of the spirit which lies behind those systems. Such a claim, of course, requires qualification as well as justification. The “doctrine of the separation of powers” is by no means a simple and immediately recognizable, unambiguous set of concepts. On the contrary it represents an area of political thought in which there has been an extraordinary confusion in the definition and use of terms. Furthermore, much of the specific content of the writings of earlier centuries is quite inappropriate to the problems of the mid twentieth century. The doctrine of the separation of powers, standing alone as a theory of government, has, as will be demonstrated later, uniformly failed to provide an adequate basis for an effective, stable political system. It has therefore been combined with other political ideas, the theory of mixed government, the idea of balance, the concept of checks and balances, to form the complex constitutional theories that provided the basis of modern Western political systems. Nevertheless, when all the necessary qualifications have been made, the essential ideas behind the doctrine remain as vital ingredients of Western political thought and practice today. To substantiate this view it will be necessary to attempt to define and use terms in a more precise way than has been generally the case in the past, and to review the evolution and history of the doctrine, important enough in itself, in order to understand its significance in the past and its relevance today. In spite of the criticisms which can be made of the idea of the separation of powers, perhaps the most important conclusion to be drawn from such a review is that the problems of earlier centuries remain the problems of today; although the context is different, and the dimensions of the problem have changed, it is nevertheless the continuity of political thought, and of the needs of political man, which emerges as the most striking aspect of the history of institutional thought.
The doctrine of the separation of powers finds its roots in the ancient world, where the concepts of governmental functions, and the theories of mixed and balanced government, were evolved. These were essential elements in the development of the doctrine of the separation of powers. Their transmission through medieval writings, to provide the basis of the ideas of constitutionalism in England, enabled the doctrine of the separation of powers to emerge as an alternative, but closely related, formulation of the proper articulation of the parts of government. Yet if we define the doctrine in the terms suggested below, it was in seventeenth-century England that it emerged for the first time as a coherent theory of government, explicitly set out, and urged as the “grand secret of liberty and good government.”1 In the upheaval of civil war the doctrine emerged as a response to the need for a new constitutional theory, when a system of government based upon a “mixture” of King, Lords, and Commons seemed no longer relevant. Growing out of the more ancient theory, the doctrine of the separation of powers became both a rival to it, and also a means of broadening and developing it into the eighteenth-century theory of the balanced constitution. Thus began the complex interaction between the separation of powers and other constitutional theories which dominated the eighteenth century. In England, France, and America this pattern of attraction and repulsion between related yet potentially incompatible theories of government provided the fabric into which was woven the varied combinations of institutional theories that characterized the thought of these countries in that eventful century. The revolutionary potentialities of the doctrine of the separation of powers in the hands of the opponents of aristocratic privilege and monarchical power were fully realized in America and France, and its viability as a theory of government was tested in those countries in a way which all too clearly revealed its weaknesses. Nevertheless, the separation of powers, although rejected in its extreme form, remained in all three countries an essential element in constitutional thought, and a useful, if vague, guide for institutional development. That this once revolutionary idea could also become in the course of time a bulwark of conservatism, is understandable, for this is the fate of many political ideas.
As the nineteenth century developed the social environment became less and less favourable for the ideas which had been embodied in the pure doctrine of the separation of powers. The attack upon the doctrine came in two waves. First, the group which in earlier years had most fervently supported the separation of powers, the middle class, now saw within its reach the control of political power through the extension of the franchise, and the need for a theory that was essentially a challenge to the power of an aristocracy diminished. However, the lessened enthusiasm for the doctrine took the form, in the period up until the Second Reform Act in England, of a re-examination and reformulation of the doctrine rather than an outright rejection of it. Any suggestion of an extreme separation of powers had to be denied, but the importance of the idea as a part of the newly emerging theory of parliamentary government was readily acknowledged. The idea of balance, which was now transferred from the earlier theory of the balanced constitution to become an integral part of the new theory, required still a separation of organs and functions, but with a different set of concepts that had to be fitted into the framework of constitutional theory. The second wave of attack upon the doctrine of the separation of powers came with what Dicey labelled “the age of collectivism.” Yet paradoxically it was the middle-class defenders of the mid-nineteenth-century status quo who, for reasons which will become apparent at a later stage, laid the ground for the virtual eclipse of the separation of powers as a coherent doctrine in England. The rise and fall of the classical theory of parliamentary government is, therefore, an integral part of the story of the separation of powers. At the centre of this development stands the figure of Walter Bagehot, whose work represents a turning-point in the history of English constitutional thought.
Changing ideas about the role of government and its structure were accompanied by a changing emphasis in ideas about the nature of sovereignty. In earlier centuries the stress upon the necessity of a single, omnipotent source of power was in general the resort of theorists of absolutism, strongly rejected by liberal constitutionalists. The defenders of liberty against arbitrary government stressed the division of power, and the limitations upon power imposed by the constitution or by a higher law. Rousseau’s association of the idea of unlimited sovereignty with the people, rather than with a monarch, led, however, to a reorientation of ideas. If absolute power were in the hands of the people, or their representatives, then it could be stripped of its associations with arbitrary government and formed into an instrument of democratic power. If the franchise could be restricted to those with a stake in the community then the idea of an unlimited, indivisible sovereign power became for the liberal individualist not a threat, but a safeguard. It became, in the hands of Bentham and Austin, not a means of arbitrary rule but an instrument for the reform of government which would increase the freedom of the individual. That it could equally well become the instrument of another class, and of a different philosophy of government, was a possibility that, if they acknowledged it, did not prevent them from attacking the earlier ideas of the division and limitation of power. It is one of the great ironies of intellectual history that those who were most concerned to establish laissez-faire busied themselves with the fashioning of those weapons which were to be used most powerfully to destroy it.
The general context of political development during the nineteenth and early twentieth centuries provided, therefore, the framework for a sharp reappraisal of the doctrine of the separation of powers, but there were other equally important, and related, intellectual challenges to the doctrine. The desire for a unified system of government, whether to achieve reform or for purposes of positive State action, led to a rediscovery of the role of discretion and prerogative in government. The idea of a “mere executive power” which had never been wholly accepted in England, except by extreme radicals, was now specifically rejected. The attack upon the Montesquieu formulation of the triad of government powers, initiated by Bentham and Austin, was taken up by the writers on parliamentary government, and further developed in Germany, France, and America, so that by the early decades of the twentieth century the beautiful simplicity of the eighteenth-century view of the functions of government lay mangled and shattered. And yet, although the attack seemed overwhelming, it was so far a merely negative criticism that no coherent formulation of the structure of government and the articulation of its parts rose up to take the place of the earlier theory. As a result the vocabulary of an earlier age continued in use faute de mieux. It was much more than a problem merely of usage, however, for the persistence of the concepts and terminology of an earlier age reflected the fact that Western society in the mid twentieth century continued to value the ideas which had been an integral part of constitutionalism for three centuries, but wished to modify them