How can stable, effective social movement organizations be created when, as Marx and Engels put it, "all that is solid melts"? That, says editor Robert Brym in his introduction to this fourth volume of proceedings of the annual S.D. Clark Symposium, is the crucial question faciong social movements and their organizers in today's fluid digital age. Contributors Howard Ramos, Lesley J. Wood, Catherine Corrigall-Brown, Tina Fetner, and Anna Slavina, as well as Brym himself, consider the many facets of mass dissent in the twenty-first century, including movement/counter-movement dynamics in the post-Trump era, the ways that modern activists mobilize in difficult contexts, and the ongoing relevance of social movements. The divergent trajectories of the religious right in Canada and the United States are also examined, while the book's final chapter argues for a deeper consideration of cross-national differences.