IN 1648, at the Treaty of Westphalia, the Protestants and Catholics of Germany, appalled by the horrors of their Thirty Years War, agreed to respect each others’ states and to desist from pre-emptive attacks. Westphalia was a good treaty, but as the invasion of Iraq has showed, people do not always find it easy to respect its tenets.

Why do we find it so difficult to coexist with people of different cultures? In a recent paper published in Nature, Ernst Fehr and his colleagues from Zurich attempted to answer this question scientifically.

Professor Fehr travelled to Papua New Guinea to examine how fairly members of one tribe will treat members of another tribe (a tribe for which they have neutral feelings, neither hating nor loving it).

The study took the form of a “sharing and punishment game”. A person was given $10 and asked to share it with another person. A third person acted as umpire and if he felt that the sharing was not fair he could punish the sharer by fining him. These different people were selected randomly from either tribe.

Professor Fehr found that sharing was often reasonably fair, with people often handing over $5. Nonetheless, there was a lot of unfairness too, and many people handed over only $3. When that happened the umpires always punished. Umpires could see when tribespeople, from whichever tribe, were being treated unfairly.

But when only $4 was handed over, the umpires punished capriciously. Consider the actions of umpires from tribe A. When someone from tribe B was unfair to a fellow B tribesman, the tribe A umpires were unconcerned (who cares what those Bs do to each other?). And if someone from tribe A was harsh to someone from tribe B, then a tribe A umpire remained unconcerned (those Bs deserve no better).

But if someone from tribe B was unfair to someone from tribe A, a tribe A umpire punished hard (lay off my people, you bully). And if someone from tribe A was unfair to a fellow A, then an A umpire punished again (we As must treat each other right). In short, umpires were biased in favour of their own tribesfolk.

Remarkably, though, when the sharing was fair and when $5 was handed over, the umpires remained capricious. When an A person gave $5 to another A person, or an A person gave $5 to a B person, or when two B people treated each other fairly, an A umpire was unconcerned. But when a B person gave $5 to an A person, an A umpire often punished. Remarkably, tribespeople felt badly treated when members of another tribe were strictly fair with them. We human beings, in short, demand preferential treatment, not fairness, from others.

Consequently, we find it hard to keep the peace because, once people have identified with a tribe, they have to be handled over generously by other tribes if they are to feel they are being treated decently. Only big-hearted people can rise to the challenge of being over generous. As Jesus said: “Blessed be the peacemakers, for they shall be called sons of God.”

In short, the price we pay for group loyalty is an exaggerated sense of entitlement — a sense that can lead to irrational resentments that can lead to unnecessary war. But in 1648, at the Treaty of Westphalia, the peacemakers showed us the way to peace — sovereignty. Under the treaty, nation states are recognised as sovereign entities, whose borders are inviolable. Consequently, pre-emptive war is proscribed: however much we hate the heretics of the other side, we promise not to invade them and vice versa, which ensures peace. In the language of the social sciences, Westphalia is a “non zero sum game”.

There are prices to be paid for Westphalia — of which tolerance for the domestic cruelties of tyrants is one — but as the Nature paper has shown, our expectations of others are so irrational that we cannot trust ourselves to remedy their faults without causing even greater mayhem.

True conservatives (who look back to 1648) as opposed to neocons or liberal imperialists (who are idealists) have long suspected that.

Terence Kealey is the Vice-Chancellor of the University of Buckingham

Times Recommends

• It’s the beginning of the affair
• Afghanistan: still a price worth paying
• Heroes of the downtrodden