Jung Chang said that Mao ruled by getting people to hate each other: ‘Mao had managed to turn the people into the ultimate weapon of dictatorship. That was why under him there was no real equivalent of the KGB in China. There was no need. In bringing out and nourishing the worst in people, Mao had created a moral wasteland and a land of hatred.

In recent philosophy there has been a growing awareness of the gap between the abstract principles proposed by philosophers and the ways in which people actually think. The kind of rationality admired in the theory of knowledge is idealization. In the real world people have to act on beliefs often based on fragmentary and unreliable evidence.

Part of the Maoist project was the deliberate construction of a new moral identity. To do this it was necessary to destroy people’s previous sense of who they were and to make sure there was no room for it grow back.

A woman who was a schoolgirl at Hiroshima asked, “Those scientists who invented the atomic bomb, what did they think would happen if they dropped it?

Above all, the sense of personal responsibility was reduced by the way agency was fragmented. Among the airmen who obeyed the order to drop the bomb, the many scientists who helped to make it, the President, the many political and military advisers involved in the decision, who killed the people of Hiroshima? No one seems to have felt that the responsibility was fully his.

o In the decision to use the bomb the base line had shifted down during the moral slide from the blockade to the area bombing of Germany and to the fire-bombing of Japan. Predictably one member of Stimson’s committee made the point that the ‘number of people that would be killed by the bomb would not be greater in general magnitude than the number already killed in fire raids’.

Atrocities are easier to commit if respect for the victim can be neutralized. For this reason, humiliation handed out by those with power can be ominous. The link between humiliation and atrocity is often found.

Those who actually dropped the bombs were less responsible than the people who took the decisions higher up the chain of command. In modern technological war, psychological responses are poorly correlated with degrees of responsibility. In people further back up the chain, this casual distance reduces the psychological resistance they have to overcome.

In its report issued that year, 1991, Amnesty International recorded protests against human rights abuses in over fifty countries, the protest to thirteen countries making specific reference to torture. These are the kinds of thing many of us have a vague background awareness of, without there being much publicity unless the perpetrators are some currently loathed regime, or unless some highly visible Westerner is among the victims.