Besides, in ordinary times it is not from the executive that the most dangerous encroachments are to be apprehended. The legislature is the aggressive spirit. It is the motive power of the government, and unless the judiciary can check it, the courts are of comparatively little worth as balance-wheels in the system. It is the subtile, stealthy, almost imperceptible encroachments of policy, of political action, which constitute the precedents upon which additional prerogatives are generally reared; and yet these are the very encroachments with which it is hardest for the courts to deal, and concerning which, accordingly, the federal courts have declared themselves unauthorized to hold any opinions. They have naught to say upon questions of policy. Congress must itself judge what measures may legitimately be used to supplement or make effectual its acknowledged jurisdiction, what are the laws "necessary and proper for carrying into execution" its own peculiar powers, "and all other powers vested by" the "Constitution in the government of the United States, or in any department or officer thereof." The courts are very quick and keen-eyed, too, to discern prerogatives of political discretion in legislative acts, and exceedingly slow to undertake to discriminate between what is and what is not a violation of the spirit of the Constitution. Congress must wantonly go very far outside of the plain and unquestionable meaning of the Constitution, must bump its head directly against all right and precedent, must kick against the very pricks of all well-established rulings and interpretations, before the Supreme Court will offer it any distinct rebuke. Then, too, the Supreme Court itself, however upright and irreproachable its members, has generally had and will undoubtedly continue to have a distinct political complexion, taken from the color of the times during which its majority was chosen. The bench over which John Marshall presided was, as everybody knows, staunchly and avowedly federalist in its views; but during the ten years which followed 1835 federalist justices were rapidly displaced by Democrats, and the views of the Court changed accordingly. Indeed it may truthfully be said that, taking our political history "by and large," the constitutional interpretations of the Supreme Court have changed, slowly but none the less surely, with the altered relations of power between the national parties. The Federalists were backed by a federalist judiciary; the period of democratic supremacy witnessed the triumph of democratic principles in the courts; and republican predominance has driven from the highest tribunal of the land all but one representative of democratic doctrines. It has been only during comparatively short periods of transition, when public opinion was passing over from one political creed to another, that the decisions of the federal judiciary have been distinctly opposed to the principles of the ruling political party.