THE Koran is the word of God, which every Muslim must follow, but its commands can be hard to interpret. So people should submit to the rule of a properly trained religious scholar. The idea is a simple one, and the father figure of Iran's revolution of 1979, Ayatollah Ruhollah Khomeini, made it the central principle of his Islamic state.

AP

Room for interpretation

But the notion of velayat-e faqih (guardianship of the jurist) has proved to be controversial as a religious doctrine and tricky in practice. The turbulence now sweeping Iran has many causes, among them a simple urge for freedom. Yet the tensions, inconsistencies and hypocrisies generated by trying to impose velayat-e faqih lie at the heart of its troubles.

Divisions among top Shia scholars are nothing new. In the main seminary towns of Najaf in Iraq and Qom in Iran, followers of competing ayatollahs have frequently clashed, sometimes with fists. One recurring split has pitted scholars who believe they should stay outside politics against those who believe they must engage in it. Ayatollah Khomeini pushed this argument to a new level. His revolutionary constitution created the post of supreme leader, placing an unelected senior scholar in overall command of the country.

Many of his fellow ayatollahs saw this as an “innovation”, a bad word in Muslim jurisprudence, signifying an unsubstantiated departure from Islam's founding texts. Some feared that immersion in worldly affairs would taint clerics and end by repelling believers from the faith. Others argued that democracy was a better way to divine God's will, or that a committee of scholars, rather than a single man, would suit the leadership function better. Ali al-Sistani, a Najaf-based ayatollah who is probably the most widely revered scholar among the world's Shias today, has stated that in order to be legitimate such a ruler should win acceptance from a majority of believers.

Ayatollah Khomeini, who died in 1989, himself once declared the popular vote a measure of legitimacy and allowed for an elected parliament and president, as well as an Assembly of Experts theoretically charged with monitoring the supreme leader. But his successor, Ali Khamenei, despite lacking both the scholarly credentials and the revolutionary aura of Khomeini, has accumulated ever more power relative to Iran's elected institutions. Under his rule, questioning the doctrine of velayat-e faqih has become taboo. Scholars who query it openly or cast doubt on Mr Khamenei's fitness for the role have been dispatched to obscurity, exiled or imprisoned. The Guardian Council, the appointed 12-man body that vets candidates and elections, summarily disqualifies anyone seen as insufficiently devoted to the doctrine.

Yet opposition is still brewing. The doubters include not only leading scholars in the seminaries of Qom, but some of Ayatollah Khomeini's closest associates, including prominent members of his own family. Today's crisis, which has seen the supreme leader abandon the pretence of neutrality in favour of the hard-line faction behind Mr Ahmadinejad, has exposed doctrinal divisions as never before.

The cheated presidential candidates have appealed directly to the scholars of Qom without challenging velayat-faqih as a doctrine. But their direct defiance of Mr Khamenei is an unprecedented show of rebellion against how it is practised. The response from Qom has been mixed. One group of mid-ranking clerics has blasted the election as a fraud, and at least four of the 19 grand ayatollahs who bestride Iran's Shia hierarchy are said to agree. So far none but Mr Khamenei has openly endorsed the official outcome.

This does not mean the supreme leader is alone. Many Shia clergymen either depend on his largesse or hold loyalty to the state and its Islamic mission above matters of personal opinion. Besides, Mr Khamenei's tenure has seen power steadily drain away from the clergy and towards Iran's security services, whose commanders he appoints. But with rumours swirling of a lobbying campaign to rally clerical support for ousting Mr Khamenei, the supreme leader may suddenly find himself facing not only a backlash from the millions of ordinary citizens who now openly denounce him as a dictator, but also from his robed and turbaned comrades.