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Evilicious 
Explaining our taste for excessive harm 
Marc D. Hauser 
Viking/Penguin 
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For Jacques and Bert Hauser, 
my parents, 
my friends, 
and my reminder 
that life should be 
lived to its fullest 
Hauser 
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Pleasure is the greatest incentive to evil. 
— Plato 
To witness suffering does one good, to inflict it even more so. 
— Friedrich Nietzsche 
Man produces evil as a bee produces honey. 
— William Golding 
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Dear reader, 
Having lived in Uganda and spoken with people who escaped from the savagery of the brutal 
dictators Milton Obote and Idi Amin, having heard stories of my father's childhood as a Jew running 
through Nazi occupied France, and reading past and present-day accounts of genocide, I am familiar with 
the horrors of evil. I have also been a student of human nature, trained as a scientist. These experiences 
have propelled me to study the causes of evil, attempt to make some progress in explaining it to myself, 
and hopefully to you. There is a great urgency to understanding this problem. None of us can afford to 
passively watch millions of individuals lose their homes, children, and lives as a result of malice. Sloth is 
a sin, especially when we live in a world where cultures of evil can so easily erupt. 
I am also familiar with and deeply moved by human kindness, our capacity to reach out and help 
strangers. When my father was in a boarding school in the south of France, hiding from the Nazis, a little 
girl approached him and asked if he was Jewish. My father, conditioned by his parents to deny his 
background, said no. The girl, sensing doubt, said "Well, if you are Jewish, you should know that the 
director of the school is handing Jewish children over to the Nazis." My father promptly called his parents 
who picked him up, moved him to another village and school, and survived to tell the story. This little girl 
expressed one of our species' signature capacities: the ability to show compassion for another person, 
even if their beliefs and desires are different. 
In preparation for writing this book, I read transcripts and descriptions of thousands of horrific 
events, listened to personal stories of survivors from financial ruin and war, worked with abused children 
who were crucified by unfit parents, and watched both fictional films and documentaries that portrayed 
psychopaths, dictators of totalitarian regimes, and their hapless victims. As one often does in these 
circumstances, I developed a tougher skin over time. But I have never lost track of the human travesties 
that result from evil. As my father's story suggests, I have also not lost sight of the fact that we are a 
species that has done great good, and will continue to do so in the future. Nonetheless, to provide a sound 
and satisfying explanation of evil we must avoid falling into more romantic interpretations of the human 
condition. Our best protection is science. This is the position I will defend. 
The topic of evil is massive. This is, however, a short book, written without exhaustive 
references, in-depth descriptions of our atrocities, and comprehensive engagement with the many theories 
on offer to explain evil. What I offer is my own explanation of evil, of how it evolved, how it develops 
within individuals, and how it affects the lives of millions of innocent victims. It is a minimalist 
explanation of evil that is anchored in the sciences. I believe, as do many scientists, that deep 
understanding of exceptionally complicated phenomena requires staking out a piece of theoretical real 
estate with only a few properties, putting to the side many interesting, but potentially distracting details. 
This book extracts the core of evil, the part that generates all the variation that our history has catalogued, 
and that our future holds. 
Sincerely, 
Akfludatfr‘----
Hauser 
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Acknowledgements 
I wrote this book while my cat, Humphrey Bogart, sat on my desk, staring at the computer monitor. 
Though he purred a lot, and was good value when I needed a break, he didn't provide a single insight. 
Nor did our other pets: a dog, rabbit, and two other cats. For insights, critical comments on my writing, 
comfort, and endless love and inspiration, there is only one mammal, deliciously wonderful, and without 
an evil bone in her body—my wife, Lilan. 
Marc Aidinoff ... a Harvard undergraduate who joined me early on in this journey, digging up 
references, collecting data, arguing interpretations, sharing my enthusiasm, while offering his own. 
Kim Beeman and Fritz Tsao ... my two oldest and closest friends. They have some of the richest 
minds around. Their knowledge of film, literature and the arts is unsurpassed. Their capacity to bring 
these riches to the sciences is a gift. 
Noam Chomsky... for inspiration, fearless attacks on power mongering, and friendship. 
Errol Morris... for heated discussion, camaraderie, and insights into evil through his 
cinematographic lens and critical mind. 
Many colleagues, students, and friends provided invaluable feedback on various parts of the 
book, or its entirety: Kim Beeman, Kent Berridge, George Cadwalader, Donal Cahill, Noam Chomsky, 
Jim Churchill, Randy Cohen, Daniel Dennett, Jonathan Figdor, Nick Haslam, Omar Sultan Hague, Lilan 
Hauser, Bryce Huebner, Ann Jon, Gordon Kraft-Todd, Errol Morris, Philip Pettit, Steven Pinker, Lisa 
Pytka, Richard Sosis, Fritz Tsao, Jack Van Honk, and Richard Wrangham. 
My agent, John Brockman...not only a great agent but a wonderful human being who supported 
me during challenging times. 
My editors at Viking/Penguin, Wendy Wolff and Kevin Doughten. Tough when needed. 
Supportive when needed. A unique blend. The book is all the better for it. 
Hauser 
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Table of Contents 
Prologue. Evilution 
Chapter 1. Nature's secrets 
Chapter 2. Runaway desire 
Chapter 3. Ravages of denial 
Chapter 4. Wicked in waiting 
Epilogue. Evilightenment 
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Prologue: 
Evilution 
"There is no such thing as eradicating evil [because] the deepest essence of 
human nature consists of instinctual impulses which are of an elementary 
nature... and which aim at the satisfaction of certain primal needs." 
— Sigmund Freud 
I was drowning. This was not the first time. It was also not because I was a poor swimmer. I was 14 
years old. A boy named Lionel James, who was the same age but twice my size, was shoving my head 
under water, roaring with laughter as I struggled to gasp some air. 
I usually managed to avoid Lionel in the pool, but sometimes he got the best of me while I was 
playing with friends. Lionel wasn't the only one who bullied me in junior high school. He was part of an 
evil three pack, including Ronnie Paxton and Chris Joffe, each much larger and stronger than I. Almost 
daily they locked me inside of the school's lockers, bruised my arms by giving me knuckle-punches, and 
gave me purple-nurples by twisting my nipples. This was no fun for me. For James, Paxton, and Joffe it 
was delicious enjoyment. Sometimes, while I was locked in my locker, my math teacher would let me 
out and then ask "Why do you get yourself into these situations?" Though I had great respect for my 
teacher's math abilities, and actually had a crush on her, she was socially daft. Did she think I asked to be 
packaged up in the locker by my tormenters? It was sheer humiliation. 
One day my mother noticed the bruises. Horrified, she asked what happened. I reluctantly told her 
the story. She said we were going to talk with the principal. I told her I would prefer water drip torture. 
She understood and we never went to see the principal. 
The person who rescued me from my misery was my father, a man who had lived through the war 
as a child, running from village to village to escape the Nazis, and in so doing, confronted thuggish farm 
boys whose weight far exceeded their IQ. My father, upon hearing that I didn't want to go to school 
anymore, offered a compromise: he would pick me up for lunch every day if I kept going to classes. I 
agreed, relishing the idea of escaping the lunch-time scene at school where James, Paxton and Joffe 
pummeled me at will without getting caught. 
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A month passed. I felt better. My father told me that it was time to go back to lunch at school, but 
with a plan, one centered around the notion of respect. The only way to command it from my tormenters 
was to fight back. "But Dad," I said, "if I hit them, they will crush me." "They might," he said, "but you 
will have gained some respect, and they may turn their attention to someone else." It seemed like a 
remarkably stupid idea. But my father lived through a war and fought his way to respect among the thugs 
in every village school. I decided to give it a go. 
I went back to school. Soon thereafter, I found myself standing behind Paxton who displayed 
biceps bigger than my head. I figured I had only one shot. I tapped him on the shoulder and swung as 
hard as I could, hitting him square in the chest. What aim. What perfection. What wasted energy. With no 
more than a flinch, Paxton looked down at me, fury in his face, and grunted "What's up with you?" With 
tears running and lips trembling, I sputtered "I can't take it anymore. You, Joffe, and James are constantly 
hitting me and locking me in the lockers. I can't take it!" And then, as if his entire brain had been rewired, 
serotonin surging to provide self-control, dopamine flowing to shift his sense of reward, the hulk spoke: 
"Really? Okay, we'll stop." And just like that, Paxton, Joffe and James stopped. No more locker games, 
no more bruises. They even saw me as a useful resource, someone who could help them pass some of 
their exams. From victim to victory. 
I was fortunate. Many are not. Thousands of children throughout the world are persecuted in a 
similar way but never fight back or if they do, are crushed for trying. Some are pushed so hard that they 
commit suicide, tragedies that increasingly make headline news reports. 
The fact that bullies often torment their victims for personal gain, cause great harm, and often 
enjoy the experience—as did Lionel James —fits well with a common view of evil. On this view, we 
think of someone as evil if they inflict harm on innocent others, knowing that they are violating moral or 
legal norms, and relishing the abuse delivered. But what of bullies who, due to immaturity or brain 
deficits, simply don't understand the scope of moral boundaries? What if they impose great harm on their 
victims, but don't enjoy the experience? What if the victims are not entirely innocent, such as those who 
double-time as bullies? 
We can debate questions like these on philosophical grounds, attempting to refine what, precisely, 
counts as an act of evildoing as opposed to some mere moral wrong, like breaking a promise or having an 
affair while married. Many have. I don't believe, however, that this is how we will achieve our deepest 
understanding. Instead, I turn to the sciences of human nature, focusing on cases where people directly or 
indirectly cause excessive harm to innocent others as the essence of evil. To explain this form of evil, we 
must dissect the underlying psychology, the brain circuits that generate this psychology, the genes that 
build brains, and the evolutionary history that has sculpted the genetic ensemble that makes us 
distinctively human. This is the approach I pursue. If I'm right about this approach, not only will we gain 
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a deeper understanding of how and why our species has engaged in evildoing, but we will learn about our 
own individual vulnerability to follow suit. This prologue provides a sampling of the central ideas minus 
the rich evidence and explanations that follow in the four core chapters of this book. 
A brief history of malice 
Homo sapiens, the knowing and wise animal, has logged an uncontested record of atrocities, 
despite moral norms prohibiting such actions: no other species has abducted innocent children into rogue 
armies and then killed those who refused to kill, tossed infants into the air as targets for shooting practice, 
gang raped women to force them to carry the enemy's fetus to term while destroying the souls of their 
powerless husbands, and mutilated and burned men to death because more humane forms of killing were 
less effective and enjoyable. These are horrific acts. They abound globally and across the ages. Many 
scholars have judged them as evil. 
Despite the pervasiveness of these atrocities, evil is commonly perceived as a defect, an 
unfortunate malignancy that has engulfed and metastasized within our species' essential goodness. Evil is 
also denied, relegated to mythology, the delusional imagination of a few madmen, the propaganda of 
imperialist nations, or the result of a rare mutation. Perhaps because of these impressions, we have an 
obsessive fascination with evil, evidenced by our fertile capacity to create and then consume films about 
genocide, cunning rapists, master criminals, corporate raiders, psychopaths and serial killers. We are of 
two minds, wanting to hide from the atrocities of evil while feeding our insatiable appetite for more. 
To understand evil is neither to justify nor excuse it, reflexively convening inhumane acts into 
mere accidents of our biology or the unfortunate consequences of bad environments. To understand evil is 
to open a door into its essence, to clarify its causes. In some cases, understanding may force us to 
exonerate the perpetrators, recognizing that they harbored significant brain damage and as a result, lacked 
self-control or awareness of others' pain. In other cases, understanding will reveal that they knowingly 
caused harm to innocent others, relishing the devastation left behind. By describing and understanding an 
individual's character with the tools of science, we are more likely to make appropriate assignments of 
responsibility, blame, punishment, and future risk to society. 
To understand evil requires facing our species' sustained record of atrocities, laying out a variety 
of cases for inspection. Former Reverend Lawrence Murphy was responsible for over two hundred 
instances of sexual abuse, luring innocent deaf children in with a saintly smile. Charles Manson, the 
illegitimate son of a sixteen year old woman and the self-proclaimed father of dozens of runaway women, 
was responsible for the brutal death of five people by means of 114 knife jabs, while also prostituting his 
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lovers, beating his wife, selling drugs, and stealing cars. Former Chairman of the NASDAQ stock 
exchange, Bernard Madoff, was responsible for initiating a Ponzi scheme involving money laundering, 
perjury, and mail fraud that caused thousands of people to suffer financial ruin. Jane Toppan, born 
Honora Kelley, was an American nurse who was responsible for killing over 30 patients by drug 
overdose, stating in her testimony that she experienced a sexual thrill when she held dying patients, and 
that her goal in life was to kill more innocent people than anyone else in history. Former military 
specialist Charles Granger was responsible for forcing nudity and sex among the Iraqi prisoners of Abu 
Ghraib, putting individuals on dog leashes, depriving them of their senses with head bags, and piling 
naked bodies into photographed still lifes, orchestrations that led to the ultimate humiliation and 
dehumanization of these prisoners. 
Depending upon how we think about the problem of evil, we might consider the individuals noted 
above as minor evildoers or not evil at all because the harms were rather insignificant, because their goal 
wasn't to directly harm anyone and then enjoy the frail of damage, or because they lacked the mental 
capacity to assume responsibility for the atrocities committed. These individuals pale in comparison with 
the most unambiguously radical evildoers of the 20-21' century—the dictators Idi Amin, Francisco 
Franco, Adolf Hitler, Kim Jong-il, Slobodan Milosevic, Pol Pot, Josef Stalin, Charles Taylor, and Mao 
Zedong. These men were responsible for the brutal deaths of approximately 80 million people combined. 
Most were mentally healthy, at least in terms of clinical diagnoses. Many relished their atrocities. All 
devised over-the-top means of ending lives. Whether by enticing or coercing their followers to torture, 
gang rape, and butcher human flesh, they went beyond what was necessary to get rid of unwanted others. 
These are excessive harms, carried out with excessive techniques. In this book, I will not only explore 
these extreme cases, but more mundane ones as well. Each case helps shape our understanding of what 
propells some individuals to cause harm on small or large scales, while others avoid it entirely, despite 
temptations to the contrary. 
Why and How? 
To explain the landscape of human atrocities, from Reverend Lawrence Murphy to Mao Zedong, we need 
an account of why we evolved this capacity and how it works. I will explain both of these problems using 
the theories and evidence of science. 
Why? Evil evolved as an incidental consequence of our unique form of intelligence. All animals 
show highly specialized abilities to solve problems linked to survival. Honey bees perform dances to tell 
others about the precise location of nutritious pollen, providing an information highway that lowers the 
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costs of individual foraging challenges. Meerkats teach their young how to hunt dangerous but energy-
rich scorpion prey, providing an education that bypasses the risks of trial and error learning. Humans 
unconsciously wrinkle their noses and pull back their lips into an expression of disgust that communicates 
information about disease-ridden and toxic substances, thereby lowering the costs of sickness to others 
who might be exposed. Each of these specializations involve exquisitely designed neural circuits and 
sensory machinery. Each specialization is used for one and only one problem—except in humans. 
Animal thoughts and emotions are like monogamous relationships, myopically and faithfully focused on a 
single problem for life. Human thoughts and emotions are like promiscuous relationships, broad-minded 
and liberated, free to couple as new problems surface. 
Unlike any other animal, the thoughts and emotions we use to solve problems in one domain can 
readily be combined and recombined with thoughts and emotions from other domains. This is powerful, 
providing great flexibility in addressing novel problems, some of which we create for ourselves. Disgust 
provides an example. Disgust originally evolved as an adaptive response to detecting substances that are 
toxic to our health, especially substances that are outside of the body but should be inside: feces, urine, 
blood, and vomit. Within the circulation of a promiscuous brain, however, disgust journeys to distant 
problems, including the moral attitude of vegetarians toward meat eaters, our revulsion toward incest, and 
abhorrence of gratuitous torture. This journey involves the same brain mechanism that serves original 
disgust, together with new connections that give voice to our moral sense. Promiscuity enables creativity. 
What the sciences reveal is that the capacity for promiscuous thinking was realized by 
evolutionary changes in the number of newly wired up brain areas. By increasing these connections, it 
was possible, for the first time, to step outside the more narrow and specialized functions of each 
particular brain area to solve a broader range of problems. Though we don't know precisely when these 
changes occurred, we know they occurred after our split from the other great apes—the orangutans, 
gorillas, bonobos and chimpanzees. We know this from looking at both the brains of these species, as 
well as the ways in which they use tools, communicate, cooperate, and attack each other. Not only are 
there fewer connections between different regions of the brain, but their thinking in various domains is 
highly monogamous, faithfully dedicated to specific adaptive problems. 
Empowered by our new, massively connected and promiscuous brain, we alone migrated into and 
inhabited virtually every known environment on earth and some beyond, inventing abstract mathematical 
concepts, conceiving grammatically structured languages, and creating glorious civilizations rich in 
rituals, laws, and beliefs in the supernatural. Our promiscuous brain also provided us with the engine for 
evil, but only as an incidental consequence of other adaptive capacities, including those that evolved to 
harm others for the purpose of surviving and reproducing. 
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All social animals fight to gain resources, using highly ritualized behaviors to assess their 
opponents and minimize the personal costs of injury. Changes in hormone levels and brain activity 
motivate and reward the winners, and minimize the costs to the losers. In a small corner of the landscape 
of aggressive fighting styles are an elite group of killers, animals that go beyond harming their opponents 
to obliterating them: ants, wolves, lions, and chimpanzees. When these species attack to kill, they 
typically target adult members of neighboring groups, using collaborative alliances to take out lone or 
otherwise vulnerable victims. The rarity and limited scope of this form of lethal aggression is indicative 
of monogamous thinking, and tells us something important about the economics — especially the costs 
and potential rewards of eliminating the enemy, as opposed to merely injuring them. Killing another adult 
is costly because it involves intense, prolonged combat with another individual who is fighting back. The 
risks of significant personal injury are therefore high, even if the potential benefit is death to an opponent. 
As the British anthropologist Richard Wrangham has suggested, animals can surmount these costs by 
attacking and killing only when there is a significant imbalance of power. This imbalance minimizes the 
costs to the killers and maximizes the odds of a successful kill. Still, the rarity of killing reinforces an 
uncontested conclusion among biologists: all animals would rather fight and injure their opponents than 
fight and obliterate them, assuming that obliteration is costly to the attacker. In some cases, we are just 
like these other animals— killophobic. 
Historical records, vividly summarized by Lieutenant Colonel Dave Grossman in his book On 
Killing, reveal that in some situations, soldiers avoid killing the enemy even though they could have. For 
example, despite the fact that Civil War regiments had the potential to kill 500-1000 individuals per 
minute, the actual rate was only 1-2 per minute. This suggests that under some conditions, killing another 
when you can see the whites of their eyes is hard. But as the history of genocides reveal, we have 
evolved ways to bypass this limitation, making us killophilic in a variety of situations. Our brain's unique 
capacity for denial is one of the liberating factors. 
By recruiting denial into our psychology's artillery, we invented new ways of perceiving the 
enemy or creating one, distorting reality in the service of feeding a desire for personal gain. Denial, like 
so many aspects of our psychology, generates beneficial and toxic consequences. Self-deceiving 
ourselves into believing that we are better than we are is a positive illusion that often has beneficial 
consequences for our mental and physical health, and for our capacity to win in competition. Denying 
others their moral worth by reclassifying them as threats to our survival or as non-human objects is toxic 
thinking. When we deny others their moral worth, the thought of killing them is no longer aversive or 
inappropriate. If we end someone's life in defense of our own, we are following our evolved capacity for 
survival. When we destroy a parasite, we are also protecting our self-interests to survive. And when we 
destroy an inanimate object or lock it away, there is no emotional baggage because we have bypassed the 
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connection to individual rights; we have cut out morality as the governor. This suite of transformations, 
enabled by our promiscuous brain, allowed us to occupy a unique position within the animal kingdom as 
large scale killers. 
Chimpanzees only kill adults when there are many attackers against one victim, with the vast 
majority of kills focused on individuals outside of their own group; most kills within the group are aimed 
at infants, where the costs to the attacker are low. Though humans also kill members of enemy groups 
when there are many against one — a pattern that is common among hunter-gatherers and other small-
scale societies—we depart from this narrow pattern in terms of numbers and the array of potential 
victims. When humans kill, we go at it with many against many, one against one, and even one against 
many, including as victims both those outside of our group and those within, young and old, same and 
opposite sex, and mating partner and competitor. 
Add the chimpanzee's adaptive capacity for coalitionary killing to the promiscuous capacity of 
the human brain, and we arrive at a uniquely aggressive species, one capable of inflicting great harm on 
others in any context. Though the modern invention of scud missiles and stealth bombers undoubtedly 
enriched our capacity to kill on a large scale by putting distance between killers and victims, these 
weapons of mass destruction were not necessary. Today, we need only travel back a few years to 1994 to 
witness the machete genocides of Rwanda, a painful memory of our capacity to wipe out close to a 
million people in 100 days with hand to hand combat. This is excessive harm, enabled by our ability to 
use denial to minimize the perceived costs of killing another person and to motivate the anticipated 
benefits. Denial turns down the heat of killing another and turns us into callous predators. 
Evolutionary changes in the connections to the brain's reward system provided a second, cost-
offsetting step, allowing us to move into novel arenas for harming others. When an animal wins a fight, 
the reward circuitry engages, providing a physiological pat on the back and encouragement for the next 
round. This same circuitry even engages in anticipation of a battle or when watching winners. The 
reward system is important as it motivates competitive action in situations that are costly. There is one 
situation, however, where the reward system is remarkably quiet, at least in all social animals except our 
own: detecting and punishing those who attempt to cheat and free-ride on others' good will. 
Punishment carries clear costs, either paid up front in terms of resources expended on physically 
or psychologically attacking another, or paid at the end if the victim fights back or retaliates. These costs 
can be offset if punishers and their group benefit by removing cheaters or teaching them a lesson. Among 
animals, punishment is infrequently seen in vertebrates, especially our closest relatives the nonhuman 
primates. When it is seen, the most common context is competition, not cooperation. Like lethal killing, 
then, punishment in animals tends to be restricted to a narrow context. Like lethal killing, punishment in 
animals is psychologically monogamous. 
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Punishment in humans is emblematically promiscuous. We castigate others whenever they 
violate a social norm, in both competitive and cooperative situations, targeting kin and non-kin. 
Punishment is doled out by the individual directly harmed and also by third party onlookers. We use both 
physical and non-physical means to discipline cheaters, including ostracism. Punishment's landscape is 
vast. 
The idea I develop here, building on the work of scholars in economics, psychology, and 
anthropology, is that our species alone circumvented the costs of punishment as an incidental 
consequence of promiscuity, including an intimate coupling between the systems of aggression and 
reward. As several brain imaging studies reveal, when we either anticipate or actually punish another, or 
even witness punishment as a mere bystander, our reward circuitry delivers a honey hit. Delivering just 
deserts, or watching them delivered, is like eating dessert. We absorb the costs of punishment by feeling 
good about ratting out the scourges, banishing them from society, and sometimes from life itself. 
Ironically, as the economist Samuel Bowles has suggested based on mathematical models and a synthesis 
of the historical record, punishment can strengthen solidarity and cooperation within the group, while 
simultaneously enhancing antagonism and prejudice toward those outside the inner sanctum. Ironically, 
the psychology that benefited cooperation among like-minded others may also have functioned to destroy 
those who have different beliefs and values. 
The emergence of promiscuous punishment was a momentous event in human history, a 
celebration of exquisite brain evolution and adaptive design. But this achievement carried a hidden cost, a 
debt that we continue to pay: A mind capable of feeling good about punishing in the name of virtue is a 
mind capable of doing bad to feel good. It is a mind that finds real or simulated violence entertaining and 
seeks ways to satisfy this interest. It is a mind that enjoys watching others suffer while singing 0 
Schadenfreude. It is a mind that is capable of feeling good about killing others who are perceived as 
parasitic on society. It is a mind that can override the anticipated costs of killing by fueling a taste for 
killing. 
Desire, denial, aggression and reward are each associated with specific psychological processes, 
distinct evolutionary histories, and specific adaptive problems. When processed by a promiscuous brain, 
these systems connect in ways that are both beneficial to human welfare and deeply deleterious. 
How? Evil occurs when individuals and societies allow desire for personal gain to combine with 
the denial of others' moral worth to justify the use of excessive harms. Everyone has desires, resources 
they want and experiences they seek. Our desires motivate us into action, often to fulfill personal needs or 
to help others. We all desire good health, fulfilling relationships, and knowledge to explain the world. 
Some also desire great wealth and power, each culture weighing in on its signature vision of what counts: 
money, land, livestock, wives, and subordinates. The desire system motivates action in the service of 
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rewarding experiences. Some actions have benign or even beneficial consequences for the welfare of 
others, while others have malignant and costly consequences. 
Exquisite studies pioneered by the American cognitive neuroscientist Kent Berridge have 
uncovered the core elements of pleasure, including distinctive systems of wanting, liking and learning. 
We, and hundreds of other species, often want things we like, and like things we want. This is, obviously, 
an adaptive coupling. Thanks to experiments at the level of genes, neurons, and behavior, we can tease 
apart these three systems. Thanks to naturally occurring situations, we can watch these systems come 
unglued over the course of addictions, leading to the paradoxical and maladaptive situation of wanting 
more and more, but liking the experience less and less. Addictions, as archetypal examples of excess, 
provide a model for thinking about evil and its trademark signature of excessive harm. 
The paradoxical decoupling between wanting and liking is seen most clearly in studies of obesity 
in rats and humans, where individuals develop skyrocketing desires for food, but fail to experience 
comparable pleasure from eating. By definition, those who become obese are prone to eat in excess. One 
reason they do is because eating, or even seeing images of food, no longer delivers the same honey hit to 
the brain as in their pre-obesity days. The reward system turns off when we turn to excess. This is 
adaptive because nothing in excess is good. But because the wanting system runs independently, the 
adaptive response by the liking system has the unfortunate consequence of making us want more even 
though we enjoy it less. The proposal I develop in this book is that the same process is involved in evil, 
especially its expression of excessive harm. It is a process that is aided by denial. 
Everyone engages in denial, negating certain aspects of reality in order to manage painful 
experiences or put forward a more powerful image. But like desire, denial has both beneficial and costly 
consequences for self and others. When we listen to the news and hear of human rights violations across 
the globe, we often hide our heads in the sand, plug our ears, and carry on with our lives as if all is okay 
on planet Earth. When doctors have to engage in slicing into human flesh to perform surgery, they turn 
off their compassion for humanity, treating the body as a mechanical device, at least until the surgery is 
over, and the patient awakes, speaks and smiles. When we confront a challenging opponent in an athletic 
competition or military confrontation, we often pump ourselves up, tricking our psychology into believing 
that we are better than we are. Denial turns down the heat of emotion, allowing a cooler approach to 
decision making and action. But doctors in denial concerning the moral worth of others can be convinced 
to carry out heinous operations for the "good" of science or the purity of their group, and military leaders 
in denial of an opponent's strength can lead their soldiers to annihilation. Individuals in denial can reject 
different aspects of reality in the service of reward, whether it is personal gain, avoiding pain, or enabling 
the infliction of pain on others. 
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In a competitive world with limited resources, our desire system never rests. This is a good thing 
as it motivates us to take care of our self-interests and strive for bigger and better. But a desire system 
that never sleeps is a system that is motivated to accrue ever larger coffers or power. To satisfy this 
inflationary need is often not possible without harming others, either directly or indirectly. To offset the 
costs of harming another, desire recruits denial. This is a recipe for evil and the creation of excessive 
harms. It is a recipe that takes two, often benign and highly adaptive ingredients that are essential for 
motivating action and promoting survival, and combines them into an explosive outcome. Seen in this 
way, our capacity for evil is as great as our capacity for love and compassion. Evil is part of human 
nature, a capacity that can't be denied. What I will show is both how this capacity works, and how some 
of us, due to biological inheritance and environmental influence, are more likely to end up as evildoers. 
Historical material on the lives of Franz Stangl and Adolf Eichmann, leaders in the Nazi 
annihilation of Jews, illustrates how desire and denial combine within individual minds to create 
excessive harms. Although this is a historical example, focused on the lives of only two men, stories like 
theirs have been recounted hundreds of times, all over the globe and across time. This pattern points to 
common mechanisms, identified in detail by the sciences of human nature. 
Stangl was a politically motivated man with a burning desire to climb to the top of the Nazi 
hierarchy. A clear path opened when he was appointed commander of the Polish prison Treblinka. 
Unbeknownst to Stangl, Treblinka was one of the Nazi's concentration death camps. To fulfill his desire 
for power therefore required harming thousands of others, or more accurately, commanding Nazi soldiers 
to harm others on his behalf. But since Stangl had no burning desire to harm the Jews, he dehumanized 
them, transforming living, breathing, feeling, and thinking people into lifeless "cargo"—his own 
expression. Stangl was dry-eyed as officers under his command killed close to one million Jews, one 
third of them children. The reward? Power and status within the Nazi hierarchy. The death of innocent 
Jews was a foreseen consequence of Stangl's desire for power, not his direct goal. 
Eichmann, Lieutenant Colonel in the Nazi regime, was considered one of the central architects of 
the Final Solution, the master plan for the extermination of Jews. Eichmann denied Jews their humanity 
by championing the pamphlets and posters that portrayed them as vermin and parasites. This 
dehumanizing transformation empowered Eichmann's belief that cleansing was the only solution to 
German integrity and power. Eichmann's reward? Elimination of the Jews. Unlike Stangl, killing Jews 
was rewarding. As the historian Yaacov Lozowick stated "Eichmann and his ilk did not come to murder 
Jews by accident or in a fit of absent-mindedness, nor by blindly obeying orders or by being small cogs in 
a big machine. They worked hard, thought hard, took the lead over many years. They were the alpinists of 
evil." 
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Stangl and Eichmann: two different routes into evil. Both possible and both equally lethal to 
humanity. 
This is a lean explanation of why evil evolved and how it develops within individuals and 
societies. It is an explanation that strips evil down to its root causes, focusing on the core psychological 
ingredients that enable us to violate moral norms and cause excessive harms to innocent others. 
A difficult journey 
This book takes you on a journey into evil. It is a story about our evolutionary past, our present state of 
affairs, and the prospects for our future. It is as much a story about you and me, as it is about all of our 
ancestors and future children. It is a story about the nature of moral decay and the prospects of moral 
growth. It is story about society's capacity to engineer great harm, and about our own individual 
responsibility to avoid joining in. 
Explaining how our genes create brains that create a psychology of desire and denial that leads to 
excessive harms provides a satisfying explanation for the landscape of evil. It explains all varieties of evil 
by showing how particular genetic combinations can create moral monsters and how particular 
environmental conditions can convert good citizens into uncaring killers and extortionists. This 
explanation will not allow us to banish evil from the world. Rather, it will enable us to understand why 
some individuals acquire an addiction to feeling good by making others feel bad, and why others cause 
unimaginable harm to innocent victims while flying the flag of virtue. This, in turn, will help us gain 
greater awareness of our own vulnerabilities by monitoring the power of attraction between desire and 
denial. 
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Endnotes: Prologue. Evilution 
Recommended books: 
There are numerous books about evil, most written by philosophers, theologians, historians, political 
scientists, and legal scholars. The following recommendations are for books about evil written by 
scientists. They are terrific, I have learned a great deal from them, and some of their ideas powerfully 
enrich the pages between these covers. 
Baumeister, R. F. (1999). Evil. Inside human violence and cruelty. New York, W.H. Freeman. 
Baron-Cohen, S. (2011). The Science of Evil. New York, Basic Books. 
Oakley, B. (2007). Mean Genes. New York, Prometheus Books. 
Staub, E. (2010). Overcoming Evil. New York, Oxford University Press. 
Stone, M. It (2009). The Anatomy of Evil. New York, Prometheus Books. 
Zimbardo, P. (2007). The Lucifer Effect. New York, Random House. 
Notes: 
• For a philosophical account of the nature of goodness that treats evil as a deviation from our species' 
repertoire, see Philippa Foot Natural Goodness (2001, Oxford, Clarendon Press). 
• For an explicit, philosophical argument for the connection between pleasure and evil, see Colin 
McGinn's Ethics, Evil and Fiction (1997, Oxford, Oxford University Press). For a comprehensive 
discussion of evil by a philosopher, including important critiques of the existing literature, see John 
Kekes' The Roots of Evil (2007, Ithaca, Cornell University Press) 
• On killing throughout history: Wrangham, R.W. & Glowacki, L. (in press). Intergroup aggression in 
chimpanzees and war in nomadic hunter-gatherers: evaluating the chimpanzee model. Human Nature; 
Bowles, S. (2009). Did warfare among ancestral hunter-gatherers affect the evolution of human social 
behaviors? Science, 324, 1293-1298; Choi, J.-K., & Bowles, S. (2007). The coevolution of parochial 
altruism and war. Science, 318, 636-640; Grossman, D. (1995). On killing: the psychological costs of 
learning to kill in war and society. New York, NY: Little, Brown. 
• For a summary of research on desire, especially the elements of wanting, liking and learning, see 
Berridge, K.C. (2009). Wanting and Liking: Observations from the Neuroscience and Psychology 
Laboratory. Inquiry, 52(4), 378-398; Kringelbach, M.L., & Berridge, K.C. (2009). Towards a functional 
neuroanatomy of pleasure and happiness. Trends Cognitive Science /3(1), 479-487. 
• The most serious treatment of Stangl can be found in the penetrating interview by Gitta Sereny (1974, 
Into that Darkness: From Mercy Killing to Mass Murder. London: Random House). There have been 
different treatments of Adolf Eichmann, most famously by Hannah Arendt in her Eichmann in Jerusalem: 
A report on the banality of evil. (1963, New York, Viking Press). Arendt's perspective on Eichmann as 
an ordinary gentleman who simply followed orders has been seriously challenged, suggesting that he was 
anything but a banal evildoer; the quote by Holocaust scholar Yaacov Lozowick is one illustration of the 
more generally accepted view that Eichmann was a radical evildoer with heinous intentions to 
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exterminate the Jews. He may have lived a calm and peaceful existence outside of his day job at Nazi 
headquarters, but this was no ordinary citizen. 
Quotes: 
• Quote by Lozowick on Eichmann and banality of evil: Lozowick, Y. (2002) Hitler 's Bureaucrats: The 
Nazi Security Police and the Banality of Evil. New York, Continuum Press, p. 279. 
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Chapter 1: 
Nature's secrets 
Nature hides her secrets because of her essential loftiness, but not by means of ruse. 
— Albert Einstein 
In Charles Darwin's day, biologists unearthed the mysteries of evolution by means of observation, 
sometimes accompanied by a simple experiment. This was largely a process of documenting the patterns 
of variation and uniformity that nature left behind. Only breeders were directly involved in manipulating 
these patterns, using artificial selection to alter the size, shape, coloration, and lifespan of plants and 
animals. 
The Darwins of today continue this tradition, but with new tools, informed by understanding of 
the genetic code and aided by technical developments in engineering, physics, chemistry, and computer 
science. These tools allow for deeper penetration into the sources of change, and the causes of 
evolutionary similarities and differences. They also enable biologists to change the course of evolution 
and the patterns of development by turning genes off or turning novel ones on, and even creating 
synthetic organisms in test tubes — a wonderful playground for understanding both questions of origin, 
change, and extinction. 
The Darwins of today are cowboys, trailblazing a new frontier of understanding. But like the 
frontier of the early American wild west, nature holds many secrets and surprises. Sometimes when we 
break through nature's guard, we gain fundamental truths about the living world, knowledge that can be 
harnessed to improve animal and human welfare. But sometimes when we break through, we create toxic 
consequences and ethical dilemmas. Tampering with nature is risky business as there are many hidden 
and unforeseen consequences. 
In 1999, the molecular biologist Joe Tsien and his team at Princeton University tampered with 
mother nature. Their discovery, published in a distinguished scientific journal, soon filled the 
newspapers, radio airwaves, and even a spot on Dave Letterman's late night television show. Tsien 
manipulated a gene that was known to influence memory, causing it to work over time. This created a 
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