The constitution drawn up, ordained, and established by a nation for itself is a law--the organic or fundamental law, if you will, but a law, and is and must be the act of the sovereign power. That sovereign power must exist before it can act, and it cannot exist, if vested in the people or nation, without a constitution, or without some sort of political organization of the people or nation. There must, then, be for every state or nation a constitution anterior to the constitution which the nation gives itself, and from which the one it gives itself derives all its vitality and legal force.
The people must be, in some way, constituted a nation for the fundamental law to be interpreted and applied; a law needs such a background for both interpretation and application. As Brownson says, "Nations have originated in various ways, but history records no instance of a nation existing as an inorganic mass organizing itself into a political community. Every nation, at its first appearance above the horizon, is found to have an organization of some sort." Thus he distinguished between the written and the unwritten constitutions:
The written constitution is simply a law ordained by the nation or people instituting and organizing the government; the unwritten constitution is the real or actual constitution of the people as a state or sovereign community, and constituting them such or such a state. It is Providential, not made by the nation, but born with it. The written constitution is made and ordained by the sovereign power, and presupposes that power as already existing and constituted.
Brownson argues that the United States has a peculiar providential constitution, one that is extremely difficult to characterize and largely misunderstood. The United States, for as long as it could be said to have any constitution at all, has simply been the United States: a union of states in which the union is not derived from the states nor the states from the union. Even when the states declared independence and claimed themselves each to have state sovereignty, they did so as a union. Brownson attributes the failure of the Articles of Confederation to its failure to fit this unwritten constitution, and the success of the newer Constitution to its much better fit to the same. The American polity is so very odd because it has no sovereign people without states; no states without union; no union without states; and neither states nor union without the sovereign people. All three go together, and if you try to pry them apart, you end up with something that's not recognizably American. As he says:
This is not a theory of the constitution, but the constitutional fact itself. It is the simple historical fact that precedes the law and constitutes the law-making power. The people of the United States are one people, as has already been proved: they were one people, as far as a people at all, prior to independence, because under the same Common Law and subject to the same sovereign, and have been so since, for as united States they gained their independence and took their place among sovereign nations, and as united States they have possessed and still possess the government.
Thus we have the American peculiarity: a sovereign nation organized into several sovereign states that participate in a sovereign union. Of course, there are governments structurally similar, in that they are federalist; but what we are talking about here is not the federalist structure of U.S. government, but the prior and more fundamental fact that makes it impossible for the U.S. to stand for any other sort of government, the fact that defeats any theory that tries to ignore it. (Brownson, of course, is reflecting on this matter in the aftermath of the Civil War, which he sees as yet another instance in which attempt to deviate from the unwritten constitution failed precisely because it was such a deviation.)