The history of the doctrine of the separation of powers provides a panorama of the complex evolution of an idea, and of the role it has played, and continues to play, in the political systems of Western countries; but, equally important, it helps us better to understand the concepts still in use today in the discussion of government, even though many of the assumptions which originally gave rise to these concepts have changed. We still talk of the legislative function or of the relation between legislation and execution, although the meaning we attach to such concepts is very different from that of earlier ages. To understand the way in which these concepts developed is an essential prerequisite for a critical reappraisal of them, in order more clearly to understand how we can best approach the analysis of political systems. Thus the idea of “function,” an essential element in the doctrine, has given rise to considerable confusion in the past, and has been bitterly attacked, yet it still plays a part in our everyday vocabulary of political analysis. The apparent rejection of the doctrine of the separation of powers cannot hide the fact that many practical problems of twentieth-century government are essentially problems with which the doctrine claimed to deal, and we have seen the emergence of terms such as “quasi-judicial,” “delegated legislation,” or “administrative justice,” which represent attempts to adapt the older categories to new problems. The truth is that we face today serious problems, both in political analysis, and in matters of practical significance in the field of government functions and their division among the agencies of government, as well as in terms of the relationships between these agencies. We are not prepared to accept that government can become, on the grounds of “efficiency,” or for any other reason, a single undifferentiated monolithic structure, nor can we assume that government can be allowed to become simply an accidental agglomeration of purely pragmatic relationships. Some broad ideas about “structure” must guide us in determining what is a “desirable” organization for government.
Yet it is not simply the need to attain an academic “understanding” of the ideas and institutions of contemporary Western society that may lead us to explore the history, and analyse the content, of the doctrine of the separation of powers. For today there are practical problems of the control of government every bit as important and difficult as in the days of Locke, Montesquieu, or the Founding Fathers. Although we may be much more sceptical than they were of constitutional theories which claim to be able to set limits to the exercise of governmental power, nevertheless we cannot merely accept without question the view that the continued concentration of power into the hands of cabinets and presidents is inevitable and cannot be restrained. The concentration of more power into such hands, or of certain sorts of power, may be “inevitable,” given certain assumptions about the military, social, and economic needs of modern societies, but which powers, how much of them, and how they can be effectively limited, are the questions we should be asking. The detail of the theories of constitutionalism may be rejected as no longer applicable, but the ethos of constitutionalism remains; we still believe in “limited government,” but we do not yet see how the limits are to be applied in modern circumstances.
In some ways the modern problems of limiting government power are much more subtle and difficult than those of earlier centuries, when liberal constitutionalists took up the cause of freedom from the exercise of arbitrary power. Today, in the West at least, there are no absolute monarchs wielding an oppressive personal power for their own aggrandizement. If there is a danger, it is rather from a process of erosion than from a direct assault upon liberty. There is no conspiracy of power-hungry men attempting to usurp our governmental systems, and the reaction that is called for from us is not the hysterical denunciation of tyranny. The instruments of the extension of government power, both politicians and civil servants, are sincere men who see merely complex practical problems that have to be solved, and which require strong and efficient government action for their solution. A protagonist of “constitutional government” cannot simply adopt the attitude that such problems must remain unsolved in the cause of “liberty”; indeed the modern liberal constitutionalist is likely to be much embarrassed by the support of many who wish to use the banner of “constitutional liberty” to restrain government action that conflicts with their own programmes, yet who are only too ready to use such governmental power, when they themselves control it, for their own ends. Yet the problem of the control of government remains.
In this work, then, the intention is to examine one great current of constitutional thought, the doctrine of the separation of powers, together with its associated theories of mixed government and checks and balances. The history of the doctrine, fascinating in itself, can tell us much about the forces that gave it birth and shape, and by tracing its various formulations light can be thrown upon the problems with which it has attempted to grapple over the years. Following upon the history of the doctrine, an attempt will be made to analyse its content and to discuss the working institutions of Britain and the United States in the light of this analysis. In this way, it is hoped, we shall be able to disentangle the elements of the doctrine which still have relevance today for the understanding of our political systems, and the value of its recommendations for modern society. Such an investigation may lay the foundation for a wider approach to the discussion of governmental structure of the kind referred to above.
A major problem in an approach to the literature on the doctrine of the separation of powers is that few writers define exactly what they mean by the doctrine, what are its essential elements, and how it relates to other ideas. Thus the discussions about its origin are often confused because the exact nature of the claims being made for one thinker or another are not measured against any clear definition. Some kind of preliminary analysis of the doctrine and its elements is therefore necessary before we step into the vast mass of material that history presents to us. The process of definition of a “pure doctrine” of the separation of powers will of necessity have an arbitrary quality, and no doubt other opinions can be put forward as to what constitutes the “essential doctrine,” on the one hand, and what are modifications of, and deviations from, it, on the other. However, no value judgement is intended in putting forward a particular definition, except to say that it is considered the most useful formulation for the purposes we have in mind. It is labelled the “pure doctrine” simply to indicate that it represents a coherent, interrelated set of ideas, with the complicating factors of related theories removed.
An initial problem in any attempt to make a clear statement of the theory of the separation of powers is the ambiguity which attaches to the word “power” in the literature. It has been used to mean the possession of the ability through force or persuasion to attain certain ends, the legal authority to do certain acts, the “function” of legislating, executing, or judging, the agencies or branches of government, or the persons who compose these agencies. A word that is used in at least five different ways within one context is clearly more of a liability than an asset in any attempt to achieve clear thinking, so that we shall as far as possible avoid its use. Wherever possible in the discussion of the ideas of political writers we shall substitute for the word “power” the appropriate synonym of person, agency, or function, according to the context but, of course, when reporting their views we shall by no means be able to do away with the term altogether. It is also difficult to avoid the use of the word in the sense of an ability, through force or influence, to achieve certain ends, and we shall use it in this sense.
A “pure doctrine” of the separation of powers might be formulated in the following way: It is essential for the establishment and maintenance of political liberty that the government be divided into three branches or departments, the legislature, the executive, and the judiciary. To each of these three branches there is a corresponding identifiable function of government, legislative, executive, or judicial. Each branch of the government must be confined to the exercise of its own function and not allowed to encroach upon the functions of the other branches. Furthermore, the persons who compose these three