This volume focuses on the debate that developed in France, Germany, Italy, and the United Kingdom after the terrorist attacks against Charlie Hebdo and the kosher supermarket, in January 2015. The book offers an in-depth analysis of the unfolding of the public debate in terms of content of claims making, framing, and justifications as well as the quality (deliberativeness) of the discourses by a variety of actors in the public sphere. The volume features a threefold comparison that considers how the debate differs across countries; how it evolved over time; and how it varies when one looks at mainstream media compared to social movement arenas. Based on a triangulation of quantitative and qualitative analyses, the volume pays particular attention to radical left, radical right, and religious actors and to issues related to migration and integration, secularism and cultural diversity, security and civil rights. Taking its starting point from the infamous attacks of January 2015, this volume aims also at contributing to a theoretical innovation by reflecting on the ways in which transformative events trigger discursive critical junctures.