Medieval heresy was often depicted as a disease, albeit not a virus ("Get medieval with al-Qaida", THES , June 13). Inquisitors saw their activities as cutting off poisoned limbs. However, the effect was not quite as "surgical" and admirable as Andrew Roach and Paul Ormerod suggest.
During the 13th century, thousands were questioned by inquisitors. A fraction were executed but many more were fined, imprisoned or lost their property. The Cathar revival, c. 1300, led by just ten perfecti, brought the arrest, interrogation and punishment of several hundred people, a number of whom had never met any Cathars but held individual beliefs that appeared suspicious.
Bernard Gui, whom Roach and Ormerod hold up as a model of successful policing, had "only" 41 people burnt alive and 307 imprisoned indefinitely.
What lessons, then, should we learn from medieval inquisition? Perhaps that it is easier to persecute and kill when believers are represented as diseases, not human beings; that detaining people on suspicion without legal representation, and the use of torture, are effective but very blunt tools of repression; and that policing mechanisms designed to uncover "hidden" ideological enemies always oppress many more people than they originally target.
Looking at the West's activities post-9/11, I suspect that those lessons have already been learnt - by the wrong people, in the wrong way. The article was not just bad history. It was also a dangerous legitimation of present evils.
John H. Arnold
School of History, Classics and Archaeology
Birkbeck College, London