Jonathan Rauch defends free inquiry as the indispensable mechanism for producing knowledge and correcting error, arguing against both right-wing fundamentalism and left-wing speech codes. The book, first published in 1993 and reissued with a new foreword addressing contemporary campus controversies, presents what Rauch calls 'liberal science'--the decentralized system of checking and criticism through which empirical knowledge advances. Rauch argues that this system requires tolerating offensive speech because the alternative--empowering some authority to determine which views are permissible--produces worse outcomes than allowing error into the marketplace of ideas. He distinguishes his position from both libertarian absolutism (speech has no harmful effects) and progressive purism (speech that harms marginalized groups should be suppressed). Rauch, a gay journalist who has written extensively on same-sex marriage, addresses how minorities benefit from free inquiry even when that inquiry produces offensive conclusions, because the same system that allows prejudice to be expressed also allows it to be refuted. The book examines historical cases of scientific controversy, showing how knowledge progresses through conflict rather than consensus. Rauch writes with analytical clarity and personal stake, as someone whose own identity has been targeted by those who would restrict speech in the name of morality.