A friend asked me that question earlier this week. And so I thought it might be helpful to share a few thoughts, from a historical perspective.
Opinions about how to answer the question vary widely. Some suggest that just a few thousand people were executed during the Inquisition, while others project that there were tens of millions of victims. So how can the estimates be so widely divergent?
There seem to be several explanations:
1. First, the imprecise nature of the historical records means that contemporary historians are forced to extrapolate on the basis of the limited information they possess.
One of the first accounts of the Inquisition came from a former Spanish secretary to the Inquisition named Juan Antonio Llorente (1756–1823). According to Llorente, the total number of “heretics” burned at the stake during the Spanish Inquisition totaled nearly 32,000. Llorente adds that another 300,000 were put on trial and forced to do penance (cf. Cecil Roth, The Spanish Inquisition [W. W. Norton, 1964; reprint, 1996], 123).
But there is considerable controversy about the accuracy of Llorente’s figures. As a result, historians must decide whether or not to take those numbers at face value. Some believe his numbers are too low, and should be adjusted higher. However, the majority of modern scholars believe his numbers are too high.
William D. Rubinstein summarizes the consensus of modern scholarship:
Nothing in the whole history of the Catholic church did more than the Inquisition to damn it in the eyes of rational, enlightened thinkers, or to give it the reputation for medieval barbarism it held in many quarters until recently. The Inquisition was only formally abolished in the early nineteenth century. Yet it also seems clear that the number of victims of the Inquisition can easily be exaggerated. Juan Antonio Llorente (1756–1823), a fierce enemy of the Inquisition, whose Critical History of the Inquisition of 1817–19 remains the most famous early work attacking everything connected with it, estimated the number of executions carried out during the whole of the period that the Spanish Inquisition existed, from 1483 until its abolition by Napoleon, at 31,912, with 291,450 “condemned to serve penances.” . . . Most recent historians regard even this figure as far too high (William D. Rubinstein, Genocide [Routledge, 2004], 34).
The conservative approach of modern scholarship can be seen in the writings of Henry Kamen, who is one of the leading authorities on the Spanish Inquisition. His work on The Spanish Inquisition is published by Yale University Press (Fourth Edition, 2014). Kamen’s research has led him to conclude: “We can in all probability accept the estimate, made on the basis of available documentation, that a maximum of three thousand persons may have suffered death during the entire history of the tribunal” (p. 253). Kamen’s estimates may be too low, but they represent the general perspective of contemporary scholars.
Modern historians also note that sixteenth-century Spain (during the height of the Spanish Inquisition) only had a total population of around 7.5 million people (cf. John Huxtable Elliott, Spain and Its World, 1500–1700 [Yale University Press, 1989], 223). Consequently, the notion that the Spanish Inquisition could be executing tens of millions of people during that same time period seems mathematically untenable.
2. Second, some earlier historians seem to have conflated the number of people killed with the number of people persecuted by the Inquisition. In other words, when they spoke of “victims of the Inquisition” they did not specify between those who were executed and those who were merely imprisoned or forced to flee because of the erupting persecution. Obviously, depending on how one defines a victim, the number of victims could vary widely. Perhaps only tens of thousands were executed, but hundreds of thousands were victimized in some way.
David Plaisted (a professor of computer science at UNC) notes that possibility in his paper titled, “Estimates of the Number Killed by the Papacy in the Middle Ages and Later” (http://www.cs.unc.edu/~plaisted/estimates.doc). He thinks the number of executions during the Spanish Inquisition could be quite a bit higher than just a few thousand. However, he acknowledges that the very large numbers (given by some earlier historians) might include everyone who was put on trial, and not just those who were killed. Also, some of the largest estimates likely include non-Protestants (such as Jewish and Muslim populations) who were expelled from Spain as a result of the persecution. If so, it helps explain where those very large estimates originated.
3. Third, confusion also stems from the conflation of the Inquisition with other events in European history. In the narrow sense, the term “Inquisition” refers to official trials conducted by Roman Catholic authorities in places like Spain and Portugal. When the question is limited to just those Inquisitions, the number of Protestants executed is likely in the thousands or tens of thousands.
However, if the term is used in a broad sense—to represent all Roman Catholic activity against non-Catholics—then the numbers rise dramatically. If the historian includes forms of torture and killing that did not involve a formal trial, along with religious wars and other forms of Catholic violence enacted against Protestants and other non-Catholics (in areas outside of Spain and Portugal), then one can easily speak in terms of millions of people who were killed.
David Plaisted acknowledges that reality in his study: namely, that the really big estimates of Protestants killed by the papacy throughout European history necessarily include those who died in religious conflicts like the Thirty Years War.
So … how many Protestants were killed during the Inquisition?
Well, that depends on how you are using the word “Inquisition.” And even then, the reality is that no one knows for sure.
However, if we are simply talking about official executions during the Spanish Inquisition, most contemporary experts would place the total number of executions between 3,000 and 10,000, with perhaps an additional 100,000 to 125,000 dying in prison as a result of torture and maltreatment. The Inquisition in neighboring Portugal resulted in even fewer such deaths (cf. Joseph Pérez, The Spanish Inquisition [Profile Books, 2006], 173; R. J. Rummel, Death by Government [Transaction Publishers, 2009], 62).