In 1731, Filippo Argelati printed for the first time the complete works of the Modenese historian Carlo Sigonio. Intended originally as an edition in five volumes, the collection was augmented by a sixth volume after the discovery in Rome of previously unknown manuscripts of Sigonio. Among the new papers were four sets of ecclesiastical censures which had been secretly directed in the 1580s against four of Sigonio’s works, and, with them, Sigonio’s responses to the papal authorities. According to Argelati, the (...) censures and Sigonio’s responses were found in two manuscripts, one from the vatican Library and the other from the city of Bologna. Until now, the veracity of Argelati’s account has never been questioned. Yet, while there is no doubt about the authenticity of the censures, which are attested also by eight other sixteenth-century manuscripts, Sigonio’s replies do raise doubts, as three-quarters of them are known only from Argelati’s edition of his works. The present article investigates the sources used by the author of the replies. This new evidence clearly proves that, in fact, the replies were written centuries after Sigonio’s death, probably in the same period as Argelati’s edition. In turn, this supports the hypothesis that Sigonio’s works were employed as an instrument to oppose the Roman Church’s political claims, in the jurisdictional debate between the papacy and the empire in the early eighteenth century. (shrink)