Montesquieu's The Spirit of the Laws (1748): Separation of Powers

The Spirit of the Laws (De l’esprit des lois), published anonymously in Geneva in 1748 by the French philosopher Montesquieu, is one of the founding works of modern political science. Its comparative study of governments argued that laws must fit the society they serve, and its account of the separation of legislative, executive and judicial powers shaped constitutions across Europe and the Americas.

Background: a magistrate and traveller

Charles-Louis de Secondat, baron de La Brède et de Montesquieu, was born on 18 January 1689 at the Château de La Brède near Bordeaux. Trained in law, he inherited from his uncle in 1716 the office of président à mortier, a senior judge, in the Parlement of Bordeaux, along with the title of Montesquieu.

He became famous in 1721 with the Persian Letters, a satirical novel in which two Persian visitors comment on French society, religion and government. In 1726 he sold his judicial office and turned to study and travel.

Between 1728 and 1731 he toured Austria, Hungary, Italy, Germany and the Netherlands, and spent about eighteen months in England, where he was elected a Fellow of the Royal Society in 1730. English politics, with its Parliament, independent courts and lively press, made a lasting impression. In 1734 he published a study of the rise and fall of Rome, and then spent roughly fourteen years on his masterpiece.

The book and its argument

The Spirit of the Laws appeared in Geneva in late 1748, in two volumes divided into 31 books. It ranges across ancient Rome, China, Japan, the Ottoman Empire, the feudal law of France and the governments of contemporary Europe.

Montesquieu’s starting point was that laws are not arbitrary. They arise from “the nature of things” and must be suited to a country’s government, physical setting, economy, religion, manners and history. This relationship between laws and circumstances is the “spirit” of the title.

He divided governments into three kinds. A republic, ruled by the people or by a part of it, depends on civic virtue. A monarchy, in which one rules by fixed laws, rests on honour and on intermediate bodies such as the nobility and the courts. A despotism, in which one rules by whim, is held together by fear.

The separation of powers

The most influential passage is Book 11, chapter 6, “On the constitution of England”. There Montesquieu defined political liberty as security under the law and argued that it could survive only where power was divided.

He identified three kinds of power: making laws, executing them and judging disputes and crimes. If the same person or body held two or all three, he warned, there could be no liberty. His conclusion, often summarised as “power should check power”, is that the arrangement of institutions must make each restrain the others.

Montesquieu presented this as a description of England, though historians note he idealised a system in which ministers sat in Parliament and the branches overlapped considerably. He drew on earlier thinkers, including John Locke and English commentators on the settlement that followed the Glorious Revolution.

Climate, commerce and slavery

Books 14 to 17 set out a theory that climate influences temperament and therefore laws, arguing for example that hot climates encourage passivity and despotism. Modern readers regard these passages as crude and coloured by prejudice, but they were an early attempt to explain institutions by natural and social causes.

Montesquieu also praised commerce as a force that softens manners and encourages peace between nations, an idea later called doux commerce. In Book 15 he attacked slavery, including a famous chapter of bitter irony that mocks the arguments used to justify the enslavement of Africans.

Reception and controversy

The book was an immediate success, going through many editions within two years and drawing praise from readers across Europe. It also provoked hostility. Jansenist and Jesuit writers accused Montesquieu of undermining religion by treating it as one social factor among many.

He replied with a Defence of The Spirit of the Laws in 1750, but in 1751 the Catholic Church placed the book on the Index of Prohibited Books. Montesquieu died in Paris on 10 February 1755, with his eyesight largely gone. Even in his last years he kept revising the text, and an edition incorporating his final corrections appeared in 1757, two years after his death, as the work continued to circulate in translation across Europe.

Influence on constitutions

Catherine the Great of Russia borrowed heavily from the book in her Nakaz (Instruction) of 1767 to a legislative commission, although her autocracy remained intact. In France, Article 16 of the Declaration of the Rights of Man and of the Citizen (1789) declared that a society without a separation of powers has no constitution.

His influence was strongest in the United States. A well-known study by the political scientist Donald Lutz found that Montesquieu was the most frequently cited modern author in American political writing between 1760 and 1805. At the Constitutional Convention and in the ratification debates, both supporters and opponents of the Constitution appealed to him.

In The Federalist No. 47 (1788), James Madison called him “the celebrated Montesquieu” and the oracle always consulted on the subject. Madison argued that Montesquieu never meant the branches to be wholly separate, only that no branch should hold the whole power of another, a reading that underpins the American system of checks and balances.

Myths and facts

Myth: Montesquieu invented the separation of powers. The idea had roots in ancient theories of the “mixed constitution”, found in Aristotle and Polybius, and in English debates of the seventeenth century. Locke had already distinguished legislative from executive power. Montesquieu’s contribution was to give the judiciary its own place and to make the division the central guarantee of liberty.

Myth: he wanted three completely separate, equal branches. Montesquieu expected the powers to overlap and restrain one another. He approved, for example, of the English monarch’s power to veto legislation and of a legislature divided into two houses that could check each other.

Myth: he was a republican who wanted to abolish the French monarchy. Montesquieu admired ancient republics but thought them suited only to small states. For a large kingdom such as France he favoured a moderate monarchy, limited by law, by the courts (the parlements) and by a privileged nobility.

Myth: the book is only about politics. Large parts deal with economics, money, population, religion, family law, the history of Roman and feudal law and the effects of geography, which is why sociologists also claim him as a founder of their discipline.

Timeline

• 1689, 18 January: Montesquieu is born at La Brède, near Bordeaux.
• 1721: The Persian Letters is published anonymously.
• 1729–1731: Montesquieu lives in England and studies its constitution.
• 1748: The Spirit of the Laws is published in Geneva.
• 1750: He publishes his Defence of The Spirit of the Laws.
• 1751: The book is placed on the Index of Prohibited Books.
• 1755, 10 February: Montesquieu dies in Paris.
• 1788: Madison analyses his ideas in Federalist No. 47.

Why it matters

The Spirit of the Laws taught that freedom depends less on good rulers than on well-designed institutions that limit one another. The separation of powers it described remains a basic principle of constitutional democracies, and its comparative method helped found the study of politics as a social science.