Any system of constitutional government must have as one of its central principles some degree of separation of powers. A system of government in which all legal power and authority is exercised by one person or group of people must depend entirely upon their self-restraint in the exercise of that power. The history of government does not suggest that such self-restraint is likely this side of heaven or utopia, and efforts to prevent the abuse of the powers of government have therefore focused on constitutional arrangements that divide and limit the powers of government.
The doctrine of the separation of powers consists of a number of elements: the idea of three separate branches of government, the legislature, the executive, and the judiciary; the belief that there are unique functions appropriate to each branch; and the assertion that the personnel of the branches of government should be kept distinct, no one person being able to be a member of more than one branch of government at the same time. The more pure or extreme the form of the doctrine, the greater the extent to which all three of these elements are insisted upon without reservation or modification. In past centuries political writers have proposed such extreme solutions in France, Britain, and America, and attempts have been made, unsuccessfully, to approximate as closely as possible to this extreme in practice. The spirit of the doctrine was expressed clearly in the Constitution of Virginia in 1776: "The legislature, executive and judiciary departments shall be separate and distinct, so that neither exercise the powers properly belonging to the other: nor shall any person exercise the powers of more than one of them at the same time.?"
A further aspect of the doctrine is the concern with the method by which the members of the executive and judicial branches are selected, for this will have implications for the extent to which the members of one branch may be able to influence the behavior of members of another. The more extreme versions of the doctrine therefore demand the direct election of members of all three branches of government in order that they should be responsible directly to the people, and not dependent upon each other. In the words of Samuel Williams, historian of Vermont, in 1794, "the security of the people is derived not from the nice ideal application of checks, balances, and mechanical powers, among the different parts of the government, but from the responsibility, and dependence of each part of the government, on the people."
The doctrine of the separation of powers, standing alone, however, has never been able to provide the kind of safeguards against the abuse of governmental power which it claims to provide. In practice we find that CHECKS AND BALANCES are required to prevent one or another branch of government from becoming too dominant. The idea of internal checks, exercised by one branch of government over the others, is drawn from the ancient theory of mixed government, and from the eighteenth-century "mixed and balanced constitution" of Great Britain. Thus JAMES MADISON, in THE FEDERALIST #48, undertook to show that unless the branches of government "be so far connected and blended as to give each a constitutional control over the others, the degree of separation which the maxim requires, as essential to a free government, can never in practice be duly maintained." All constitutional systems of government are therefore an amalgam of the separation of powers and checks and balances. The exact composition of this mixture was a central problem for the Framers of the federal Constitution, and their solution distinguished presidential-congressional government from parliamentary systems.
The emergence of a full-blown doctrine of the separation of powers was the result of a long process of development, involving the refinement of a set of concepts, including the idea of law itself, which today we largely take for granted. In early times the idea of law was very different from the modern concept of legislation or statute law. The latter view of law, consciously drafted and adopted by human rather than divine will, did not emerge clearly until the battle between king and parliament in seventeenth-century England sharpened the perception of law, lawyers, and politicians. The more radical opponents of royal power conceived of a parliament that was representative of the people, making laws which the king, or some other executive power, should put into effect. In the turmoil of civil war, this doctrine of the separation of powers was fashioned by a number of writers until it reached a recognizably modern form.
As the British constitutional crisis deepened, the doctrine was refined by those who, like JOHN MILTON, pointed to the arbitrary character of the Long Parliament, Henry Ireton in the Whitehall debates of 1649, and JOHN LILBURNE in The Picture of the Councel of State asserting that "the House itself was never (neither now, nor in any age before) betrusted with a Law executing power, but only with a Law making power." John Sadler in his The Rights of the Kingdom of 1649 asserted the basis of the separation of powers very clearly. The three powers of government, legislative, judicial, and executive, "should be in Distinct
Subjects; by the Law of Nature, for if Lawmakers be judges, of those that break their Laws; they seem to be judges in their own cause: which our Law, and Nature itself, so much avoideth and abhorreth, so it seemeth also to forbid, both the Lawmaker, and the Judge to Execute."
The execution of Charles I and the establishment of republican government stripped away the remaining vestiges of mixed government and left the separation of powers as the sole constitutional principle for the organization of the government of Great Britain. The Commonwealth produced the first written constitution of modern times, the Instrument of Government of 1653, and the doctrine of the separation of powers clearly inspired its authors. This document vested the supreme legislative authority in the lord protector and the people assembled in Parliament, but in effect the role of the protector in legislation was to be limited to a suspensive veto of twenty days. The Instrument also provided that "the exercise of the Chief Magistracy and the administration of the Government ? shall be in the Lord Protector, assisted with a Council." Although the Instrument of Government was never an...