Separation of powers
Principle dividing government into distinct branches to prevent tyranny.
Separation of powers is a principle of governance that functionally differentiates several types of state power—usually legislation, adjudication, and execution—and requires these operations to be conceptually and institutionally distinct and clearly articulated, thereby maintaining the integrity of each branch. It is intended to prevent power centralization, democratic backsliding, and tyrannical government, and is closely linked to notions of checks and balances.
The concept has deep historical roots. The ancient historian Polybius described the Roman Republic as a mixed government, detailing its system of checks and balances among the Senate, Consuls, and Assemblies, and credited Lycurgus of Sparta with the first such government. During the English Civil War, parliamentarians viewed the English system as having three branches—the King (executive), the House of Lords, and the House of Commons (legislative)—with the executive holding only executive powers. A key early document proposing a tripartite separation was the Instrument of Government, written by General John Lambert in 1653, which established a legislative Parliament and two executive branches (the Council of State and the Lord Protector), all elected and mutually checking one another. Later, following the Crown’s use of the judiciary to prosecute opponents in the 1680s, English thought developed the idea that judicial powers should also be separated from the executive.
John Locke, in his *Two Treatises of Government*, distinguished legislative, executive, and federative (foreign policy) powers, though he did not require them to be held by entirely separate institutions. He held the legislative power supreme, deriving its authority from the people, and argued it could not govern arbitrarily, tax without consent, or delegate its lawmaking authority. Montesquieu, in *The Spirit of Law*, is commonly associated with the tripartite system, describing a distribution of power among a legislature, an executive, and a judiciary. He argued that if any one body held two or more of these powers, liberty would be lost, as the same entity could enact, execute, and adjudicate tyrannical laws. He also noted that if the legislature appoints the other branches, the power to appoint implies the power to revoke, undermining true separation.
- field
- Political philosophy, constitutional law
- known_for
- Tripartite system of legislative, executive, and judicial powers
- key_thinkers
- Polybius, John Locke, Montesquieu
- related_concept
- Checks and balances
Lore & Background
The concept of separation of powers has ancient roots. Polybius, in his Histories, described the Roman Republic as a mixed government ruled by the Senate, Consuls, and Assemblies, and explained the system of checks and balances in detail, crediting Lycurgus of Sparta with the first government of this kind. During the English Civil War, parliamentarians viewed the English system as composed of three branches—the King, the House of Lords, and the House of Commons—with the first having executive powers only and the latter two legislative powers. A further development was the idea that judicial powers should be separated from the executive branch, following the Crown's use of the juridical system to prosecute opposition leaders after the Restoration.
Reader's Guide
He believed legislative power was supreme because it has law-giving authority and derives its authority from the people. He argued that each power should only exercise its own functions, or liberty would be lost. The separation of powers doctrine is often modified by the notion of checks and balances, a distinct idea developed from the ancient theory of mixed government. In most modern constitutions, these two concepts are closely associated, though they conflict to some extent. Constitutional provisions, notably those of the United States Constitution, may reflect compromises between them, leading the terms to be used interchangeably. A government with checks and balances comprises more than one institution exercising state power, with each intended to have some influence over the other, requiring both interdependence and independence.
Did You Know?
- Polybius credited Lycurgus of Sparta with the first government of mixed government and checks and balances.
- John Locke distinguished legislative, executive, and federative powers, but noted that one body or person could share in two or more of the powers.
- Montesquieu argued that if the same person or body held legislative and executive powers, liberty would be lost.
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