One of the main contributions of Ronald H. Coase was to demonstrate how mainstream economics was based on a contradictory amalgam of costly physical inputs and free institutional resources, and to give origin to the economics of institutions: each institution is a mode of allocation and organization of economic resources that is to be investigated. In particular, none of the institutions (including the market) is a free lunch. The Coasian approach regards institutions as costly substitutes and provides a fundamental starting point for comparative institutional analysis. However, Coase neglected two issues deriving from the observation that institutions are not cost-free. First, when institutions are costly, one should not only consider their possible substitutes but also how complementary institutions affect their costs, as well as the costs of the possible institutional substitutes. Second, the economic analysis should also take into account that the transition from one institutional setup to another cannot occur in costless meta-institutions. The initial conditions may substantially affect the final institutional arrangements. Both the novelty of Coase's approach and its limits were grossly undervalued. In particular, the costly institutions assumption requires a view of economics as a historical discipline.

In biology, the laws that regulate the structuring and change of complex organisms, characterised by interlocking complementarities, are different from those that shape the evolution of simple organisms. Only the latter share mechanisms of competitive selection of the fittest analogous to those envisaged by the standard neoclassical model in economics. The biological counterparts of protectionism, subsidies and conflicts enable complex organisms to exit from long periods of stasis and to increase their capacity to adapt efficiently to the environment. Because of their interlocking complementarities, most institutions share the laws governing the structure and change of complex organisms. We concentrate on the complementarities between technology and property rights and consider historical cases in which organisational stasis has been overcome by mechanisms different from (and sometimes acting in spite of) competitive pressure. The evolution of institutions cannot be taken for granted; but even when institutions seem frozen forever by their interlocking complementarities, their potential for change can be discovered by analysis of those interactions.

Posner considers purposeful organisations. Legal persons are fictitious non-mortal species whose evolution has played a major role in economic development. In what sense can they be said to have a purpose? Thanks to several important mutations, the status of legal persons was transferred from public bodies to business corporations. This evolutionary journey is complementary to the Coasian view, which, moving in the opposite direction, explains the firm as a centralization of market transactions. If the corporation emerged also from a process of decentralization of public attributes, some features of public legal persons, are lacking in its business mutation. Also some ways of motivating people are only available to the original species.