A suicide bombing near the Iran-Pakistan border killed at least 31 Iranian nationals, including senior Revolutionary Guard commanders.

The guessing is that the bombing was carried out by Sunni minority tribes. Whoever the culprit, here’s the lesson to remember: Iran is not a nation-state. It was built as a multiethnic empire, and even today Persian speakers make up only about half the population. (51% is the conventional estimate.)

Iran is much more Shiite (over 80% at least) than it is Persian. But it’s an interesting question to what extent Iran’s distinctive Shiism should be understood as an expression of Persian nationalism. If so, that too might enflame the resentment of non-Persians against the regime.

Shiism identifies the early Arab caliphs as the most evil villains in history, the murderers of the family of the prophet Muhammad. It rejects the supreme authority of the early, Arab-speaking, schools of Islamic law in favor of reinterpretation by later generations, Arab and non-Arab alike.

Shiism incorporates pre-Islamic customs and folkways into religious practice.

And while Shiism came late to Iran (it was introduced by the Safavid monarchs – themselves ironically Turkish speakers, not Persian), it spread amongst the population only after it had entirely vanished from almost everywhere in the Arab world.

Bernard Lewis taught us not to be distracted by lines on the map: national identity was weak in the Islamic world, religious identity strong. It may prove a very urgent question: Are the Persians the exception to the rule? And might this Persian exceptionalism irritate non-Persians to such an extent as actually to prove a liability and danger to the Iranian regime?