 Mersenne’s criticisms are based on a careful reading and exposition of the adverse doctrines, to the point that Mersenne has been sometimes taken to task for offering the enemies of religion a much too complacent advertisement. It has been remarked (Carraud 1994: 152) that the discourse of others (le discours d’autrui) holds a distinctive place in Mersenne’s writings: it is neither dismissed as in Descartes, nor deftly re-appropriated as in Leibniz, but rather faithfully produced and reported in order to be discussed on its own level and according to its own merits. This is the case, for example with the cabbalistic “sefirot” and numerological methods which are patiently, almost sympathetically, expounded in the Impiété. The same holds for Giordano Bruno’s doctrine. However heretical the man was, his arguments in favor of the infinity and plurality of the worlds (from his De Infinito) are not simply dismissed or brushed aside. The Christian philosopher reports them quite accurately in the second part of the Impiété des déistes, before answering and criticizing them.