Constitutionalism Justified analyzes leading Frankfurt School theorist Rainer Forst's theory of a basic right to justification, unique in combining insights from philosophy, constitutionalism, and legal theory. Drawing upon Kant's critical philosophy and Habermas's discourse theory, he has developed fresh perspectives on core topics like the concept of justice, the relation between modernity and emancipation, and human rights. The contributors to this volume explore Forst's work from three different perspectives: philosophy, legal philosophy, and constitutional theory. The first part of this volume addresses the philosophical argument of the basic right to justification, including the influence of Kantian thought on this right, the deontological versus teleological fundamentals, the tension between moral pluralism and universalism, and the relation of the right to justification with social and distributive justice. The second part covers how the right to justification is embedded in constitutional and legal frameworks. It explores the implications that Forst's right to justification has for conceptualizing constitutional democracy and its foundations, and how the moral right to justification may translate into particular practices of justification that are constrained by a legal framework. This includes discussion of the value of constitutionalism in general, of the relation between the formal structure of democracy and substantive justice, of the inclusion of outsiders to the constitutional setting, and of proportionality analysis and judicial review as forms of justification. The book concludes with Rainer Forst's reply to his interlocutors, making the book a valuable source for future research.