The 2013 conference at University College London aimed to undertake, in the words of the preliminary announcement, a reassessment of the phenomenon traditionally known as ‘Catharism’ through a debate in a non-confrontational spirit, with the aim of reconsidering without assumptions the strength of the evidence for dualist beliefs and for an organized movement of adherents to them. Eighteen months on the predominant recollection of a quite exceptionally stimulating and enjoyable occasion is that it left among its participants a surprising degree of agreement on such facts as are capable of being established – and at least as profound a disagreement as before on what they mean, for there was little, either then or since, to suggest that any mind has been much changed. It was ever thus. It is hardly news that differences in reading small pieces of evidence may lead to widely divergent conclusions. Nevertheless, that despite the best efforts of all the participants discussion focused with ever sharper intensity on ever diminishing detail reinforces the suspicion that there is more at stake in the disagreement about the nature and origins of ‘Catharism’ than a straightforward difference of scholarly opinion. Peter Biller's comment, in his introductory remarks, that the passions run much higher in this debate than in its counterpart over early Waldensianism, even though on the face of it the issues are very much the same, has been amply fulfilled. This chapter, however, eschewing wider issues, will attempt to clarify the methodological differences which still put us at cross purposes, and in particular the implications of the difference between looking forward to the crucial period in debate from an earlier standpoint, or back from a later one.

In respect of the facts divergence on the main question was not great. It was agreed that clear evidence of the presence of organized dualism in Europe, and a fortiori between the Rhone and the Garonne, before the Albigensian crusade is very slight at best, and that after 1250 it is both abundant and substantial. The traditionalists attached considerable weight to the following: a donation of revenues in 1189 to a woman who had joined the heretici;