The theory of spontaneous order has a long tradition in the history of social thought, yet it would be true to say that, until the last decade, it was all but eclipsed in the social science of the twentieth century. For much of this period the idea of spontaneous order—that most of those things of general benefit in a social system are the product of spontaneous forces that are beyond the direct control of man—was swamped by the various doctrines of (to use Friedrich A. Hayek's phrase in Law, Legislation and Liberty) 'constructivistic rationalism.' No doubt the attraction of this rival notion of rationalism stems partly from the success of...