This book represents the first translation into English and critical study of an unedited work composed in Spanish around 1650 by rabbi Saul Levi Morteira (c. 1596-1660), Obstáculos y oposiciones contra la religión christiana en Amsterdam (Arguments against the Christian Religion in Amsterdam). Arguments was produced in order to encourage the practice of halachic (biblical/rabbinic/Talmudic) Judaism among émigrés descended from conversos, Spanish and Portuguese Sephardic Jews forced to convert to Catholicism. Most of these émigrés had grown up as crypto-Jewish conversos in post-Tridentine Iberia, constrained by the Inquisition from secretly observing no more than a minimal set of practices that were far removed from halachic Judaism. Although they settled in tolerant Amsterdam in order to practice Judaism openly, these émigrés also viewed their Catholicized Sephardic traditions as essential components of their spiritual identity. In Arguments, Morteira depicts an encounter that takes place in France, in 1616, between two conversos, a Portuguese peregrino (pilgrim) and an amigo (friend), who has emigrated to Amsterdam out of a desire to practice Judaism openly. During the theological debate between these two characters that comprises the majority of Arguments, the repeated emphasis on the spiritual obligations placed on Jews symbolizes Morteira's program of rejudaization, and the depiction of the peregrino's reluctance to relinquish his Catholicized beliefs reflects the general spirituality of Amsterdam's converso émigrés. The debate leads to an apocalyptic vision of a Jewish homeland, whose restoration is only possible if conversos choose to embrace rejudaization, which is a manifestation of early modern Zionism and a democratic process that deeply impacted Morteira's most renowned student, Baruch Spinoza.