Publishers are rushing to reprint Voltaire's 1763 Treatise on Tolerance following a run on copies after the deaths of 12 people in the attack on the offices of Charlie Hebdo , according to French publisher Gallimard. Written after the execution for murder of Protestant merchant Jean Calas, championed by Voltaire as a wrongly convicted victim of Catholic persecution, the treatise has also done well on amazon.fr, with editions including a free Kindle ebook and a €2 (HK$18) paperback, and becoming the No 1 bestseller in religion, philosophy and other categories. Two hundred and fifty years after Voltaire's campaign resulted in Calas being posthumously declared innocent, the author's name and image were hard to avoid in the wake of the Charlie Hebdo murders. It was down Paris' Boulevard Voltaire that record numbers (including 44 world leaders) marched a week ago, and it was a portrait of him that the Palace of Versailles put on display in tribute to the jihadists' victims. A poster showing Voltaire's bust with a J e suis Charlie black band illustrated articles and appeared on social media. Voltaire, who was born in Paris in 1694, defended freedom of religion and freedom of expression. The austere keepers of the flame of the Société Voltaire argued that "it was also Voltaire that [the killers] wanted to assassinate", meaning the Enlightenment legacy of sceptical rationality, secularism, free-ranging curiosity and battles against censorship that he embodied.