RELIGIONS invite stereotypes, holy texts even more so. Non-Muslims often see Islam as a faith followed by people who hew so closely to an unchanging set of words that they ignore awkward new facts sooner than contradict its message. For critics, this attachment to a text encourages extremists—like Boko Haram, a group that in December attacked Nigerian churches: hotheads can generally find a passage that seems to justify their violence.

Such passages abound in the Koran, just as they do in the founding texts of Christianity, Judaism and many other religions. There is also a long tradition of interpreting such verses in reassuring ways. For example, it is often stressed that the Koran's injunction to “slay the unbeliever wherever you find him” relates to a specific historical context, in which the first Muslims were betrayed by a pagan group who had signed a truce.

But when it comes to parsing holy writ, there is one big difference between Islam and most other text-based faiths. Barring a brief interlude in the ninth and tenth centuries, and a few modern liberals, Muslims have mostly believed that the Koran is distinct from every other communication. As God's final revelation to man, it belongs not to earthly, created things but to an eternal realm. That is a bigger claim than other faiths usually make for their holy writings.

The Koran may be interpreted but from a believer's viewpoint, nothing in it can be set aside. Yet, at least in the calm, superficially courteous world of Western academia, debating the precise text of the Koran is increasingly common—as at a conference hosted by the School of Oriental and African Studies (SOAS), part of the University of London, in November. One organiser was Muhammad Abdel Haleem, an Egyptian-born professor who has translated the Koran into stylish modern English, drawing acclaim from many, but grumbles from purists. Other contributors included a professor from Turkey, and a scholar based in Iran. But most were non-Muslims who study the text as they would any other written material—as prose whose evolution can be traced by comparing versions. New techniques, such as the use of digital photography, help compare variations and solve puzzles. All participants implicitly accepted the idea that methods used to analyse Homer, say, or German myths might elucidate the Koran.

In much of the Islamic world, even the agenda of such a meeting would be controversial. What can be debated in most Muslim countries differs hugely from what is discussed in the West. Staff at a London-based Islamic research body, the Institute for Ismaili Studies, have ranged from radicals like Mohammed Arkoun, a leader of the French deconstructionist school, to traditional Sunni or Sufi scholars. They follow the trail of al-Suyuti, a 15th-century Egyptian who accepted the existence of slightly different versions of the Koran.

Such diversity under a single roof would be impossible now in Karachi or in Cairo, the bastion of Islamic scholarship. There, the interpretation of Islam and its history is strictly a task for believers. Non-Muslim offerings would be called “orientalism”, based on colonial arrogance. Muslims in such places who take a different view face not only academic ostracism but physical danger. Egypt's leading advocate of a liberal reading of the Koran—Nasr Abu Zayd, who died in 2010—was denounced as an apostate, forcibly divorced from his wife and had to spend his later life abroad. The rise of Islamism in Egypt offers no prospect of a friendlier climate.

Meanwhile, scholars in Europe, stimulated by the manuscripts in great European libraries, are working hard to find out how and when the Koran's written form was standardised. In America more effort has gone into relating the Koran to what is known from other sources about political and social history. Patricia Crone, of America's Institute for Advanced Study, once argued that Islam originated in a revolt by Semites against Byzantine and Persian power. She has revised her views, but copies of her 1977 book “Hagarism” change hands for hundreds of dollars.

A burst of new Koranic scholarship erupted at SOAS in the 1980s. These days, it is one of several British campuses where scholars say they find it hard to get funding for work that threatens orthodoxy—a change they ascribe to the influence of conservative Saudi donors. But in France, the home of literary theory, and Germany, the fatherland of textual analysis, free-ranging study of the Koran continues. If you want to argue that partial versions of Hebrew and Christian stories are visible in the Koran, or that its historical portions are inaccurate, nobody will stop you.

Most Muslim children are told that they need know only one thing about the Koran's origin: that it was revealed over a period of 23 years by the angel Gabriel to Muhammad. But Islam has more to say than that. A well-known narrative tells how the fourth ruler of the Muslims, Caliph Uthman, realised that several variants of God's revelation were circulating, and established a single version, ordering the destruction of all the others. Non-Muslim scholars, too, see signs of a conscious, but not wholly successful, effort to settle on a definitive form. The continuing variations are not all trivial. Dots over a single letter can change the tense or person of a verb, notes Keith Small, an American participant in the SOAS event. His book, “Textual Criticism and Qur'an Manuscripts”, says efforts to standardise went on for four centuries after Uthman.

Before the beginning

Excitement surrounds the study of some Koranic material found in Yemen in 1972. Early analysis of images of these folios suggests some may precede the first big standardisation. This study is being undertaken in Germany, not Yemen. But in the light of the Uthman story, the survival of divergent early material (which escaped the standardisers' efforts) need not be unbearably shocking. After all, Islamic tradition also credits Muhammad with accepting at least seven oral versions of the Koran, albeit differing only a little.

Turkey and Iran stand out as mainly Muslim countries where, in academia at least, it is possible to talk about the Koran's textual origins. Turkey's secular constitution helps to safeguard free inquiry. Ankara University and Istanbul University still reflect the rationalist ethos of a secular republic; the Islamist tone of Turkey's present government affects newer campuses.

If Iran is a little more open than most Arab countries, that is because of Shia Islam's stress on theology, and the interpretation of texts, as a continuous enterprise. A Paris-based Shia writer, Mohammad Ali Amir-Moezzi, has caused a stir recently by arguing that the Sunni/Shia split was really over the text of the Koran.

Most Shias would say this overstates the schism. On core beliefs Iran's Shia clergy remain united: they agree that the text they now have is exactly what Muhammad was told. Such tenacity is a reminder that if people expect Islam to change into something like liberal Christianity—treating scripture as a useful but fallible aid to belief—they are wrong. As Mustafa Akyol, a Turkish writer, says: “If you say the Koran is a human text, then you cease to be Muslim.” Over hadiths, sayings about Muhammad's life, there is flexibility; some can be weeded out as unsound or outdated. But nothing in the Koran can be dismissed.

Yet some attitudes can shift, Mr Akyol adds. His book, “Islam without Extremes”, cites slavery as an issue where the Koran's words can be reread. The text favours freeing slaves, but does not demand the abolition of the practice. “Does that mean God condones slavery, or that God spoke within the norms of the seventh century which are open to change?” he asks, noting that several Muslim theologians have said the latter. As it happens Christians have made similar points, picking over the words of Saint Paul. Islam, like Christianity, offers rigidity for those who yearn for it. But it leaves room for nuance too.