5–18
Rate of death in conflicts in greater Europe, 1400–2000
230
5–19
Length of military conscription, 48 major long-established nations,
1970–2010
256
5–20
Military personnel, United States and Europe, 1950–2000
257
5–21
Percentage of territorial wars resulting in redistribution
of territory, 1651–2000
259
5–22
Nonnuclear states that started and stopped exploring
nuclear weapons, 1945–2010
273
5–23
Democracies, autocracies, and anocracies, 1946–2008
279
5–24
International trade relative to GDP, 1885–2000
286
5–25
Average number of IGO memberships shared by a pair
of countries, 1885–2000
290
5–26
Probability of militarized disputes between pairs of democracies
and other pairs of countries, 1825–1992
294
6–1
Rate of battle deaths in state-based armed conflicts, 1900–2005
301
6–2
Rate of battle deaths in state-based armed conflicts, 1946–2008
301
6–3
Number of state-based armed conflicts, 1946–2009
303
6–4
Deadliness of interstate and civil wars, 1950–2005
304
6–5
Geography of armed conflict, 2008
306
6–6
Growth of peacekeeping, 1948–2008
314
6–7
Rate of deaths in genocides, 1900–2008
338
6–8
Rate of deaths in genocides, 1956–2008
340
6–9
Rate of deaths from terrorism, United States, 1970–2007
350
6–10
Rate of deaths from terrorism, Western Europe, 1970–2007
351
6–11
Rate of deaths from terrorism, worldwide except Afghanistan
2001–and Iraq 2003–
352
6–12
Islamic and world conflicts, 1990–2006
366
7–1
Use of the terms
civil rights, women’s rights, children’s rights, gay rights,
and
animal rights
in English-language books, 1948–2000
380
7–2
Lynchings in the United States, 1882–1969
384
7–3
Hate-crime murders of African Americans, 1996–2008
386
7–4
Nonlethal hate crimes against African Americans, 1996–2008
387
7–5
Discriminatory and affirmative action policies, 1950–2003
390
7–6
Segregationist attitudes in the United States, 1942–1997
391
7–7
White attitudes to interracial marriage in the United States, 1958–2008
391
7–8
Unfavorable opinions of African Americans, 1977–2006
392
7–9
Rape prevention and response sticker
400
7–10
Rape and homicide rates in the United States, 1973–2008
402
7–11
Attitudes toward women in the United States, 1970–1995
404
7–12
Approval of husband slapping wife in the United States, 1968–1994
409
7–13
Assaults by intimate partners, United States, 1993–2005
411
7–14
Homicides of intimate partners in the United States, 1976–2005
411
7–15
Domestic violence in England and Wales, 1995–2008
412
7–16
Abortions in the world, 1980–2003
428
7–17
Approval of spanking in the United States, Sweden,
and New Zealand, 1954–2008
436
7–18
Approval of corporal punishment in schools in the United States,
1954–2002
438
7–19
American states allowing corporal punishment in schools, 1954–2010
438
7–20
Child abuse in the United States, 1990–2007
440
7–21
Another form of violence against children
441
7–22
Violence against youths in the United States, 1992–2003
443
7–23
Time line for the decriminalization of homosexuality,
United States and world
450
7–24
Intolerance of homosexuality in the United States, 1973–2010
452
7–25
Antigay hate crimes in the United States, 1996–2008
454
7–26
Percentage of American households with hunters, 1977–2006
467
7–27
Number of motion pictures per year in which animals
were harmed, 1972–2010
469
7–28
Vegetarianism in the United States and United Kingdom, 1984–2009
471
8–1
Rat brain, showing the major structures involved in aggression
498
8–2
Human brain, showing the major subcortical structures involved
in aggression
502
8–3
Human brain, showing the major cortical regions that regulate
aggression
503
8–4
Human brain, medial view
504
8–5
The Prisoner’s Dilemma
533
8–6
Apologies by political and religious leaders, 1900–2004
544
9–1
Implicit interest rates in England, 1170–2000
610
9–2
The Flynn Effect: Rising IQ scores, 1947–2002
652
10–1
The Pacifist’s Dilemma
679
10–2
How a Leviathan resolves the Pacifist’s Dilemma
681
10–3
How commerce resolves the Pacifist’s Dilemma
682
10–4
How feminization can resolve the Pacifist’s Dilemma
686
10–5
How empathy and reason resolve the Pacifist’s Dilemma
689
PREFACE
T
his book is about what may be the most important thing that has ever happened in human history. Believe it or not—and I know that most people do not—violence has declined over long stretches of time, and today we may be living in the most peaceable era in our species’ existence. The decline, to be sure, has not been smooth; it has not brought violence down to zero; and it is not guaranteed to continue. But it is an unmistakable development, visible on scales from millennia to years, from the waging of wars to the spanking of children.
No aspect of life is untouched by the retreat from violence. Daily existence is very different if you always have to worry about being abducted, raped, or killed, and it’s hard to develop sophisticated arts, learning, or commerce if the institutions that support them are looted and burned as quickly as they are built.
The historical trajectory of violence affects not only how life is lived but how it is understood. What could be more fundamental to our sense of meaning and purpose than a conception of whether the strivings of the human race over long stretches of time have left us better or worse off? How, in particular, are we to make sense of
modernity
—of the erosion of family, tribe, tradition, and religion by the forces of individualism, cosmopolitanism, reason, and science? So much depends on how we understand the legacy of this transition: whether we see our world as a nightmare of crime, terrorism, genocide, and war, or as a period that, by the standards of history, is blessed by unprecedented levels of peaceful coexistence.
The question of whether the arithmetic sign of trends in violence is positive or negative also bears on our conception of human nature. Though theories of human nature rooted in biology are often associated with fatalism about violence, and the theory that the mind is a blank slate is associated with progress, in my view it is the other way around. How are we to understand the natural state of life when our species first emerged and the processes of history began? The belief that violence has increased suggests that the world we made has contaminated us, perhaps irretrievably. The belief that it has xxi decreased suggests that we started off nasty and that the artifices of civilization have moved us in a noble direction, one in which we can hope to continue.
This is a big book, but it has to be. First I have to convince you that violence really has gone down over the course of history, knowing that the very idea invites skepticism, incredulity, and sometimes anger. Our cognitive faculties predispose us to believe that we live in violent times, especially when they are stoked by media that follow the watchword “If it bleeds, it leads.” The human mind tends to estimate the probability of an event from the ease with which it can recall examples, and scenes of carnage are more likely to be beamed into our homes and burned into our memories than footage of people dying of old age.
1
No matter how small the percentage of violent deaths may be, in absolute numbers there will always be enough of them to fill the evening news, so people’s impressions of violence will be disconnected from the actual proportions.
Also distorting our sense of danger is our moral psychology. No one has ever recruited activists to a cause by announcing that things are getting better, and bearers of good news are often advised to keep their mouths shut lest they lull people into complacency. Also, a large swath of our intellectual culture is loath to admit that there could be anything good about civilization, modernity, and Western society. But perhaps the main cause of the illusion of ever-present violence springs from one of the forces that drove violence down in the first place. The decline of violent behavior has been paralleled by a decline in attitudes that tolerate or glorify violence, and often the attitudes are in the lead. By the standards of the mass atrocities of human history, the lethal injection of a murderer in Texas, or an occasional hate crime in which a member of an ethnic minority is intimidated by hooligans, is pretty mild stuff. But from a contemporary vantage point, we see them as signs of how low our behavior can sink, not of how high our standards have risen.
In the teeth of these preconceptions, I will have to persuade you with numbers, which I will glean from datasets and depict in graphs. In each case I’ll explain where the numbers came from and do my best to interpret the ways they fall into place. The problem I have set out to understand is the reduction in violence at many scales—in the family, in the neighborhood, between tribes and other armed factions, and among major nations and states. If the history of violence at each level of granularity had an idiosyncratic trajectory, each would belong in a separate book. But to my repeated astonishment, the global trends in almost all of them, viewed from the vantage point of the present, point downward. That calls for documenting the various trends between a single pair of covers, and seeking commonalities in when, how, and why they have occurred.
Too many kinds of violence, I hope to convince you, have moved in the same direction for it all to be a coincidence, and that calls for an explanation. It is natural to recount the history of violence as a moral saga—a heroic struggle of justice against evil—but that is not my starting point. My approach is scientific in the broad sense of seeking explanations for why things happen. We may discover that a particular advance in peacefulness was brought about by moral entrepreneurs and their movements. But we may also discover that the explanation is more prosaic, like a change in technology, governance, commerce, or knowledge. Nor can we understand the decline of violence as an unstoppable force for progress that is carrying us toward an omega point of perfect peace. It is a collection of statistical trends in the behavior of groups of humans in various epochs, and as such it calls for an explanation in terms of psychology and history: how human minds deal with changing circumstances.
A large part of the book will explore the psychology of violence and nonviolence. The theory of mind that I will invoke is the synthesis of cognitive science, affective and cognitive neuroscience, social and evolutionary psychology, and other sciences of human nature that I explored in
How the Mind Works
,
The Blank Slate
, and
The Stuff of Thought
. According to this understanding, the mind is a complex system of cognitive and emotional faculties implemented in the brain which owe their basic design to the processes of evolution. Some of these faculties incline us toward various kinds of violence. Others—“the better angels of our nature,” in Abraham Lincoln’s words—incline us toward cooperation and peace. The way to explain the decline of violence is to identify the changes in our cultural and material milieu that have given our peaceable motives the upper hand.
Finally, I need to show how our history has engaged our psychology. Everything in human affairs is connected to everything else, and that is especially true of violence. Across time and space, the more peaceable societies also tend to be richer, healthier, better educated, better governed, more respectful of their women, and more likely to engage in trade. It’s not easy to tell which of these happy traits got the virtuous circle started and which went along for the ride, and it’s tempting to resign oneself to unsatisfying circularities, such as that violence declined because the culture got less violent. Social scientists distinguish “endogenous” variables—those that are inside the system, where they may be affected by the very phenomenon they are trying to explain—from the “exogenous” ones—those that are set in motion by forces from the outside. Exogenous forces can originate in the practical realm, such as changes in technology, demographics, and the mechanisms of commerce and governance. But they can also originate in the intellectual realm, as new ideas are conceived and disseminated and take on a life of their own. The most satisfying explanation of a historical change is one that identifies an exogenous trigger. To the best that the data allow it, I will try to identify exogenous forces that have engaged our mental faculties in different ways at different times and that thereby can be said to have caused the declines in violence.