Enlightenment Now: The Case for Reason, Science, Humanism, and Progress

First among them is the emission of greenhouse gases and the threat they pose of dangerous climate change. People sometimes ask me whether I think that humanity will rise to the challenge or whether we will sit back and let disaster unfold. For what it’s worth, I think we’ll rise to the challenge, but it’s vital to understand the nature of this optimism. The economist Paul Romer distinguishes between complacent optimism, the feeling of a child waiting for presents on Christmas morning, and conditional optimism, the feeling of a child who wants a treehouse and realizes that if he gets some wood and nails and persuades other kids to help him, he can build one.¹⁰⁸ We cannot be complacently optimistic about climate change, but we can be conditionally optimistic. We have some practicable ways to prevent the harms and we have the means to learn more. Problems are solvable. That does not mean that they will solve themselves, but it does mean that we can solve them if we sustain the benevolent forces of modernity that have allowed us to solve problems so far, including societal prosperity, wisely regulated markets, international governance, and investments in science and technology.

CHAPTER 11PEACE

How deep do the currents of progress flow? Can they suddenly come to a halt or go into reverse? The history of violence provides an opportunity to confront these questions. In The Better Angels of Our Nature I showed that, as of the first decade of the 21st century, every objective measure of violence had been in decline. As I was writing it, reviewers warned me that it could all explode before the first copy hit the stores. (A war, possibly nuclear, between Iran and either Israel or the United States was the worry of the day.) Since the book was published in 2011, a cascade of bad news would seem to make it obsolete: civil war in Syria, atrocities in the Islamic State, terrorism in Western Europe, autocracy in Eastern Europe, shootings by police in the United States, and hate crimes and other outbursts of racism and misogyny from angry populists throughout the West.

But the same Availability and Negativity biases that made people incredulous about the possibility that violence had declined can make them quick to conclude that any decline has been reversed. In the next five chapters I will put the recent bad news in perspective by going back to the data. I’ll plot the historical trajectories of several kinds of violence up to the present, including a reminder of the last data point available when The Better Angels of Our Nature went to press.¹ Seven years or so is an eyeblink in history, but it offers a crude indication of whether the book capitalized on a lucky instant or identified an ongoing trend. More important, I’ll try to explain the trends in terms of deeper historical forces, placing them within the narrative of progress that is the subject of this book. (In doing so I’ll introduce some new ideas on what those forces are.) I’ll begin with the most extravagant form of violence, war.

For most of human history, war was the natural pastime of governments, peace a mere respite between wars.² This can be seen in figure 11-1, which plots the proportion of time over the last half-millennium that the great powers of the day were at war. (Great powers are the handful of states and empires that can project force beyond their borders, that treat each other as peers, and that collectively control a majority of the world’s military resources.)³ Wars between great powers, which include world wars, are the most intense forms of destruction our sorry species has managed to dream up, and they are responsible for a majority of the victims of all wars combined. The graph shows that at the dawn of the modern era the great powers were pretty much always at war. But nowadays they are never at war: the last one pitted the United States against China in Korea more than sixty years ago.

Figure 11-1: Great power war, 1500–2015

Source: Levy & Thompson 2011, updated for the 21st century. Percentage of years the great powers fought each other in wars, aggregated over 25-year periods, except for 2000–2015. The arrow points to 1975–1999, the last quarter-century plotted in fig. 5–12 of Pinker 2011.

The jagged decline of great power war conceals two trends that until recently went in opposite directions.⁴ For 450 years, wars involving a great power became shorter and less frequent. But as their armies became better manned, trained, and armed, the wars that did take place became more lethal, culminating in the brief but stunningly destructive world wars. It was only after the second of these that all three measures of war—frequency, duration, and lethality—declined in tandem, and the world entered the period that has been called the Long Peace.