Today — Easter Sunday — is the day on which we were promised, through the resurrection of Christ, that evil would be conquered. It has not happened yet. Evil is as potent a force in human affairs as it ever was. It is also as much of a puzzle. What is it? Why is it? Where does evil reside? In the universe, in society or in you and me?

Three devastating psychological experiments in the 20th century seemed to suggest answers to these questions. The first — the Asch conformity experiment — showed that people could be led into denying the evidence of their own eyes by their desire to conform, blindly to accept the authority of the group. The second — the Milgram experiment — showed that people were prepared to subject others to potentially lethal electric shocks because they were encouraged to do so by authority figures. And the third — the Stanford prison experiment (SPE) — showed that perfectly ordinary well-balanced people could be turned into savage tyrants or cowering victims simply by the situations in which they found themselves.

Now Philip Zimbardo, the mastermind behind the SPE, has written his own account of the experiment and its meaning, and of his role in the investigations of the horrific — and, crucially, photographed — abuses at Iraq’s Abu Ghraib prison. Zimbardo’s book The Lucifer Effect: How Good People Turn Evil (Rider, £18.99) is a polemic. The author believes passionately that anybody can “turn evil”. He does not believe in evil as a disposition — a character trait — but as the product of a situation. Evil thus resides not in people but in the system that creates these situations.

The experiment, conducted in 1971, could not have been more simple nor, on the face of it, more harmless. Student volunteers were divided into prisoners and guards. The prisoners were taken to a mock-up jail in Stanford University where the guards imposed a regime designed to suppress individuality and humiliate.

With horrific speed the guards turned into ever more creative abusers and, occasional rebellions apart, the prisoners into pathetic cowering deindividualised wrecks. The fact that they all knew the situation was entirely artificial did nothing to stop the slide into barbarity.

Watching it all with forensic detachment was Zimbardo, whose future wife Christina Maslach, a social psychologist, joined the experiment’s “parole board”. He admits he was drawn into the increasingly desperate logic of the situation. But Maslach was horrified and persuaded him to cut the SPE from its planned two weeks to six days on ethical grounds. Would he do it again?

“The answer is yes. Do I feel remorse about the kids’ suffering? Yes, but I’ve worked hard all these years to make sure the gain is worth the cost and I’ve done it — in lectures, I work in prison reform, I helped change one legal ruling based on the research. It did a lot of good.”

When the Abu Ghraib abuses came to light in 2004 Zimbardo saw striking similarities with the SPE. Isolated within the confines of the prison, a group of guards expanded their assigned roles to include horrific acts of abuse against Iraqi prisoners. Zimbardo was struck by the instant reactions of the army authorities — that this was just a case of a few bad apples: “How could they possibly know that?” he asks.

For him the bad-apple theory is never right. It is the rotten barrel that turns the apples bad. He provided evidence for the defence of one of the guards — Ivan “Chip” Frederick — who, he argued, had no pathology preceding the incidents to suggest he was a bad apple. His evidence was rejected and Frederick received an eight-year sentence.

At the heart of the bad-apple argument is a theory of evil. This is that it resides within individuals. Evil, for Zimbardo, is in the system, not the individual. The extraordinary and unique plasticity of the human brain enables us to create systems and roles that engender evil. That very plasticity, however, can offer hope. Zimbardo believes that if we accept the lessons of these experiments we can construct better systems. Furthermore we should educate for heroism.

There was a hero at Abu Ghraib — Joseph Darby, an extravagantly ordinary individual who passed on the pictures of abuse to higher authorities — and in most theatres of evil, heroes emerge, albeit in a minority. Parents, Zimbardo believes, should get away from the “don’t be a hero” advice often given to children and replace it with active encouragement to speak out against evil.

Is this strictly situational explanation of evil the right conclusion to draw from these three sensational experiments?

The first thing to note is the context. Solomon Asch’s conformity experiments were conducted in 1951, Stanley Milgram’s obedience to authority experiments in 1963 and the SPE eight years later. Milgram had specifically set out to explain the way Germans had so easily accepted the Holocaust, and both Nazism and Stalinism cast their terrible shadows over all these experiments. All three studies can in fact be seen as responses to the 20th century phenomenon of industrialised evil. Confronted with Auschwitz, the normal human response is: how could anybody do that? Implicit in that response is the statement: I couldn’t.

But the experiments show we could. Nothing in the volunteers’ background indicated the possibility of evil behaviour. These people were you and me.

The simple bad-apple argument is an inadequate response to Abu Ghraib. This was a systemic failure in the US military that created a climate in which Iraqi prisoners could be regarded as sub-human. But bad appleism is also challenged by Christian theology. Christ rose on this day as a sign that we could be redeemed from the original sin.

This, for Christians, lies at the heart of theodicy — the explanation of the ways of God to man. Evil exists because of our free will and disobedience. Why a good, omnipotent God should allow this to happen has been the subject of 2,000 years of agonised and inconclusive debate. But the implication of the idea of original sin is clear: nobody can cast the first stone because nobody is free from sin.

Furthermore the situationist conclusion drawn from these experiments has been challenged by psychologists who point out that the responses were not uniform. Some did indeed refuse to accept the opportunity for evil. They did this either by walking away — a passive acceptance of evil reflecting Edmund Burke’s statement, “All that is necessary for the triumph of evil is that good men do nothing” — or heroically challenging the evil-doing system.

If there are such varied responses, such heroism, then surely character — disposition — must play a part? Intuitively this feels convincing. It is, for example, possible but not strictly plausible to explain Hitler solely as a force unleashed by the system. There do seem to be people unusually endowed with a capacity for evil. One might say such people are unleashed by a system; but could it not equally plausibly be said that such people create the evil system?

And finally there is an awkward logical problem with the purely systemic explanation. Systems engender evil, says Zimbardo. But systems are made by humans. Society is a human construct. Blaming systems or society may reduce the burden of guilt on the individual, but it does nothing to exculpate humanity. We systematically do evil. Zimbardo blames this on the plasticity of the human brain. But who is doing the moulding? Only humans can be placed in the dock.

This is the ultimate justification for the concept of original sin. Evil exists only in the human realm. A lion is innocent of murder when it kills a gazelle; humans are uniquely guilty when they herd others of their kind into gas chambers. Systemically or individually, we and we alone are responsible for these rivers of blood and oceans of tears. The human truth of the need for a god to die for this unendurable guilt is why, in spite of our disbelief, we still call this day Easter Sunday.

www.bryanappleyard.comwww.bryanappleyard.com

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• Looking for romance on the Blairs' love bus
• Children 'immersed in culture of violence'
• Hunt for black gold sweeps the country