vast expansion in recent years of national legislative power in the regulation of commerce among the States and in the expenditure of the national revenues; and verbally at least Marshall laid the ground for these developments in some of the phraseology above quoted from his opinion in McCulloch _v._ Maryland. Nondelegability of Legislative Power ORIGIN OF DOCTRINE At least three distinct ideas have contributed to the development of the principle that legislative power cannot be delegated. One is the doctrine of separation of powers: Why go to the trouble of separating the three powers of government if they can straightway remerge on their own motion? The second is the concept of due process of law, which precludes the transfer of regulatory functions to private persons. Lastly, there is the maxim of agency "_Delegata potestas non potest delegari_," which John Locke borrowed and formulated as a dogma of political science.[19] In Hampton Jr. & Co. _v._ United States,[20] Chief Justice Taft offered the following explanation of the origin and limitations of this idea as a postulate of constitutional law: "The well-known maxim '_Delegata potestas non potest delegari_,' applicable to the law of agency in the general and common law, is well understood and has had wider application in the construction of our Federal and State Constitutions than it has in private law. The Federal Constitution and State Constitutions of this country divide the governmental power into three branches. * * * in carrying out that constitutional division * * * it is a breach of the National fundamental law if Congress gives up its legislative power and transfers it to the President, or to the Judicial branch, or if by law it attempts to invest itself or its members with either executive power or judicial power. This is not to say that the three branches are not co-ordinate parts of one government and that each in the field of its duties may not invoke the action of the two other branches in so far as the action invoked shall not be an assumption of the constitutional field of action of another branch. In determining what it may do in seeking assistance from another branch, the extent and character of that assistance must be fixed according to common sense and the inherent necessities of the governmental co-ordination."[21] FUNCTIONS WHICH MAY BE DELEGATED Yielding to "common sense and the inherent necessities of governmental co-ordination" the Court has sustained numerous statutes granting in the total vast powers to administrative or executive agencies. Two different theories, both enunciated during the Chief Justiceship of John Marshall, have been utilized to justify these results. First in importance is the theory that another department may be empowered to "fill up the details" of a statute.[22] The second is that Congress may legislate contingently, leaving to others the task of ascertaining the facts which bring its declared policy into operation.[23]