"You must learn what to fear and what not to fear," Ayaan Hirsi Ali's grandmother told her when she was a girl in Somalia. In 1992 Ali fled her sequestered life and arranged marriage and emigrated to Holland, eventually becoming a member of Parliament. Today she is the target of Muslim extremists for her reformist views on women's rights and for her radical film, Submission. Her new memoir, Infidel (Free Press), fleshes out the fierce polemics of her 2006 essay collection The Caged Virgin, and unveils the motives behind her self-emancipation.