In seeking an answer to this question, it is necessary to recur, as we have constantly been obliged to do, to the nature of the government which the Constitution was made to supersede. In that system, the experiment had been tried of a union of States,--each possessed of a complete government of its own,--which was intended to combine their several energies for the common defence and the promotion of the general welfare. But this combined will of distinct communities, expressed through the action of a common agent, was wholly unable to overcome the adverse will of any of them expressed by another and separate agent, although the objects of the powers bestowed on the confederacy were carefully stated and sufficiently defined in a public compact. Thus, for example, the treaty-making power was expressly vested in the United States in Congress assembled; but when a treaty had been made, it depended entirely upon the separate pleasure of each State whether it should be executed. If the State governments did not see fit to enforce its provisions upon their own citizens, or thought proper to act against them, there was no remedy, both because the Congress could not legislate to control individuals, and because there was no department clothed with authority to compel individuals to conform their conduct to the requirements of the treaty, and to disregard the opposing will of the State. This defect was now to be supplied, by giving to the national authority, not only theoretically but practically, a supremacy over the authority of each State. But this was not to be done by annihilating the State governments. The government of every State was to be preserved; and so far as its original powers were not to be transferred to the general government, its authority over its own citizens and within its own territory must, from the nature of political sovereignty, be supreme. There were, therefore, to be two supreme powers in the same country, operating upon the same individuals, and both possessed of the general attributes of sovereignty. In what way, and in what sense, could one of them be made paramount over the other?