“I converted to Christianity because I was convinced by Jesus Christ as a character, as a personality. I loved him, his wisdom, his love, his unconditional love. I didn’t leave [the Islamic] religion to put myself in another box of religion. At the same time it’s a beautiful thing to see my God exist in my life and see the change in my life. I see that when he does exist in other Middle Easterners there will be a change…

As the son of a Muslim cleric, he says he had reached the conclusion that terrorism can’t be defeated without a new understanding of Islam. Here he echoes other defectors from Islam such as the former Dutch parliamentarian and writer Ayaan Hirsi Ali.

Do you consider your father a fanatic? “He’s not a fanatic,” says Mr. Yousef. “He’s a very moderate, logical person. What matters is not whether my father is a fanatic or not, he’s doing the will of a fanatic God. It doesn’t matter if he’s a terrorist or a traditional Muslim. At the end of the day a traditional Muslim is doing the will of a fanatic, fundamentalist, terrorist God. I know this is harsh to say. Most governments avoid this subject. They don’t want to admit this is an ideological war.

“The problem is not in Muslims,” he continues. “The problem is with their God. They need to be liberated from their God. He is their biggest enemy. It has been 1,400 years they have been lied to.”