Journal or Book Title
Encyclopedia of Witchcraft: The Western Tradition
Perhaps the most famous of all medieval inquisitors, and certainly one of the most important and influential, Bernard Gui is best known for his monumental inquisitor's handbook, Practica inquisitionis heretice pravitatis (The Practice of the Inquisition of Heretical Depravity), written around 1324. Although he never described anything like the full stereotype of witchcraft as it would appear in later centuries, he did include in this work several sections dealing with learned demonic magic, or necromancy, as well as more evidently popular forms of sorcery. The Practica inquisitionis became one of the most widely read of all medieval inquisitorial manuals, second only to the later Directorium inquisitorum (Directory of Inquisitors) of the Catalan inquisitor Nicolas Eymeric. Gui's descriptions of sorcery thus seem very important, particularly in terms of shaping later clerical, and especially inquisitorial, thought on this subject.
Bailey, Michael D., "Bernard Gui" (2006). History Publications. 61.