Constitutionalism and the Separation of Powers. M. J. C. Vile

of the separation of powers, yet these two theories have been closely connected with each other over much of their history. The theory of mixed government is much the older of the two, as old as political theory itself, and it remained a part of English political thought well into the nineteenth century. The two doctrines are not merely logically distinct, but to a considerable extent they conflict with each other. The theory of mixed government was based upon the belief that the major interests in society must be allowed to take part jointly in the functions of government, so preventing any one interest from being able to impose its will upon the others, whereas the theory of the separation of powers, in its pure form, divides the functions of government among the parts of the government and restricts each of them to the exercise of its appropriate function. Furthermore the class basis of the theory of mixed government is overtly lacking from the doctrine of the separation of powers. But it would be quite untrue to say that the latter does not have any class bias. The theory of mixed government had as its central theme a blending of monarchy, aristocracy, and democracy, and, as we shall see, there is a tendency to equate these, in some stages of the development of the doctrine of the separation of powers, respectively with the executive, judicial, and legislative “powers.” The latter doctrine assumes that the legislature will, or may, be taken over entirely by the democratic element, and that checks upon “mob rule” will therefore have to be applied by branches of the government largely or wholly outside the legislature. The battle for the control of the “chief mark of sovereignty,” the legislative power, may be won by the proponents of popular rule, but there are methods of ensuring that this power is subjected to limitations, one of them being the maintenance of the bicameral system, another the decentralization of the government under a federal constitution, and the third the separation of functions among different agencies so that movements of popular opinion in the legislature can be slowed down by the other branches of government.

      This is the “shift” which took place between the two doctrines, but of course it was not achieved overnight. The succession was effected extremely slowly, as slowly in fact as the success of “democracy” in the make-up of the legislature was recognized. In mid-seventeenth-century England, the later doctrine was quickly born and adopted in the revolutionary conditions which temporarily destroyed the monarchy and the House of Lords, but this was a situation too far ahead of its time to be maintained. The Restoration introduced a long period in which the two doctrines were combined in an amalgam which recognized the class element in the control of the legislative power. When democratic movements gained the ascendency the theory of mixed government dropped out, and the theory of the separation of powers became the major theory of constitutional government, but only rarely in its pure form. In the Constitution of the United States we find it combined with the idea of “checks and balances,” the old theory of mixed government stripped of its class connotations, and now in a subordinate role. The later history of the relationship between the doctrine and democratic theory became more and more involved as the twentieth century accepted the principle of democracy, only to find that the centre of power had again moved away from legislative bodies towards the executive branch.

      Though the theory of mixed government is not logically connected with the theory of the separation of powers, the former theory provided suggestive ideas which formed the basis of the new doctrine. Both theories are concerned with the limitation of power by instituting internal checks within the government. The terminology of the “powers” of government came to be applied both to the representative organs of mixed government, and to the functionally divided agencies of the separation of powers. The threefold mixture of monarchy, aristocracy, and democracy was a particular case of a general theory of limited government, in which the people exercised a check upon the monarch, or some other combination of powers prevented the dominance of a single person or group.⁵⁰ In the ancient world the theory of mixed government figured principally in the work of Aristotle, Plato, and Polybius. Plato emphasized the belief in moderation and compromise which is the basis of the theory. Too much power concentrated in one place, either in nature or in the State, leads to the “wantonness of excess”; only in the observance of the mean can arbitrary rule be avoided.⁵¹ The preservation of Sparta was the consequence of its constitution, which consisted of a dual kingship, a council of Elders, and the Ephors elected by lot, and was thus “compounded of the right elements and duly moderated.”⁵² Later Plato asserted that democracy and monarchy are the “two mother forms of states from which the rest may be truly said to be derived.” Both forms of these are required in some measure.⁵³ He emphasized the basic element of the theory of mixed government—its frank recognition of the class basis of society. But the classes, with their potentially conflicting interests, must be harmonized through a constitutional structure ensuring that each class can play a part in the control of those decisions in which its interests will be affected.⁵⁴

      Aristotle criticized Plato’s formulation of the theory by insisting that we shall “come nearer the truth” if we seek to combine more than two of the basic forms in a State, for “a constitution is better when it is composed of more numerous elements,”⁵⁵ although Aristotle himself wrote elsewhere of the best form of State as a combination of democracy and oligarchy.⁵⁶ He placed even more emphasis than Plato upon the value of the mean in politics, and upon the need for each part of the State to have a proportionate share in government: “Proportion is as necessary to a constitution as it is (let us say) to a nose.”⁵⁷ Indeed it is a criterion of a proper mixture of democracy and oligarchy that it should be capable of being described indifferently as either.⁵⁸ Aristotle also made a closer examination of the class basis of the mixed constitution, stressing the moderating influence of a middle class, and equating the feasibility of establishing a successful mixed constitution with the existence of an extensive middle class in the State.⁵⁹ Polybius, in his analysis of the Roman Republic, developed the theory to a greater degree than his predecessors, and, by adapting the theory to encompass the elected consuls of Rome as the “monarchical” element, he provided the pattern for the transformation of the theory of mixed government into a theory of checks and balances, in which the agencies of government might not all have a distinct “class” to represent, but might, of themselves, provide an institutional check within the government structure.⁶⁰

      The importance of the ancient theory of mixed government for our theme, therefore, is its insistence upon the necessity for a number of separate branches of government if arbitrary rule is to be avoided. This view of the “separation of agencies” was not based upon the efficiency to be achieved by the division of labour, nor upon the functions which are “proper” to different branches of the government. The various branches were expected to play a part in all the tasks of government, but their representative character enabled them to prevent the use of that power in ways which would be prejudicial to the interests they represented. As we have seen, this “separation of agencies” is an essential part also of the doctrine of the separation of powers. The theory of mixed government opposed absolutism by the prevention of the concentration of power in one organ of the State, and the doctrine of the separation of powers starts from the same assumption. The vitally important step in the emergence of the latter doctrine is the attribution of distinct functions to the agencies of government, and in this respect the critical difficulty of the transition from one to the other is that the three agencies of the mixed government, King, aristocratic assembly, and popular assembly, do not correspond to the executive, legislature, and judiciary in the doctrine of the separation of powers. The transition takes a long while in the development of the theory, and is the explanation of much of the confusion about the nature of the functions of government that we have to some extent already observed.

      There are, therefore, two major steps to be noted in the transformation of this ancient theory into the modern doctrine of the separation of powers. First, the insistence that particular agencies should be restricted to particular functions. Second, the emergence of a recognition of an independent judicial branch, which will take its place alongside King, Lords, and Commons. The first of these is achieved in the seventeenth century, the second is fully attained only in the eighteenth. It is these developments we must now trace.

      The ancient tradition of mixed government was transmitted to medieval Europe, was echoed and restated, and was used to support the view that royal power should be subjected to feudal and popular restraints. In the thirteenth century Aquinas