In 1864, somewhere in the Colorado Territory of the United States, a former Methodist minister named Col. John Milton Chivington instructed his men to destroy an Indian village: "Kill and scalp all, little and big ... Nits make lice." During the seven hours of the attack, a 6-year-old bearing a white flag was shot dead on the spot. One soldier carved out a woman's genitals and brandished them on a stick. Bodies were mutilated, brains knocked out, infants clubbed.

In this case of genocide, the perpetrators were 700 American soldiers, and the victims, 500 noncombatant Southern Cheyenne and Arapaho Indians. But a similarly horrific example might have surfaced from Babi Yar or Dili, Srebrenica or Rwanda. Genocides in vastly different cultures share this reality: Scores of innocent people die at the brutal hands of ordinary men.

James Waller, a professor of psychology at Whitworth College in Spokane, Wash., suggests that perpetrators of genocide -- those who commit what Waller calls "extraordinary human evil" -- aren't just ideologically committed sociopaths or else passive weaklings who've been forced to pull the trigger. And contrary to what historians such as Daniel Jonah Goldhagen, the author of "Hitler's Willing Executioners," contend, there isn't a far-reaching cultural explanation for why one ethnic, religious or political group decides to slaughter another. Instead, according to Waller, complex forces in human nature make all of us capable of committing acts of genocide.

Salon spoke to Waller from his office in Spokane about how even healers become killers, how women can be just as brutal as men, and why we should expect more cases of genocide in the future.

Some people don't like your explanation of the motives of genocide perpetrators because they feel you're somehow justifying what these murderers have done.

I've spoken on this topic a lot, and often that comes from Jewish voices in the audience who feel as if this is too apologetic for the perpetrators. I was worried about that a lot. It seems to me that there are two mistakes you could make. One would be to just morally condemn these acts and not try to understand them. That doesn't seem to be terribly helpful. The other mistake would be to try to understand these acts of extraordinary evil but, "I'm not going to morally condemn them." That's irresponsible.

What I'd like to do is neither of these things. We can understand how perpetrators come to commit extraordinary evil and at the same time hold them morally and legally accountable. In most cases, they haven't been forced to do it. They've made choices.

Many people will want to know if you found differences according to gender. The generalization is that men commit these crimes. Is that true?

I struggled with this. At this point, virtually all we have in terms of perpetrator behavior is male behavior, and that's pretty much been the focus of my book in its entirety because those are the records we have. Were I to write this book 10 years from now, I think that would change tremendously. Since the fall of the [Berlin] Wall in 1990, and the opening of Eastern Europe, we've opened up tons of archives in Eastern Europe having to do with the Holocaust that we didn't have access to before. Those archives are being translated, sorted, analyzed, and it's still going to be a few years before that dwindles down to people like me.

But the people working in those archives -- I'm thinking of one woman in particular, Susannah Heschel from Dartmouth College -- tell us two things. One is there were a lot more female perpetrators in the camp systems in Nazi Germany than we ever thought before. Thousands more. The second thing is that these female perpetrators had the capacity to be just as brutal, just as sadistic, as any of the male perpetrators that we have records of.

So what Susannah Heschel would argue is that we're not talking about a difference in capacity to commit evil between males and females. Probably what we're looking at is a difference in opportunity. In other words, most of the genocides have occurred in male-dominated societies. Males have been welcomed into the military, females have typically not been. Women simply haven't had the types of opportunities to exhibit the type of evil and cruelty that men have had the opportunity to exhibit in genocide and mass killings. The more we uncover information, the more we'll see female perpetrators.

You see that in Rwanda as well. One of the first people convicted for crimes of genocide in Rwanda was a woman. The first woman in history to be convicted of that. Certainly, survivors from the Holocaust have written about the brutality of their female guards and so on, but we've tended to view them as extraordinarily evil females. We've not seen that as part of the general female pattern of responding to authority.

Why do you think that genocide is more and more likely to occur? What conditions will make it continue to happen?

First: exponential population growth. Second: the scarcity of resources. Those two things really set the stage for continuing collective violence like we see today in the Sudan. In the Middle Ages, if you had wanted to kill 6 million people, like the Nazis killed the Jews, you would have had to travel far and wide to get your hands on that many people. Today, it doesn't require that much mobility.

My own pessimism comes more from understanding human nature and the relative ease with which ordinary people can come to commit extraordinary evil. Until we fully understand and appreciate that, we're kind of at a loss to try and stop it. It seems to me that some of our discussion still revolves around the idea that perpetrators of genocide are very much on the fringe, and that there aren't a lot of these people. But when we recognize how relatively easy it is for ordinary people to become involved in this, that just takes the discussion to a different place.

What do you mean by "extraordinary human evil"?

In the range of human evil, some of it is very ordinary -- gossip, slander, the petty evil we perpetrate every day. But at some level, it takes a qualitative jump and evil becomes rather extraordinary. I focus on one extraordinary part of evil having to do with genocide and mass killing -- the murder of innocent men, women and children outside of military conflict. It's extraordinary in the sense that a political, social or religious group has come to power and they decide to exterminate another group of people living in their midst.

In the book, you say that we don't really use the word "evil" that much anymore, but in the last year, President Bush has used it quite a bit and, in many ways, to his advantage. Has the meaning of it changed?

I had pretty much argued up to that point that we never use this word "evil." It's an archaic word that brings with it a ton of baggage. And then obviously after Sept. 11 you see it used all the time. In some ways, it was an attempt to capitalize on something extraordinary. As a descriptor, that's fine and helpful, but in other ways, the word "evil" tends to carry with it a mystifying, supernatural quality that takes it away from humanity. That's what I've tried not to do.

So terrorism falls under your definition of extraordinary evil as well?

It does. When people talk about terrorism they talk about terrorism from below, like Osama bin Laden expressing a grievance against some country, state or institution. It's really renegade terrorism. But my book focuses more on state-sponsored terrorism. One of the things I'm trying to play out now is that while we're all captivated with the idea of terrorism from below, in truth, it's state-sponsored terrorism that claims millions of more lives over the course of history.

The reason why you want to get away from the mystifying sense of the word "evil" is because you think it's something we're all capable of?

Yes, I want to bring us to the ordinariness of it rather than having it out there as some extrahuman capitalization in a big evil being or figure. The more distance that we put between ourselves and this discussion of evil, the harder it becomes to do anything about it. So I wanted very much to bring it in the discussion of ordinary.

It seems that there are two general camps on this. One says that perpetrating genocide is a cultural phenomenon. Yours says that this is something that everyone's capable of. But does a perpetrator's culture have anything to do with why they kill?

The culture group says that every time a case of genocide and mass killing comes up, look at that culture and see what about the culture led to it. What I want to say is that the answer to this problem lies less in the broad cultural influences and more in the nature of what it means to be human and what humans are capable of.

One of the big examples from the culture group is Daniel Jonah Goldhagen's book, "Hitler's Willing Executioners," which was very popular. What about his argument doesn't hold up for you?

It had two parts to it. He hypothesized the existence of something he called "eliminationist anti-Semitism." He said that Germany was in the grips of -- even before Hitler came to power -- this diabolical, demonic, unusually violent form of anti-Semitism that existed nowhere else in the world.

His second proposition was to say that this eliminationist anti-Semitism was the single cause of the Holocaust. Scholars have taken him to task on both of those because in truth, the anti-Semitism in Germany at the time Hitler came to power didn't seem to be that different -- or certainly that much worse -- than anti-Semitism in France, Austria, Hungary, Poland or Russia, and maybe even the United States. The notion that this was the single cause of the Holocaust ... again, [the Holocaust] was simply too complex a phenomenon to reduce to one ideological issue of anti-Semitism, even if you could argue that that type of anti-Semitism existed at the time.

So I think that he wanted to say this was a very unique form of cultural ideology and that's why the Holocaust happened. But if this is so unique, then why do we see this same type of genocide and killing occurring in culture after culture over the past century, and the centuries before that, as well?

Wouldn't he say, though, that we haven't seen something on the same scale as the Holocaust? That other cultures haven't achieved the same numbers of victims?

It's a good question. One of the weaknesses of his book was that it wasn't a comparative study of genocide. He needed to look more broadly at other 20th century genocides to test his own thesis. He didn't do that. But I'm not sure [that if he did] he would see the Holocaust as such an unusual, unique form of collective violence that really it can't be compared with anything else, as many Holocaust scholars do.

What was particularly disturbing in Germany's case, and in many others, was the passivity of many of the citizens. Is passivity evil?

There certainly is a form of more diffident, passive, indifferent evil. If you want to stand back and just look at the general issue of how genocide occurs, many people have argued that it's because many people sat back and allowed it to occur. I certainly think that the evil I focus on in the book would not be possible had it not occurred in a world of relative indifference.

In any of these cases that you studied did you come across individuals who -- under the same conditions and sharing the same ideology as other perpetrators -- for some reason didn't pull the trigger? Why were they able to resist?

There were many cases of people who resisted. What's interesting to me are the people who are caught in the web of military forces and they could shoot, but they choose not to shoot. You find case after case of non-shooters. Is there anything about those people that would explain that? That's a very elusive question. In retrospect, the non-shooters will say, "I didn't do it, because I felt it was morally wrong and I'm a moral, religious person." But at the time, it's hard to get a finger on exactly what they were thinking at the time they did it. We know that often they said things like, "I don't have the stomach for it" or "I'm not man enough for it." To say it's a wrong thing to do condemns all your colleagues who are doing it. To say you don't have the stomach for it just condemns yourself.

A lot of people want to believe that these killers are simply psychopaths or crazy. Why don't you think that's an adequate explanation?

It's easier for me to sleep at night if I think that perpetrators of genocide and mass killing are lunatics or insane or only found in cultures like Germany. I don't blame people for jumping to those explanations. But for me it begins with the issue of numbers. We know that 6 million Jews died in the Holocaust, but very seldom do we step back and ask the question: How many people does it take to kill 6 million people? We know that 800,000 Rwandans died in 100 days, but again, how many people does it take to kill 800,000 people?

If you want to say that the only people who do this are lunatics or insecure, then I just don't know if you can round up that many people like that in a given society to commit the scale of atrocity that we see in genocide. You simply can't rely on the fringes of society to do that. A lot of ordinary people are going to have to be recruited into that effort as well.

Which also brings up the question of groups, the "diffusion of responsibility" explanation. That does have quite a bit to do with this, don't you think?

It does. Gustav LeBon and M. Scott Peck and others would say that the group is the main factor, or the only factor. It's important to understand that the group leads to a diffusion of responsibility; it does lead to some collective mindset that can be dangerous. But that plays itself out in concert with a wide range of other factors as well.

But group killing is a significant part of cases of genocide. When people are asked in Rwanda how many people were involved in perpetrating the killing, the estimates of perpetrators run as high as 1 million. More perpetrators than victims -- because so much of the killing was done by groups of perpetrators kicking and beating one or two victims to death at a time. I want to put that in its place with all the factors.

One of the most disturbing factors that you talk about is how humans obey authority. Is that just human nature or does it also vary from society to society?

It's part of human nature to have some proclivity for obedience to authority, and you can make a case pretty easily for why this has had survival benefits for us as a species and why it still does. There's certainly some part of our human nature to function in a hierarchy of some type, and hierarchies tend to apply obedience to authority at some level.

But the other part of it is just as true as well -- there are cultural differences in how highly obedience to authority is prized. Not only cultural differences, but generational differences. The generation after World War II in Germany, particularly in West Germany, tended to have very low evidence of obedience to authority. There was almost a backlash effect to their parents and grandparents who were so subservient to authority.

In the Rwandan culture, which tends to be very authoritarian and male dominated, there certainly were responses to male figures in families that were much stronger than there would have been in some other cases of genocide. There are some subtle nuances from case to case.

In Rwanda and the Balkans, neighbors often killed neighbors. How did they turn on people they'd known all their lives?

And in the Holocaust you had incidences of this, too -- I'm thinking of Jan Gross' book, entitled "Neighbors," about a small village in Poland named Jedwabne where the Catholic half of the village killed the Jewish half simply because they were given permission to do so. You realize how thin this veneer of civilization is that we put up. We say we live as neighbors and in a community, but when something happens structurally that says now you have permission to persecute, to take from, to even kill people that you've lived with for years, the relative ease with which people can do that is incredible.

The relative ease with which American citizens could say in World War II that we need to round up all Japanese Americans and put them in camps and take their property is striking. That wasn't genocide but certainly it's part of the removal of our neighbor's humanity. In our climate of fear in response to terrorism, I think we could pretty easily turn on people who have been our neighbors.

Or on our patients. You spend a good amount of time exploring the case of the Nazi doctors. What interested you about them?

Here you have people pledged to healing. They're pledged to do the opposite of the thing they end up doing -- which is killing. My initial draw to it was: How do people professionally and personally pledged to heal come to see killing as part of their mission?

Robert J. Lifton said it very well in one of his interviews with a Nazi doctor. The doctor said, "If a patient comes to me with a gangrenous appendix, I have to remove that appendix; I take out a part of their body to save the larger body." The doctor saw the Jews as the gangrenous appendix in Germany, so he could kill Jews because it was part of healing the larger national body of Germans.

One of the striking things in the study of perpetrators is how they live with themselves morally. It's not that difficult because this really isn't a moral issue for them. They've removed the victims from their universe of moral obligation. What they're doing to the victims isn't really a moral problem because the victim's not part of their moral universe in the way that for some of us a bug or an insect isn't. Killing it is just not a moral problem for us because we don't feel that moral obligation.

We always hear about the dehumanization of victims, but how does it actually work and what's the process behind it?

It allows us to more easily commit the evil that we want to commit because we're not committing it upon someone who's a moral equal or a fellow human. You see it in wartime: military groups and countries describe the enemy in certain terms -- like Vietnam, with "gooks." We do what we need to strip our enemy, our victims, of their humanity. In many ways for us it's a psychological defense mechanism because if we see their faces, if we know they're human, if we know they have a husband, wife, children, mother, father, those things make it more difficult to kill.

In the book, I refer to Franz Stangl, a commandant at Treblinka, who was asked after the war was over: When all the inmates came to Treblinka, you knew you were going to kill them in 24 hours, so why all the humiliation? Why the beating? Why did they have to run around naked? Why did you spit on them and call them names? Stangl's response was incredible. He said that they did that because it made it easier for their men to do what they had to do.

That is something that all these genocide cases have in common. You describe how when Americans slaughtered Native Americans, they ripped out women's body parts. Why wasn't it enough to just kill them?

It's one thing to understand killing, but killing with brutality and killing with zest and killing by taking trophies as American soldiers did with massacres of American Indians, is another thing. Why is that necessary? You'll even notice that in executions throughout World War II, the person's back is always toward the executioner. There really is no logistical reason for that in terms of ease of killing, it's more just a psychological defense of not having to see the victim.

The us-them mentality seems to work here too. It's unsettling that studies have found that that doesn't necessarily have anything to do with a preexisting prejudice.

Most people don't understand how easy it is to develop us-them [mindsets]. Experiments have been done where people come in and a coin is flipped to decide if they're going to be in group A or group B. The groups have no interaction whatsoever, but you ask the groups to evaluate each other on attractiveness, intelligence, warmth, honesty and so on. People in the groups, even though they don't know the people in their group or the other group, tend to just favor their own group. They see their group as more attractive, healthier, less likely to be institutionalized at some point.

Us-them thinking doesn't require a lot to become operative. Any simple way we want to divide ourselves as us-them will develop a pattern of thinking that favors my group and disfavors the outgroup. That can start off very innocuous but pretty quickly can become dangerous.

These ideas help explain how people can come to perceive a distant enemy, but it's harder to get your mind around how the average Joe could actually come to beat or mutilate someone to death. You explain that people blame victims because they want to believe that the world is a just place. So obviously [the victims must] deserve what they're getting, and so it's OK to continue to harm them. Is this how people rationalize genocide?

It's a basic truism and one of the great lessons we learn from social psychology -- this tendency to want to believe that the world is a fair and just place. Again, if you ask anyone directly they'll say, "Well, I know that bad things happen to good people and good things happen to bad people and I know the world's not fair and just," but the truth of it is that's what we tend to revert to. It's what allows us to leave our home in the morning and think that when we come back in the evening, our loved ones will still be there. [We believe that] the world's fair and just and if they don't do anything stupid nothing bad is going to happen to them. Intuitively, we look for a way to blame victims for their own victimization. If we can find that, then it kind of restores our sense that the world is fair.

Did perpetrators acknowledge this in the testimony you read?

We certainly see it in how the Nazis viewed the Jews. They would say that Jews were the cause of this and that, and they weren't easy to get along with. This is why they had to suffer.

How much does this have to do with a warped sense of self-preservation and fear? I know the Rwandan genocide happened very quickly, partly because the government incited the Hutus about the Tutsi "threat." How much does the idea that you need to kill to survive have to do with it?

That's a big part of it, and that's where propaganda comes in as well. The victim groups get depicted as the enemy of all things good, and "if we don't get rid of them, they're going to get rid of us." To me, this is one of the odd paradoxes you see in a perpetrator behavior. On one hand, they're saying that the victim group is stupid, immoral, lazy and can't do anything. On the other hand, the victim group's preparing to take over the world. The Nazis were the worst at this. Unfortunately, I think that's a very easy thing to incite.

What about the factor you describe as the merger of role and person? Is this just an extension of the idea that people supplant who they are with what they do, with their "job"?

Yes, I don't think anyone would quarrel with the idea that what someone believes affects how they behave. But the merger of role and person says that the opposite is also true -- how you behave starts to affect your belief system. It's kind of counterintuitive but we know that the best ways to change attitudes and beliefs is often not to try to change them directly but to change the way people behave. For example, if I meet you and you're behaving a certain way, I stand outside you and assume your behavior reflects some underlying beliefs.

The same thing happens with me: It's almost as if I see myself behaving and on same level I think, "Well if I'm acting this way, then that must be how I believe. It must be how I feel." If you told me to behave in some way that was very inconsistent with how I believe, I could do that, and I could keep saying to myself that I'm only doing it because you make me do it. But over the course of time, we start to lose that distinction. Beliefs start to conform to behaviors.

In the testimonies that you read, did the perpetrators express regret or maybe even disbelief? What were they like?

This has been the hardest thing for me. It was a nightmare because you never know what to read in perpetrator testimony. Are they saying what they feel they're supposed to say? Are they saying what they felt at the time and can they remember what they felt 40, 50 years ago? You read a lot of testimony from the Holocaust that says, "I'm sorry I did it, I shouldn't have done, I was a victim of circumstances, I was told to do it, if I didn't do it, I thought I would be in trouble, I regret what I did." On and on and on. But that's what we'd expect a perpetrator in the Holocaust to say. Often our question is just about the veracity of perpetrator testimony. Do they really deeply feel regret?

I'm more struck by some of what seemed to me to be the more honest testimonies that say, "I am sorry for what I did but the Jews deserved it. They brought it upon themselves. I do still think they're a danger today." It seems to me those are people who are saying they're sorry as a social apology but seriously don't regret what they did at the time.

Which I guess is what makes people think that an ideological commitment has so much to do with becoming a perpetrator. But what you're saying is that there are plenty of people with the same ideological commitments who don't actually pull a trigger and off someone.

And there are plenty of people who pull the trigger and don't have the ideological commitment, who do it for other reasons. I look at the Balkans and to me, a large part of that conflict has been a land grab. Political analysts have often said that it's centuries-old ethnic conflict, but I'm more persuaded by others who have said that this is just people trying to get more land than they have. It's a land grab masquerading for Milosevic as an ethnic conflict. Over time, even people without the ideological commitment start to kill, and the killing starts to form the ideological commitment inside of them.