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).

  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. []

Intercultural Processes of Interaction and their Participants in the Western Mediterranean: Norman Sicily (1061–1194) and the Kingdom of València (1238–1276) in Comparison

Eric Böhme, Konstanz

Abstract: Im Rahmen des hier vorgestellten Habilitationsprojektes werden in zwei miteinander zu vergleichenden Fallstudien zu Sizilien und zur Iberischen Levante jeweils Phasen bedeutender Umbrüche in den Blick genommen, die durch den Herrschaftswechsel von islamischer zu christlicher Oberherrschaft konstituiert wurden. Die neuen Herrschaftsstrukturen konnten nur über permanente Kommunikations-, Interaktions- und Aushandlungsprozesse etabliert und stabilisiert werden. Eine bedeutende Rolle dabei spielten Mediatoren, die einen zentralen Untersuchungsgegenstand des Projektes darstellen. Im Rahmen einer komparativen Analyse der Austauschprozesse zwischen den bereits ansässigen und neu zugewanderten Gesellschaftsgruppen sowie den neuen Herrschaftsträgern gilt es, Rückschlüsse über die möglichen Rollen, Motivationen und Verhaltensmuster dieser Vermittler sowie über sich etablierende Kommunikationsmechanismen unter ihrer Beteiligung zu ziehen. Die Ergebnisse des Projektes sollen die Forschungsdiskussion zu Kommunikations- und Interaktionsdynamiken in den multireligiös und multikulturell geprägten Gesellschaften des Euromediterraneums um einige neue Perspektiven erweitern.

Both the Iberian Peninsula and Southern Italy can be considered particularly interesting zones of contact in the Western Mediterranean where, in the course of many centuries, Muslims, Jews, and Christians frequently engaged in processes of interaction which could be characterised by peaceful and pragmatic conveniencia1 as well as by violence. In order to initiate and conduct communication and interaction between different cultures and religions effectively, all participants made use of mediators capable of acting as agents between the sides. Through combining and applying different verbal and cultural competences, these ‘border crossers’ were able to assume a variety of roles in processes of communication, interaction and negotiation.

Within the scope of the research project outlined here, this phenomenon shall be analysed in two case studies ultimately to be compared with each other. The first case study will deal with Norman Sicily. Featuring a multicultural population of both Muslims and Greek Orthodox Christians, Siqilīya was ruled until the second half of the 11th century by the Islamic dynasty of the Banī Kalb which, however, was unable to directly exert authority over large parts of the island. Instead, different petty rulers strove to extend their respective reach of influence thus creating a situation which facilitated the expansion of Norman rule from the Southern Italian mainland in 1061. Still, it took several decades for Roger I and his followers to force the whole island under Latin-Christian authority; Balarm/Palermo resisted until 1072, Siraqūsa/Syracuse until 1086 and Nūṭus/Noto fell only in 1091.

The comparative case study will focus on the Kingdom of València which was formed during the 1230s and 1240s in the context of the rapidly progressing expansion of the Crown of Aragón into the eastern parts of al-AndalusMuslim rule over the so-called Šarq al-Andalus had gradually fragmented after the collapse of Almohad rule, thus constituting a situation quite similar to the circumstances in Sicily. After the conquest of the city of València in 1238 in the wake of the crusade of King James I of Aragón, the new ‘Christian’ kingdom was formally established as part of the Crown of Aragón and in the following years expanded to cover vast territories between Qalʿa Murīla / Morella in the north and Šīšūna/Xixona in the south.

In both cases to be studied, the invasion and gradual expansion of Latin-Christian rule into regions which for centuries had been part of the dar al-islām constituted immense tension fields originating in a quite similar outset. In Sicily as well as in the Iberian Levant, the vast majority of the population did not adhere to the Latin-Christian faith of the conquerors and their comparatively small number of followers. This extraordinarily asymmetrical ratio between ‘rulers’ and ‘ruled’ balanced out only in the course of many decades by means of migration processes as well as guided measures such as waves of expulsion or the recruitment of Latin-Christian settlers. Initially, the non-Latin population groups and their traditional way of living received a basic and frequently chartered degree of respect and protection by the rulers and their functionaries which, at times, deliberately fostered the coexistence of cultures and religions. However, the omnipresent and in part rapidly progressing discrimination and gradual exclusion of non-Latins from most spheres of social and political interaction repeatedly triggered uprisings against the new rulers and their foreign elites.

Against the background of this extraordinarily strained basic situation in both regions, the new structures of rule could only be established and stabilised by means of constant processes of communication, interaction, and negotiation. As mentioned above, mediators were of central importance in these processes and therefore will be the focus of the research project presented here. By analysing the multitude of processes of interaction which arose between the already resident and newly immigrated population groups as well as the representatives of the new rulers, it will be the main task to draw conclusions on the possible roles, motivations and behaviour patterns of these mediators as well as the mechanisms of communication established with their participation.

Concerning its basic theoretical approach, the research project connects to the DFG project ‘Mediation von Herrschaft an den Grenzen Lateineuropas im Spätmittelalter’ (Chair of Medieval History, Leipzig University). Through their particular dynamics, the phases of changes of rulership in the two chosen border regions of ‘Latin’ Europe provide a suitable framework for analysing processes of interaction and negotiation between new and old elites. Against this backdrop, processes of integration and disintegration as well as aspects of legitimisation and delegitimisation of rulership are phenomena to be touched upon as well. The term ‘rulership’, which in itself is perceived as an analytical category requiring constant reflection, denotes a complex practice characterised by communication and discourse within a larger field of action. The field itself and thus the tangible individuals or groups acting in it are in turn influenced by overarching macro structures. The analysis will not focus on the ‘ruler(s)’ but on the ‘ruled’ groups and the interactions between them.

In order to examine this field, the research project will utilise a triad of terms which as well are perceived as analytical categories in need of constant reflection: MediationMediators und Mediatisation. The term Mediation denotes individual processes and moments in which rulership and its reach are subject to negotiation. Of central importance for analysing this phenomenon are Mediators as tangible participants in these processes of negotiation. The third term Mediatisation describes processes through which rulership in certain fields of action is outsourced on specialised and partly newly formed institutions and thereby made ‘mediatable’, at least to an extent. The consistent application and reflection of these terms is supposed to foster a better grasp of the characteristics of the border regions examined, without falling back on the notorious Central European paradigm of ‘modernisation’. The main questions to be treated using this theoretical approach and grid of criteria are:

  1. Which concrete moments of interaction between the resident ethnic, religious, social, and legal groups and the new authorities can be traced?
  2. How did these groups assert their demands towards the rulers and their representatives?
  3. Who were the mediators (or mediator groups) in the underlying processes of communication, interaction and negotiation? What potentially motivated them to participate?
  4. Which patterns or mechanisms of communication and/or interaction between the participating sides (‘ruled’ – ‘mediators’ – ‘rulers’) emerged and were established?
  5. Change of perspective: Which strategies did the rulers and their representatives apply in order to establish their authority over and within the heterogeneous structures of the different interest groups?

For both case studies, the foundation on which these questions shall be treated is formed by a very heterogeneous selection of sources from different genres and cultural backgrounds. Concerning the situation in the Kingdom of València, the first sources to be analysed are those whose creation context is directly connected with the establishment of Latin-Christian rule over the subjected territories. This is the case for the Llibre de Repartiment del Regne de València and the Cartes de poblament which certified the recognition of certain rights and obligations of individual Muslim communities as a result of negotiations conducted in the run-up to their capitulation. Narrative sources such as the works of Ibn al-Abbār or the quatre grans cròniques can also contribute useful information on these processes of negotiation. For the analysis of interaction processes in later decades, documentary material and legal texts such as the Furs de València or the Llibres de la Cort will be the most relevant groups of sources.

The second case study on Sicily can draw on a broad base of sources as well. The expansion and consolidation of Norman rule is mainly recorded in Latin and Arabic narrative works. As in the Iberian Peninsula, documentary material is of utmost importance for the analysis of intercultural and interreligious processes of interaction in later decades. This includes not only Latin charters, but also the Arabic respectively Arabic-Greek production of the royal dīwān. Furthermore, a small number of legal texts is available for interpretation as well.

In conclusion, it should again be emphasised that the extraordinary linguistic, religious, and cultural heterogeneity of the social structures in Norman Sicily as well as in the Kingdom of València steadily produced fields of tension which in turn caused the formation of particular dynamics in the ubiquitous processes of communication, interaction, and negotiation. Analysing the establishment and consolidation of these important realms in the Western Mediterranean from the perspective of the mediators in these processes and comparing the results for both case studies in detail is the central concern of the research project presented here. The consistent application of the outlined methodological framework in studying the main questions shall result in a monographic study adding new perspectives to the scholarly discussion on the dynamics of communication and interaction in the multireligious and multicultural societies of the Mediterranean region.

Photo: Muslims kneeling before James I of Aragón, Cantiga 169 of the Cantigas de Santa Maria of Alfonso X., in: Codex E, Ms BI2, f. 226r., Biblioteca de El Escorial, URL: [].

  1. Cf. Brian Aivars Catlos, Muslims of Medieval Latin Christendom, c. 1050–1614, Cambridge / new York 2014, 515–535. []
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