Sparked by the recent threats to an open and pluralistic society in both Europe and the United States, The Fragility of Tolerant Pluralism is an exploration of social and political philosophy. Using the early sixteenth century as a lens to view our own struggles with multiple visions of a good society, the book looks at tolerant pluralism in the light of the twin challenges of resurgent nationalisms and Islamist terrorism. The book makes a case not only for social toleration, but for a deep pluralism that both values and celebrates difference. It also suggests that the radical sects in Europe in the early sixteenth-century challenged the political and religious monisms of both Catholic and Protestant territories, hence planting the seeds of tolerant pluralism. The struggles faced in the sixteenth-century both reflect and inform our own pressing concerns today and as such, The Fragility of Tolerant Pluralism draws six lessons for our current situation.