All government is a conspiracy. Each governmental conspiracy has a constitution as its alibi. The constitution describes the way in which the political power of the society is concentrated and places the source of that concentration somewhere other than in the mere fact of power. Because of that dislocation, the constitution is the source not only of political power but also of political duty. The subjection of the organs of government to the constitution runs parallel to the subjection of the people governed to the constitutional power of the organs of government. The constitution justifies constitutional power and constitutional duty by making both of them derivatives from one and the same source.
The prior question of whence the constitution itself derives its authority is, for all everyday practical purposes, answered by the mere fact of the constitution. The constitution is self-proving in practice because it is used as the source of maxims affecting the behaviour of those who exercise physical force with actual impunity, or who control its exercise. To preach or to act against the constitution may or may not be permitted by the legal rules of the given society (themselves derived ultimately from the constitution), but it will in any event be ineffective whenever it comes into collision with power exercised, to the point of physical force, under authority derived from the constitution. A revolution occurs when the exercise of constitutional power, to the piont of physical force, ceases or is overridden by the exercise of unconstitutional power, if necessary by the application of greater physical force.