The Theory of Communicative Action (TCA) is the main work of Jürgen Habermas, probably the most influential thinker of the Federal Republic of Germany. At the center of the book is the concept of communicative rationality: Whoever uses language must always presuppose the possibility of rational exchange. The freer the exchange of arguments is, the more rationality and freedom are enabled. In the lifeworld of modern societies, such rationalization has advanced as never before. At the same time, however, rationality is also limited and threatened. The societal subsystems of capitalist economy and modern state are well suited to ensure material reproduction, to relieve the lifeworld of these tasks and to enable freedom. Their steering media money and administrative power, however, also have the tendency to encroach on the lifeworld, to colonize it and to displace communication. Habermas’ work has been and continues to be intensively discussed in all its aspects – in communication studies as well as in numerous other disciplines from the social sciences and humanities. The present text summarizes the most important backgrounds, arguments and counterarguments.