Montesquieu’s approach to the definition of the functions of government resembles a review of the history of the uses of these concepts. Chapter 6 of Book XI begins: “In every government there are three sorts of power, the legislative; the executive in respect to things dependent on the law of nations; and the executive in regard to matters that depend on the civil law.” This is clearly a restatement of Locke’s division of government functions, except that Montesquieu does not use the term “federative power” for the executive power in regard to external affairs. He still uses the term “executive” to cover all internal affairs, both governmental and judicial; in other words he adopts, though only momentarily, the twofold division of functions into legislative and executive so familiar to the seventeenth century and earlier. Montesquieu then immediately redefines his terms. He affirms that he intends to use the term “executive power” exclusively to cover the function of the magistrates to make peace or war, send or receive embassies, establish the public security, and provide against invasions. He now seems to wish to confine the term “executive power” to foreign affairs, for he does not make it at all clear that the power to “establish the public security” has any internal connotation—in other words, for Locke’s “federative power” read “executive power.” Furthermore, Montesquieu announces that he will call the third power, by which the magistrate punishes criminals or decides disputes between individuals, the “power of judging.”49 This appears to represent an attempt to reconcile the authority of Locke with the heightened appreciation of the separate existence of the judicial power as distinct from the royal power which had emerged in the early eighteenth century. But this formulation leaves out of account any “executive” acts other than foreign affairs, for the judicial power is confined to disputes between the prince and the individual, and between individuals. Montesquieu has not so far, then, managed to reconcile the seventeenth-century vocabulary with the facts of eighteenth-century government; the vital distinction between the internal acts of the executive and the acts of the judiciary is obscured. However, when he goes on to use these terms he drops both definitions and uses them in a very much more modern way; the three powers are now “that of enacting laws, that of executing the public resolutions, and of trying the causes of individuals,” clearly including internal as well as external affairs in the executive power. It is in this final sense that Montesquieu discusses the relationships between the powers of government, and it is, of course, basically the modern use of these terms. The importance of this transition in his use of words cannot be overemphasized. Not only does he bridge the gap between early modern and later modern terminology, but he also obscures one of the basic problems of a threefold definition of government functions. Locke and others had been bothered by the fact that the “ruler” had two aspects to his function. He had to carry out the law where it was clear and easily stated, principally in internal affairs, but he had also to act in areas where the law could not be laid down in detail and where his prerogative must remain almost wholly untrammelled, that is to say largely in external affairs. Thus between them Locke and Montesquieu state at least four functions of government, not three: the legislative, the executive, the “prerogative,” and the judicial. To bring the two middle ones together as “executive” obscures the fact that in large areas of government activity those responsible for day-to-day government decisions will not be “executing the law,” but exercising a very wide discretion. However, the idea that there are three, and only three, functions of government, was now established, except perhaps in the minds of those English lawyers who had actively to define the prerogative powers of the Crown.
The most important aspect of Montesquieu’s treatment of the functions of government is that he completes the transition from the old usage of “executive” to a new “power of judging,” distinct from the putting of the law into effect, which becomes the new executive function. However, it is in his treatment of the “power of judging” that Montesquieu’s greatest innovatory importance lies. He treats the puissance de juger as on a par, analytically, with the other two functions of government, and so fixes quite firmly the trinity of legislative, executive, and judicial which is to characterize modern thought. Vitally important also is the fact that he detaches this power from the aristocratic part of the legislature and vests it unequivocally in the ordinary courts of the land, although the noble house of the legislature is to have the role of a court of appeal. However, he still does not give the courts the position they were soon to achieve in American thought; he does not accord the judicial branch an exactly equal status with the legislative and executive branches, although he clearly intends the judiciary to be independent of the other two. He sees these two agencies as permanent bodies of magistrates,50 which represent real social forces, the monarch, the nobility, and the people. The judiciary, however, “so terrible to mankind,” should not be annexed to any particular class (état) or profession, and so becomes, in some sense, no social force at all—“en quelque façon nulle”—representing everyone and no one.51 The judiciary, therefore, is to be wholly independent of the clash of interests in the State, and this emphasis upon judicial independence is extremely important for the development of the doctrine.
Montesquieu devotes considerable attention to the nature and composition of the judiciary, but his approach to this problem is very much a reflection of his general scheme, and does not bear much relation to the actual practice in England. In Book VI he had developed his ideas about the judicial function in the differing forms of State. In a despotic government the caprice of the prince is the basis of the law, and judging will be an arbitrary process without rules. In a monarchy, however, the prince rules according to the laws; these must be relatively stable and applied in a cool, aloof fashion. The judges in a monarchy, therefore (and Montesquieu is clearly thinking of the parlements), must be learned in the law, professional, and skilled in the reconciliation of potentially conflicting rules. But the closer the form of government approaches that of a republic, the more fixed and settled are the rules of law, and the more the judges must follow the letter of the law.52 In Rome, he avers, the judges had only to decide matters of fact, and then the punishment was clearly to be found in the laws. In England the jury gives its verdict on the facts and the judge pronounces the punishment inflicted by the law, “and for this he needs only to open his eyes.”53 In Book XI he describes a judicial system without professional judges. He rejects the idea of the judiciary power being lodged in a “standing senate,” and affirms that it should be exercised by persons drawn (tirées) from the people, on an ad hoc basis for fixed periods of short duration. In other words a system of juries, which would apparently be judges of both fact and law, because the laws would be so clear and explicit as to require no professional knowledge in the judges.
Two further aspects of Montesquieu’s treatment of the judiciary require emphasis. First, his insistence that in republics the judges must abide by the letter of the law is of great importance for later views of the judicial function. In England in medieval times the judges were well aware that they “interpreted” the law, and from time to time were aware that they were making law through “interpretation.” The role of the judges in making the law was also recognized in the seventeenth century. But Montesquieu insists that to allow the judges to exercise discretion is to expose the people to the danger that the private opinions of the judges might render the laws uncertain, and that people would then live in society “without exactly knowing the nature of their obligations.” The judges must be “no more than