While the COVID-19 pandemic thrust solidarity into the forefront of global consciousness, the attention of researchers has seemingly shifted elsewhere in the aftermath. Despite its profound relevance during the crisis, interest in the subject seems to have ebbed when we examine recent publications in political sciences. It becomes imperative not only to ponder what enduring aspects of solidarity persist as a research issue but also how we can transcend its relegation to a mere crisis response tool or political rhetoric. In other words, the academic challenge now extends beyond understanding solidarity within the context of crisis—instead, it beckons researchers to explore avenues for sustaining its relevance beyond episodic upheavals. The pandemic laid bare the stark inequalities etched across class, gender, and race, urging a critical examination of solidarity's role in mitigating, or subverting such disparities. Solidarity, as a concept, also appears notably fragile in the present day. In an era marked by various societal challenges and divisions (neoliberalism, identitarian closure …), we believe that the academic field can play a crucial role in fortifying the notion that organizing mutual aid and fostering solidarity are imperative political and social endeavors. By dedicating scholarly attention to these issues, we aim to contribute to a deeper understanding of the dynamics at play and, in turn, advocate for the sustained importance of solidarity in navigating the complexities of our contemporary world. This Eurostudia dossier seeks to reignite scholarly curiosity around solidarity by delving into the nuanced intersections of solidarity with justice, democracy, and equality. The thematic questions posed to contributors aim not only to dissect the essence, shapes, and functions of solidarity but also to envision it as a dynamic force capable of shaping societies in times of calm as well as chaos. Solidarity is not only a reactive mechanism, but it can also be a proactive force that permeates the fabric of societal structures. The dossier aims to kindle a transatlantic dialogue that extends beyond disciplinary boundaries, fostering an interdisciplinary exploration of solidarity's enduring relevance. It brings together a diverse array of perspectives and scholarly insights that collectively delve into the multifaceted dimensions of solidarity. From virtue ethics to political engagement, from ecological concerns to the tension with individual liberty, the articles featured in this special issue offer a comprehensive exploration of solidarity in its various forms. The contributions in this special issue raise fundamental concerns that illuminate the complexity of solidarity in varied contexts. They tirelessly question: What is solidarity, and what should be its fundamental nature? How does it manifest itself in contemporary political dynamics and what tensions run through it? One observation emerges unanimously: each contribution engages in a political theory approach, mobilizing influential thinkers or highlighting conceptual tensions. This theoretical choice unintentionally leads to a sidelining of empirical questions. Philip Schwarz initiates our exploration by navigating the ethical landscape of public health, particularly amidst the Covid pandemic. Drawing on Alasdair MacIntyre's concept of Acknowledged Dependence, Schwarz establishes a virtue-ethical foundation for understanding solidarity as a response to mutual dependence. Within this framework, acts of solidarity are framed as uncalculating giving, fostering a community where each individual owes this giving to one another. Milan Bernard and Pascale Devette challenge the traditional socio-legal conception of solidarity, proposing a politicized approach rooted in Hannah Arendt's concepts of action and story and Hartmut Rosa's ideas on resonance. Their exploration emphasizes the difficult, unstable, and precarious measure of solidarity between conflicting demands, rooted in a radically plural idea of political community and democratic commitment. This contribution echoes that of Mathilde Duclos by emphasizing the political dimension of conflict in the conceptualization of solidarity. Quentin …