The man who may help decide the future of Syria sits in a tidy, two-story house at the end of a drab street of a London suburb, about 2,200 miles from home. Upstairs is his office. Downstairs is a television tuned to the Arabic-language network al-Arabiya, broadcasting another news bulletin on his country, from which he was forced to leave 26 years ago.

"I live here like a stranger," said Ali Sadreddin Bayanouni, the leader of the outlawed Muslim Brotherhood, the most powerful opposition movement in Syria.

Bayanouni's years of exile, though, are tempered by the modern world. Each day, dozens of e-mails arrive from among 300 addresses in Syria, keeping him abreast of the latest at home. He stays in contact with his fellow Brotherhood leaders, flung across Jordan, Saudi Arabia and Europe. His British cell phone is inundated with text messages. Over last week's Muslim holiday, he received one he called especially memorable. The well-wisher said that, next year, he hoped Bayanouni would be in Damascus. "This regime is probably going to collapse," Bayanouni said bluntly. "It could happen in a week, it could take a year."

For Bayanouni and other exiles, and for Syrian officials and activists inside the country, these days are unlike any in a generation, perhaps any in Syria's modern history. Together, they are retooling ideologies, staking out visions and positioning themselves for a place in Syria's future, even as its present remains opaque amid the crisis over a U.N. investigation that implicated Syrian officials in the assassination of former Lebanese prime minister Rafiq Hariri in February.

The debate goes to the heart of questions that have remained unanswered since Syria's independence in 1946: What is the nature of Syrian society, religious or secular? How is its identity best represented? And will Syria's combustible diversity lead to its disintegration?

After 42 years of Baath Party rule, Syria is often portrayed as a country shackled by dictatorship. But in the debate over its identity is a more nuanced portrait of a country every bit as complex as neighboring Iraq and Lebanon. It also reflects the same forces reshaping the rest of the Arab world: tensions between Islamic and secular activists, attempts by government reformers to salvage ideologies many see as obsolete, and moves toward civil society that are frustrated at almost every turn.

In Syria, some of those currents have converged in an unusual way in Middle Eastern politics: Secular and religious figures, still tentatively, are adopting the same language to press for change in the face of authoritarianism.

Both spectator and participant in the debate, Bayanouni sits over a small cup of Turkish coffee and a plate of pastries for which Syria is famous. He interrupts a conversation to watch an al-Arabiya report on possible involvement of President Bashar Assad's relatives in Hariri's death.

"Syrian society today is destroyed," he said. "The primary aim right now is to transform society into a new era where political and democratic life will be rebuilt." He describes himself as optimistic, but says it almost as if he were reassuring himself.

Plotting a Return

Bayanouni is a rare figure in the Muslim Brotherhood, one of the Arab world's oldest Islamic organizations. Founded in 1928 in Egypt, chapters are spread across the Arab world, answering in name to the Egyptian Brotherhood but operating on their own. Syria's Brotherhood was founded in 1945. Bayanouni entered the leadership in the 1970s. As its leader since 1996, he has tried to reform its positions, winning unlikely accolades from other opposition figures, including secular activists who have spent their careers trying to stem Islam's growing influence in Syrian life.

At 67, Bayanouni defies the image of a religious scholar. A father of seven, he is a trim, athletic man, fond of tennis, volleyball and swimming, with a knack for table tennis. He has the probing mind of a sharp lawyer, with a political sense that has helped him navigate the ebb and flow of the Brotherhood's fortunes over decades of sometimes violent activism.

In the early years of Syrian independence, the Brotherhood built support in cities such as Homs, Hama and Aleppo, populated by Syria's majority Sunni Muslims. Long in competition with the secular Baath Party and Communist Party, it proselytized with the slogan, "Islam is the solution," insisting that the ills of the modern world could be treated by a renewed faith.

In the 1970s, the struggle brought the group into conflict with Hafez Assad, a military leader from the minority Alawite sect, an offshoot of Shiite Islam. The Brotherhood and splinter groups assassinated Baathists and Alawite officers and launched attacks in Damascus and elsewhere. The government responded with brute force, leading to what some describe as a civil war, culminating in the crushing of an uprising in 1982 in Hama where estimates of the dead range from 10,000 to 30,000. The movement's leadership was killed, jailed or exiled, its organization inside Syria dismantled.

"The organization made a mistake by being dragged into this battle with the regime," Bayanouni said.

Since then, Bayanouni has been engaged in a process of trying to lay the groundwork for the Brotherhood's return to Syrian politics. His effort is still shadowed by fears that the fall of Assad's government would inaugurate conservative Islamic rule, reversing decades of state-sponsored secularism. The effort, over the objections of some in his group, also marks one of the most decisive shifts in Syrian opposition politics in recent years.

"The organization is not going to be an alternative to this regime," he said. "The alternative will be a broad-based national government to which the Muslim Brotherhood will contribute, as does any other political force."

Among the various Syrian political factions -- Islamic activists, Arab nationalists, Syrian nationalists, communists and other leftists -- nearly every party has abandoned the revolutionary, generation-old notion that it alone can serve as the agent of change. The Baath Party has not; the constitution still declares it "the leading party of both the society and the state." In Bayanouni's words, and in a spate of declarations, the Brotherhood has forsworn that role, mirroring reforms of the group in other countries including Egypt and Jordan.

In 2002, Bayanouni published a national charter that called for a democratic state and rejected violence. In 2004, the Brotherhood disavowed the idea that "we consider ourselves to be the movement that represents all Muslims." In the same document, it endorsed women's rights and said it would seek only the gradual introduction of Islamic law, leaving the actual legislation to elected representatives. (Requiring women to wear the veil, segregating education or banning alcohol "are not a priority at this point," Bayanouni said in the interview.) A year later, in a National Call for Salvation, the Brotherhood disavowed revenge for past crimes and called for political parties and free elections.

Last month, it joined secular and minority opposition groups in endorsing what was called the Damascus Declaration, a four-page manifesto hailed by a still-feeble Syrian opposition as a blueprint for an alternative to Assad's government and a first for cooperation between secular and religious activists.

"The Muslim Brotherhood," Bayanouni said, "is ready to accept others and to deal with them. We believe that Syria is for all its people, regardless of sect, ethnicity or religion. No one has the right to exclude anyone else."

While the moves have won Bayanouni respect among Syria's opposition, fears still run deep that a chasm remains between the Brotherhood's promises and intentions. Anxiety is particularly strong among Syria's minorities -- Christians and Shiite Muslim offshoots such as the Ismailis, Alawites and Druze. To many, the Brotherhood remains an instrument for domination by Syria's Sunni majority. The same fears originally gave rise in part to the Baath Party's Arab nationalism, which was offered as a more encompassing identity than narrow religious sectarianism.

And in Bayanouni's home, his words can still carry an edge. He says the Brotherhood is only one of many Islamic groups, and he claims the government exaggerates his organization's power to frighten secularists and minorities. But in the same moment, he insists the Brotherhood is the only group representing the Sunni majority and the one with the most support. "Everyone recognizes this," he said.

A Militant Undercurrent

In Damascus, Mohammed Habash, a member of parliament and representative of what he calls the liberal trend in political Islam, speaks with a calm that belies the iconoclasm of his words. His ideas are unusual for a Muslim scholar: Islam is not the only path to salvation, he insists, and the prophet Mohammad made mistakes. Reinterpretation is mandatory, he said. The veil, for instance, is not an obligation.

Habash's worry is not the secularism that has dominated Syrian life, but the example of neighboring Iraq, where a more militant brand of Islam filled the void after the collapse of 35 years of authoritarian rule. "I believe we're headed for black days. Let's be honest. You can't put sugar on death," he said, quoting a proverb.

While the Brotherhood's words have assured some in Syria, others worry that the Brotherhood itself may be overshadowed by more militant Islamic groups that would feed off the growing religiosity of Syrian society. That trend is often expressed in outward signs of piety. The spread of the veil is the most striking manifestation. So are men's beards and the burgeoning crowds that turn out for Friday prayers, even in such ritzy Damascus districts as Malki and Abu Rommaneh.

No one knows the strength of the more militant current, whose voice remains largely unarticulated. But reports of the emergence of militant cells -- Jund al-Sham, for instance -- have sent a chill through secular Syria.

"I do not fear the Muslim Brotherhood of the 1950s," said Nabil Sukkar, a former World Bank economist in Damascus. "Moderate Islamists are welcome. I don't think they pose a threat whatsoever. The fear is the extremist Islamists and whether or not they are the majority. I don't know the answer."

Habash estimated 50 percent of Syrians to be religious. Of those, 10 percent are liberal, he said; the rest are inclined to a more traditional or militant reading of Islam. Their influence in the event of change is what worries him. "Conservative Muslims are sleeping now in political life," he said.

Echoing the official line, Habash added: "There's no chance for radicals under the government of Bashar Assad. But if he is gone, the radicals maybe have a chance to do something in Syria."

Political Alternatives

Bouthaina Shaaban has a vision for a secular Syria, an alternative to Habash's fears. A government minister, she is seeking to modernize a ruling ideology deemed by critics to be obsolete and perhaps irredeemable.

As a 16-year-old girl, Shaaban joined the Baath Party when it was still imbued with the ideals of Arab unity and socialism as a means of development. Her loyalty to the Assad family runs deep: After a personal plea to the elder Assad, he revised a law that made it possible for her to attend college. Her fear of the family's demise runs deep.

"There's nothing wrong with the theories of the Baath Party. The Baath Party is a secular party for a start." the 52-year-old minister said. "It says equality between men and women, it gives every Syrian from any social, or religious or political background the right to join the Baath Party. But there were many things that were not done right by the Baath Party, there are many things that need to be fixed. Now the Baath Party is at a stage that if it wants to survive, it has to reform itself."

She has her prescription: a new law for political parties, a market economy and, eventually, free elections. Her model, she said, is Syria in the early 1970s, when there was a sense of economic development, not the 1940s, with its semblance of democratic life. Her remark suggested that the government is dedicated to development over liberalization, modernization over democratization. But the question remains as to what degree of tolerance it will provide.

"I'm not optimistic at all," said Maen Abdul-Salam, a 35-year-old, soft-spoken activist and writer, who smiles rarely. He, too, has a secular vision: the emergence of a vibrant civil society, despite the government's efforts to prevent it. "I'm not optimistic for one simple reason: I hear every day the Syrian authority is willing to change and reform, but I haven't heard one comment that we made a mistake. You can't reform if you don't admit mistakes. You can't go forward if you don't say 'I'm sorry.' "

Abdul-Salam had his own encounter with promises of reform. With another activist, he began planning a conference on women's rights in Damascus in 2001. He went to the minister of social affairs, who promised permission in two days. Two years later -- after more than 100 additional visits, sometimes sitting for six hours at a time outside the minister's office -- he was still waiting. He finally held the conference in 2003 at Damascus University, whose well-connected president provided the facilities.

With little money, Abdul-Salam runs a publishing house, Etana, a name taken from Assyrian mythology. The house is an alternative to starting a nongovernmental organization, which is next to impossible. He was politicized by the "Damascus Spring," a brief period in 2000-2001 that saw a flourishing of long-repressed dissent. And now he sees his mission as creating more space for openness.

"It's like breaking through the wall," Abdul-Salam said. "It's saying to people you have the ability to do something. You can change, you can force change, you can push the red lines the authorities have put in front of you. They can fall."

But he worries about the legacy of decades of authoritarianism that have depoliticized society, wrecking the lively civic culture of the 1940s and 1950s. There is no representation, no rule of law, and in that vacuum, he said, people identify themselves according to their sect and ethnicity -- Sunni, Alawite, Christian and so on. To him, identity has to be based on citizenship, equal rights under one law.

"I'm hoping that change will come from society itself," he said.

'Accept the Other'

At his home in London, Bayanouni talks about returning to the alleys of Jubaila, the quarter of Old Aleppo where he grew up. His father died while in prison in 1975, his mother after he went into exile in 1979. But, he said smiling, he will visit the rest of his family. "There are relatives I don't even know," he said.

For some Islamic activists, years in the West radicalize them, reinforcing their alienation in a culture that's not their own. Not Bayanouni. He said his time in exile helped him reconsider his beliefs.

"One of the things I learned," he said, "was to accept the other."

And in that is perhaps one of the greatest ironies of Arab politics today. To a remarkable degree, albeit with different inflections and still untested, some secular and religious activists are speaking a common language of citizenship and individual rights in the face of authoritarian governments. Bayanouni, echoing Abdul-Salam, said he wanted to see "a civil state based on democratic institutions."

"The religion of the majority is Islam, and the ethnicity of the majority is Arab," he said. "Those are facts on the ground, but citizenship is the base on which people should interact. Whatever is the result of the democratic process should be accepted."

Ali Sadreddin Bayanouni, leader of Syria's outlawed Muslim Brotherhood, the country's most powerful opposition group, at his home in a London suburb.