Separation of powers

• 1. Introduction

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  Separation of powers sits at the foundation of nearly every modern democracy, yet the idea that government must be divided against itself to stay free took centuries to develop. The question that haunted political thinkers across the ancient world, through the English Civil War, and into the age of revolutions was a simple and dangerous one: what stops the people who hold power from keeping it forever? Polybius, writing about the Roman Republic in his Histories, offered an early answer. He saw Rome's system of Senate, Consuls, and Assemblies as a form of mixed government, and he credited Lycurgus of Sparta with inventing the first government of that kind. The principle Polybius was describing would later carry a name, and that name would become one of the most argued-over phrases in constitutional history. This is the story of how separation of powers was theorized, fought over, written into constitutions, and then complicated by the discovery that separating power is not, by itself, enough.

• 2. The English Origins

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  During the English Civil War, parliamentarians framed their conflict with the Crown in constitutional terms. They saw the English government as three parts: the King, the House of Lords, and the House of Commons. Their argument was that the first should hold only executive power, and the latter two only legislative power. Out of this conflict came one of the earliest documents to formally propose a tripartite separation: the Instrument of Government, written by the English general John Lambert in 1653. Lambert's document was adopted as England's constitution for several years during the Protectorate. It created a legislative branch in Parliament and two executive branches, the English Council of State and the Lord Protector, with all three designed to hold checks upon each other. After the Restoration, the idea that judicial power must also be separate gained urgency. The Crown had used the courts to prosecute opposition leaders in the late reign of Charles II and through the short reign of James II, specifically during the 1680s. That experience made the argument for judicial independence concrete rather than merely theoretical.

• 3. Locke's Three Powers

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  John Locke published his Two Treatises of Government in 1690, and in it he drew a distinction that would shape all subsequent debate. Locke named three types of power: legislative, executive, and federative. Legislative power, in his account, carried the right to direct how the force of the commonwealth would be employed. Executive power was the ongoing task of putting existing laws into effect. Federative power was something different entirely: the management of war, peace, leagues, and alliances with communities outside the commonwealth, which we would now call foreign policy. Locke was careful to note that these were separate powers, not necessarily separate institutions. He observed that executive and federative powers, though distinct in kind, are often held by a single body. His hierarchy was clear: legislative power stood supreme, because, as he wrote in the Second Treatise, what gives laws to another must be superior to him. Yet that supremacy was not absolute. Locke held that the legislature could not govern arbitrarily, could not seize property or levy taxes without the consent of the governed, and could not pass its law-making authority to another body. That last restriction he described in a section that would later be known as the nondelegation doctrine.

• 4. Montesquieu's Framework

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  Montesquieu published The Spirit of Law in 1748, and the argument he made in it became the version of separation of powers that most constitutions would eventually absorb. He built his model on two historical cases: the Roman Republic, which he believed had divided its powers so effectively that no single actor could seize control, and the British constitutional system, where he saw a division among the monarch, Parliament, and the courts. Montesquieu described three sorts of power in every government: the legislative, the executive in respect to things of the law of nations, and the executive in regard to matters of civil law, which he preferred to call the judiciary. His argument for keeping these separate was stated starkly. When legislative and executive powers are united in the same person, he wrote, there can be no liberty. When judicial power is not separated from the other two, the life and liberty of the subject would be exposed to arbitrary control. He went further still: there would be an end to everything if the same man or body were to exercise all three powers at once. Montesquieu also addressed the question of where executive power should sit. He argued it belonged in the hands of a single monarch, on the grounds that execution requires speed, and speed is better achieved by one person than by many. That argument would prove more contested than almost anything else he wrote.

• 5. Checks and Balances

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  Separation of powers and checks and balances grew up alongside each other, but they are not the same idea. Checks and balances descended from the ancient theory of mixed government, and its logic points in a different direction. Where separation of powers insists on division, checks and balances insists on interdependence. Each branch must have the tools to push back against the others. In Federalist No. 78, Alexander Hamilton cited Montesquieu to argue that the judiciary was a separately distinct branch of government, not merely an appendage of the executive. Before Hamilton made that case, many colonists had conceived of judges as operating within the executive branch. James Madison articulated the necessity of mutual constraint in Federalist No. 51. His argument was that the private interest of every individual may be a sentinel over the public rights; rivalry between institutions could substitute for the good motives that citizens cannot reliably expect their governors to possess. Thomas Paine took a sharply different view. In Common Sense, he used the image of a machine in which the heaviest wheel always sets the others in motion, arguing that constitutional checks cannot actually stop the dominant power in a system, only slow it down. Paine went further and rejected the theory that English liberty rested on constitutionally guaranteed checks and balances at all. In his reading, English freedom owed everything to the character of the English people, not to any structural arrangement in the constitution. Immanuel Kant, meanwhile, sided with Madison: he held that a workable state could be built even from a nation of devils, provided the constitution set opposing factions against each other.

• 6. Beyond Three Branches

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  The standard model of three branches, legislative, executive, and judicial, does not capture every approach that governments have taken to dividing power. An electoral branch, responsible for overseeing election administration and boundary delimitation, has been established as its own distinct institution in Bolivia, Costa Rica, Panama, Nicaragua, and Venezuela. Taiwan's Control Yuan performs auditing and holds the power to impeach public officials for misconduct; in other countries, including the United States, those functions are folded into the legislature through bodies like the Government Accountability Office and the impeachment processes of the House and Senate. Sweden recognizes four branches, adding an administrative branch alongside the traditional three. The most elaborate division comes from Sun Yat-sen's five-branch system adopted by the Republic of China. That system added a Control Yuan and an Examination Yuan to the standard three, and was originally intended for all of China. The Republic of China never extended it to the mainland, losing most of that territory to the Communists during the Chinese Civil War. Sweden's four-branch and Taiwan's five-branch systems show that the number three, however historically dominant, reflects a set of intellectual choices rather than a logical necessity.