The first chapter motivates with the question of what role ideologies play in democratic societies, how they function, and how they contribute to conflict or polarization. It is an introductory overview of the book’s argument. It argues that ideologies fulfill fundamental psychological needs as a reaction to the human problem of incomplete information. This chapter introduces the functions of belief systems and ideologies and describes how these provide us with orientation and influence everyday decisions. Furthermore, the quality of ideological leadership is critically examined. Problems such as normative issues, lack of information, deception, and unsuitable ideological instruments for achieving goals are also discussed. Ultimately, the analysis aims to understand the role of ideologies from a human rational decision-making perspective. Thus, this chapter lays the foundation for the study of “The Economics of Ideology”. It identifies the main issues and leads to the central thesis: People make decisions under incomplete information. Therefore, belief systems and ideologies fulfill a number of important functions. While ideologies themselves serve psychological needs, they are used as a cognitive framework for rational decisions once they have been adopted through a Bayesian Learning process. They influence decisions in a wide range of areas, from consumption and work to politics. Because ideologies and their narratives are embraced by organizations, these organizations can deliver both good and bad leadership through their narratives. A short summary of each chapter then guides the reader through the line of argument of this idea.