Summary - This essay examines the foundations of the Hayekian theory of order, moving from The Sensory Order and showing its connections with Menger's Untersuchungen and with Hayek's methodological writings of the 30's and 40's. A particular attention is reserved to the relationship between the social distribution of knowledge and the "cultural and spontaneous" formation of an order, and to the process of affirmation of ideas. Taking "exchange" as a constitutive element of every form of "civil association", the theoretical perspective of spontaneous social institutions emerges in the contraposition between the system of catallactis - or market logic - and the democrati decisional model - or logic of political choice. A special emphasis is placed on the problem of the selection and the possible achievement of individual expectations in the process of catallactis and in democratic political processes, and on the relationship between "temporary subjective equilibria" and the emergence of an order. The limits of Hayekian solutions are the examined. Finally, there follows a critical analysis of the capacity of the democratic state to politically produce "certainty" in an historical context in which geographical boundaries of political sovereignity do not coincide anymore with market borders.