In 1755, the Portuguese city of Lisbon was struck by a massive, deadly earthquake. As Deirdre McCloskey recently wrote, in the century that followed, three big ideas swept through Europe that would also shake the world. One of those ideas was fantastically fruitful, while the other two proved to be disastrously destructive.

First to sweep through was the bright idea of, in the words of Adam Smith, “allowing every man to pursue his own interest in his own way, upon the liberal plan of equality, liberty, and justice.” In the first half of the 19th century, this idea became known as liberalism.

Then, just as liberalism began to transform the world, two pernicious ideas began to vie with it. Nationalism and socialism began to capture the imaginations of intellectuals and would eventually displace liberalism completely in the hearts and minds of the West.

Liberalism unlocked humanity’s creative potential, yielding the first ever rise of widespread abundance through industrial mass production. Nationalism and socialism unleashed humanity’s capacity for destruction, unleashing the first ever rise of industrial-scale mass murder.

The twin banes of nationalism and socialism followed the boon of liberalism remarkably quickly. To understand why, we must consider a fourth big idea that historically links the other three: the idea of the people’s state.

Liberty, the People’s State, and the Glorious Revolution

The ideas of individual liberty and of the modern people’s state emerged in close conjunction, because the two had a common enemy: the hereditary, divine princely state. In the old order, kings claimed absolute authority over their subjects by hereditary and divine right: by inheriting his crown from his predecessor and having his rule blessed by the church on behalf of God.

In 17th-century England, the proto-liberals called the Whigs challenged these pretensions, both with arms and arguments. The great manifesto of the so-called “radical Whigs” was John Locke’s 1689 work Two Treatises of Government. Against royal authoritarianism, Locke advanced the individual’s rights to life, liberty, and property. And against royal autocracy by divine and hereditary right, Locke drew an alternate picture of government as merely an instrumental institution, created by the people and for the people: that is, empowered by the public for the sole purpose of securing their individual rights.

According to Locke, the state is not the royal family’s private property. Whether democratic or not, proper government is a public institution: what we might call a people’s state. Anything else is not legitimate rule but tyranny.

In Locke’s view, the state is a servant of the people with a specific job. If that servant is not performing its function, or worse still, if it is deliberately trampling on the very rights it was tasked to protect, then it has broken the “social contract”: the terms and conditions upon which it was hired. In such cases, the people may exercise their right of revolution: the right to fire (abolish or secede from) their government and hire (establish) a new one. This contractual, business-like notion of government was easy for the town-based, largely bourgeois Whigs to grasp and accept.

It was a short step from wanting a “government by the people and for the people” to wanting a “government of the people.” After all, what better way to keep the state on task and remind it who’s boss than for the people to actively oversee and guide the government? Indeed, after the Whigs overthrew King James II in the so-called Glorious Revolution of 1688, the chief result, aside from the liberal English Bill of Rights, was the empowerment of Parliament over the new constitutional joint monarchy of King William III and Queen Mary.

From Locke onward, the cause of liberty was bound up with the cause of the people’s state. Indeed, the bond was so tight that they were considered a single cause: the people’s state (and eventually democracy in particular) was considered an essential plank of liberalism. Liberals considered the people’s state, or “political liberty,” to be an indispensable guardian of individual liberty, just as much as they considered the unaccountable princely state to be a standing threat to freedom.

The American Revolution

By the Enlightenment decades of the 1760s and 70s, the Lockean ideals of individual liberty and the people’s state had crossed the Atlantic to the American colonies, where they became the creed of the founding generation. So strong was their love of liberty and intolerance for despotism that they rose in resistance to an arbitrary tax regime that today would be considered miniscule. After Britain tried to overcome that defiance with lethal military force, resistance turned to revolution.

Throughout the Declaration of Independence that announced and justified the American Revolution in 1776, Thomas Jefferson echoed, even paraphrased, Locke’s second Treatise. King George III had not only failed in his duty to protect the rights of Americans, but had actively violated them. And these infringements were so recurrent as to demonstrate “a design to reduce them under absolute Despotism.” As Locke had explained, these were precisely the conditions that called for revolution.

King George had broken the terms and conditions of the social contract. So the American people no longer had any obligation to keep him on as their security provider. He was fired, and the Declaration of Independence was his pink slip. George didn’t take his firing well, so it took the Revolutionary War to escort him off the premises.

The founders had so much faith in the people’s state as a guarantor of liberty that they then went beyond England’s example of constitutional monarchy and parliamentary government. After exiting the Constitutional Convention, Benjamin Franklin was asked what kind of government had been created. He answered, “A republic, if you can keep it.” A republic is a people’s state by definition, derived from the Latin respublica, or “concern of the people.”

The French Revolution

The dream of a people’s state for liberty next travelled to France. The monarchy in France was so autocratic that the Estates General (France’s parliament) hadn’t convened in 175 years. But in 1789, the cash-strapped Bourbon king Louis XVI resuscitated the institution in order to raise desperately needed funds. The French Revolution started when members of the Third Estate (representing French commoners) broke away from the session, formed an independent National Assembly, and vowed to give France a constitution.

A Parisian mob gathered in support of the Assembly, stormed the Bastille, and seized the weapons cache within to give the budding people’s state a military upper hand over the demoralized monarchy. In a portent of wider brutality to come, the mob also decapitated the commander of the Bastile and paraded through the city with his head on a pike.

After a brief abortive period of constitutional monarchy, France too became a republic, even more thoroughgoing than the American one. Whereas the American republic was constituted as a federal government with a bicameral legislature and strictly limited suffrage, France’s First Republic was a national government with a unicameral legislature and, for a time, universal adult male suffrage. To secure the new republic against a return of the monarchy, the deposed king was beheaded.

At first, the theory of the people’s state as a champion of liberty seemed to work out in practice. The earliest legislative acts of Revolutionary France were predominantly liberal. Because of peasant resistance, feudalism had already been declining under the monarchy. But the National Assembly finished it off by abolishing serfdom outright. Then it passed a Declaration of the Rights of Man and of the Citizen, which contained the Lockean pronouncemen