This brilliant, cross-disciplinary work challenges the separatist doctrines which have come to dominate our understanding of the world. Appiah revives the ancient philosophy of Cosmopolitanism, which dates back to the Cynics of the 4th century, as a means of understanding the complex world of today. Arguing that we concentrate too much on what makes us different rather than recognizing our common humanity, Appiah explores how we can act ethically in a globalized world.