The relationship between the state and the market has been an important area of scholarly inquiry in many academic disciplines. In The Fourth Branch, Brian J. Cook examines state-market interaction through the role of the administrative state in the United States' commercial republic. Cook defines a commercial republic as a political regime that “conjoins popular, limited, and active government… and a market system anchored in a broad domain of private property rights and centered on business enterprise” (p. 13). Since administration is one of the main points of contact between the government and the various interests within the polity, Cook posits, the structure of the administrative state is crucial for the proper functioning of the American commercial republic.

In the first half of The Fourth Branch, Cook reviews the evolution of the state-market relationship in the United States. The changing social basis of the regime is of particular importance for Cook's discussion as he documents how it evolved from the Madisonian preference for a landed economic class to the Hamiltonian belief that it should revolve around a new capital-holding class. The primary consequence of this development is that business interests now dominate the administrative state, which, Cook argues, undermines the aims of a commercial republic.<