"Those who cannot remember the past," wrote the perennially misquoted George Santayana, "are condemned to repeat it." Recent events in Iran are served equally well by another famous line: "Rebellion against tyrants is obedience to God."
The mullahs are not having a good few weeks. The death of Grand Ayatollah Montazeri, Iran's most learned Ayatollah and articulate dissident, on 19 December, at the beginning of the holy month of Muharram, could not have come at a worse time. The regime feared his death would provide impetus to the protestors. It was right. But its significance lies as much in the timing as in his demise.
Sunday 27 December was Ashura, the tenth day of Muharram, when clashes between protestors and the state reached new levels. Ashura is the day of mourning for the Imam Husayn, martyred by the caliph Yazid at Karbala in 680AD. The event sits at the centre of the Shia consciousness and its political message - martyrdom of the good at the hands of a despot - fills the national imagination.
During Ashura, the annual re-enactments of Husayn's death see thousands weep in the streets for a man killed over 1,300 years ago. This collective memory has long been a catalyst mobilising the Iranian people to political action. No one understood this more than Ayatollah Khomeini himself, who repeatedly attacked the shah, calling him Yazid, during the revolution. The message then as now was political but the medium was religious.
Thirty years ago, the political grievances of the Iranian people combined with the religious calendar to bring down the shah. In December 1978, on Ashura, protests turned to huge outpourings of rage. The regime responded in the only way it knew how: violence. It didn't work. Weeks later, the shah fled.
Crowds mourning both Montazeri and Husayn now fight the authorities in greater numbers. Ashura once again mobilises the people. This does not mean that revolution is imminent. But the government is becoming desperate and increasingly violent. It is criminal but, to use one last quotation: "It's worse than a crime; it's a mistake."