Steven Runciman's 1947 book The Medieval Manichee: A Study of the Christian Dualist Heresy is often the foundation book in historiography of medieval manichaeism. The name 'Cathar' is used to describe many groups of people, and has been led in particular by historians such as Bernard Hamilton. Hamilton is foremost among those who believe in the continuity of Manichaeanism across east and west Europe, from late Antiquity through the high middle ages. Hamilton refers to virtually any heretical group in Europe during the middle ages as Cathar, following the ecclesiastical use of the term 'Cathar'.

However, in the last 20 years the sources which have been used to support these argument have come under new scrutiny to astonishing effect.

The first thing that has been done is severing the eastern influences from western groups, such as those which have been called the Cathars.

Cathari first appears in late antiquity in the writings of St Augustine, wherein he accuses them of heretical dualist beliefs. We don't see this term used in Christian writings for centuries there after, until the late 11th century in fact. Suddenly we begin to see ecclesiastical accusations and attacks on heresy greater increase such that historians like RI Moore have identified it as part of a new development in western society of the high middle ages: that of institutional persecution of heretics and lepers. In the early 12th century the term 'Cathar' starts getting used by Benedictines in the Rhine valley, and that is then picked up by Cistercian abbots and monks, in fact in a letter between Eckbert of Schonau and Bernard of Clairvaux. This point is most important because the Cistercians are the chief fomenters against heresy in the 12th and 13th century.

Cistercians from Bernard of Clairvaux through Alain de Lille, all exceptional thinkers and writers, come under the influence of nascent Parisian university which begins to emphasize logic and historicity: and this is welded to the medieval ecclesiastical tradition of using tropes in writing. So we have Manichaeism, Arianism, Donatism, and all sorts of antique notions of heresy being re-applied to the high middle ages context with fervent passion and intellectualism. But singularly lacking in details of the supposed real heresies.

Although the Cistercians use the term Cathar once or twice, as does the Pope in a bull in the 1170's, none of these refer to the geographically specific group we have come to know as The Cathars of Southern France. In fact, even the Cistercians who visit the south of France after 1150 on preaching expeditions never use the term Cathar, and they do not refer to specific dualism or specific Manichaeism they encounter there.

Well, this is the historian's debate at the moment, and a lot has been hinging on one piece of evidence that has been the linchpin connecting eastern Manichaeism, or Bogomilism, with the heretics of France: the Cathar Council of St Felix in 1167. There is one single document testifying to this meeting between supposed Cathars and an emissary from the Bogomils of the Balkans, and this document purports that the meeting setup the Cathar Church in France with a half dozen bishoprics. This would be the smoking gun, right? Yes, except the document is a transcription in the appendix of a book written in the late 1600s. We have no original. In fact one of the leading historians of medieval French heresy, Monique Zerner, assembled a group of historian specialists over 10 years ago to debate this document's authenticity. And that group brought in sub-specialists of the kind that make France the envy of medievalists around the world: comparative medieval philologists and manuscript authenticators. As it turns out the specialists believe the text is authentic to 13th century writing, but may be a forgery of 12th century it purports to be.

So, the debate rages. But the focus in the last 10 years has shifted, thanks to Zerner and Moore, to actual evidence.

Beyond all the Cistercian and papal tracts, and beyond the letters back and forth between Pope, counts and king of France inciting a crusade against the heretics of the south, we have only one other set of documentar evidence: the registers of the inquisitions of heretics in southern France after the Albigensian crusade. These are the words of those who lived with heretics, at least as transcribed and paraphrased into latin by Dominican scribes. And from all of these thousands of interviews across dozens of towns a cities which were the hotbeds of heresy we find no signs of dualism or Manichaeism.

Medieval Manichaeism existed in the Balkans, and with some likelihood briefly in Northern Italy. But the evidence of Manichaean Catharism of southern France doesn't exist.