By José Luis Estévez, Davor Salihović, and Stoyan V Sgourev
In the High Middle Ages, Europe witnessed the emergence of new religious movements that arose at the intersection between monastic and ecclesiastical reform and popular ideals of ascetic poverty and apostolic life. Their movements’ challenge to Church-dominated activities and doctrines quickly provoked persecution. Violent campaigns, including crusades across territories from Languedoc to Bosnia, stand as the most infamous episodes.
The Church’s more systematic response to heterodox movements, however, was the introduction of inquisitorial tribunals. Staffed by members of mendicant orders, these tribunals wielded the authority to identify suspects, establish guilt through interrogation, extract confessions, and pronounce sentences—ranging from prescribed prayers and pilgrimages to property confiscation, imprisonment, or execution at the stake.
This new system was deployed across the epicenters of heretical activity, creating the image of the Inquisition as a monolithic, ruthless machine. Yet the survival of groups like the Waldensians—an ascetic movement founded around 1170 and condemned as heretical in 1215—demonstrates its limits. Conventional history often credits the survival of Waldensians to a retreat into remote locations, placing them beyond the Inquisition’s reach. But what if the story isn’t just one of escape? What if it was also about these communities adapting to the very system designed to destroy them, and about critical weaknesses in that system itself? This is the possibility our recent research brings to light.
We begin with a crucial insight: behind its fearsome reputation, the inquisitorial system was notoriously fragmented and operationally haphazard. It functioned without centralized oversight, often failing to ensure its own agents adhered to the Church guidelines. Its effectiveness hinged not on bureaucratic efficiency, but on the individual jurisdiction, personal zeal, and often amateurish judgment of its inquisitors—who regularly lacked formal legal training. Thus, moving beyond the prescriptions codified in Papal bulls and inquisitorial manuals, we examined the system’s messy reality through a detailed case study: the trial against the Waldensians in the small town of Giaveno, Italy, during the winter of 1335.
The Sacra di San Michele, whose abbot held lordship over Giaveno and sat alongside Inquisitor Albert during the interrogations.
The Giaveno trial provides a textbook example of the Inquisition’s escalating methodology. The inquisitor, Albert of Castellario, arrived in this village to investigate reports of heresy. His process began not with force, but with persuasion: a week of interviews followed by a “period of grace,” offering clemency for voluntary confessions and denunciations. Dissatisfied with the meagre results, Albert escalated to compulsory summonses, and when those too proved insufficient, resorted to the torture of a few suspects. This harsh measure proved decisive, yielding the flood of testimony and names that he sought.
Number of denunciations by calendar date and relationship between witnesses and the accused. This chart reveals the impact of Inquisitor Albert’s methods on the behavior of the residents of Giaveno. The period highlighted in red corresponds to the days when Albert resorted to torturing three suspects: Iohannes Gauterii, Stephanus Vet, and Bernardus de Rosseto. This moment marked a turning point, not only yielding a greater number of names but also increasing denunciations of close associates—fellow congregation members and family members—a pattern that was almost entirely absent during the earlier, voluntary phase of the process. Source: Estévez, Salihović & Sgourev, 2024, PNAS Nexus
On the surface, these methods—compulsory summonses, relentless interrogation, and torture—appear brutally effective, successfully compelling suspects to inform on even close acquaintances and family members. However, a deeper analysis of the resulting web of denunciations also reveals a process of rapidly diminishing returns. The information grew increasingly redundant, as witnesses consistently converged on the same safe targets: already-known suspects, individuals previously denounced, and those who had fled the village, thus escaping punishment.
Number of denunciations by calendar date, showing new names versus repeated names. This chart demonstrates that the increase in accusations primarily yielded redundant information. While the rate of discovering genuinely new names remained low and constant throughout the process, the probability of the inquisitor hearing names he already knew increased significantly. Source: Estévez, Salihović & Sgourev, 2024, PNAS Nexus.
We argue that, faced with coercive pressure, close-knit communities such as the Waldensians appear to have developed a strategy of sacrificing a few to protect the wider group by channeling the inquisitor’s scrutiny toward select individuals. This reflects a sophisticated approach to communal self-defense. Therefore, while the Inquisition’s methods were highly efficient for short-term intelligence gathering, they were ultimately ill-equipped to eradicate religious dissent from adaptive adversaries. In fact, ironically, the violence intended to break the community’s spirit may have strengthened the very bonds of solidarity it sought to destroy.
This unintended outcome was not the only flaw in the system. The Inquisition’s reliance on individual zeal introduced its own systemic biases. A critical case in point is gender. Through a dual analysis—assessing both the credibility of testimony and the urgency of summonses—we found that Inquisitor Albert consistently gave greater weight to the testimony of men than women. This bias persisted even when evidence clearly showed the deep active involvement of women in the Waldensian community of Giaveno. Consequently, besides being outmaneuvered by the defense strategies of the community, the inquisitor actively undermined his own process by allowing gender preference to distort the information he collected.
Time to summons by gender. This chart reveals a significant gap between men and women, demonstrating Inquisitor Albert’s preference for prioritizing male suspects over female ones after they had been reported. Source: Salihović & Estévez, 2025, Social Science History.
The gender bias exhibited by Inquisitor Albert reveals a paradox: the very social invisibility that marginalized women in public life could, ironically, afford them a degree of protection within the early inquisitorial system. Admittedly, given women’s generally subordinate status in pre-modern societies, an inquisitor reflecting this societal norm might appear unremarkable. Yet, one significant implication is that medieval women may have received far less scrutiny from inquisitors than historians have traditionally assumed—at least until the 15th century, when the emerging witch craze likely reversed this dynamic.
In conclusion, our research posits that the persistence of heresy in the late Middle Ages was not solely a matter of geographic isolation but a consequence of operational flaws within the Inquisition itself. For all its terrifying power, the Giaveno case demonstrates that the medieval Inquisition was far from flawless machinery. It was an institution riddled with contradictions: simultaneously systematic and haphazard, efficient in extracting confessions yet ultimately ineffective in achieving its goal of eradication, blind in its zeal yet myopic to a fundamental part of the community—its women. This fallibility created unforeseen avenues for resistance. Paradoxically, it was the close-knit communities the Inquisition meant to destroy that proved most adept at exploiting its faults.
By José Luis Estévez, Davor Salihović, and Stoyan V Sgourev
In the High Middle Ages, Europe witnessed the emergence of new religious movements that arose at the intersection between monastic and ecclesiastical reform and popular ideals of ascetic poverty and apostolic life. Their movements’ challenge to Church-dominated activities and doctrines quickly provoked persecution. Violent campaigns, including crusades across territories from Languedoc to Bosnia, stand as the most infamous episodes.
The Church’s more systematic response to heterodox movements, however, was the introduction of inquisitorial tribunals. Staffed by members of mendicant orders, these tribunals wielded the authority to identify suspects, establish guilt through interrogation, extract confessions, and pronounce sentences—ranging from prescribed prayers and pilgrimages to property confiscation, imprisonment, or execution at the stake.
This new system was deployed across the epicenters of heretical activity, creating the image of the Inquisition as a monolithic, ruthless machine. Yet the survival of groups like the Waldensians—an ascetic movement founded around 1170 and condemned as heretical in 1215—demonstrates its limits. Conventional history often credits the survival of Waldensians to a retreat into remote locations, placing them beyond the Inquisition’s reach. But what if the story isn’t just one of escape? What if it was also about these communities adapting to the very system designed to destroy them, and about critical weaknesses in that system itself? This is the possibility our recent research brings to light.
We begin with a crucial insight: behind its fearsome reputation, the inquisitorial system was notoriously fragmented and operationally haphazard. It functioned without centralized oversight, often failing to ensure its own agents adhered to the Church guidelines. Its effectiveness hinged not on bureaucratic efficiency, but on the individual jurisdiction, personal zeal, and often amateurish judgment of its inquisitors—who regularly lacked formal legal training. Thus, moving beyond the prescriptions codified in Papal bulls and inquisitorial manuals, we examined the system’s messy reality through a detailed case study: the trial against the Waldensians in the small town of Giaveno, Italy, during the winter of 1335.
The Giaveno trial provides a textbook example of the Inquisition’s escalating methodology. The inquisitor, Albert of Castellario, arrived in this village to investigate reports of heresy. His process began not with force, but with persuasion: a week of interviews followed by a “period of grace,” offering clemency for voluntary confessions and denunciations. Dissatisfied with the meagre results, Albert escalated to compulsory summonses, and when those too proved insufficient, resorted to the torture of a few suspects. This harsh measure proved decisive, yielding the flood of testimony and names that he sought.
On the surface, these methods—compulsory summonses, relentless interrogation, and torture—appear brutally effective, successfully compelling suspects to inform on even close acquaintances and family members. However, a deeper analysis of the resulting web of denunciations also reveals a process of rapidly diminishing returns. The information grew increasingly redundant, as witnesses consistently converged on the same safe targets: already-known suspects, individuals previously denounced, and those who had fled the village, thus escaping punishment.
We argue that, faced with coercive pressure, close-knit communities such as the Waldensians appear to have developed a strategy of sacrificing a few to protect the wider group by channeling the inquisitor’s scrutiny toward select individuals. This reflects a sophisticated approach to communal self-defense. Therefore, while the Inquisition’s methods were highly efficient for short-term intelligence gathering, they were ultimately ill-equipped to eradicate religious dissent from adaptive adversaries. In fact, ironically, the violence intended to break the community’s spirit may have strengthened the very bonds of solidarity it sought to destroy.
This unintended outcome was not the only flaw in the system. The Inquisition’s reliance on individual zeal introduced its own systemic biases. A critical case in point is gender. Through a dual analysis—assessing both the credibility of testimony and the urgency of summonses—we found that Inquisitor Albert consistently gave greater weight to the testimony of men than women. This bias persisted even when evidence clearly showed the deep active involvement of women in the Waldensian community of Giaveno. Consequently, besides being outmaneuvered by the defense strategies of the community, the inquisitor actively undermined his own process by allowing gender preference to distort the information he collected.
The gender bias exhibited by Inquisitor Albert reveals a paradox: the very social invisibility that marginalized women in public life could, ironically, afford them a degree of protection within the early inquisitorial system. Admittedly, given women’s generally subordinate status in pre-modern societies, an inquisitor reflecting this societal norm might appear unremarkable. Yet, one significant implication is that medieval women may have received far less scrutiny from inquisitors than historians have traditionally assumed—at least until the 15th century, when the emerging witch craze likely reversed this dynamic.
In conclusion, our research posits that the persistence of heresy in the late Middle Ages was not solely a matter of geographic isolation but a consequence of operational flaws within the Inquisition itself. For all its terrifying power, the Giaveno case demonstrates that the medieval Inquisition was far from flawless machinery. It was an institution riddled with contradictions: simultaneously systematic and haphazard, efficient in extracting confessions yet ultimately ineffective in achieving its goal of eradication, blind in its zeal yet myopic to a fundamental part of the community—its women. This fallibility created unforeseen avenues for resistance. Paradoxically, it was the close-knit communities the Inquisition meant to destroy that proved most adept at exploiting its faults.
Further Readings:
Estévez, José Luis, Davor Salihović, and Stoyan V Sgourev. 2024. “Endogenous Dynamics of Denunciation: Evidence from an Inquisitorial Trial.” PNAS Nexus 3 (9): pgae340. .
Salihović, Davor, and José Luis Estévez. 2025. “Gender Bias in Medieval Inquisitions and Its Place in Shaping Knowledge about the Heterodox.” Social Science History, 1–31.
Top Image: Waldensian Bible. IE TCD MS 258 fol. 2r
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