When a Muslim radical murdered the Dutch director Theo van Gogh for a film criticising Islam, Christoph Luxenberg saw his name ripple through Internet forums 1,000 times and immediately knew why.
"The safety of experts on Islam is topical again," he said -- in a surprisingly detached tone for the author of a critique of the Koran who fears it could one day spark similar anger.
Van Gogh, murdered last week for a film slamming Muslim treatment of women, set out to be provocative. But such is the apprehension among critics of Islam that even an obscure German professor of ancient Semitic languages keeps a very low profile.
"Christoph Luxenberg" is a pseudonym. The professor hides his work from his own students -- even those who recommend it to him, not knowing he is its author. He gives interviews by phone and offers little hint of who he really is or where he lives.
This has served Luxenberg well over the past four years, when his book "The Syro-Aramaic Reading of the Koran" was only available in dense academic German. But he doesn't know what to expect when an English translation appears next year.
"I fear a strong reaction in the Islamic world," he told Reuters late on Wednesday by telephone. "My Muslim friends tell me that many people will jump on this book."
The fate of Islamic reformers in the Arab world is sobering.
In the 1990s in Egypt, the writer Faraq Foda was gunned down for criticising fundamentalists and Cairo University professor Nasr Hamid Abu Zaid was forced to divorce his wife and flee abroad for examining the Koran in its historical context.
Luxenberg thinks the academic nature of his work sets him apart from Salman Rushdie, the British writer threatened with death in 1989 by fundamentalists insulted by his novel "The Satanic Verses", which toys with the idea that the Koran is not infallibly divine.
But although he originally thought he could publish under his own name, Muslim friends warned him not to. He said van Gogh's murder "confirms how right they were".
NO VIRGINS, NO VEILS?
Luxenberg's book is a linguistic analysis of the Koran that appears arcane -- but could be explosive underneath.
He argues that many words that are hard to understand in the Arabic text actually came from Aramaic, a related tongue widely spoken in the Middle East when the Muslim holy book was written.
His work recalls that of German Biblical scholars of the 19th century, who changed Christians' understanding of their scriptures by uncovering their multi-layered history.
Luxenberg's analysis is strictly linguistic, not theological, but it inevitably ends up questioning some traditions and dogmas that Muslims hold central to their faith.
For example, he says the Koranic passage promising men "virgins" in heaven -- often cited as a supposed incentive for male suicide bombers -- really used a word for "white raisins".
The passage traditionally taken as an instruction to women to wear headscarves actually tells them to wear a belt or an apron around their loins, Luxenberg argues.
SHAKING CENTRAL DOGMAS
Even more seriously, he shakes a central dogma by saying Mohammad's title as "seal of the prophets", meaning last of the men chosen by God to proclaim his word on earth, actually only means that he confirms what the prophets said.
His thesis that the Koran had Aramaic forerunners, possibly Christian writings, also challenges the tradition that the Koran was dictated in Arabic to Mohammad by the Angel Gabriel and consists of the actual and unchangeable words of God.
"If you challenge that, quite a few things fall apart, so the Muslims don't want to accept this," Luxenberg said, adding that liberal Muslims had encouraged him to continue his work.
"My work does not question the Koran, only the traditional exegesis of the Koran -- what men have read into it."
"I'm not afraid," he continued. "I know what I'm doing is serious and I'm not doing it to destroy Islam. But it would do Islam good if Muslims could discuss it freely. That would help them progress in so many ways."