Why is it that for two centuries American politics, government, and law have been so intimately and persistently involved with the explication de texte of a brief and ambiguously worded late eighteenth-century document? That is the core question in American constitutional history. Americans are not the kind of people, one would think, to make obeisance to a form of words. And the public life of other nations has gone on without such close and continuous reference to their constitutions. One answer is that the Constitution of the United States laid down a structure, and implicitly a philosophy, of government that for the better part of two centuries has fulfilled the needs of American public life. Its major features the view that sovereignty and power emanate from the people; as much attention to the constraints on, as to the powers of, government; the legislative, executive, and judicial branches balanced off (indeed, played off) against each other; a federalism in which particular tasks of government are allocated to the nation and to the states -have had continuing vitality. The document is a short one, its guidelines are broad, but it has demonstrated a notable capacity for setting the rules of the American political and governmental game. As well imagine an Anglo-American legislative body without Robert's Rules of Order, or a serious poker game without Hoyle, as American public life without the Constitution.' A second answer is that, however tangentially and ambiguously, the Constitution has defined the boundaries of debate over persistent, never-resolved issues in American public life. The great ongoing contentions between liberty and equality, between individual freedom and social responsibility, between the nation and the states, and between the State and the citizen, have always been expressed in constitutional terms. The history of the Constitution as definer of the form of government and framer of public policy agendas in short, the history of American constitutionalism may be understood in terms of two broad, chronologically consecutive themes, each of them (by that happy temporal coincidence that is so important a part of the historian's stock in trade) dominating a century of our national public life.