In the Muslim world, radicals, reformers, activists and academics are all struggling to reshape their religion. The debates often take place in cyberspace, or on Arabic-language satellite broadcasts.
Other Muslims are trying to rescue their faith from extremism. Some scholars say it's an "Islamic Reformation," borrowing from a Christian era that lasted more than 100 years — and was often violent and bloody.
For centuries, distinguished scholars interpreted scripture and law for the Muslim community. But that authority, at least among Sunni Muslims, has eroded.
Bernard Heykal, a professor of Islamic history at New York University, says the current condition is also shaped by mass literacy and the rise of a middle class.
"Today you have large number of Arabs and Muslims who can pick up books, read them for themselves," Heykal says, "and also have the consciousness and sense of personal autonomy and independence to think that they can interpret these sources and texts for themselves."
The result is what Heykal calls "interpretative chaos."
And that can lead to increasingly selective interpretations — as in some cases, in which some followers can cite violent passages and ignore the complexity of the Koran.
These new interpretations get wide distribution on Web sites, says religious scholar Reza Aslan.
"Some of these fatwas are being issued by very legitimate authorities," Aslan says. "And some of them are being issued by wackos who have never studied Islam in any way."
And, Aslan says, because there is no central religious authority, it's up to individual Muslims to decide what to follow.
One place that has felt the profound ripple is Denmark, as was seen in the violent response to cartoons of Islam's Mohammed, which were published in a Danish newspaper last year.
That instance led many Muslims to debate what a proper response was — and how their religion should be portrayed in the modern world.
Heykal says it is part of a battle of ideas — one that could continue for decades.
"You have a lot of creative and innovative thought going on in the Muslim world," he says, "but it happens to be much more of the dark variety that you talk about, than it is the light, I think."
"But Muslims have to feel some confidence. And at the moment, there is a communal sense that they're under attack — and that they are engaged in a fight for the very survival of the religion."