When al-Qaeda destroyed the Twin Towers almost exactly 19 years ago, the aims of the terrorists were not fully understood by many in the western media. Osama bin Laden intended not just to wage war against the non-Muslim world but to present himself — and his jihadi narrative — as the new voice of Islam. He was fighting a war of ideas, as well as one of terror. One of the best ways to understand and combat the ideological side of the jihadi movement is to read the works of the philosopher Bassam Tibi, who has been fighting fundamentalist ideas for the past four decades.

His work — speeches, essays and more than 40 books — tracks the methods by which Islamists operate. With forensic precision, he details the ways in which they are inimical to most of Islam’s history. ‘To protect themselves against criticism,’ he once wrote, ‘Islamists invented the formula of “Islamophobia” to defame their critics.’ The word ‘serves as a weapon against all who do not embrace Islamist propaganda, including liberal Muslims’.

I’ve been an admirer of his work for years and flew to Frankfurt to meet him and to hear his story first-hand. He grew up in Damascus and became hafiz (someone who has memorised the Quran) at the age of six. There was a clash of civilisations in his head. ‘My family was against colonialism, against imperialism, against the hegemony of the West — but we were still admirers of the West,’ he says. ‘We would go to the Quranic school, then after Friday prayers go to a party with kids and dance rock ’n’ roll. The culture we looked up to was American.’ He had his eye on Harvard but his father — a property magnate whose company had built half of the new buildings in Beirut — was keen on Germany because it had sided with the Arabs in the first world war. So Tibi went to Hamburg in 1962 and never came back.

‘I came to Germany as an anti-Semite,’ he admits. ‘We were educated that way. I used to fight with my brother who was two years younger. My mother — who was not an anti-Semite but this is just the language we used then — said to me in Arabic: “Leave him. You can do this to a Jew but not to your brother.” Then I met two Jews and they changed my life.’

They were the philosophers Theodor Adorno and Max Horkheimer, the founders of the Frankfurt School of critical thinking. They had fled Nazi Germany for America and only returned after the second world war. They wanted to find out why, after the Enlightenment, with all of its logic and beauty, humanity in the 20th century had started ‘sinking into a new kind of barbarism’.

Tibi had similar questions about Islam and Islamism. Ernst Bloch (a third Jew) anchored Tibi’s thinking in Islamic rationalism. Bloch wrote about Ibn Sina — born in the Samanid Empire in around 980, the golden age of Muslim civilisation — who had plenty to say about human equality and the intertwining of Arabic and western thought.

‘Bloch says the Enlightenment started in medieval Islam,’ Tibi tells me. Tibi makes an important distinction between mufti Islam, the world of the fatwa-givers (a type of Islam that’s on the rise in Britain too), and the world of Enlightenment Islam, highlighted by Bloch. The mufti world of Islam is ‘leading Muslims backwards’, Tibi says. He seeks to explain, revive and promote the Islam of early Enlightenment — the ‘Islam of Light’.

I ask him when he first noticed that something was going wrong in the Muslim world. ‘It started with the Six Day War,’ he says. Israel’s victory was a massive humiliation for the secular Arab regimes in the eyes of their citizens, especially when Israel gained the Gaza Strip and the Sinai Peninsula from Egypt. At the time, Tibi hoped that the response to this would be a new Arab Enlightenment. Instead, religious extremists rose to positions of power. His first physical confrontation with them came in 1979 when he presented an academic paper in Cairo and was denounced as a heretic.

He has long thought it interesting that Arabs constitute only a fifth of the world’s Muslims, yet seem to direct most modern Muslim thought. ‘If you want to know where Islam is going,’ he says, ‘you don’t go to Turkey. You go to Egypt.’ His early work on Cairo’s political institutions drew him to the attention of the political scientist Samuel P. Huntington, who went on to acquire worldwide fame with his 1993 essay ‘The Clash of Civilizations’, in which he argued that faith (especially Islam) would be the world’s next battle line.

It’s an argument that Tibi had tried to talk him out of long before. ‘I was trying to correct his knowledge about Islam. It’s a conflict, I said, not a clash. Dealing with Huntington was like dealing with an Islamist: it’s all about language. If you “clash”, it’s over. But in a conflict, there is a conflict resolution. We can negotiate, we can talk. We say: “There is a western Islamic conflict, and there are ways to deal with it.” But a “clash”? The word is essentialised. It’s saying that we Muslims are backward people.’

Tibi is also an expert in sharia law, which is often deployed by fundamentalist states in the name of being true to Islam. But Tibi argues that it is not fundamental to the religion. ‘If God believed what the Islamists believe, the term “sharia” would occur every second or third page in the Quran. But it is mentioned only once. And not in the meaning of law, but in the meaning of morality or guidance. The Quran was revealed in the 7th century. The sharia schools in Sunni Islam were created in the 8th century, 100 years later.’ The use of sharia in the modern political and confrontational sense, he says, started with the Muslim Brotherhood in Egypt in the 20th century.

Tibi argues that the Islamist agenda is far more modern than the fundamentalists want to admit, and springs from the political totalitarianism invented in the last century. Taking Hannah Arendt’s definition of the term, he categorises all aspects of this ‘political religion’ as authoritarian. He draws out the modern, totalitarian nature of Islamism in his research: for example in his analysis of the works of Hassan al-Banna, who founded Egypt’s Muslim Brotherhood in 1928. It was this movement, Tibi says, that came up with the idea of modern-day jihadism and enforced the notion of Islam being incompatible with western values.

‘When I sit with civilised Europeans, they look at me. I am a Muslim, I am a democrat: what do they think is wrong with me? What do they dislike about me being a Muslim? They say, “But you are more European than a Muslim.” I say no. That’s why I coined the term Euro Islam, European Islam.’

Using the language of medieval Muslim rationalists from Farabi to Ibn Rushd, famous in the Latin West as Averroes, Tibi defines Islam of the Enlightenment as advocating the primacy of reason. He also takes a definition of Enlightenment from Kant: that reason is the court in front of which every-thing must establish itself. But Ibn Rushd made this point in the 12th century, he says. ‘So why are we Muslims now dismissed as underdeveloped people when our greatest philosopher, Ibn Rushd, foresaw things six centuries ahead of the greatest philosopher of Europe?’ In fact, he says, Ibn Rushd perhaps has more relevance to our age, ‘the age of the return of religion’, because his work focused on the unity of faith and reason.

This certainly is the battleground now. The much-needed reformation of Islam will not be about headscarves and beards. Terrorism will only end when scripture is not taken literally. In pursuit of such an enlightened future, Tibi’s work can remind westerners — and Muslims — of a different, less divergent history.