Queen Isabella I of Castile and Inquisition


Queen Isabella I of Castile is a key figure in Spanish history. Her rule following her marriage to King Ferdinand of Aragon, saw the unification of the Spanish kingdom and the conclusion of the Reconquista. She further solidified the power of the unified crown by employing a group of Inquisitors to spread Catholicism throughout the country by using forced conversion methods against non-Christians. Ultimately, this unification and subsequent ventures across the Atlantic Ocean allowed Spain to become an empire and rise to eminence. This paper will examine her campaign for territorial and religious unity of Spain, and her use of the Inquisition to these ends.

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Before the Inquisition

Before Queen Isabella and King Ferdinand’s reign, and during its first years, Christianity was not the only religion in Aragon and Castile. Jews practiced their religion in relative freedom, tolerated by the previous monarchs. However, religious tensions eventually led to civil unerst, spurred on by Catholic authority figures. This unrest culminated in 1391, when a third of Spain’s Jewish population was killed, and another third forcibly converted to Christianity1. These converts would be called conversos or New Christians, and would later play a significant part in Isabel’s campaign of reunification.

At the time, profession of the Christian faith was necessary for admission into public office. After their conversion, some New Christians or their descendants would make their way into such positions, seizing significant political power in the process2. Some of these conversos were appointed by Isabella herself, as a way of “gaining royal control within towns”3. Thus, with a significant number of her supporters within the Kingdom of Castille, she has secured a strong political advantage for herself.

Those same New Christians ultimately gave Isabella a reason to initiate an inquisition in Castille. In what Andres Bernaldez called the Mosaic heresy, conversos retained their customs and worship even after converting to Catholicism: “for the most part they were secret Jews”4. The unflattering language used by this chronicler reflects the general view and illustrates the religious tensions at the time. Following 1473’s riots in Córdoba, which saw mass murder of conversos, whether they has converted in good faith or not. Thus, an inquisition was seen as a means of protecting true converts from false accusations.

However, a regular inquisition would not be in Isabella’s best interest. Its officials would be assigned by the papacy be out of royal control. While it would likely strengthen the kingdoms’ religious unity, it would also weaken the monarchs’ hold on their subjects. Therefore, the monarchs requested the Pope to institute an inquisition in Castile, but at the same time concede them the right to appoint priests to it5. In 1478, the bull was issued, and two years later, in 1480, two inquisitors were named by Isabel and Ferdinand. This amendment of the usual papal procedure would prove to be instrumental for Isabella’s campaign.

The Inquisition as a Tool

The Inquisition was more than a means to protect true converts and seek out apostates. Ferdinand and Isabella had intended to use it as a tool for asserting their control over the nobles in Castille and Aragon. Altabé points out that since intermarriage with Jews was common among the noble families, and “the Inquisition would render the nobility too frightened to defy [Ferdinand’s] authority”6 (1992, 3). As mentioned previously, the Papal bull instituting it also allowed the monarchs to choose their representatives as its officials. Therefore, these officials, wielding the significant power of the Inquisition, would be dependent on, and answerable to, the crown. This campaign is mentioned in Bernaldez’ writings, stating that many prominent, rich, and learned people were seized and executed. With their agents in these positions, the King and Queen would now have a direct means of pressuring nobles or other people of influence into compliance or eliminate them if they refused.

Isabella’s control over the inquisition is evident in its ultimate choice of targets during her rule. The conditions it established, under which the accused never knew what they were being tried for or who had accused them, essentially allowed anyone to be persecuted and convicted. The grounds for accusation and conviction could be as arbitrary ascelebrating a Jewish holiday with a relative7. Wealth or social position were irrelevant in such inquisitorial trials, however, those conversos close to Isabella herself remained immune. It can be inferred from this that she was taking steps to at least keep her supporters in positions of influence, and possibly directed the inquisitors towards her undesirables.

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Another part the inquisition played in Isabella and Ferdinand’s campaign of reunification was the place it occupied in their jurisdiction. At their marriage, the two monarchs’ kingdoms were not united; Isabella retained rule over Castile, while Ferdinand controlled the Kingdom of Aragon. As an institution nominally within the Church’s authority, the inquisition operated across their borders and, therefore, was a means for them to unify the two kingdoms’ administrations8. Additionally, it served as an information-gathering institutions for the monarchs, once again strengthening them politically.

The Inquisition, of course, worked for its religious goal — that of enforcing Catholic conversions — as well. While it was criticized, even by its contemporaries, for its cruelty, even its proponents argued that its primary target is apostates — people who kept practicing the customs despite supposedly converting away from them9. Thus, the inquisition was a campaign of conversion, rather than extermination, as greater penalties (I. e. death) were imposed on reneging conversos than on openly practicing Jews.

A third purpose of the monarch-controlled Inquisition was enriching the crown. Confiscation of property was commonly inflicted upon the accused, sometimes as part of their reconciliation. Some of this wealth was paid back to the monarchs by the inquisitors10. It was noted that although repressions against the wealthy and influential reduced Seville’s income from merchants and tax farmers11, the ever-increasing confiscations made up for it. In particular, confiscated wealth was directed towards funding war for Granada, used to fund the campaign against the last remaining Emirate in the Iberian Peninsula.

Granada, Territorial Unification

While the inquisition was forcibly conversing Jews, the Catholic Monarchs’ attention went to another obstacle towards religious and territorial unity: Granada. At the time, that city was embroiled in civil and political strife. The war to conquer it started in 1482 and lasted a decade. Wholly Isabella’s initiative, as Ferdinand argued in favor of recapturing the French provinces of Rosellón and Cerdaña first12. However, in 1484 he joined the campaign with a well-trained army equipped with the newest artillery. This support would prove crucial to conquering the heavily fortified towns surrounding Granada.

The war effort’s initial funding was limited, as the Inquisition was, at the time, driving revenues down and other means of procuring said funding were necessary13. However, as mentioned above, confiscations from conversos made during the conflict were explicitly meant to go towards it. Finally, Granada was conquered in 1492, ending the last Muslim ruler’s reign in Iberia and uniting most of the peninsula under Spanish rule.

Expulsion of the Jews and Muslims

Isabella’s quest for religious unity took another major step in 1492, soon after the capture of Granada. Within months, a royal decree was made public that gave all the Jews three months to leave Spain, leaving all of their wealth behind14. While the decision was heavily mired in religious rhetoric, as Isabella would claim it as God’s will rather than her or Ferdinand’s, it still accomplished economic and political goals. First, all the items left behind were subject to confiscation, once again to be used for the crown’s endeavors15. Second, it eliminated a potentially disruptive element, one of the sides of religious tensions. Even though some of the displaced Jews would return, they could only do so as conversos.

The next obstacle on the path to religious unity was a different minority: Muslims, or, as they were called in Spain at the time, Moors. Isabella’s treatment of them was significantly less nuanced, compared to the Jewish conversos. Initially following the capture of Granada, they were allowed to keep their property, language and custom by the Treaty signed at the city’s surrender16. However, they would still be forcibly converted, which was perceived as not honoring the treaty17. This led to uprisings in 1499-1501, which gave the monarchs justification for another religious expulsion. Ultimately, in 1500 they were given the same choice: convert or leave18. Like the Jews before, this eliminated a major foreign religion from the kingdoms’ society, at least officially.

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Aftermath: Columbus and the Empire

Ultimately, those repressions led to Catholicism becoming the only religion in Spain. While technically the kingdoms of Castile and Aragon remained separate for some time after Isabella and Ferdinand’s deaths, the territories were now unified under the monarchs’ authority. The Inquisition played a significant role in supporting this authority, primarily through religious enforcement19. Thus securing the borders, national and religious unity, Isabella had to find a new frontier to exploit.

Christopher Columbus provided an opportunity for such a frontier in 1485. At the time, the crown was too busy with its campaign against Grenada, but seven years later, in 1492, the Queen agreed to fund the explorer’s expedition. Although initially she was reluctant, her treasurer, Luis de Santángel, convinced her to take this small risk for such a large chance of glory for God and her kingdom20 (Stockwell, 2013, 1483). This has proven worthwhile as Isabella funded three more expeditions and initial colonization efforts of the Americas. Those colonies would become the key to the future Empire’s wealth and might.

By the late 15th century, with the liberation of Granada and exile of the last Moorish ruler from Iberia, Isabella’s dedication to the Catholic cause was uncontested. In a 1493 bull, Pope Alexander IV mentioned that she had sought discovering new lands “to the end that you might bring to… the profession of the Catholic faith their residents and inhabitants”21 (Pope Alexander VI, 1493, para. 2). This bull authorized Isabella to send expeditions to explore and establish colonies in the newly-discovered Americas. It is possible that her dedication to Catholic ideals and combating other religions was a contributing factor to this authorization.

Plans for colonization were already underway in 1494, during Columbus’ second voyage. Then, he writes a letter to the monarchs, primarily discussing his planned towns, stipulations for the procurement and division of gold. It also dedicated a paragraph to describing a budget for “building churches and adorning the same, and for the support of the priests or friars”22 (Columbus, 1494, para. 10). This highlights the monarchs’ intent to spread their influence, and Catholic unity, to the New World.


Queen Isabella’s rule was a tumultuous time for the kingdoms of Castile and Aragon. Although their territories were not yet united officially, the two monarchs have successfully claimed most of the Iberian Peninsula. To that end, they employed the Inquisition, which they controlled, rather than the Pope. Isabella used the institution not only as a religious tribunal protecting legitimate converts and seeking out apostates, but as a powerful political tool, as well. First, the political situation at the time allowed her to leverage secret Jewish customs, however minor, to blackmail people of influence within the two kingdoms. Second, it caused massive amounts of forced conversions and ensured loyalty of these newly converted subjects. Finally, due to its confiscations, the Inquisition served to fund the queen’s military campaign to capture Granada (and, in turn, more forced conversions) and Christopher Columbus’ expeditions. All of these facts, taken together, have allowed Spain to become an empire and one of the major world powers in the 16th century.


Primary Sources

Bernaldez, Andres. “Recollections of the Reign of the Catholic Kings.” In The Spanish Inquisition, 1478-1614: An Anthology of Sources, edited by Lu Ann Homza, 1–8. Indianapolis: Hackett Publishing Company, Inc., 2006.

Columbus, Christopher. “Letter to King Ferdinand and Queen Isabella.” Internet History Sourcebooks Project. Web.

Pope Alexander VI. “Papal Bull Inter Caetera, 1493.” Papal Encyclicals, 2000-2017. Web.

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Secondary Sources

Altabé, David Fintz. “The Significance of 1492 to the Jews and Muslims of Spain.” Hispania 75, no. 3 (1992): 728-731. Web.

Lea, Henry C. “The First Castilian Inquisitor.” The American Historical Review 1, no. 1 (1895): 46-50. Web.

Liss, Peggy K. Isabel the Queen: Life and Times. Philadelphia: University of Pennsylvania Press, 2004.

Rubin, Nancy. “The Convex Mirror: A Queen, An Heiress, and Biographical Blindness.” American Imago 55, no. 2 (1998): 205-13. Web.

Stockwell, Mary. “Isabella of Castile (1451–1504).” In Encyclopedia of World Trade: From Ancient Times to the Present, edited by Cynthia Clark Northrup. Routledge, 2013.


  1. David Fritz Altabé, “The Significance of 1492 to the Jews and Muslims of Spain.” Hispania 75, no. 3 (1992): 729.
  2. Henry C. Lea, “The First Castillan Inquisitor.” The American Historical Review1, no.1 (1895).
  3. Peggy K. Liss, Isabel the Queen: Life and Times (Philadelphia: University of Pennsylvania Press, 2004).
  4. Andrés Bernáldez, “Recollections of the Reign of the Catholic Kings.” In The Spanish Inquisition, 1478-1614 An Anthology of Sources, edited by Lu Ann Homza, (Indianapolis: Hackett Publishing Company, Inc., 2006), 3.
  5. Lea, “The First Castillan Inquisitor”.
  6. Altabé, “The Significance of 1492”, 729.
  7. Altabé, “The Significance of 1492”, 729.
  8. Liss, Isabel the Queen.
  9. Liss, Isabel the Queen.
  10. Liss, Isabel the Queen.
  11. Liss, Isabel the Queen.
  12. Liss, Isabel the Queen.
  13. Liss, Isabel the Queen.
  14. Altabé, “The Significance of 1492”, 729.
  15. Liss, Isabel the Queen.
  16. Altabé, “The Significance of 1492”.
  17. Altabé, “The Significance of 1492”.
  18. Nancy Rubin, “The Convex Mirror: A Queen, An Heiress, and Biographical Blindness.” American Imago 55, no. 2 (1998).
  19. Liss, Isabel the Queen.
  20. Mary Stockwell, “Isabella of Castile (1451-1504).” In Encyclopedia of World Trade: From Ancient Times to the Present, edited by Cynthia Clark Northrup (Routledge, 2013).
  21. Pope Alexander VI. “Papal Bull Inter Caetera, May 4, 1493.” Papal Encyclicals, 2000-2017
  22. Columbus, Christopher. “Letter to King Ferdinand and Queen Isabella.” Internet History Sourcebooks Project.
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