Solidarity has been at the root of social change throughout history, bringing people together across their differences to challenge injustice within societies. In their new book, Solidarity: The Past, Present, and Future of a World-Changing Idea, Leah Hunt-Hendrix and Astra Taylor examine the sociological concept that is at the heart of social transformation. Hunt-Hendrix joins host Richard Aldous to share her thoughts on both the concept and the social movements with which it is intimately linked.