In January 1208 a papal legate was murdered beside the Rhône River. Pope Innocent III accused Raimon VI, count of Toulouse, and heretics of the murder. He called upon all Christians to attack the count and to exterminate heretics between the Garonne and Rhône Rivers — a vast region that is now southern France — in a great crusade. This holy war, the first in which Christians were promised salvation for killing other Christians, lasted twenty bloody years and, imbued with a moral imperative to mass murder, ushered genocide into the West.

Although heretics were a feverish obsession amongst Latin Christian intellectuals during the last decades of the twelfth century, the idea of a grand exterminating holy war was the singular innovation of Innocent III. The threat from heresy and the necessity of eliminating that threat were fundamental in creating the Christ-like world that Innocent III struggled all his life to achieve. As the Son of God used His humanity to save the world, so ordinary men and women could use their humanity to imitate His divinity and so save themselves. This ability to resemble Christ through earthly activity, so much so that you really were Him, was the sublime religious phenomenon of the later Middle Ages. No other monotheistic religion has ever celebrated or promoted such a godly imitative ideal amongst ordinary believers. Previous popes had blessed wars between Christians but none had ever linked annihilating bloodshed with the redemptive gift of being like Him. “Love God, choose the Lord, seek Him, possess Him, enjoy Him,” motivated pope in sacred council and crusader in butchering frenzy.

This is not at all the same as saying that such redemptive slaughter was (or is) inherent or inevitable in Christianity (or in any religion). Neither is it arguing that the Albigensian Crusade was some sort of violent aberration in the history of Christianity. It is an argument for specificity in the study of religion, especially sacred violence. A seemingly straightforward and unexceptional claim — except when it comes to the history of religion. All too frequently, historians define religion by abiding doctrines, perennial philosophies, and timeless ideals. Scriptural consistency and theological cogency are what supposedly make religions, not poorly articulated thoughts or anomalous opinions, which get tossed aside as notional (and historical) irrelevancies. The scholarly fallacy behind it all is that pure principles form the core of every religion and that no matter how many civilizations rise and fall through the millennia, how many prophets come and go, the principles enduringly persist. Weightless, immaterial, untouched by historical contingency, they waft over centuries and societies like loose hot-air balloons. By combining these untethered beliefs almost any history (secret or otherwise) can be strung together. Meanings are elusive, resemblances ubiquitous. The past is not simply another country, it is an entirely different universe. At a time when the world is haunted by religiously inspired warfare, it is crucial that we rethink the ways religiion is studied. Religion must be seen as more than floating ideas, more than just ideology with gossamer wings.

A contemporary twist on these idealist assumptions is a high-minded empathy about past beliefs. Analysis is not based upon the interpretation of historical evidence but upon the emotional authenticity of a judgement. This posturing easily slips into claiming that only the religious can truly understand religion — and more stridently into insisting that only Christians can fathom Christianity, Jews unravel Judaism, Muslims decode… This blurring of thinking and feeling (and morality) surrounds us nowadays. Historians must forgo this consoling confusion, for it means taking sides, it means getting even with the past.

Insight into the Albigensian Crusade is advanced in no way, shape, or form, if I tell you how religious I am or if I express outrage that the pope exhorted all Christians to exterminate heretics. What happened during the crusade was horrific, but sanctimoniously grieving for the fallen neither comforts the dead nor helps the historian avoid the pitfalls of relativism. A history wrapped in mourning crêpe — whether on the Crusades, the Holocaust, the Gulag, the British Empire, the Inquisition, the Great Leap Forward, the Indian Wars, or Antebellum Slavery — might have its heart in the right place (when not on its sleeve) but its sincerity may be distortingly sentimental.

Any meditation upon the past that starts with the presumption that some things are universal in humans or in human society — never changing, inert, immobile — is to retreat from attempting an historical explanation. Studies are lauded which argue that there is, say, a pervasive male manner (with other men, with women, with meat) imprinted into masculine genes over a month of prehistoric Sundays. Or that minds always respond in similar ways to tragedy. Or that hereditary behaviourial traits impose habits (and occasionally beliefs) from one generation to the next. Or that religion is a primal response to primal fears. Millennia are flattened out, if not totally erased, in essentialism. Historical specificity is either dismissed as irrelevant or seen as epiphenomenal graffiti scratched upon (and so disfiguring) unchanging customs and concepts. Arguing for immutable values from biology is no different to arguing for immutable values from theology — selfish genes, selfish doctrines, they both deny history. Assuming that why we do what we do, why we think what we think, is somehow or other beyond our control, and that we would be this way in mind and body whether we lived in Cleveland in 1952 or Toulouse in 1218, forfeits the vitality and distinctiveness of the past to the dead hand of biological determinism, cognitive hotwiring, psychological innateness, liberal pleas for bygone victims, conservative pleas for God-given principles, and amaranthine mush about authenticity.

The Albigensian Crusade introduced genocide into the West by linking divine salvation to mass murder, by making slaughter as loving an act as Christ’s sacrifice on the cross. This ethos of redemptive homicide is what separates the crusade massacres from other great killings before the thirteenth century. The Albigensian Crusade was a holy war unlike any other before it and, in its own bloody sibylline way, a terrible prediction of so much sacred violence in the world for the next millennium.