THE MODERN VIEW that there are three functions of government, legislative, executive, and judicial, evolved slowly over many centuries, and it is important to realize that the categories which today form the basis for much of our thinking about the structure of government and its operation are the result of a gradual development of ideas that reflects problems concerning the nature of government, first clearly perceived in seventeenth-century England, and still today in process of being worked out. These “functions” of government reflect the response to particular problems in Western societies, and the demand for particular sets of values to be embodied in institutional structures and procedures. The roots of these ideas are to be found in the ancient world, where thinkers wrestled with similar problems, although not unnaturally their responses were somewhat different. Nevertheless the ideas of the ancients about the nature of law, and about the means of controlling power in civil societies, provided much of the basic material to which writers in later ages were to turn for ammunition in the great battles over the control of the machinery of the State.

      There is an essential connection between the notion of government according to law and the concept of the functions of government. This connection forms the basis of the concern with function down through the ages, and is the explanation of the persistence of this concept in spite of the many attacks made upon it. Government according to law presupposes at least two distinct operations, the making of law, and putting it into effect. Otherwise we are left with a formless and unstable set of events which gives no basis for a constitution, or in the Greek context, for a moderate government. Thus Aristotle divided political science into two parts: legislative science, which is the concern of the law-giver, and politics, which is a matter of action and deliberation, or policy; the second part he subdivided into deliberative and juridical science.¹ The major division here between legislation and action was not the modern distinction between legislative and executive, for the Greeks did not envisage the continuous or even frequent creation of new law which is implicit in the modern view of the legislative function. The work of a divinely-inspired legislator who set the foundations of a legal system might need to be amended from time to time to meet new conditions, but this must be done only infrequently and with great caution, for frequent change could lead to the undermining of the general respect for law.² When he distinguished the three elements in every constitution which the good legislator must consider, Aristotle described them as the deliberative element, the element of the magistracies, and the judicial element.³ The function of the deliberative element here did have some relation to the modern notion of the legislative function, for Aristotle described it as being dominant in the enacting of laws, and being concerned with common affairs, but this must be seen within the general view of the nature of legislation mentioned above. Furthermore, the deliberative element was also concerned with what we should call judicial and executive functions.

      When we turn from the idea of distinct functions to the view that these should be entrusted to distinct groups of people, we find little to support it in Aristotle. It is true that in the Constitution of Athens, attributed to him, the impropriety was stressed of the execution by the council of a citizen who had not been tried in a law-court,⁴ but this was a matter of attributing certain tasks to the proper agency, a matter of due process, rather than the assertion of a doctrine of the separation of persons. In fact the guiding principle of the Athenian Constitution, the direct participation of all citizens in all functions of government,⁵ was directly opposed to any such doctrine. Thus Aristotle asserted that “Whether these functions—war, justice and deliberation—belong to separate groups, or to a single group, is a matter which makes no difference to the argument. It often falls to the same persons both to serve in the army and to till the fields”; and more specifically, “The same persons, for example, may serve as soldiers, farmers and craftsmen; the same persons again, may act both as a deliberative council and a judicial court.”⁶ Thus the major concern of ancient theorists of constitutionalism was to attain a balance between the various classes of society and so to emphasize that the different interests in the community, reflected in the organs of the government, should each have a part to play in the exercise of the deliberative, magisterial, and judicial functions alike. The characteristic theory of Greece and Rome was that of mixed government, not the separation of powers.⁷

      The greatest contribution of ancient thought in the sphere in which we are concerned, was its emphasis upon the rule of law, upon the sovereignty of law over the ruler. It emphasized the necessity of settled rules of law which would govern the life of the State, give it stability and assure “justice for equals.” “He who commands that law should rule may thus be regarded as commanding that God and reason alone should rule; he who commands that a man should rule adds the character of the beast.”⁸ This emphasis upon law, upon the importance of settled rules, was essential to the thought of the Greeks, for they were deeply convinced of the importance of making proper arrangements for the way in which the State should go about its business. Constitutional provisions had for them a real significance in determining the impact of the government upon the citizen, and were not, as some modern writers seem to suggest, of little importance in determining the outcome of political situations. As a corollary of the rule of law was the assertion, in both Greek and Roman thought, of the generality of law. Aristotle insisted that “law should be sovereign on every issue, and the magistrates and the citizen body should only decide about details”;⁹ “law can do no more than generalize.”¹⁰ The same attitude was expressed by the Roman rule in the code of the XII Tables that no law may be passed against an individual.¹¹ But if the law can deal only with generalities, then there must be provision for giving discretion to those who have to apply the law to individual cases, or who have to make decisions on issues on which the law-giver, because of the generality of the language he must use, was unable to pronounce.¹² As we have seen above, the distinctions drawn here by Aristotle do not correspond exactly with the distinction between the legislative and executive functions defined in later ages, but they do deal with the difference between making a general rule on the one hand, and judging particular instances, on the other. When the conception of law as a relatively unchanging pattern was later replaced by the idea of a system of law subject to human control, then the basis of a twofold division of the functions of government was ready to hand.

      The connection between modern theories of law and sovereignty and the emergence of the concepts of the legislative, executive, and judicial functions of government is very close. The idea of an autonomous “legislative power” is dependent upon the emergence of the idea that law could be made by human agency, that there was a real power to make law, to legislate. In the early medieval period this idea of making law by human agency was subordinated to the view that law was a fixed unchanging pattern of divinely-inspired custom, which could be applied and interpreted by man, but not changed by him. In so far as men were concerned with “legislation” they were in fact declaring the law, clarifying what the law really was, not creating it. Legislation was in fact part of the judicial procedure.¹³ Law was seen as the embodiment of the law of God in the custom of the community, and the actions of the King in his Council making formal statements of the law were seen as clarificatory acts. There could, therefore, be only one “function” of government—the judicial function; all acts of government were in some way justified as aspects of the application and interpretation of the law. The participation of Parliament in the promulgation of law was seen as an aspect of this judicial function of government; the High Court of Parliament advised the King upon the issues which came before him for decision, and declared the law as a court declares it, but in a more formal way, and usually, but not always, in general terms.¹⁴ Of course, this is not to say that there was a medieval or early modern view of a “judicial function” equivalent to our modern view of that function. Rather it was a way of looking at government which encompassed the whole range of governmental acts, whilst recognizing that there were differing agencies involved, differing tasks to be performed, and differing procedures to be employed. This recognition formed the basis for the lists of the “parts of sovereignty” that were later evolved by writers on government, and again at a later stage provided the starting-point for the formulation of new distinctions of the functions of government.

      Authorities differ upon the extent to which this view carried over into the later medieval and early modern periods of English history.