The 44-year-old author who shot to international fame with the 1998 novel "The Elementary Particles," was defending himself against four French Muslim groups that sued following his comments in an interview with the literary magazine Lire.
In the interview, published last September, the magazine asked Houellebecq his personal feelings about Islam. "You could call it hate," the author was quoted as saying. He said he rejected all monotheistic religions but said that, "The most stupid religion is Islam."
The comments created an uproar in France's large Muslim community and drew criticism from abroad, particularly in Morocco which has a large immigrant population in France. He faces charges of provoking racial hatred.
A large crowd attended the hearing at the Paris court, including several writers who were to testify on Houellebecq's behalf. The presiding judge expelled a group from the far-right National Republican Movement wearing T-shirts with anti-Islamic slogans. "The freedom of literature must be defended in France against Islamic totalitarianism," said Jean-Yves Gallou, an official of the far-right party.
Houellebecq gave the interview to promote his latest novel, "Platform," which was released in August and became an instant best seller.
In the novel, the main character, whose girlfriend dies in an attack by Muslim extremists, says that every time he learns a Palestinian child or pregnant woman has been shot, he feels a "shiver of enthusiasm."