On the morning of 1 November 1755, the churches of Lisbon were full. It was All Saints' Day, and candles burned on every altar as the faithful of one of Europe's richest cities knelt to pray. At around half past nine, the ground began to move. Within minutes, great stone naves were collapsing onto the congregations beneath them.

Over the next hours a tsunami and a firestorm followed, and together they would kill tens of thousands. But the shockwaves travelled further than any wave. They reached the salons of Paris and the studies of Geneva, and they cracked something Europe's thinkers had spent decades building: the confident belief that the universe was, at heart, arranged for our good.

The first shock struck at around 9:40 in the morning. Modern seismologists estimate its magnitude at somewhere between 8.5 and 9, with an epicentre far out in the Atlantic. Survivors described several violent jolts over a few minutes. Churches, palaces and tall townhouses crumbled, and clouds of dust darkened the sky.

Many survivors fled to the open ground by the river, believing it was safer. Around forty minutes later, they watched the water pull back from the harbour, exposing the seabed and the wrecks of lost cargo. Then the sea returned as a wall. Waves swept over the waterfront and dragged people into the Tagus. Meanwhile, the candles of All Saints' Day had toppled onto wooden altars and hangings. Fires spread through the ruins and burned for about five days.

To a deeply Catholic society, the sequence read like scripture: earth, water and fire, unleashed on a holy day. Preachers declared it divine punishment for Lisbon's sins. Yet the pattern of destruction refused to cooperate. Great churches fell, while parts of the Alfama, a district known for its sailors' taverns and brothels, largely survived. If this was judgement, what exactly was being judged?

Takeaway

When disaster strikes, people reach for meaning before they reach for explanations. The gap between the two is often where new ways of thinking are born.

Before 1755, many educated Europeans found comfort in a philosophy known as optimism. The German thinker Gottfried Leibniz had argued that a perfect God must have created the best of all possible worlds. The English poet Alexander Pope put it more bluntly: Whatever is, is right. Suffering existed, but it served a larger plan we simply couldn't see.

Voltaire found this unbearable. Within weeks of the news reaching him, he wrote his Poem on the Lisbon Disaster, a furious challenge to anyone who could look at crushed children and call it part of a harmonious whole. Was Lisbon more sinful than Paris or London, he asked, where people went on dancing? A few years later he sharpened the attack in Candide, whose foolish tutor Pangloss keeps insisting all is for the best as catastrophes pile up around him.

Jean-Jacques Rousseau wrote back with a very different angle. Nature, he pointed out, had not built twenty thousand houses of six and seven storeys crammed together. Had people lived more simply and spread out, far fewer would have died. Some perished, he added, because they went back for their possessions. Responsibility, in other words, was partly human.

Takeaway

Rousseau's reply echoes every time we ask whether a disaster was truly natural, or whether choices about where and how we live turned a tremor into a tragedy.

While philosophers argued, someone had to deal with the dead. That task fell to Sebastião José de Carvalho e Melo, the king's chief minister, later known as the Marquis of Pombal. He is often credited with the blunt order to bury the dead and feed the living, though the phrase may be legend. Either way, it captures his approach: act first, theorise later.

Pombal had bodies removed quickly to prevent disease, controlled food prices and organised shelter. Then he rebuilt the heart of the city, the Baixa, on a rational grid of wide, straight streets. His engineers designed buildings around a flexible wooden lattice, later called the Pombaline cage, intended to bend rather than shatter. According to a popular story, they tested models by marching troops around them to imitate the shaking ground.

Most remarkable of all, Pombal sent a questionnaire to parishes across Portugal. How long did the shaking last? Did the sea rise or fall? Did wells change? Did animals behave strangely? Here was a government treating an earthquake as a physical event to be measured, not only a sign to be interpreted. Historians see in those answers an early step towards modern seismology.

Takeaway

Pombal never settled whether God was good. He simply asked different questions, and sometimes the most radical move is to change what you are asking.

Lisbon's ruins didn't end faith, but they changed the conversation. After 1755, it became harder to treat catastrophe purely as a message from heaven, and easier to see it as something to be measured, understood and prepared for.

Walk through Lisbon's Baixa today and you are walking through that shift. Every building code, early-warning system and post-disaster survey carries a trace of the same question: what can we learn, and what could we have done differently?