Fifty years ago, the two leading German philosophers and sociologists since the Second World War, Jürgen Habermas and Niklas Luhmann, embarked on a sweeping and contentious debate that would continue for decades. Their coauthored 1971 book Theory of Society or Social Technology laid out their opposing positions on meaning, communication, consensus, and dissent—and ultimately the foundations of modern social thought. Habermas and Luhmann would elaborate their disagreement in the years to come in a controversy whose aftershocks divided social theorists by presenting what appeared to be two fundamentally divergent views of the nature of society and what systems theory was capable of explaining. This is the first book in English about one of the most important conflicts in social theory today. Gorm Harste analyzes the Habermas-Luhmann debate from its inception through Habermas’s most recent works, exploring issues such as methodology, ideology, truth, history, and politics. He contextualizes their positions in terms of how each grappled with the legacy of Nazism and sought to provide grounding for an antitotalitarian politics. Harste follows the evolution of the debate, as the fundamental dispute over the normative and practical desirability of agreement and disagreement came to touch upon political questions including the rule of law, the separation of powers, human rights, individualization, and secularization. Ultimately, Harste emphasizes the convergence between Habermas and Luhmann—and the pressing need for social theorists to further unite these two formative accounts of contemporary society.