ADVOCATUS DIABOLI, devil’s advocate, the name popularly given to the promoter of the Faith (promotor fidei), and officer of the Sacred Congregation of Rites at Rome, whose duty is to prepare all possible arguments against the admission of any one to the posthumous honors of beatification and canonization.  This functionary is first formally mentioned under Leo X.(1513- 1521) in the proceedings in connection with the canonization of St Lorenzo Giustiniani.  In 1631 Urban VIII made his presence, either in person or by deputy, necessary for the validity of any act connected with the process of beatification or canonization. 

The phrase, “devil’s advocate,” has by an easy transference come to be used of any one who puts himself up, or is put up, for the sake of promoting debate, to argue a case in which he does not necessarily believe.