An introductory foreword concerning the relations between mercy and justice which are expressed in some recent pontifical papers of Pope Francesco and their actuation in canon law. Equity and canon law in thought of Giuseppe Capograssi. Cluny at the epoch of Alger of Liege and his life. Mercy and canon law in his De Misericordia et Iustitia; the some concerning Gratian’s Decretum. Relationship between De Misericordia and Decretum: passages in which there is concordance and others in Decretum without concordance.


Keywords: Mercy; Justice; canon law; Cluny; Alger of Liege; De Misericordia et iustitia; Decretum Gratiani.