Mixed constitution
The concept of the mixed constitution, i.e., a constitution which is a mixture of elements characteristic of different constitutional types, has its origins in the classical world of ancient Greece and Rome, specifically in the thought of the philosopher Aristotle (384-322 BCE) and the historian Polybius (c203-c120 BCE).
In Politics III 6-7 Aristotle classifies ‘simple’ constitutions by reference to two criteria: the size of the sovereign body - does one individual rule, do a small number of individuals rule, or do the many rule? – and the way in which power is exercised – is it exercised justly, for the common good, or unjustly, solely to promote the interests of the ruler or rulers? On the basis of these criteria he distinguishes six types of constitution, three ‘correct’ types, where power is exercised justly: monarchy (the rule of one individual), aristocracy (the rule of a few), and ‘polity’ (politeia, the Greek word for ‘constitution’, which Aristotle uses as his name for the constitution under which the many rule justly); and, corresponding to these, three ‘deviant’ types, where power is exercised unjustly: tyranny, oligarchy, and democracy (for Aristotle the word demokratia here, though not always, has a pejorative sense). Later in the Politics he suggests that a constitution of one type may be improved by the addition of elements characteristic of another type – see, e.g., IV 8-9, and the statement at IV 12, 1297a6ff that ‘the better mixed a constitution is, the longer it will last’.
In Book VI of his Universal History Polybius maintains that each of Aristotle’s six constitutional types is inherently unstable (VI 4, 6-11). Power corrupts: rulers who begin by governing in the common interest may come to govern solely in their own interests - a tendency which is exacerbated by the hereditary principle: those born into positions of power and privilege are more likely to take for granted the advantages of their position and to have a weakened sense of its responsibilities (VI 7, 7). There is therefore, Polybius argues, an inevitable cycle of constitutional change (anakuklōsis tōn politeiōn, ‘cycle of constitutions’, VI 9, 10). Monarchy degenerates into tyranny as the single ruler or his successor succumbs to the temptation to neglect the common interest and to govern solely in his own interests; the tyrant is sooner or later overthrown by a small group of the most powerful men in the state; initially they govern in the common interest, but after a time they, or their successors, begin to govern in their own interests, i.e., become oligarchs; they in turn are overthrown by the many, who after a time come to govern unjustly, and democracy degenerates into ochlocracy or mob-rule. The anarchy which results is eventually brought to an end by a single powerful individual, who establishes himself as sole ruler and initially rules justly but after a time succumbs to the temptations of power …., and the cycle begins all over again. (The idea that one form of constitution naturally degenerates into another shapes Plato’s account of constitutional types in Republic VIII & IX – though the constitutional types described by Plato do not correspond exactly to those distinguished by Aristotle and Polybius.)
To remedy the inherent instability of each of the ‘simple’ constitutional types Polybius advocates the adoption of a mixed constitution, i.e., a constitution which combines elements characteristic of each of the three ‘correct’ constitutions. A mixture of all three types, he believes, is best (VI 3, 7): the distribution of power between a single individual, a few, and the many, and the system of checks and balances generated by this distribution will serve to protect a mixed constitution against change (VI 15). There are of course, as both Aristotle and Polybius recognise, many different ways in which elements characteristic of each of the ‘simple’ constitutions may be combined, and hence many different forms of mixed constitution. In VI 11 Polybius presents the constitution of the Roman Republic, which he greatly admired, as a fine example of a mixed constitution. Sovereignty, he argues, is divided between the two consuls (the two supreme magistrates) whom he identifies as a monarchical element in the constitution, the Senate (an aristocratic element), and the people (a democratic element). The consuls, appointed annually, are the twin heads of the executive arm of government: they have absolute authority as military commanders and are responsible for bringing matters, as appropriate, either before the Senate or before the popular assembly and for implementing whatever decisions are taken by these bodies. The Senate, whose members are former magistrates, controls the treasury and advises the magistrates in all matters of domestic and foreign policy. However, major decisions cannot be taken without the approval of the people: declarations of war, peace treaties, and all legislative proposals must be formally ratified by the popular assembly, which also elects the consuls and other magistrates, Polybius comments that under this system sovereignty is so divided between the consuls, the Senate, and the people that it is impossible to say whether the constitution is monarchic, aristocratic, or democratic.
The concept of the mixed constitution has been widely discussed and defended in the modern world, and many contemporary states have what may reasonably be described as a mixed constitution. Polybius’ account of the constitution of the Roman Republic is known to have influenced the ‘Father’ of the American constitution, James Madison (1751-1836), who refers to Polybius in Federalist Paper No. 63 and describes the American constitution as a mixed constitution in Federalist Paper No. 40, the monarchical element being the President, the aristocratic element the Senate, and the democratic element the House of Representatives.
