The two-hundred-year process of adaptation and evolutionary change within the U.S. federal system has been well documented and analyzed by numerous scholars of varying academic disciplines. The everchanging and emerging patterns of interrelationships within the federal system have been variously described and characterized as old and new, as adversarial and accommodating, as dual and cooperative, as decentralized and centralized, as a legal concept and a process of negotiation, and as a constitutional structure versus a series of pragmatic arrangements. Various metaphors have been applied to the federal system, such as layer and marble cakes, surging waters, picket fence. Though they have added color, these metaphors and their cumulative effect have added to our internally inconsistent stock of knowledge on the federal system.