This article makes a plea for a joint study of intellectual and economic history. Mental perceptions affect economic decisions and variables, while economic realities influence the evolution of ideas. We use the case of Castilian noblemen and their management of landed property to illustrate these interrelations. This was driven to a large extent by the «moral economy» of the group, which provided a moral justification of its privileged place in society. However, during the early modern age new ideas and economic difficulties eroded these concepts and attitudes, and led to an increasing interest of nobility towards an efficient management of their properties. The delicate equilibrium between gains and prestige –intended as an indirect means to acquire wealth– as well as the intermingling of religious worries make it difficult to get a balanced view of the real situation and its evolution, which is none the less necessary.