We are one humanity, but seven billion humans. This is the essential challenge of global ethics: how to accommodate the tension between our universal and particular natures. This tension is, of course, age-old and runs through all moral and political philosophy. But in the world of the early twenty-first century it plays out in distinctive new ways. Ethics has always engaged twin capacities inherent in every human: the capacity to harm and the capacity to help. But the profound set of transformations commonly referred to as globalization—the increasing mobility of goods, labor, and capital; the increasing interconnectedness of political, economic, and financial systems; and the radical empowerment of groups and individuals through technology—have enabled us to harm and to help others in ways that our forebears could not have imagined. What we require from a global ethic is shaped by these transformative forces; and global ethics—the success or failure of that project—will substantially shape the course of the twenty-first century.