialstanding. This view has important implications for how we should think of the political and moral value of equality, for how our social and political institutions should be designed, and also for how we should conduct ourselves in a range of contexts including the family, the workplace, and theuniversity classroom.