In 1933, a darkness descended upon Germany. A political regime – the Nazi Party – began to dismantle one of the most vibrant, intellectual nations on Earth. We look back, and it feels like a singularity of evil. I certainly remember being taught that the Nazis were bad and everyone else was good. Even Star Wars was framed like this, with the Jedi vs. the Dark Side. But this is an oversimplification: the human behaviour at the core of the Nazi regime was not new and is not unique.

 

We tend to see the Third Reich as a historical anomaly, but the blueprint for authoritarianism is as old as civilization itself. Think of the Roman Empire, where under tyrannical emperors, free thought was treason. Consider ancient Chinese dynasties, going back 2,500 years, that codified thought control. Or my favourite anecdote to share in every physics class: the story of Giordano Bruno, burned at the stake by the Roman Inquisition for merely suggesting that the Sun was maybe, just possibly, perhaps at the centre of our solar system. Imagine being publicly murdered for having an idea.

 

This pattern isn't limited to ancient empires. Consider Renaissance Florence, where the zealot Girolamo Savonarola seized moral control of the city. He then orchestrated the infamous "Bonfire of the Vanities," persuading citizens to burn objects of vanity – cosmetics, fine art, and books deemed immoral. Imagine having to burn your own belongings because someone in power told you that you should. This event was a stark, pre-modern echo of the same authoritarian impulse: the belief that ideological purity must be enforced through the physical destruction of independent thought and culture. The suppression of dissent is a recurring, insidious feature of history.

 

The 19th-century German-Jewish poet Heinrich Heine saw the horror of this pattern, writing chillingly, "Where they burn books, they will ultimately burn people." He was trying to show how leaders, in an attempt to hold onto power, can slide from apparently trivial actions to overt violence shockingly easily and quickly. The concentration of power, the suppression of dissent, the use of language to control a population’s mind—it is a repetitive, dangerous loop in human history.

 

Yet here is what was unique about the Nazi holocaust: what came after.

 

The unimaginable tragedy of the Second World War shook humanity to its core. And for the first time on a global scale, we looked into the abyss and learnt a collective lesson. We built institutions, treaties, and democratic norms designed to prevent this kind of descent. As psychologist and historian Steven Pinker argues, we have lived through the most peaceful era in recorded human history since 1945. It is also, by many metrics, the most prosperous and – in important respects – the freest period humanity has ever known.

 

But the peace we enjoy is not necessarily society's natural state. It will not maintain itself. It is a hard-won artifact of conscious effort. Because if the natural state of humanity is anything, it is a gradual, insidious trend toward the comfortable certainty of authoritarianism. 

 

The moment this trend begins, it attacks the most fragile thing we possess: free speech. It starts with language control – deciding which words and thoughts are permissible. It is an attempt to enforce a monoculture of the mind. But a civilization with a single thought is weak and stagnant.

 

This brings me to the scientific community in 1930s Germany, one of the world's finest, and the home of the greatest ideas in physics that have defined the last century: quantum theory. My AP Physics 2 students are about to learn all about this, and their minds will be blown. However, the Nazis labeled these ideas, pioneered by Jewish scientists like Albert Einstein, as "Jewish Science." So they were ridiculed and suppressed. The response from the intellectual community was a form of courageous free speech: they voted with their feet and fled the country.

 

Over 100 of the world's top physicists fled. Einstein left for Princeton. Brilliant minds like Lise Meitner were forced out, moving to Sweden. The list goes on. Each departure was a declaration that they would not be silenced.

 

In one incredible act of defiance, Hungarian chemist George de Hevesy took Nobel Prize medals belonging to his colleagues Max von Laue and James Franck. To prevent the Nazis from seizing the gold, he dissolved the medals in a powerful mixture of nitric and hydrochloric acid. He hid the liquid in his lab. Then, after the war, he reversed the process and had the Nobel Foundation recast the medals. This was a chemical act of resistance, a silent scream of intellectual freedom against tyranny.

 

And then there is Werner Heisenberg, one of the most brilliant physicists of the 20th century, a founder of quantum theory. During the Second World War, Heisenberg led the Nazi atomic weapons project. The history of his involvement is intricate and still debated by historians. One interpretation is that he and his team genuinely tried but were hampered by miscalculations, resource shortages, and the Allies' disruption of supply lines. Another view, supported by some evidence and postwar accounts, is that Heisenberg quietly slowed progress – perhaps through subtle errors or under-emphasizing feasibility. Did he deliberately sabotage the project from within to avoid delivering such a weapon to Hitler? Whatever the full truth, the German program never came close to building a bomb, while the Manhattan Project in the US did. The movie Oppenheimer depicts this drama brilliantly.

 

So, what is the ultimate lesson here?

 

Evidence strongly suggests the key to a more tolerant, safer, and less war-prone civilization is not brute strength or economic power; it is the culture that free speech creates – a culture of debate, challenge, and disagreement. A scientific breakthrough is just an idea that survived peer review. A tolerant society is just an idea that survived centuries of open, honest, and sometimes painful, conversation.

 

Most civilizations throughout history have not been free, safe, or fair. That is the baseline. Our current, extraordinary state of peace and tolerance is not a genetic inheritance. It is not a given – it’s a deliberate cultural choice. It takes work. It takes the conscious, moment-to-moment decision to defend the right of others to say what you may not want to hear.

 

We must celebrate the achievements that human civilization has accomplished so far. But we must also keep talking about these difficult historical truths. They make us who we are. We must keep debating our ideas. Because the moment we stop doing the work – the moment we mistake our hard-won freedom for our natural state – is the moment the ancient, dark, authoritarian loop begins again.