Converso Unbelief in Fortalitium Fidei by Friar Alonso de Espina

Thomas Hendrik Kaal, Queen Mary University London

Zusammenfassung: In seinem Werk Fortalitium Fidei (c. 1464) entwirft der Franziskanermönch Alonso de Espina eine neue Konzeption der Häresie des Judaisierens. Anstatt Judaisieren lediglich als klandestine Fortführung jüdischer Glaubensvorstellungen und Praktiken zu verstehen, sah er darin eine noch schlimmere häretische Verirrung. Den judaisierenden conversos warf er vor, jedwede religiöse Tradition aufgegeben zu haben und der zuerst von Epikur vertretenen Überzeugung zu folgen, dass die menschliche Seele mit dem Tod erlösche. Dieser von Espina propagierte Diskurs bereitete den Weg für die Verknüpfung zwischen den Neuen Christen und der Leugnung der Unsterblichkeit, die sich später in den Akten der Spanischen Inquisition gegen Ende des 15. Jahrhunderts nachweisen lässt.

Abstract: In his Fortalitium Fidei (c. 1464), the Franciscan friar Alonso de Espina outlines a new conception of the Judaizing heresy. Instead of seeing Judaizing merely as a clandestine continuation of Jewish beliefs and practices, he saw it as an even worse heretical aberration. He argued that most conversos had abandoned all religious traditions, sharing the conviction, first held by Epicurus, that the human soul expires after death. Espina’s discourse paved the way for the link between the New Christians and the denial of immortality, which can be observed in the files of the Spanish Inquisition produced at the end of the 15th century.

The trial records of the Spanish Inquisition feature an astonishing number of people who were accused of not believing in the immortality of the soul.1 The majority of these individuals were conversos, that is to say Iberian Jews who had been forcibly converted to Christianity in the course of the 15th century, as well as their numerous descendants. Brought before the tribunals on suspicion of Judaizing, these conversos seem to have disregarded both the Christian and the Judaic religion.2 Instead of following either of the two laws, they were said to act on the maxim that there was nothing to human life except being born and dying (nada que nascer e morir). Scholars have tended to interpret such testimonies as evidence of a secret current of religious skepticism among the New Christians, sometimes called ‘popular Averroism’.3 The alleged disbelief in immortality is seen as a precursor of subsequent religion-skeptical tendencies among the descendants of Iberian Jews, culminating in the skeptical philosophy of 16-century Marranos such as Uriel da Costa and Baruch de Spinoza.4

This article forms part of an ongoing research project that re-examines the relationship between conversos and religious skepticism in 15th century Castile. It aims to show that disbelief in immortality formed part of a stereotypical view of the New Christians, which emerged decades before the first inquisitorial tribunal began its work in Castile.5

One of the first contemporary authors to associate conversos with disbelief in immortality was the Franciscan friar Alonso de Espina (c.1410–1465). His magnum opus bears the programmatic title Fortalitium Fidei contra iudeos, saracenos aliosque christiane fidei inimicos (“The Fortress of Faith against Jews, Saracens and all other Enemies of the Christian Faith”).6 The text was one of the most ambitious heresiological treatises written in the late Middle Ages. It exposes what the Franciscan perceived as the war of Christianity against its various enemies: Jews, Muslims, heretics, and demonic forces, each of which are dealt with separately in one of five books. Espina paints the bleak picture of a society under siege: as depicted in the above illustration, Jews would attack the fortress of faith with their blind rejection of the gospel, Muslims would threaten the Christian kingdoms with war and demons wreak havoc like never before; but worst of all, the foundations of the faith were about to be completely undermined by heretics. Here, Espina pointed to the conversos as the main threat to religious orthodoxy. He argued that the majority of New Christians had succumbed to a particularly wicked heretical deviation, which would even exceed the blind unbelief of the Jews.7

For Alonso de Espina, the Judaizing heresy of the conversos was far worse than a simple relapse to Jewish customs. He conceptualized it as a deliberate denial of all religious traditions. Rendering the results of an alleged Toledan inquiry, the friar claimed that many New Christians had abandoned both the Jewish and the Christian law. They would consider the teachings of the church to be a massive swindle (truffa) and disregard both the Old and New Testament as silly fairytales, written to mislead the simpleminded. Instead of following any of the established religious traditions, the New Christians would deny the afterlife and live only for material pleasure and success. To summarize their wicked irreligiosity, Espina stated that the conversos believed in nothing but “being born and dying”—the very formulation that later featured in the trial records of the Spanish Inquisition.8 The friar warned that mortalist ideas as believed by the New Christians could easily spread to other parts of society. He admitted that even the most pious believer might occasionally wonder whether the Christian claims about the afterlife were actually true. Since the devil would constantly try to dissuade people from the true faith, the presence of heretics who denied immortality posed an immediate threat to the inner stability of a Christian society. The spread of mortalist ideas thus had to be stopped at all costs. Espina argued vehemently that the only way was to establish a general inquisition in Castile, which should put an end to the Judaizing heresy.9

Fortalitium Fidei had a considerable impact on the debate about the New Christians in the last decades of the 15thcentury. Following the argument set out by Alonso de Espina, disbelief in immortality emerged as a distinctive feature of crypto-Judaism. Scholars like Ana Echevarría have argued that Fortalitium Fidei served as an important handbook for the early Spanish Inquisition.10 This would explain why many first-generation inquisitors categorized disbelief in immortality as tantamount to Judaizing. Rather than evidencing an averroistic current among the conversos, the plethora of mortalist statements recorded by inquisitors thus seems to point to the cultural hinterland that gave rise to the inquisition in the first place. The testimonies demonstrate that in the context of inter-religious conversion, radical unbelief served as a particularly effective accusation to vilify any form of religious deviance.

Photo: Alfonso de Espina, Fortalitium Fidei, Basel 1475, in:, URL: [] (01.02.2023).

Diesen Blogbeitrag zitieren
Thomas Hendrik Kaal (2023, 1. Februar). Converso Unbelief in Fortalitium Fidei by Friar Alonso de Espina. Blog der Arbeitsgemeinschaft Iberomediaevistik. Abgerufen am 24. Mai 2024, von

  1. See for example the evidence from Soria, El Tribunal de la Inquisición en el Obispado de Soria (1486–1502), Carlos CARRETE PARRONDO (ed.), (Fontes Iudaeorum Regni Castellae, 7), 1985, Salamanca. The records have been anaylized by MONSALVO ANTON, José M. 1984: »Herejia conversa y contestacion religiosa a fines de la Edad Media. Las denuncias a la Inquisicion en el obispado de Osma«, Studia historica: historia medieval, Vol. 2, pp. 109–138 and EDWARDS, John 1988: »Religious Faith and Doubt in Late Medieval Spain. Soria circa 1450–1500«, Past & Present, Vol. 120, pp. 3–25. []
  2. See PASTORE, Stefania 2016: »Doubt in Fifteenth-Century Iberia«, in GARCÍA-ARENAL, Mercedes (ed.), After Conversion. Iberia and the Emergence of Modernity, Leiden, pp. 283–303. []
  3. MÁRQUEZ VILLANUEVA, Francisco 1994: »Nasçer e morir como bestias (criptojudaísmo y criptoaverroísmo)«, in DÍAZ ESTEBAN, Fernando (ed.), Los judaízantes en Europa y la literatura castellana del siglo de oro, Madrid, pp. 273–293. []
  4. This interpretation has been spearheaded by NIEWÖHNER, Friedrich 1988: Veritas sive varietas. Lessings Toleranzparabel und das Buch Von den drei Betrügern, (Bibliothek der Aufklärung, 5), Heidelberg and YOVEL, Yirmiyahu 2009: The Other Within. The Marranos: Split Identity and Emerging Modernity, Princeton. []
  5. The project ties in with the methodology of WELTECKE, Dorothea 2010: “Der Narr spricht: Es ist kein Gott”. Atheismus, Unglauben und Glaubenszweifel vom 12. Jahrhundert bis zur Neuzeit, (Campus historische Studien, 57), Frankfurt am Main. []
  6. The earliest Latin manuscript, preserved in the Archive of the Burgo de Osma Cathedral, dates back to 1464 (Codex No. 154). All quotations in this article are from the 1487 incunabulum of the work printed in Lyon. []
  7. On Jews and heretics in Fortalitium Fidei see CAVALLERO, Constanza 2016: Los enemigos del fin del mundo. Judíos, herejes y demonios en el Fortalitium Fidei de Alonso de Espina (Castilla, siglo XV), Buenos Aires. and VIDAL DOVAL, Rosa 2015: Misera Hispania. Jews and Conversos in Alonso de Espina’s Fortalitium Fidei, (Medium aevum monographs, 31). []
  8. “Sexta, quod fides catholica erat quedam truffa et quod nihil aliud erat in hac vita nisi nasci et mori et quod totum aliud vanitas erat”, Alonso de Espina, Fortalitium Fidei, II, 6, 1, f. 53 v.a. []
  9. “et specialiter iuxta posse suum laborat quod faciat eum dubitare quod sit altera vita nisi hec, et quod debeat fieri resurrectio mortuorum, quia si hoc facit eum credere vel in hoc dubitare, statim homo sic deceptus dimittit se cadere in omnem peccatum, et elongatur ab omni virtute, et perdit omnem timorem et amorem Dei, et vivit desperatus qui perdidit totam fidem et spem Dei”, Alonso de Espina, Fortalitium Fidei, II, 6, 13, f. 63 v.a. []
  10. Echevaria, Ana 2022: »The Perception of the Religious Other in Alonso de Espina’s Fortalitium Fidei: A Tool for Inquisitors?«, in Constable, Olivia Remie (ed.), Interfaith relationships and perceptions of the other in the medieval Mediterranean. Essays in memory of Olivia Remie Constable(Mediterranean perspectives), Basingstoke, pp. 161–195. []

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