ABSTRACT
Reports of heresy begin again shortly after 1100 and increase in number, and heresy shows its importance by engaging the attention of the greatest churchmen of the period, Peter the Venerable and St Bernard of Clairvaux, and of a steady sequence of Church councils. There is the evidence, whose varying quantity and survival is both an opportunity and a problem; 'absence of evidence is not evidence of absence', as the early medievalist's adage goes. The chapter looks at the ways lenses and filters transmit, refract or colour a view of the major heresies of the central Middle Ages, Catharism and Waldensianism, hoping to say something about these heresies themselves as well as the struggle to see them. In 2001, the theme of 'Through a Glass Darkly' was the way the post-medieval world colours the lenses through which one looks at medieval heretics.
