19. There is an opinion that parties in free countries are useful checks upon the administration of the government, and serve to keep alive the spirit of liberty. This, within certain limits, is probably true; and in governments of a monarchical cast, patriotism may look with indulgence, if not with favor, upon the spirit of party. But in those of a popular character, in governments purely elective, it is a spirit not to be encouraged. From their natural tendency, it is certain there will always be enough of that spirit for every salutary purpose; and there being constant danger of excess, the effort ought to be by force of public opinion, to mitigate and assuage it. A fire not to be quenched, it demands a uniform vigilance to prevent its bursting into a flame, lest, instead of warming, it should consume. 20. It is important, likewise, that the habits of thinking in a free country should inspire caution in those intrusted with its administration, to confine themselves within their respective constitutional spheres, avoiding, in the exercise of the powers of one department, to encroach upon another. The spirit of encroachment tends to consolidate the powers of all the departments in one, and thus to create, whatever the form of government, a real despotism. A just estimate of that love of power, and proneness to abuse it, which predominates in the human heart, is sufficient to satisfy us of the truth of this position. The necessity of reciprocal checks in the exercise of political power, by dividing and distributing it into different depositories, and constituting each the guardian of public weal against invasions by the others, has seen evinced by experiments ancient and modern, some of them in our country and under our own eyes. To preserve them must be as necessary as to constitute them. If, in the opinion of the people, the distribution or modification of the constitutional powers be in any particular wrong, let it be corrected by an amendment, in a way which the Constitution designates; but let there be no change by usurpation: for though this, in one instance, may be the instrument of good, it is the customary weapon by which free governments are destroyed. The precedent must always greatly overbalance in permanent evil any partial or transient benefit which the use can at any time yield.