The division of the powers of government among the three departments, executive, legislative, and judicial, rests on the assumption that while no one of them is in itself sovereign and unlimited in authority, yet each is independent of the others. The theory involves, first, a limitation of each department to its own sphere of action; and, secondly, absolute independence and supremacy within that sphere. This principle of exclusion is, however, rather a general principle than a rule of exact application. The functions of the three departments of government do necessarily, to some extent, overlap. The legislature not only makes the laws which the executive enforces, and which the judiciary applies in the determination of controversies, but it has the exclusive power of taxation and appropriation of money, and, for the funds necessary to carry on the other branches of the government, those branches are therefore dependent upon the legislature. On the other hand, the executive department controls the military force, and for the protection which the legislature and the judiciary may require, they are dependent on the executive. Furthermore, each department in the performance of the functions assigned to it may have occasion to exercise powers and duties analogous to those of the other departments; for instance, the executive department, in determining whether money shall be collected for taxes or claims paid out of appropriations, must often decide judicial questions; and the judicial department, on the other hand, in repressing interruption or preventing interference with its proceedings, or in providing the material means for carrying on its operations, may exercise functions analogous to those of the executive or the legislature. It will not, therefore, be possible to draw any very definite line between the functions of the three departments, although some important questions affecting their relations have been definitely settled and should be well understood.