Douglass North's writing on institutional change recognized from the very start that such change depends on cognition and beliefs. Yet, although he focused on individual beliefs, we argue in this paper that such beliefs are social constructs. We suggest that institutions – rules, expectations, and norms – are based on shared cognitive rules. Cognitive rules are social constructs that convey information that distills and summarizes society's beliefs and experience. These rules have to be self-enforcing and self-confirming, but they do not have to be ‘correct’. We describe the characteristics of such rules in the context of a market for ideas, and illustrate their importance in two developments central to the growth of modern economies: the rise of the modern state with its legitimacy based on consent, and the rise of modern science-based technology that was the product of the scientific revolution and the Enlightenment.