Over a career spanning nearly seven decades, Jürgen Habermas - one of the most important European philosophers of the twentieth and twenty-first centuries - has produced a prodigious and influential body of work. In this Lexicon, authored by an international team of scholars, over 200 entries define and explain the key concepts, categories, philosophemes, themes, debates, and names associated with the entire constellation of Habermas's thought. The entries explore the historical, philosophical and social-theoretic roots of these terms and concepts, as well as their intellectual and disciplinary contexts, to build a broad but detailed picture of the development and trajectory of Habermas as a thinker. The volume will be an invaluable resource for students and scholars of Habermas, as well as for other readers in political philosophy, political science, sociology, international relations, cultural studies, and law.