Medieval Heresies

Between the tenth and fourteenth centuries, a chain of dualist movements challenged the authority of the Latin and Byzantine churches. The Paulicians of Armenia, whose Key of Truth preserves their own liturgy and doctrine in their own words, transmitted a radical reading of Christianity eastward into the Byzantine Empire, where the Bogomils of Bulgaria developed a full cosmological dualism — the material world as the creation of a fallen or evil demiurge. From the Balkans, these ideas traveled west into Languedoc, where the Cathars (or Albigensians) built a parallel church with its own bishops, rituals, and theology of two principles. The Albigensian Crusade (1209–1229) and the subsequent Inquisition sought to destroy them utterly. Guillaume de Tudèle's La Chanson de la Croisade contre les Albigeois, composed in Occitan by a witness to the events, records the siege of Béziers and the devastation of the Languedoc from inside the conflict.

Most Cathar texts were burned. What survives comes largely through hostile sources: Bernard Gui's Practica Inquisitionis Heretice Pravitatis, the Inquisitor's manual that catalogues heretical beliefs in order to detect and prosecute them, and the depositions preserved in Inquisition archives. Charles Schmidt's Histoire et Doctrine de la Secte des Cathares ou Albigeois (1849) was the first modern attempt to reconstruct Cathar theology from these fragments. The Waldensians of Piedmont, a parallel movement rooted in apostolic poverty rather than cosmological dualism, left a richer textual record — Pierre Boyer's History of the Vaudois (1692) is among the earliest European accounts, while Todd and Bradshaw's Books of the Vaudois documents the surviving Waldensian manuscripts. Philippus van Limborch's History of the Inquisition (1731) provides the broader institutional context in which all these movements were suppressed.