The third element in the doctrine, and the one which sets the separation of powers theorists apart from those who subscribe to the general themes set out above but are not themselves advocates of the separation of powers, is what, for want of a better phrase, we shall describe as the “separation of persons.” This is the recommendation that the three branches of government shall be composed of quite separate and distinct groups of people, with no overlapping membership. It is perfectly possible to envisage distinct agencies of government exercising separate functions, but manned by the same persons; the pure doctrine here argues, however, that separation of agencies and functions is not enough. These functions must be separated in distinct hands if freedom is to be assured. This is the most dramatic characteristic of the pure doctrine, and is often in a loose way equated with the separation of powers. The final element in the doctrine is the idea that if the recommendations with regard to agencies, functions, and persons are followed then each branch of the government will act as a check to the exercise of arbitrary power by the others, and that each branch, because it is restricted to the exercise of its own function will be unable to exercise an undue control or influence over the others. Thus there will be a check to the exercise of the power of government over “the people” because attempts by one branch to exercise an undue degree of power will be bound to fail. This is, of course, the whole aim and purpose of the doctrine, but it is just here that the greatest theoretical difficulty is to be found; and as a result what we have termed the pure doctrine has therefore been modified by combining it with some rather different doctrine to produce a complex amalgam of ideas about the limitations to be placed upon government authorities. The pure doctrine as we have described it embodies what might be called a “negative” approach to the checking of the power of the agencies of government. The mere existence of several autonomous decision-taking bodies with specific functions is considered to be a sufficient brake upon the concentration of power. Nothing more is needed. They do not actively exercise checks upon each other, for to do so would be to “interfere” in the functions of another branch. However, the theory does not indicate how an agency, or the group of persons who wields its authority, are to be restrained if they do attempt to exercise power improperly by encroaching upon the functions of another branch. The inadequacy of the controls which this negative approach to the checking of arbitrary rule provides, leads on to the adaptation of other ideas to complement the doctrine of the separation of powers and so to modify it.
The most important of these modifications lies in the amalgamation of the doctrine with the theory of mixed government, or with its later form, the theory of checks and balances. The connections between these theories will be examined more fully in the ensuing chapters; from an analytical point of view the main consideration is that these theories were used to import the idea of a set of positive checks to the exercise of power into the doctrine of the separation of powers. That is to say that each branch was given the power to exercise a degree of direct control over the others by authorizing it to play a part, although only a limited part, in the exercise of the other’s functions. Thus the executive branch was given a veto power over legislation, or the legislative branch was given the power of impeachment. The important point is that this power to “interfere” was only a limited one, so that the basic idea of a division of functions remained, modified by the view that each of the branches could exercise some authority in the field of all three functions. This is the amalgam of the doctrine of the separation of powers with the theory of checks and balances which formed the basis of the United States Constitution. Related to this, and to its predecessor in time, is an amalgam of the doctrine of the separation of powers with the theory of mixed government to produce a partial separation of functions. That is to say that one function, the legislative, was to be shared, but other functions were to be kept strictly separate. This was a basic element in eighteenth-century English constitutionalism, the theory of balanced government. These modifications of the doctrine have of course been much more influential than the doctrine in its pure form.
The idea of a partial separation of functions is an important one, for it does not cease to be significant simply because it is partial. We shall consider the objections made against Montesquieu, for example, on the grounds that he did not believe in the separation of powers because he gave to the branches of government certain powers over each other which amounted to a participation in the exercise of the functions of another branch. But Montesquieu did not give each branch an equal part to play in the exercise of each function of government—far from it; he set up a basic division of functions and then imposed certain control mechanisms upon this fundamental division. A similar modification of the pure doctrine can be seen in the area of the separation of persons. The pure doctrine demands the complete separation of the personnel of the three branches of government, but this can be modified to introduce a partial separation of persons. That is to say that some people may be allowed to be members of more than one branch of the government, although a complete identity of personnel in the various branches will be forbidden. Again, as with the separation of functions, such an approach does not mean that the idea of the separation of powers has been wholly jettisoned. The degree of separation will become important. How many people are to be allowed to be members of more than one branch, who will they be, and what will be their function and authority? The answers given to these questions in the mid nineteenth century provided the basis of the parliamentary system of government. Thus we can see the pure doctrine as an ideal for an extreme separation of “powers,” but we can then introduce various modifications and discuss their effects, and try to determine the points at which the doctrine no longer plays a significant part in the resulting amalgam.
Two further concepts must be mentioned which have not figured to any great extent in the literature on the separation of powers, but whose relation to the doctrine is of great importance. The first, an extremely ancient concept, is the idea of procedure as a check to the exercise of power. The belief that “due process” is an essential part of constitutional government is of great antiquity, and it runs parallel with ideas of mixed government and the separation of powers, but has relatively rarely been explicitly linked with those ideas and made an integral part of those theories. The second notion, a much more modern one, is the idea of process in government. This term, although used in different ways, indicates an awareness that government and politics do not consist in the automatic operation of formal procedures, but that there is a whole complex of activities around these procedures which determines the exact way in which they will be operated, sometimes in fact bringing about through the medium of the procedure exactly the reverse of what the procedure was intended to achieve. The concern of political studies with the role which political parties and groups play in the processes of government makes it impossible any longer to discuss a theory like that of the separation of powers purely in terms of the more formal, legal institutions of government. If the theory has anything to offer it must be able to cope with the complexities of “politics” as well as the structure of governments.
The long history of the doctrine of the separation of powers reflects the developing aspirations of men over the centuries for a system of government in which the exercise of governmental power is subject to control. It illustrates how this basic aspiration towards limited government has had to be modified and adapted to changing circumstances and needs. It offers a rich mass of material, of human thought and experience, on a subject which remains today a matter of vital importance. To follow the course of this history should be of interest in itself, but it is also an essential step towards the understanding of the ideas of the past which have helped to shape our own, and towards the reformulation of these ideas into a more coherent theoretical approach to the nature of modern constitutional government.
