New inquisitors needed guidance, and the need was met by a series of manuals written in the thirteenth and early fourteenth centuries by old hands. The most famous of these is the one by Bernard Gui, a Dominican who spent close to a quarter-century conducting investigations. Born around 1261, probably of lesser nobility, he joined the order in 1279. He received a good education and served as prior in a series of southern French convents before being appointed an inquisitor in 1307. He remained such, with his base of operations at Toulouse, until 1324, when he was rewarded with a bishopric. During that period he passed sentence on 930 people that we know of. The sentences passed on them add up to a total of 394 pages in a very large book.

Gui's manual, actually entitled Practica inquisitionis heretice pravitatis (The Conduct of Inquiry Concerning Heretical Depravity), was finished in 1323 or 1324, but he seems to have worked on it off and on throughout the latter part of his career. It is divided into five parts, the first three of which deal with procedure. The fourth presents a series of documents (papal bulls, etc.) which define the inqusitior's authority. In the fifth and most interesting part Gui takes his readers on a tour of contemporary heresy. The part translated here deals with the Beguins.