On the subject of the long history of enmity between Saudi Arabia and Iran, which is currently driving much of the Middle East's violence and since the new year has worsened considerably, there is an anecdote the Saudis like to tell.

That anecdote has appeared in the New York Times, PBS, and books, and is often repeated privately. Here is how a 2001 New York Times story recounted it (flagged by the Washington Post's Adam Taylor):

Prince Bandar bin Sultan, the Saudi ambassador in Washington, in an interview last month drew a stark comparison between Saudi Arabia today and Iran under the shah. He offered this anecdote: In the late 1960's, the shah sent King Faisal a series of letters that said: ''Please, my brother, modernize. Open up your country. Make the schools mixed women and men. Let women wear miniskirts. Have discos. Be modern. Otherwise I cannot guarantee you will stay in your throne.'' King Faisal wrote back: ''Your majesty, I appreciate your advice. May I remind you, you are not the shah of France. You are not in the Élysée. You are in Iran. Your population is 90 percent Muslim. Please don't forget that.'' Prince Bandar concluded, ''History proved our point.''

This is a pretty revealing anecdote, but it's not revealing in the way that Bandar intends.

I don't think most historians would agree that Iran had a revolution because the shah, Mohammad Reza Pahlavi, was insufficiently Islamist. Rather, I think they would point to Pahlavi's brutal police state, his perceived fealty to foreign powers, the corruption and Pahlavi excesses that outraged Iranian middle classes, and ultimately internal fissures within Iranian society and state institutions that allowed non-state civil society groups to organize against the state.

I also suspect most scholars would dispute Bandar and Faisal's implication that modernization is impossible in countries that are "90 percent Muslim." Indonesia is majority Muslim, and Jakarta feels pretty modern and cosmopolitan to me. There are plenty of discos and miniskirts in Beirut.

What's most revealing about Bandar's anecdote isn't that it's wrong. It's that it appears to earnestly reflect the Saudi government's worldview: its deeply held belief that modernization will bring violent revolution and that Muslim populations will only accept anti-modern ultra-conservatism.

This helps explain a key contradiction in the Saudi system: Saudi Arabia's ruling royals are, by all appearances, personally fairly liberal (relatively speaking), yet they enforce some of the most conservative laws on Earth and promote an ultra-conservative official state ideology. This is in part because Saudi leaders believe, as the Faisal anecdote shows, that Muslim-majority societies can only be ruled and kept stable by holding back modernity and giving the people ultra-conservative rule.

To understand how the Saudis arrived at this way of thinking, it helps to know the history of how Saudi Arabia came to be. The vast country was first unified by an 18th-century alliance between the ambitious al-Saud family and the followers of a puritanical fundamentalist named Muhammad Ibn Abd al-Wahhab. The Sauds wanted to conquer and unify the area we now call Saudi Arabia, and Wahhab wanted to spread his ultra-austere and anti-modern brand of Islam, known today as Wahhabism. It worked, and though the state collapsed in 1818, it re-formed in the 1920s in much the same way: with the Saud family allying with a Wahhabist group called the Ikhwan ("brotherhood") to conquer most of the Arabian peninsula and call the new country Saudi Arabia.

Ever since then, the Saudis have ruled in an implicit bargain with the hard-line Islamists who helped them rise: The Saudis would rule, and the Islamists would have a state officially aligned to the Wahhabist interpretation of Islam. Obviously the Saudis don't need the Wahhabists to go out and conquer desert tribes anymore, but they do provide the Saudi regime with both ideological legitimacy and a base of support among the clerical establishment and its hard-line followers.

Throughout Saudi modern history, you can see the royal family dancing between the obvious need to be part of the modern world and its belief that it needs to satisfy the Wahhabist hard-liners. They'll roll back restrictions on women one day and then clamp down the next. It's why they'll fund extremists (or part of why they do it, anyway) even though these extremists often end up declaring war on the Saudi royal family. It's why they seek close ties with the United States yet spread an official Wahhabist ideology that often portrays the Americans as enemies of Islam.

These are contradictions that make life difficult for many Saudi citizens, particularly women and young people; that lead the Saudi royal family to oppose the democratization that they believe can only empower extremists; and that make the Saudi system itself more unstable — just as the shah had warned.