The opening line of Charles Dickens’s A Tale of Two Cities retains its universality to this day. “It was the best of times, it was the worst of times,” Dickens writes, “it was the age of wisdom, it was the age of foolishness, … it was the spring of hope, it was the winter of despair.”

Dickens’s classic novel, set in London and Paris during the French Revolution, decries both the social injustices of the despotic ancien régime and the excesses of the French revolutionaries. When asked his opinion of the French Revolution almost two centuries later, former Chinese Premier Zhou Enlai reportedly answered that it was “too early to say.” That quip – though possibly the result of a misunderstanding – perfectly captures Dickens’s own ambivalence about the period of which he wrote.

The Enlightenment ideals that inspired the French to rise up against Louis XVI also drove the American Revolution. And both were set against the backdrop of another sea change: the onset of industrialization. The combination of more liberal political regimes and transformational scientific advances inaugurated the most prosperous period in the history of humankind.

The late British economist Angus Maddison once estimated that whereas global per capita GDP did not even double between 1 AD and 1820, it increased more than tenfold between 1820 and 2008. And this spectacular growth has been accompanied by equally extraordinary improvements in a wide range of socioeconomic indicators. Global average life expectancy, for example, has risen from 31 to almost 73 years in just two centuries.

Two centuries ago, the science and medical communities had not yet accepted the germ theory of disease, and the smell of beef was commonly thought to cause obesity. Today, such beliefs seem grotesque, owing to rapid progress in our scientific understanding. Not only can we now read the human genome; we are also learning how to edit and write it.

For Harvard psychology professor Steven Pinker, such achievements are signs that “the Enlightenment is working.” Moreover, Pinker argues that more moral progress has been achieved in the last few centuries than most macroeconomic measurements can reflect. For example, he points to the expansion – both geographic and substantive – of protections for individual and collective rights, as well as an overall reduction in violence.

The sheer magnitude of the Enlightenment’s achievements tends to be undervalued, because we are prone to remembering and normalizing catastrophes rather than quotidian improvements. But while this bias is detrimental to decision-making, so, too, is excessive complacency. After all, there are plenty of reasons – many of which are secondary effects of the Enlightenment – for people to feel uneasy about the future.

In his 2013 book, The Great Escape, Nobel laureate economist Angus Deaton shows how progress in reducing aggregate privation, famine, and premature death over the past 250 years has left many social groups behind. While inequality at the global level has recently been mitigated by the economic rise of countries like China, numerous studies find that inequality within countries has been increasing. In countries such as the United States, broad segments of the population lack access to adequate medical treatments, and even democracy seems to be eroding.

Today’s conventional wisdom links the emergence of populist movements around the world, including the election of President Donald Trump in the US, to the people who have missed out on the benefits of globalization. Yet many of Trump’s policies – not least slashing taxes for the rich – are intended to perpetuate the privileges of the economic elite. Trump has done very little to address the fears of those who feel left behind, but he is attempting a classic bait-and-switch to disguise this fact. Accordingly, he singles out China as the source of Americans’ economic woes.

The result of Trump’s “America First” approach and fear mongering about all things foreign has been to undermine global cooperation. Nationalism, one of the potentially harmful legacies of the late-eighteenth-century social revolutions, has made a comeback on the heels of rising nativist and xenophobic fears.

Likewise, the Enlightenment’s scientific and technological legacy has not been wholly positive. The theories of Albert Einstein and the discovery of fission in 1938 made nuclear power possible, but also led to the bombings of Hiroshima and Nagasaki, and to the disasters at Chernobyl and Fukushima. Similarly, technological progress has left critical national infrastructure potentially vulnerable to cyberattacks. And, as the 2008 crisis revealed, financial engineering carries many risks of its own.

All of these dangers are accompanied by what is perhaps the greatest threat humanity has ever faced: climate change. The peculiarity of this threat lies in the fact that it has not manifested in the form of a single, sudden shock. Rather, it is a cumulative phenomenon, which we might still be able to mitigate. Just as technological advances got us into this predicament, so might they rescue us from it. After all, technological innovation, along with an international effort to adopt the 1987 Montreal Protocol, is how the world put a stop to the erosion of the ozone layer.

Fortunately, scientific rationality is capable of creating tools to remedy its own excesses. Unfortunately, however, the state of political leadership today may mean that these tools remain unused. The world is in desperate need of leaders who are willing to maximize the benefits of science and technology through collective management and international cooperation. Without such leadership, what is quantifiably the best of times could very well become the worst.

Javier Solana was EU High Representative for Foreign and Security Policy, Secretary-General of NATO, and Foreign Minister of Spain. He is currently President of the ESADE Center for Global Economy and Geopolitics, Distinguished Fellow at the Brookings Institution, and a member of the World Economic Forum’s Global Agenda Council on Europe.

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