Editor's note: James Dawes, director of the Program in Human Rights at Macalester College, is the author of "Evil Men" (Harvard University Press, 2013).
(CNN) -- A Syrian rebel carves the heart out of a dead man and bites it. His comrades nearby cheer: "God is great."
This is from a video that is circulating on the Internet. The appalling footage has all the world asking: What kind of people could do this?
We tell ourselves these men must be monsters, people utterly unlike us, people we could never understand. But we don't say this because it is true. We say this because it is comforting to think so. The far more frightening possibility we must face is that such evil is not diabolically inhuman or beyond understanding. It is human -- very human.
How can ordinary men commit such horrific acts? The war criminals I have met did not start out by desecrating corpses, torturing villagers or murdering children. They got there slowly. There are some men who are natural monsters, but most monsters are made.
This is how you make them.
First, take a man (and yes, it is most often a man) and isolate him. Separate him from his family and friends and put him in an information bubble, an echo chamber cut off from the outside world. Make him conform to the values of his new group by exploiting his insecurity and need for approval. This is the first step in any war.
Second, train him to think that the world is painted in black and white, not shades of gray. Train him in either-or, binary thinking. Either you are my friend or my enemy. Either you are pure or impure. Either the people you love are safe or they are in immediate peril. Either you are all right or you are all wrong.
Third, physically exhaust him. Break down his body and spirit -- through brutal training or prolonged combat -- until he can't think straight. Subject him to a system of harsh and arbitrary punishment and equally arbitrary rewards. Condition him to feel helpless. A man who feels like he has lost control over his life is a dangerous man, because hurting others feels like control.
Fourth -- and this is the most important part -- start small. Work up to atrocity step by step. Put him into a strange and frightening environment with minimal regulation. Let the aggression escalate. Each violent act he commits while trying to survive will make the next act feel easier, more natural.
The first time he kills a villager, it is terrifying. The second time, it is hard. The third or fourth time, it starts to feel almost easy. Eventually, he finds himself competing with his fellow soldiers to see who can do it fastest, most often, most creatively.
Watching videos like this, and thinking thoughts like this, it is easy to lose hope. In war, are we doomed always to descend into barbarism?
The answer is no. The nightmare video from Syria is not inevitable. The very same steps used for creating monsters can also be used to stop monstrosity -- you just need to reverse the steps. Some people are born moral heroes, but most are made. And this is how you make them.
First, take a young man and start small. Work up to altruism and moral courage step by step. Each small thing he does to attend to the suffering of another or stand up against injustice will make the next act feel easier, more natural. Second, give him a clear system of rules with predictable consequences. Teach him he has the ability to make choices about his life, and that these choices matter. Third, teach him that the world's problems aren't as simple as us-versus-them, good-versus-evil. Teach him that there aren't easy solutions to complex problems. Teach him to tolerate, without fear and anxiety, life's difficult ambiguity and uncertainty.
And finally -- to those of you, like me, who are parents of young boys -- teach him to seek out "the other": Other clubs and groups, other sources of information, other places to see, other kinds of people, other cultural values. Spoil him with diversity, so that if there ever comes a time when he is called to war, he will always remember to see the world through the other's eyes. He will fight, but he will fight against an enemy that he sees as a person, like him. He will see their humanity, and in so doing, he will preserve his own.
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The opinions expressed in this commentary are solely those of James Dawes.