Even though standard economic theory traditionally ignored any motives that may drive incentivized social decision making except for the maximization of personal consumption utility, the idea that ‘preferences for fairness’ (following social norms) might have an economically tangible impact appeared relatively early. I trace the evolution of these ideas from the first experiments on bargaining to the tests of the hypothesis that pro-sociality in general is driven by the desire to adhere to social norms. I show how a recent synthesis of economics approach with psychology, sociology, and evolutionary human biology can give rise to a mathematically rigorous, psychologically plausible, and falsifiable theory of social norms. Such a theory can predictwhich norms should emerge in each specific (social) context and is capable of organizing diverse observations in economics and other disciplines. It provides the first glimpse at how a unified theory of normative decision making might look like.