As I stand on a dusty street under the Karachi sun, already blazing at 9am, it strikes me that I am being rejected. I am at a Christian-run school to talk to the headmaster about religious discrimination, but his assistant has just refused to let me speak to him.
"You're not the only person I'm dealing with," she snaps. "The father doesn't have time for all this." When I speak to the acquaintance who suggested that I interview the headmaster, he shrugs. "Don't be offended," he says. "He is prominent, so he is easily identifiable. Are you surprised he is scared to talk?"
Pakistan was conceived as a secular state but one where Islam is the main religion. "We have many non-Muslims - Hindus, Christians and Parsis - but they are all Pakistanis," said the country's founder, Muhammad Ali Jinnah, in a celebrated speech. However, in the late 1970s and 1980s, the dictator General Zia-ul-Haq engaged in a repressive programme of "Islami-sation". Among his actions was the introduction of a set of blasphemy laws under which a person can face indefinite imprisonment or even the death penalty for criticising either the Prophet Muhammad or the Quran.
The present debate is not about the existence of the legislation (many countries have blasphemy laws, as did the UK until 2008), but about the exceptionally harsh penalties and the very light burden of proof. Hardly any evidence is required - the accuser can even refuse to repeat the blasphemy in court for fear of committing the crime himself - and so the law is frequently used as a means of settling personal scores or stirring up sectarian tension.
The matter came to international attention last November when Aasia Bibi, a Christian mother-of-five, was sentenced to death for "insulting the Prophet". Throughout her trial, she did not have access to a lawyer. Her case was taken up by three politicians in the ruling Pakistan Peoples Party, who called for reform: Salman Taseer, governor of Punjab (Pakistan's most populous state), Shahbaz Bhatti, the minorities minister, and Sherry Rehman, a prominent backbencher.
The consequences speak for themselves. Taseer was shot by his bodyguard on 4 January, Bhatti was assassinated on 2 March and Rehman is living in semi-hiding. On 2 February, the prime minister, Yousuf Raza Gilani, told his government that he would not touch the law and that all reform proposals would be shelved.
It is easy to see why people might be afraid to speak out in favour of change. Taseer's daughter Shehrbano is a recent graduate working as a journalist in Lahore. "Very few people condemned my father's murder," she tells me when we speak on the phone. "Everyone was so petrified that they'd be next. That's how …