Honour has a lot to answer for. Consider the thousand or so women in Pakistan who are murdered each year by relatives in the name of family honour. These murders are not endorsed by the state of Pakistan. They are illegal. Nor do they have the sanction of Islam. Any number of Islamic scholars, mullahs and ayatollahs have declared honour killings to be contrary to their religion.

Alas, it is not uncommon for honour to trump even the combined might of morality, law and religion. Many abhorrent customs, from slavery to suttee, have drawn strength from the sentiment. Yet, for those who aim to bring such customs to an end, honour is not just a problem - it also may provide a solution.

Among moral philosophers, the idea of honour - of earning the respect of people whose judgment you care about - is not riding high these days. It has an uncomfortable connection to old hierarchical codes at odds with our democratic values. Its appeal seems primal, pre-rational. Wouldn't it be nice to think that rational moral argument, not this antiquated legacy of our carnage-ridden past, could be the engine of moral progress?

But that is not how cultural change works. The respect, or disrespect, of our peers is an immensely powerful mechanism. That is why honour - and its reciprocal sentiment, shame - is peculiarly well suited to turn private conscience into public norms.

Consider the practice of foot-binding in the East. For centuries, it was regularly denounced for its cruelty and even forbidden by imperial edict. Yet the custom perished only when it came to be seen as a threat to national honour. As one mandarin warned in the late nineteenth century, foot-binding made China "a laughingstock in the eyes of foreigners."

Then there is the curious case of duelling in Britain, which was always opposed by the state and the Church. For all that, in 1829, when Britain's Prime Minister, the Duke of Wellington, took to the field, he was the fourth prime minister in a century to have done so, and the second while in office. In the early nineteenth century, duelling became especially popular, a legacy, in part, of the Napoleonic wars and the spread of military culture. But by mid-century the practice was pretty much dead. What happened?

A number of factors played a role, not least the rise of a new ruling elite of traders and industrialists, who had little sympathy for the warrior ethic. But something else was going on, too. A duel was an affair of honour because it attested to membership in an exalted class. By the first decades of the nineteenth century, duels increasingly began to take place between the wrong sort of people, and their capacity to bring distinction was swiftly exhausted. In the 1850s, the great Liberal parliamentarian Richard Cobden merrily observed, "As soon as the linen-drapers' assistants took to duelling, it became very infamous in the eyes of the upper classes ... Now nothing would be so ridiculous as any nobleman or gentleman thinking of resenting an insult by going out and fighting a duel about it."

Could honour be mobilized against honour killing? The practice is not just a problem in Pakistan. It can be found in Afghanistan, India, Turkey and across the Arab world. But Pakistan is the worst offender and the place where complicity among magistrates and investigators makes justice particularly elusive. The cost of honour killing cannot be measured just by body count. It is a form of sexual terrorism and frightens many women into accepting marital abuse. It also allows men to rid themselves of inconvenient women with impunity (allegations of zina, unchastity, being far easier to make than to refute). It is a longstanding custom with deep, pre-Islamic social roots.

And it finds support among people of all classes and education levels. Take the case of Afsheen Musarrat, a young woman studying computer science at the university in Multan, a major city of Pakistan's Punjab province. Born to a landowning family of engineers, lawyers and civil servants, she fell in love with a boy in her class and rejected an arranged marriage. Her father strangled her with her own scarf. She was his favourite daughter, but what choice was there? "Look, sir," he told the police, "when I have no honour, I have nothing else."

More and more, however, outsiders are engaging with insiders to persuade Pakistanis that these killings are not just illegal, un-Islamic and immoral but that they stain the nation's honour. Indeed, a common complaint in Pakistan is that activists who draw attention to these problems are damaging the country's good name. But that very response shows that even traditionalists care about how they are regarded by the "decadent" West.

Over the past decade, the strategy of "collective shaming" has brought pressure on Pakistan's political authorities to mitigate the more egregious abuses of women's rights. Step by small step, the country's parliament has begun to remove obstacles to prosecuting those who kill their female relatives in the name of honour. In 2004, a year after Afsheen's murder, a law was passed to make explicit the fact that honour killing is a crime and to set minimum sentences for the offense. Two years later, Pakistan enacted a bill that removed the requirement for a victim to produce four male witnesses in order to prosecute a rape. Previously, accusers lacking such witnesses were simply admitting to having had sex outside marriage and were liable to be punished for it.

Still, it is important not to exaggerate the significance of what is on the law books. Two years ago, in the remote village of Baba Kot in Baluchistan, three young women who wanted to marry against the will of their families were marked for death by a gathering of elders. When two of their older women relatives protested, they were assigned the same penalty. The bodies of the five were dumped into a ditch.

In contrast to earlier debates over high-profile honour killings, most members of Pakistan's Senate responded to the case with clear disapproval. The provincial assembly in Sindh unanimously passed a resolution calling the killings "a heinous crime against humanity." This year, the National Assembly passed a bill protecting women from workplace harassment, and when a lawmaker denounced it as reflecting "hostility" to God (who, he said, wanted men to have authority over women), he was booed by his colleagues. That was a significant moment. In these matters, scorn is more powerful than syllogisms.

Emancipating Pakistani women from the threat of honour killing will require more than the urgings of morality, religion and reason. In order to align what people know with what they do, we must try to reshape their codes of honour, using shame and even carefully calibrated ridicule. Pakistanis who now take honour killing for granted need to recognize that their country is disgraced by allowing these wrongs.

This is easier said than done, but other customs that once seemed imperishable - like duelling and foot-binding - have vanished within a generation, and in Pakistan new conceptions of honour are already being imagined. Perhaps soon, there will be no honour in honour killing.

Kwame Anthony Appiah teaches philosophy at Princeton University and is the author of The Honor Code: How Moral Revolutions Happen. He is in Australia as a guest of the Melbourne Writers Festival, and will be a panellist on Monday's Q & A on ABC1 and ABC News24 at 9.35pm AEST.

An earlier version of this piece appeared in the Wall Street Journal.