To form a more perfect Union, To establish justice, To insure domestic tranquillity, To provide for the common defense, To promote the general welfare, To secure the blessings of liberty to themselves (“the people of the United States”) and their posterity.[55] This exercise of power by Congress is essentially _political_, and Congress alone is judge of “the choice of means and is empowered to use any means which are in fact conducive to the exercise of a power granted by the Constitution.”[56] This conclusion is inevitable. A legislative body could exist on no other principle. Thus it follows that necessity is supremacy, in the case of congressional legislation. To any understanding of American constitutional law, comprehension of this principle is fundamental. 20. May Congress abuse its powers? Possibly. The remedy is through popular election of members of either House, and repeal of the laws which—even though their constitutionality be sustained by the courts, may, in the judgment of the people, transcend limits popularly supposed to be placed on Congress. Thus there are two checks on congressional legislation: the courts of law and the votes of the people. It follows that the American sovereign—the people—may by their votes approve or condemn congressional legislation—approval or condemnation resulting in a continuance or a change of membership of Congress, in conformity to the relative strength of political parties. It is here that part of the unwritten constitution is disclosed. The written Constitution contains no reference to political parties, but actual government in the United States is by and through political parties who, as organized agencies of the public mind, give expression, in large measure, to the unwritten constitution. Interpretation of the Constitution, and of course, of the powers of Congress, is largely interpretation by political parties. 21. Two interpretations of the Constitution have evolved in America, the strict, or literal, commonly called the Jeffersonian, and the liberal, or interpretation according to the spirit of the Constitution, commonly called the Hamiltonian. Chief Justice Marshall was a disciple of Hamilton and enthroned his ideas in the decisions of the Supreme Court for thirty years, and these the first thirty years of the existence of the Court. Later judges, whatever their politics, have rarely departed from the course of interpretation laid down by Marshall. To what extent the political convictions of a judge determine his judicial decisions, and to what extent party doctrines find utterance in the decisions of courts of law are matters of opinion quite as diverse as the men who hold them. Yet, in order to understand American constitutional law it is necessary also to be familiar with American political and constitutional history. Without that history, that law lacks background and circumstance.[57]