This chapter examines the basic functions of belief systems and ideologies from an economic perspective. Belief systems and ideologies offer individual ways of dealing with the challenges of a complex world. It is argued that they alleviate the human information problem, create a coherent worldview, serve psychological needs, suggest forms of togetherness, and provide orientation for everyday decisions. At the same time, the chapter emphasizes the crucial role of organizations in shaping and disseminating ideological narratives and ideas, and in expanding ideological influence. The developed economic model provides a framework for analyzing the dynamics of organizations, their recruitment strategies, and their potential influence on the population, with a particular emphasis on the changing role of communication technologies such as the Internet and social media. This chapter thus provides valuable insights into the interplay between individual needs, ideological offers, and organizational and communicative strategies.