[In 1762 Jean Calas, a Protestant of Toulouse, was done to death by torture on the wheel on the false charge of having slain his son, a suicide. His widow and children were put to the torture to extort a confession, in utter lack of evidence. Voltaire devoted years of unremitting labor to agitating the terrible crime and raising money compensation for the victims. His pamphlets aroused substantial sympathy and protests in England and over the Continent. His efforts led to the writing of over one hundred plays, poems, and pamphlets on the case. Voltaire had the satisfaction of witnessing the triumph of his long struggle. He narrates the facts in this Treatise, which expands into a sweeping exposure of the cruelties committed in the name of religion, in all ages and countries.]