Abstract
The article presents another of those ingenious mind, rebels to the yoke of religion, typical of the Italian
Renaissance. Converted to Calvinism and therefore condemned to death by the Inquisition, Guglielmo Grataroli
(1516-1568) became a defender of heterodox doctrine. His translation of a report of the Waldensian massacre in
Calabria became part of the history of Protestant martyrs. He was the author of numerous treatises on various
subjects, for which he widely used the works of Giovanni Michele Alberto da Carrara, Antoine Mizauld and
Gerolamo Cardano. The perfect correspondence of the topics discussed makes it probable that Giordano Bruno knew
his writings. In particular, the De mutatione temporum, eiusque signis perpetuis may have inspired the De’
segni de’ tempi, a Bruno’s lost opera. This allows us to conjecture the content of the work with greater reliability.