In this chapter, it is argued that ideologies also play a central role in everyday decisions. The rules and recommendations of the adopted belief system or ideology are a cost-effective heuristic alternative to one’s own costly information searches. The integration of such ideological rules into economic decision models in various areas of life enables a deeper understanding of human behavior in subjectively rational actions. The modeled examples underscore the subjective rationality of ideologically influenced decisions and the necessity of taking greater account of convictions and values in economic research. Examples are modeled that describe ideologically influenced decisions in the areas of consumer choice, career choice, and politics. Furthermore, the important distinction between individual and collective rationality is emphasized again, and it is pointed out that ideologically motivated individual decisions do not necessarily lead to desirable collective outcomes, even if this is often claimed. Collective rational behavior in such situations only emerges when everyone has sufficient information and understanding of the overall situation and acts rationally from this overall perspective. Finally, implications for empirical research are discussed.