Ludwig von Mises, whose major writings predated Rand's important contributions to epistemology, regarded praxeological truths as a priori. As should be clear from Section 1, however, our concept of human action and of the principles connected with it derive from our common experience as acting human beings. In a philosophical sense, therefore, praxeology is not truly aprioristic but is rooted in real-world observation—although it does not rely upon reams of economic data or surveys of producers and consumers.