Preámbulo a la Conversión de los Moros is the draft of a Jesuit refutation of Islam from the second half of the seventeenth century, written in the spirit of Ignatian spiritual conquest. This critical genetic edition allows readers to trace the author's sources and follow the development of his knowledge and perception of Muhammad, Islam, and Muslims—understood not only as a religious challenge but also as a political threat and a form of subversion. Though his image of Islam is largely second-hand and shaped by the history of the Moriscos, it also draws on missionary encounters with Muslim captives, which lead him to temper his polemical tone and offer a distinctive vision of a world that remained, in many respects, unknown.