4 Enlightenment Ideas That Changed the World

The Enlightenment helped combat the excesses of the church, establish science as a source of knowledge, and defend human rights against tyranny.

It also gave us modern schooling, medicine, republics, representative democracy, and much more.

So how did one movement inspire so much change?

Here are the 4 most powerful ideas behind these revolutions, and how they reshaped our world forever.

Separation of powers

Ever since the Greeks, debate raged as to the best form of government. But it was only during the Enlightenment that Europe really began to question traditional forms of authority.

Baron de Montesquieu’s seminal ‘Spirit of the Laws’ (1748), admired and heavily quoted by the Founding Fathers, described a principle of good governance that would go on to shape modern politics. 

Montesquieu observed in England a rudimentary separation of powers: the executive (the government of the King), the legislature (parliament) and the judiciary (the law courts).

Each branch exercised power independent of one another, keeping each other in check.

Reading of Voltaire’s tragedy of the Orphan of China in the salon of Marie Thérèse Rodet Geoffrin in 1755, by Lemonnier, c. 1812

Image Credit: Anicet Charles Gabriel Lemonnier, Public domain, via Wikimedia Commons

It was not a new idea – the Romans had enjoyed republican government – but it was the first time it had emerged in the contemporary world. 

Montesquieu’s book was a bestseller. Progressives across Europe began to argue for a more rational and constitutional form of limited government which would separate the powers of executive, legislature, and judiciary.

When the American colonies won their War of Independence in 1776, their government was the first to guarantee a separation of powers.

By the mid-20th century, it had become the most popular form of government worldwide. 

Rights of man

Prior to the Enlightenment, the notion that all men had equal rights was rarely held. Hierarchy was so entrenched that any deviation from it was deemed dangerous.

Any movement that threatened or disputed this hierarchy – from John Wycliffe’s Lollards to the German Peasants’ Revolt – was crushed.

Both church and state defended this status quo with theoretical justification such as the ‘divine right of kings’, which claimed that monarchs had a God-given right to rule – implying that any challenge to this rule was against God. 

But in the 17th century, scholars such as Thomas Hobbes began to question this God-given legitimacy.

Theories formed about the relationship between the state and their subjects. The state offered protection to its subjects, and in return they swore their loyalty.

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John Locke took this a step further, asserting that all men possessed inalienable rights from God that entitled them to life, liberty, and property: what he called “natural rights”.

If the state did not provide and protect these “natural rights”, then the people had a right to withdraw their consent.

The Enlightenment thinkers took Locke’s ideas a step further. The Founding Fathers established the United States’ Constitution upon Locke’s natural rights, expanding them to include “the pursuit of happiness”.

Other Enlightenment thinkers, like Thomas Paine, made these rights more and more egalitarian. 

By the end of the 18th century, declarations of the rights of man had made the full journey from theory to reality: France joined the United States in popular uprising.

Although it would be another century before these concepts became more widespread, they could not have happened without the Enlightenment. 

Benjamin Franklin, one of the Founding Fathers who drafted America’s Declaration of Independence, guaranteeing constitutional rights

Image Credit: David Martin, Public domain, via Wikimedia Commons

Secularism

The absolutism of the pre-modern world was based on two powers: the state, and the church.

While kings could claim the loyalty of their subjects by force, the church usually buttressed these monarchies with theories that justified their hierarchy – God gave his power to kings, who commanded their subjects in His name.

Disputes between the church and the state could disrupt this relationship – as Henry VIII’s tumultuous divorce from Catholicism proved – but generally their mutual support was firm. 

The theorists of the Enlightenment exposed this relationship between sacred and profane power.

Using the sectarian bloodshed of the 17th century as proof, they argued that states should not have any influence in religious affairs, and vice-versa.

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The Treaty of Westphalia (1648), which ended the religiously-motivated 30 Years War, created a precedent by asserting that states could not violate each others’ sovereignty, even over spiritual matters.

Religion stopped being a valid motive for foreign warfare, and freedom of worship began to be accepted.

Voltaire, one of the Enlightenment’s most celebrated thinkers, was at the forefront of this debate.

Like many of the era’s thinkers, he was a Deist, refuting the Church’s stranglehold of the sacred. Instead, Deism prized direct experience of the sublime through nature.

For a Deist, evidence of God was all around us in the splendour of natural phenomena – and you didn’t need a priest to decipher it for you. 

By the end of the 18th century, the idea of a formal separation of church and state was coming to seem more and more inevitable.

It paved the way to a future where fewer and fewer people would claim any kind of religion whatsoever.

The engraving by Stefan du Pérac was published in 1569, five years after the death of Michelangelo

Image Credit: Étienne Dupérac, CC0, via Wikimedia Commons

Materialism

As science developed, an old question began to be asked with new urgency: what made living things different from non-living things?

A century earlier, French philosopher René Descartes had sparked a new rationalist approach with his ‘Discourse on the Method’ (1637).

Over the course of the 17th and 18th centuries, that rationalism spread, providing the foundation for a materialistic view of man and the universe.

New theories, such as Isaac Newton’s groundbreaking concepts of gravity and thermodynamics, seemed to point towards a mechanistic understanding of life. Nature was like one big clockwork machine, working in perfect unison.

It supported both the new discoveries of natural philosophers like Newton, while also maintaining an important role for God. 

Inevitably, these ideas began to seep into the political and cultural discourse. If things were mechanically ordered, shouldn’t society be as well?

Rather than being animated by some ineffable spirit, perhaps man was driven by nothing more than a network of cogs. These questions are still debated today.

Even among the radicals Enlightenment, this was a fringe idea. Few thinkers fully divorced themselves from the concept of a creator.

But the seed of materialism had been planted, and it eventually flowered in the mechanistic (and Godless) theories of Marxism and fascism.