"The whole world is moving towards God," Iran's President Mahmoud Ahmadinejad has written to his American counterpart George W Bush. "Would Your Excellency not wish to join?" Initially, the letter was supposed to be a private message from the Islamic Republic to the Bush administration. But once Washington had dismissed it as irrelevant to the issues at hand, its text was leaked to reporters in Teheran. To some in Washington, Ahmadinejad's epistolary exercise may look like another of his quirks. But it is based on a long historic tradition and fits into a framework of religious practice developed by Muslims over the past 14 centuries. Prophet Muhammad himself initiated the practice of writing letters to "the rulers of the world." In 625 AD, having consolidated his position in Medina and established a secure power base for his rule, the Prophet decided it was time to call on "the infidel" to abandon their faith and submit to Islam. Accordingly, he dictated three letters: to Khosrow Parviz, the Persian King of Kings, a Zoroastrian; and to Emperor Heraclius of Byzantium and the Ethiopian monarch Negus, who were Christians. THE PROPHET'S offer to the three recipients of his letters was simple: convert to Islam and secure a place in paradise or cling to your beliefs and face the sword of Islam. The Persian monarch, apparently angered that Muhammad had put his own name before that of the "King of Kings," ordered his security services to find the "insolent letter writer" and bring him to the court in Ctesiphon, the capital of the Persian Empire at the time. According to Islamic folklore Muhammad escaped capture by the King of Kings' agents only because, soon after the incident, Khosrow Parviz was murdered by his son and designated heir. And within a decade the Persian Empire had disintegrated with most of its territory falling to the armies of Islam. The Byzantine emperor and the Ethiopian monarch, however, replied to Muhammad's letter in brief but polite terms, pending investigations about his actual status and pretensions. Again, according to Islamic folklore, this is why Byzantium managed to prolong its life by several centuries while Ethiopia escaped Muslim conquest altogether. The tradition of writing letters achieved a new dimension under Ali Ibn Abi-Talib, the prophet's cousin and son-in-law and the fourth Caliph. Ali used letters in the service of two Islamic duties: tahzir (warning) and da'awah (invitation). The tahzir part consists of admonitions to all those, Muslims and non-Muslims, who might have strayed from the "right path" as traced by the Caliph. The da'awah part was a call to non-Muslims to abandon whatever faiths they had and convert to the new religion that was, in the words of the Koran, the ultimate and eternal version of "The Only Truth." Some three centuries later it was the turn of Muhammad Ibn Hassan, the last of the 12 imams of Shi'ism, known as the "Hidden Imam," to use letter writing as a means of communicating with the outside world. The Hidden Imam, whose return Ahmadinejad regards as imminent, addressed most of his letters to Muslims in general and his most ardent partisans in particular. But, as tradition demanded, he was not prepared to settle for anything less than a full and unconditional conversion of the entirety of humanity to his version of the faith. FAST FORWARD to 1987, we see the late Ayatollah Ruhallah Khomeini demonstrating his own epistolary talents by writing a letter, composed in the style of the Prophet, to Mikhail Gorbachev, then the leader of the now-defunct Soviet Union. Khomeini's letter came in response to a message sent by Gorbachev through his ambassador Vladimir Vinogradov, offering the Islamic Republic a strategic partnership with the USSR. Gorbachev wanted the Islamic Republic to help him prevent the victory of the US-backed Islamist Muhjahedin in Afghanistan. In exchange, Gorbachev would support the Islamic Republic in the face of mounting American pressure. Khomeini, however, was not interested in that kind of deal-making. As a good Muslim leader he would not be satisfied with having "something," he wanted everything. Thus he composed a letter inviting Gorbachev to convert to Islam before he could receive help in Afghanistan or anywhere else. Needless to say the Soviet leader politely declined. IT WOULD be wrong to dismiss Ahmadinejad's letter to Bush as just another of the Islamic leader's many weird habits. It would be more prudent, and better politics, to take Ahmadinejad seriously and to try and understand him on his own terms. Despite its many spelling and grammatical errors, and naive undergraduate style, Ahmadinejad's letter contains a crucial message: the present regime in Iran is the enemy of the current international system and is determined to undermine and, if possible, destroy it. It would be sheer folly to dismiss that message as the product of a 50-year-old teenager's folie de grandeur. Ahmadinejad believes that the Hidden Imam is about to return and that it is the duty of the Islamic Republic to provoke a "clash of civilizations" to hasten that return. As he asserts in his letter, Ahmadinejad also believes that the liberal democratic model of market-based capitalist societies has failed and is rejected even in its traditional homeland. Ahmadinejad has been impressed by the extent of recent riots in France in which the extreme Left provided the leadership while the Muslim sub-proletariat offered much of the muscle in the streets. Rather than ignoring Ahmadinejad's letter, President Bush should reply to him by inviting him to abandon Khomeinism and convert to liberal democracy. For, when all is said and done, the fight over Iran today is not about real or imagined nuclear weapons; it is about the kind of Iran with which the Middle East, indeed the whole world, can feel comfortable. Ahmadinejad's letter shows that a majority of Iranians, let alone the world as a whole, cannot feel comfortable with the kind of Iran he represents.