At the beginning of the thirteenth century, the Cathars, a group of heretical Christians, rose toprominence in what is now the Languedoc in southern France, but was then a patchwork of city-states and principalities beholden to neither king nor bishop. The Cathars held revolutionary beliefs that threatened the authority of the Catholic Church as well as the legitimacy of feudal law: They thought the idea of Hell to be a sham; they rejected all sacraments, including marriage; they thought private property an absurd notion and that all things worldly were corrupt; and they gave women religious status equal to men. The powerful Pope Innocent III, elected in 1198 and determined to restore the church's power after a century of erosion, resolved to eradicate the Cathars. He recruited the forces of France (at that time a fraction of its current size), and in a series of crusades between 1209 and 1229 the Cathars and their supporters were effectively exterminated. By the time the wars were finally over, the territory of France reached to the Mediterranean, and a terrifying new force—The Inquisition—had been unleashed that would torment Europe for centuries. The Perfect Heresy eloquently chronicles one of Western civilization's most mind-boggling tales. As he did in his highly praised Back to the Front; Stephen O'Shea brings long-ago events to life through the energy of his prose and the clarity of his insight. Full of colorful and passionate personalities, his latest book sheds new light on the thirteenth century and on the timelessness of religious intolerance.