SACCONI, RANIERO. – Dominican inquisitor, born in Piacenza at the beginning of the 13th century, died on 21 July 1262.
Educated in heresy and a leader of heretics, through the efforts of St. Pietro da Verona he abjured his error and donned the Dominican habit (1245). From then on he collaborated with St. Pietro in suppressing the Cathars. He happened by chance to escape the conspiracy plotted against him and Pietro da Verona, in which the latter fell as a martyr (6 April 1252). From 1254 he was head of the Inquisition of Lombardy. In 1259 he was compelled to leave Milan because of the opposition of the new podestà, Uberto Pallavicini. On 21 July 1262 Urban IV summoned him to Viterbo so that he might give him an account of his inquisitorial activity in Lombardy.
He wrote (in 1250) a Summa de Catharis et Leonistis seu de pauperibus de Lugdano (ed. in E. Martène-A. Durand, Thesaurus novus anecdotorum, V, Paris 1717, cols. 1761-76; in Duplessis d’Argentré, Collectio Judiciorum de novis erroribus, I, ibid. 1724, pp. 48-57; and in A. Dondaine, Un Traité, cited in the bibliography, pp. 64-78). It is a severe indictment of his former fellow believers; strictly speaking, it is not a refutation of their errors but a list of errors useful to inquisitors. The work (divided into two parts: the first devoted to the Cathars, the second, shorter, to the “poor of Lyon”) is of great historical interest because, in addition to the common doctrine, it enumerates the beliefs proper to the various heretical Churches. It is the best source for knowledge of the doctrine of Giovanni di Luigio.