Cultural beliefs that are reflected in homo economicus were transmitted from ancient Indo-European civilizations to Frankish society. I use medieval texts to demonstrate that Gaul's conquest by the Franks sustained and possibly cultivated these beliefs, rather than set them back, even in the absence of developed markets. The cultural presence of homo economicus allows us to apply economic analysis in studying the early Middle Ages. It also suggests that the emergence of capitalism during the commercial revolution, the Enlightenment, and the rise of classical economics as a science in Western Europe are products of these cultural beliefs.