NK: Erdogan once said that Islam was flawless. Well, Islam is pure and has been pure for 14 centuries. For strict Muslims, Islam is metaphysical, the scripture and all its laws come directly from God. Therefore, this religion is above all other things. By contrast, the Bible was written by ordinary earthly people, it can be attributed, and it can — indeed it must — be interpreted. Not the Koran. The Koran has no human author. It comes straight from Allah. This is why Islamic scripture is not questioned and has been turned into an ideology. Either you believe or you are an infidel and therefore an outcast. This is really a very narrow concept of religion. Man is not allowed to ask questions, to formulate doubt. There is no science or scholarship. As long as this continues, there cannot be a secular, moderate Islam.

KH: A moderate Islamism would also be a contradiction in terms, wouldn't it? It seems to me that all "isms" are ideologies by definition, and in this particular case we are even talking about an ideology that inspires terrorists, people who use violence to spread their faith. But let me make another, more important point. The dogma according to which scripture cannot be questioned and challenged is not entirely foreign to the Christian world, either. Remember Galileo? He was formally rehabilitated by the Vatican only in 1992. It took us many centuries to emancipate ourselves from the dogma of scripture. It even took us ages to understand and internalise individual accountability. The concept of linear time was adopted no earlier than during the papal revolutions between the 11th and 13th centuries, together with the idea that every individual can — and must — contribute something for mankind to deserve the second coming of Christ, the parousia. My point is that Islam may simply be lagging behind. Apart from that, the patterns of cultural evolution in both cases look very similar. This means that things might still change, that Islam might grow up some day. People like Necla, who call for an Age of Enlightenment in the Muslim world, deserve great credit for their work. The remaining question is just how strong fundamentalist resistance will prove in the end.

NK: What we need is a helpful consensus about the role of religion. Religion, for me, is a quest — a quest of faith, of meaning. Religion should not be taught as the embodiment of truth as such. You cannot just posit rules and oblige everybody to follow them. In Western civilisation, the decisive progress came with secularisation, with the Enlightenment, when it was finally tolerated that people ask questions and analyse historical processes. A society that doesn't allow for the active use of reason is bound to stagnate.

DJ: Churches are emptying but mosques are multiplying. That is the problem. Is Angela Merkel right when she says that Christianity is an essential part of the German and the European identity? Or is Sarrazin right when he says that Germany is abolishing itself? There seems to be a contradiction here. I agree that one of the good things about Christianity is that its scriptures can be interpreted and this allows the faith to evolve. But right now, here in Western Europe both Catholic and Protestant churches are in retreat. And that leaves a vacuum. On the other hand, a radical Islam seems to be growing in popularity. That may not be rational, but isn't it still a threat?