Torture as a tool of jurisprudence was little known in the darkest part of the Dark Ages. The ability of human beings to discover the truth was thought to be limited. Thus the reliance not on judges or juries but on iudicium Dei—the judgment of an all-knowing God—to determine guilt or innocence. This often took the form of trial by ordeal. The accused would be submerged in water, or made to walk on red-hot coals, or forced to plunge an arm into boiling water. If he or she suffered no harm, or if the wounds healed sufficiently within a certain period of time, then it was the judgment of God that the accused was innocent. This regime was common in Europe for many centuries. It was unquestionably primitive and certainly barbaric. In its favor, it was devoid of hubris about what mere mortals can ever really know.

The late-medieval revolution in legal thinking—manifest everywhere, from Church courts to secular ones—took the pursuit of justice out of God’s hands and put it into the hands of human beings. In his book Torture, the historian Edward Peters explains that the medieval legal revolution was based on one big idea: when it came to discovering guilt or innocence—or, more broadly, discovering the truth about something—there was no need to send the decision all the way up the chain of command, to God. These matters were well within human capacity.

But that didn’t quite settle the issue, Peters goes on. When God is the judge, no other standard of proof is needed. When human beings are the judges, the question of proof comes to the fore. What constitutes acceptable evidence? How do you decide between conflicting accounts? In the absence of a confession—the most unassailable form of evidence, the “queen of proofs”—what form of questioning can properly be applied to induce one? Are there ways in which the interrogation might be … enhanced? And in the end, how do you know that the full truth has been exposed—that a bit more isn’t waiting to be discovered some little way beyond, perhaps with some additional effort? So it’s not hard to understand, Peters concludes, how torture comes into the picture.

From time to time, exhibits of torture instruments go on tour. The effect is oddly Disneyfied—a theme-park view of interrogation. The very names of the instruments reinforce a sense of distant fantasy: Brazen Bull, Iron Maiden, Judas Cradle, Saint Elmo’s Belt, Cat’s Paw, Brodequins, Thummekings, Pilliwinks, Heretic’s Fork, Spanish Tickler, Spanish Donkey, Scold’s Bridle, Drunkard’s Cloak. They could just as easily be the names of pubs, or brands of condoms, or points of ascent on a climbing map.

The Inquisition rarely resorted to these specific instruments. It relied on three different techniques, all of them used today. Before a session began, the person to be interrogated would be brought into the torture chamber and told what was about to be done. The experience of being in conspectus tormentorum was often enough to compel testimony. If not, the session commenced. A physician was generally in attendance. Meticulous records were kept; the usual practice was for a notary to be present, preparing a minutely detailed account. These documents survive in large numbers; they are dry, bureaucratic expositions whose default tone of clinical neutrality is punctuated matter-of-factly—“Oh! Oh!”—by quoted screams.

The first technique used by the Inquisition was known in Spanish as the garrucha (“pulley”) and in Italian as the strappado (“pull” or “tug”). It was a form of torture by suspension, and worked through simple gravity. Typically, the hands of the person to be interrogated were tied behind his back. Then, by means of a rope threaded through a pulley or thrown over a rafter, his body would be hoisted off the ground by the hands, and then be allowed to drop with a jerk. The strain on the shoulders was immense. The weight of the body hanging from the arms contorted the pleural cavity, making breathing difficult (asphyxiation was the typical cause of death in crucifixion, for the same reason).