Friedrich Hayek opposed the view of Lionel Robbins, Ludwig Mises and most textbooks which identifies “human action” or “human behavior” as the subject matter of economic science. Instead, Hayek shares the view of Carl Menger and Adam Smith which identifies undesigned social order as the object of explanation in social science:
The discovery that there exist in society orders of another kind which have not been designed by men but have resulted from the action of individuals without their intending to create such an order, is the achievement of social theory — or, rather, it was this discovery which has shown that there was an object for social theory. It shook the deeply-ingrained belief of men that where there was an order there must also have been a personal orderer. It had consequences far beyond the field of social theory since it provided the conceptions which made possible a theoretical explanation of the structures of biological phenomena. And in the social field it provided the foundation for a systematic argument for individual liberty.
From F. A. Hayek, “Kinds of Order in Society”, New Individualist Review.