The concept of communication is one of the most important achievements of the sciences in the 20th century. Dirk Baecker traces the development of this concept from Plato's "Sophist" to Claude E. Shannon's mathematical theory of communication. He demonstrates that communication should not be understood, as is often the case, as transmission, but rather as selection - as a mutual selection within a space of possibilities that is thereby opened up. This new concept of communication allows, on one hand, for the determination of the form of communication as a social process of assigning and utilizing degrees of freedom, and on the other hand, for the description of the various forms of communication in interaction, organization, social movements, and society.