Separation of church and state in the context of "Age of Enlightenment"

The constitution of the United Kingdom comprises the written and unwritten arrangements that establish the United Kingdom of Great Britain and Northern Ireland as a political body. Unlike in most countries, no official attempt has been made to codify such arrangements into a single document, thus it is known as an uncodified constitution. This enables the constitution to be easily changed as no provisions are formally entrenched.

The Supreme Court of the United Kingdom and its predecessor, the Appellate Committee of the House of Lords, have recognised and affirmed constitutional principles such as parliamentary sovereignty, the rule of law, democracy, and upholding international law. It also recognises that some Acts of Parliament have special constitutional status. These include the Magna Carta, which in 1215 required the King to call a "common counsel" (now called Parliament) to represent the people, to hold courts in a fixed place, to guarantee fair trials, to guarantee free movement of people, to free the church from the state, and to guarantee rights of "common" people to use the land. After the Glorious Revolution, the Bill of Rights 1689 and the Claim of Right Act 1689 cemented Parliament's position as the supreme law-making body, and said that the "election of members of Parliament ought to be free". The Treaty of Union in 1706 and the Acts of Union 1707 united the Kingdoms of England, Wales and Scotland, the Acts of Union 1800 joined Ireland, but the Irish Free State separated after the Anglo-Irish Treaty in 1922, leaving Northern Ireland within the UK. After struggles for universal suffrage, the UK guaranteed every adult citizen over 21 years the equal right to vote in the Representation of the People (Equal Franchise) Act 1928. After World War II, the UK became a founding member of the Council of Europe to uphold human rights, and the United Nations to guarantee international peace and security. The UK was a member of the European Union, joining its predecessor in 1973, but left in 2020. The UK is also a founding member of the International Labour Organization and the World Trade Organization to participate in regulating the global economy.

François-Marie Arouet (French: [fʁɑ̃swa maʁi aʁwɛ]; 21 November 1694 – 30 May 1778), known by his nom de plume Voltaire (/vɒlˈtɛər, voʊl-/, US also /vɔːl-/; French: [vɔltɛːʁ]), was a French Enlightenment writer, philosopher (philosophe), satirist, and historian. Famous for his wit and his criticism of Christianity (especially of the Catholic Church) and of slavery, Voltaire was an advocate of freedom of speech, freedom of religion, and separation of church and state.

Voltaire was a versatile and prolific writer, producing works in almost every literary form, including plays, poems, novels, essays, histories, and even scientific expositions. He wrote more than 20,000 letters and 2,000 books and pamphlets. Voltaire was one of the first authors to become renowned and commercially successful internationally. He was an outspoken advocate of civil liberties and was at constant risk from the strict censorship laws of the Catholic French monarchy. His polemics witheringly satirized intolerance and religious dogma, as well as the French institutions of his day. His best-known work and magnum opus, Candide, is a novella that comments on, criticizes, and ridicules many events, thinkers and philosophies of his time, most notably Gottfried Leibniz and his belief that our world is of necessity the "best of all possible worlds".

In the history of Mexico, La Reforma (from Spanish: "The Reform"), or reform laws, refers to a pivotal set of laws, including a new constitution, that were enacted in the Second Federal Republic of Mexico during the 1850s after the Plan of Ayutla overthrew the dictatorship of Santa Anna. They were intended as modernizing measures: social, political, and economic, aimed at undermining the traditional power of the Catholic Church and the army. The reforms sought separation of church and state, equality before the law, and economic development. These anticlerical laws were enacted in the Second Mexican Republic between 1855 and 1863, during the governments of Juan Álvarez, Ignacio Comonfort and Benito Juárez. The laws also limited the ability of Catholic Church and Indigenous communities from collectively holding land. The liberal government sought the revenues from the disentailment of church property, which could fund the civil war against Mexican conservatives and to broaden the base of property ownership in Mexico and encouraging private enterprise. Several of them were raised to constitutional status by the constituent Congress that drafted the liberal Constitution of 1857. Although the laws had a major impact on the Catholic Church in Mexico, liberal proponents were not opposed to the church as a spiritual institution, but rather sought a secular state and a society not dominated by religion.

The Juárez Law reduced the power that military and ecclesiastical courts held. The Lerdo Law forced land held in collective ownership to be sold to individual owners. It aimed at creating a dynamic real estate market, creating a class of yeoman farmers owning their own land, and raising revenue for the state. The measure was intended to strip the Church of most of its property, as well as to break Indigenous communities' collective ownership of land.

The Reform War (17 December 1857 – 11 January 1861) or War of Reform (Spanish: Guerra de Reforma), also known as the Three Years' War (Spanish: Guerra de los Tres Años), and the Mexican Civil War, was a complex civil conflict in Mexico fought between Mexican liberals and conservatives with regional variations over the promulgation of Constitution of 1857. It has been called the "worst civil war to hit Mexico between the War of Independence of 1810–21 and the Revolution of 1910–20". Following the liberals' overthrow of the dictatorship of conservative Antonio López de Santa Anna, liberals passed a series of laws codifying their political program. These laws were incorporated into the new constitution. It aimed to limit the political power of the executive branch, as well as the political, economic, and cultural power of the Catholic Church. Specific measures were the expropriation of Church property; separation of church and state; reduction of the power of the Mexican Army by elimination of their special privileges; strengthening the secular state through public education; and measures to develop the nation economically.

The constitution had been promulgated on 5 February 1857 was to come into force on 16 September 1857. There was intense opposition from Conservatives and the Catholic Church over its anti-clerical provisions, but there were also moderate liberals, including President Ignacio Comonfort, who considered the constitution too radical and likely to trigger a civil war. The Lerdo Law forced the sale of most of the Church's rural properties. The measure was not exclusively aimed at the Catholic Church, but also Mexico's indigenous peoples, which were forced to sell sizeable portions of their communal lands. Controversy was further inflamed when the Catholic Church decreed the excommunication of civil servants who took a government-mandated oath upholding the new constitution, which left Catholic civil servants with the choice of losing their jobs or being excommunicated.

Most people in Belgium do not belong to a religion. Christianity is the largest religion, with the Catholic Church representing the largest community, though it has experienced a significant decline since the 1950s (when it was the nominal religion of over 80% of the population). Belgium's policy separates the state from the churches, and freedom of religion is guaranteed by the country's constitution.

A secular state is an idea pertaining to secularity, whereby a state is or purports to be officially neutral in matters of religion, supporting neither religion nor irreligion. A secular state claims to treat all its citizens equally regardless of religion, and claims to avoid preferential treatment for a citizen based on their religious beliefs, affiliation or lack of either over those with other profiles.

Although secular states have no state religion, the absence of an established state religion does not mean that a state is completely secular or egalitarian. For example, some states that describe themselves as secular have religious references in their national anthems and flags, laws that benefit one religion or another, or are members of the Organisation of Islamic Cooperation and of the International Religious Freedom or Belief Alliance.

Secularism is the principle of seeking to conduct human affairs based on naturalistic considerations, uninvolved with religion. It is most commonly thought of as the separation of religion from civil affairs and the state and may be broadened to a similar position seeking to remove or to minimize the role of religion in any public sphere. Secularism may encapsulate anti-clericalism, atheism, naturalism, non-sectarianism, neutrality on topics of religion, or antireligion. Secularism is not necessarily antithetical to religion, but may be compatible with it. As a philosophy, secularism seeks to interpret life based on principles derived solely from the material world, without recourse to religion. It shifts the focus from religion towards "temporal" and material concerns.

There are distinct traditions of secularism like the French, Turkish, American and Indian models. These differ greatly, from the American emphasis on avoiding an established religion and freedom of belief, to the French interventionist model, and more. The purposes and arguments in support of secularism vary widely, ranging from assertions that it is a crucial element of modernization, or that religion and traditional values are backward and divisive, to the claim that it is the only guarantor of free religious exercise.

Laicism (also laicity, from the Ancient Greek "λαϊκός" "laïkós", meaning "layperson" or "non-cleric") refers to a legal and political model based on the strict separation of religion and state. The French term laïcité was coined in 1871 by French educator and future Nobel Peace Prize laureate Ferdinand Buisson, who advocated for secular education. In some countries, laicism is constitutionally enshrined, while others—primarily Western states—do not explicitly define themselves as Laicist but implement varying degrees of separation between religion and government.