Frank A. Kafker : Diderot' s Role in the Calas Affair. It is well known that Diderot played no public role in Voltaire 's campaign to rehabilitate Calas. Almost surely the main reason for Diderot's lack of involvement is that he put a priority on completing the Encyclopédie and feared that if he created a further scandal, he risked persecution and provoking the authorities to stop publication of the work. On the other hand, Diderot did act behind the scene in defense of Calas. A document written by Diderot found at the Bibliothèque municipale de Metz combined with information available from printed sources reveal his passionate interest and participation in the Calas Affair despite the public reticence. Also after the royal administration ...