The connection of economic theory and behavior is one of the central topics of this book - and also a central issue in economic thinking of Horst Todt to whom this book is dedicated. The contributions deal with topics of normative and descriptive decision-making: They investigate, for instance, the emergence of decisions or the role of imitation as a competitive principle. A number of contributions treat special decision-making problems on a micro or on a macro level, whereas others concentrate on the principle questions of decision-making or on the conceptualization of important but fuzzy notions like power or solidarity.