Voltaire was a French writer and philosopher famous for his sharp wit and his fierce defense of free speech and religious tolerance. He wrote plays, essays, and the novel Candide, often using humor to criticize unfair rulers and ideas, and he personally campaigned to overturn the wrongful conviction of Jean Calas, a Protestant unjustly executed by French authorities, eventually clearing the man's name after his death. He remains one of the most influential thinkers of the Age of Enlightenment.