Any American high schooler can tell you that the separation of powers is one of the defining features of American government. The division of political power into the legislative, executive, and judicial branches is a well-known practice in many Western countries. But where did this idea originate? This idea did not derive wholly from Enlightenment or modern thinkers. On the contrary, the division of powers was first proposed by Polybius, a Greek thinker of the second century BC.

Polybius was born around 208 BC in Arcadia, a region located in Greece’s Peloponnese. His father, Lycortas, was a politician and loyal ally to the Achaean league, a federalist organization among Greek city-states that aimed to preserve local independence through collective action. Following in his father’s footsteps, Polybius became a statesman and cavalry commander in the Achaean league. The focus of his political career was the preservation of the league’s independence through cooperation with the powerful Roman hegemony.

The Achaean league was initially aligned with Rome in opposition to the kingdom of Macedonia. When the league began to contemplate the idea of an alliance with Macedonia, the Romans reacted quickly by seizing a swathe of hostages to ensure Greek loyalty. These hostages were kept in Rome for a trial that never came. They were eventually permitted to return home, but only after seventeen years in captivity.

Polybius was among the hostages captured and transported to Rome. However, unlike his fellow Greeks, Polybius was fortunately treated well by his host Aemilius Paulus. The pair had met while on campaign and had become good friends. As a result, while in Rome, Polybius was hosted by Aemilius and tutored his two sons. Thanks to his friendship with Aemilius, Polybius not only avoided miserable living conditions, but he also had access to the elite of Roman society. From this vantage point, Polybius was ideally poised to study the unique and unprecedented Roman constitution.

From City to Empire: The Rapid Rise of Rome

By the time that Polybius was writing, Rome had expanded from a meager city state to an ancient superpower. In the beginning, Rome had few if any natural advantages; it was inland and therefore cut off from trade, located on infertile soil, and surrounded by enemies. For years, the early Romans were a hardy, agrarian people who had to work extremely hard simply to sustain themselves. Traditional wisdom would predict a depressingly short history of liberty for the Roman people, who would eventually be dominated by their enemies due to their lack of resources. Against all odds, traditional wisdom was soundly thrashed as Rome progressed from strength to strength, overcoming their Italian enemies and expanding out into the wider Mediterranean. Many stunned spectators questioned how such an austere, agrarian civilization had come to dominate the Mediterranean with such unprecedented success. Polybius sought to answer this question in his book, The Histories.

Polybius believed that Rome’s constitution was effective for two reasons. Firstly, the constitution adapted to suit human nature. Secondly, it prevented what he referred to as “anacyclosis,” a cyclical theory of political evolution and decay.

Human Nature: Self-interest and Fear

Many ancient political theorists believed that political theory was limited by the nature of man. Therefore, any theory of politics must start with an examination of man’s nature and faculties. At first, Polybius believed that people were united due to their own weakness and fear. Thus, the strongest man among them rose to a position of power. This order resembled little more than the actions a herd of sheep or a flock of birds.

Humans cease to resemble animals when they begin to apply reason. According to Polybius, “when one human sees another wronged,” they “will notice the thing and be displeased at what is going on, looking to the future and reflecting that they may all meet with the same treatment.” They “will naturally be displeased and offended by such conduct, sharing the resentment of their injured neighbour and imagining themselves in the same situation.”¹ Through moral imagination and sympathy, an idea of justice is formed. “Ferocity and force having yielded to reason,” the alpha transforms; what was an alpha now becomes a king.²  Polybius’s account of the origins of justice bear a striking resemblance to the moral theories that Adam Smith would later articulate in The Theory of Moral Sentiments.³

Polybius describes humans as rational and self-interested creatures.⁴ The duality of fear and sympathy rule our lives. As long as fear exists, people will cooperate and sympathise with one another, producing a stable society. Problems arise when members of a society lack the imaginative capacity to put themselves in the place of others. This results in the unsympathetic person practicing little if any restraint and benefiting themselves at the expense of others.

Anacyclosis: The Cycles of Government

Polybius stated emphatically “that all existing things are subject to decay and change is a truth that scarcely needs proof; for the course of nature is sufficient to force this conviction on us.”⁵ According to Polybius, this maxim of nature can also be applied to political orders. This was not a new idea in Greek political thought. Aristotle believed in a cyclical theory of government in which each order begins pure but rapidly decays to its corrupted form.⁶ Polybius, like his fellow-Greek predecessors, believed in a cycle of governments. For the Greeks, governments came in three varieties: monarchy (rule by one), aristocracy (rule by the few) and democracy (rule by many). These forms of government were distinguished as far back as Herodotus, writing in the fifth century BC.⁷

Polybius believed that, like other animals, humans naturally formed a herd for the purpose of mutual protection.⁸ Given the nature of herds, “it is a necessary consequence that the man who excels in bodily strength and in courage will lead and rule over the rest.”⁹ Therefore the cycle of political orders—anacyclosis—began with monarchy, the rule of one.

Monarchy to Tyranny

The first monarch would be an honorable man worthy of the right to rule due to his staunch upholding of justice. As a result, his rule would be respected even when his physical strength waned in later life.¹⁰ Sadly, this state of peaceful affairs would not last. As the king reaches old age, it would be necessary that he choose a successor to inherit his position. Because the first king had lived a life of hardship and toil, he would be an austere figure who conducted his leadership as a first among equals. Polybius wrote that the first kings “were exempt from all vituperation or jealousy, as neither in their dress nor in their food did they make any great distinction, they lived very much like everyone else, not keeping apart from the people.” ¹¹

The successor to the first king would not prove so virtuous. Growing up in luxury and privilege, the new king would act as if he were superior to his subjects. His tastes would become excessive and offensive to the populace at large. As a result of his lack of virtue, he would eventually become a tyrant.

Aristocracy to Oligarchy

Unable to bear the humiliation of injustice, the best of men would rise up against the new tyrant. These rebels would not usurp power for selfish gain since, according to Polybius, they were “of the noblest, most high-spirited, and most courageous, because such men are least able to brook the insolence of princes.”¹² When they prevailed, harmony would once again be restored: “these chiefs gladly assumed this charge and regarded nothing as of greater importance than the common interest, administering the private and public affairs of the people with paternal solicitude.”¹³

But yet again, the same issue would rear its ugly head, namely the problem of succession. The sons of these noblemen would not grow up to emulate their courageous fathers. Instead, “having no experience of misfortune and none at all of civil equality and liberty of speech, and having been brought up from the cradle amid the evidences of the power and high position of their fathers,” these petulant aristocrats would indulge in all kinds of greed, lust, and excess.¹⁴ Consequently, they would meet the same fate as the kings: a violent overthrow.

Democracy to Mob Rule

The people of this exhausted society had lost faith both in monarchy and in aristocracy. Since both rule by one (monarchy) and rule by the few (aristocracy) had proved to be unreliable systems, the new political order was to be based upon rule by the many, or democracy. As with all of Polybius’s political orders, democracy experienced its moment of flourishing glory.

For a time, the founders of this new democracy valued equality and freedom of expression.

The next generation, as always, proved problematic. Growing up in a society of equals, the new generation—especially the richer members—no longer valued the virtue of equality, instead aiming for preeminence. When these people “lust for power and cannot attain it through themselves or their own good qualities, they ruin their estates, tempting and corrupting the people in every possible way.”¹⁵ This new political order rapidly degenerates into violence and anarchy. Those who lust for preeminence band together and “massacre, banish, and plunder, until they degenerate again into perfect savages and find once more a master and monarch.”¹⁶

The central problem in anacyclosis, as Polybius characterizes it, is the lack of continuity between successive generations. The justice of the monarch decays to the pride of the tyrant. The virtue of the aristocrat decays to the indulgence of the oligarch. The equality of the democrat decays to the greed of the mob. Unsurprisingly, this decline culminates in anarchy. Reverting once more to step one, the grim sequence began again. Was there any solution to this miserable and eternal cycle?

The Greek Solution to the Cycle

Each system of government has its own virtues, but each has an inherent vice. Using the analogy a ship, borrowed from Plato, Polybius explains that iron can rust, wood has its worms, and timber is subject to pests.¹⁷ Similarly, “each constitution has a vice engendered in it and inseparable from it.”¹⁸ This theory of decaying cyclical affairs was common amongst Greek thinkers.¹⁹ Aristotle proposed that the solution was to unite and blend the political orders together.²⁰ By having a mixture of all of the orders, the vices inherent in each are nullified. Aristotle and Plato aimed to eliminate disagreement and conflict while promoting harmony and unanimity. The idea that a mixed constitution would yield a peaceful society was an idea that dominated political thought in the ancient Greek world.²¹ Polybius, however, departed from this consensus drastically.

Polybius’s Solution

For Polybius, the function of politics is not to create unanimity, but rather to preserve liberty through stability. This idea is evident in his praise of the Spartan constitution, where Polybius notes that Sparta enjoyed a “lasting heritage of freedom.”²² Polybius asserted that anacyclosis, with its constant gravitation towards despotism, is detrimental to liberty. Thus it is necessary that the cycle be halted and stability maintained.

How did the Romans preserve their liberty? One might argue that the Romans were made great by their leaders who displayed great personal and civic virtue. There are many examples throughout Roman history of selflessly dedicated and brave leaders, such as Cincinnatus, who gave up absolute power for a simple agrarian life.²³ However, this was not the reason that Rome succeeded. Polybius did not believe that virtue alone was enough to engender a stable and free society.²⁴ He disregards Athens, rejecting it as an unhelpful model to follow precisely because its moments of greatness were achieved by great men.²⁵ Shortly after these great men perished or were ousted, Athens, according to Polybius, collapsed back into mediocrity, confusion and destitution.²⁶

Another issue for Polybius was that human nature is not particularly malleable. Political theory has to adapt to human nature, not vice versa.²⁷ Rather than hoping blindly for virtuous leadership which was not guaranteed, Polybius firmly believed in reliance upon good rules and institutions to preserve an orderly liberty.

If humans are, as Polybius theorized, self-interested animals driven by both fear and sympathy, the solution must be to institutionalize fear in order to promote sympathy. Instead of attempting to eliminate social conflict altogether, Polybius proposed that humans should aim to make conflict productive and useful. Fear can be institutionalized and conflict can be made productive by the combination of the three simple forms of government, i.e. monarchy, aristocracy and democracy.

In another radical move for his time, Polybius rejected the solution of a mixed constitution. Polybius never uses the word “mixed.” Instead, he uses the words “composition,” “arrangement,” “balance” and “equilibrium.” Polybius’s ideal political order is not mixed like the ingredients in a cake are mixed into a single homogenous entity. On the contrary; each piece is separate and distinct and has a different role.²⁸ This concept of the separation of power is the key to the success of Rome, which Polybius describes as having dominion over almost the entire world.²⁹

Innovation in the Roman Government

Polybius identifies and discusses three institutions of the Roman government: the Consuls, the Senate, and the Popular Assemblies. Each embodied one of the three orders of government.

Monarchy was represented by the two Consuls. The Consuls had the power to command armies and presided over the Senate and the Popular Assembly. The Senate filled the role of the aristocracy. This was an advisory council of ex-magistrates who were members for life. In theory, the Senate was merely an advisory body, but in practice, its authority extended to a variety of public policy issues. Domestically, the Senate presided over courts, had power over tax revenue, and provided the main arena for political debate. On matters of foreign policy, the Senate was responsible for declaring war and negotiating with foreign ambassadors. Finally, democracy was represented by the Popular Assembly, which had the sole power to pass legislation, elect magistrates, and even ratify or reject foreign policy treaties.

Unlike his predecessors, including Plato and Aristotle, Polybius did not aim to establish harmony and unanimity. Rather than eliminate conflict entirely, he wished instead to make it useful.³⁰ By molding politics around human nature, Polybius’s account of the Roman constitution demonstrates how conflict, since it cannot be avoided, should instead be utilized in the most productive manner possible for the common good.

According to Polybius’s account of human nature, we are fundamentally self-interested beings who aim to increase our power. However, we are also responsive to fear. Each part of the government has a separate and distinct function. Given the separate nature of each facet of the government’s jurisdiction, each part will naturally fear the encroachment of the others beyond their proper limits. This fear generated a surprisingly beneficial type of conflict. Each of Polybius’s institutions would compete against the others in order to protect its own realm of authority. Their mutual fear of losing their respective powers would thereby produce the stability Polybius valued.

The Roman constitution also made it difficult for one particular group or individual to seize power. Each part of the government controlled a different area of life and each was interdependent on the others, so none could wholly dominate. In spreading power out and giving each office a particular function, the Romans instituted checks and balances that guaranteed an orderly liberty by preventing government overreach and decentralizing power.

Polybius after Rome

Polybius’s work was widely referenced and employed by a variety of thinkers throughout history, including the Roman statesman and philosopher Cicero, the Renaissance writer Nicólo Machiavelli, and, most importantly, Charles-Louis de Secondat, Baron de La Brède—better known as Montesquieu. In his seminal work On The Spirit of Laws, Montesquieu drew heavily from Polybius’s analysis in book six of The Histories.

On the Spirit of Laws was constantly cited by the Founders, who were aware of Montesquieu’s debt to Polybius. The Founders could hardly ignore the ancient influence on Montesquieu’s thought as they were fully immersed in a culture of Classicism. From a young age, males were educated in a curriculum filled to the brim with classical authors including Homer, Virgil, Horace, Plutarch, Cicero, Sallust, Livy, and Tacitus, to name just a small sample.³¹ As Noah Webster put it, “the minds of the youth are perpetually led to the history of Greece and Rome.”³²

A knowledge of classical authors was possessed by every educated male in the Early American Republic. The idealized image of Republican Rome was constantly evoked as a model to follow by the Founders, who agreed with Polybius’s premise that the key to Rome’s triumph was its masterful implementation of the separation of powers.

In John Adams’s A Defense of the Constitutions of Government of the United States of America, he cites Polybius numerous times and even dedicates an entire chapter to his theories. Praising the Roman constitution’s separation of powers, Adams writes:

The Roman constitution formed the noblest people and the greatest power that has ever existed. But if all the powers of the consuls, senate, and people had centered in a single assembly of the people, collectively or representatively, will any man pretend to believe that they would have been long free, or ever great?³³ 

James Madison, discussing the separation of powers, stated that “no political truth is certainly of greater intrinsic value.”³⁴ In Federalist 63, Madison cites Polybius, and he dedicates Federalist 47 entirely to the separation of powers. The influence of Polybius can be keenly felt when Madison writes: “The accumulation of all powers, legislative, executive, and judiciary, in the same hands whether of one, a few or many, and whether hereditary, self appointed, or elective, may justly be pronounced the very definition of tyranny.”³⁵

Polybius’s account of the Roman Republican constitution was a widely appreciated work, gaining praise from thinkers including as Machiavelli, James Harrington, Algernon Sidney, Montesquieu, John Adams, and James Madison. Polybius demonstrated that virtue alone was not enough to preserve liberty. An orderly set of rules that distribute and limit power is essential for a free republic to endure the test of time.

1. Polybius,The Histories 6.6. ↩
2. Polybius,The Histories 6.6. ↩
3. Christopher Berry, Social Theory and the Scottish Enlightenment (Edinburgh, 1997), pp. 162-163. ↩
4. Benjamin Straumann, Crisis and Constitutionalism: Roman Political Thought from the Fall of the Republic to the Age of Revolution (Oxford, 2016), p. 154. ↩
5. Polybius,The Histories 6.57. ↩
6. Aristotle, Nicomachean Ethics 1120b. ↩
7. Herodotus, The Histories 3.80-82. ↩
8. Polybius,The Histories 6.5. ↩
9. Polybius,The Histories 6.5. ↩ 
10. Polybius,The Histories 6.6. ↩
11. Polybius,The Histories 6.5. ↩
12. Polybius,The Histories 6.7. ↩
13. Polybius,The Histories 6.8. ↩
14. Polybius,The Histories 6.8. ↩
15. Polybius,The Histories 6.9. ↩
16. Polybius,The Histories 6.9. ↩
17. Plato, Republic (488a–489d). ↩
18. Polybius,The Histories 6.10. ↩
19. David E. Hahm, ‘The Mixed Constitution in Greek Thought’ in Ryan K. Balot, ed., A  Companion to Greek and Roman Political Thought (New Jersey, 2009), pp. 178-199. ↩
20. Jed Atkins, Roman Political Thought (Cambridge, 2018), p. 23. ↩
21. David E. Hahm, ‘The Mixed Constitution in Greek Thought’ in Ryan K. Balot, ed., A  Companion to Greek and Roman Political Thought (New Jersey, 2009), pp. 178-99. ↩
22. Polybius, The Histories 6.48. ↩
23. Livy, The History of Rome 3.29. ↩
24. Benjamin Straumann, Crisis and Constitutionalism: Roman Political Thought from the Fall of the Republic to the Age of Revolution (Oxford, 2016), p. 157. ↩
25. Ibid. ↩
26. Jed Atkins, Roman Political Thought (Cambridge, 2018), p. 22. ↩
27. Frank William Walbank ‘A Greek look at Rome: Polybius VI Revisited’ in Polybius, Rome and the Hellenistic World: Essays and Reflections (Cambridge, 2002), p. 281. ↩
28. Benjamin Straumann, Crisis and Constitutionalism: Roman Political Thought from the Fall of the    Republic to the Age of Revolution (Oxford, 2016), pp. 156-58. ↩
29. Polybius,The Histories 6.2. ↩
30. Jed Atkins, Roman Political Thought (Cambridge, 2018), p. 24. ↩
31. Bernard Bailyn, The Ideological Origins of the American Revolution (Harvard, 1967), p. 24. ↩
32. Carl J. Richards, The Founders and the Classics: Greece, Rome, and the American Enlightenment (Harvard, 1995), p. 13. ↩
33. John Adams, A Defence of the Constitutions of Government of the United States of America, Vol.1 XXX. ↩
34. The Federalist Papers, No. 47. ↩
35. Ibid. ↩