It has to be borne in mind that by far the greater part of our contemporary evidence for the history of mediæval heresies is hostile evidence, consisting of denunciations of them by orthodox theologians, the treatises of inquisitors who condemned their adherents, notes made of evidence given by defendants. Only those heretics who were themselves philosophers or theologians—and these, such as Siger of Brabant, Wycliffe and Hus, are relatively very few—have left their own records behind them. Due allowance, therefore, has to be made in using most contemporary authorities for considerable bias.
I
Inquisitorial Treatises
These are, on the whole, the most generally valuable of contemporary sources. The two most important for the period dealt with in this book are:
Nicholas Eymeric, Directorium Inquisitorum cum commentariis F. Pegnae (Rome, 1585; also Venice, 1607).
Bernard Gui, Practica Inquisitionis haereticae pravitatis (ed. C. Douais, Paris, 1886).
Eymeric was inquisitor in Aragon in the latter half of the fourteenth century. His compendious work is probably the most authoritative of all inquisitorial treatises, being a complete exposition of the principles of the tribunal and the doctrines of the different sects with which it had to deal, and giving the minutest details of its procedure. Bernard Gui, appointed inquisitor at Toulouse in 1306, was the most vigorous and remarkable of those who helped to stamp out Catharism in Languedoc after the Albigensian crusades.
The following treatises are not contemporary, but they are valuable as expositions of the permanent principles and methods of the tribunal. They are also useful for the occasional comments made by these later experts on the work of their predecessors:
J. Simancas, De Catholicis Institutionibus.
A. Bzovius, Historiae Ecclesiasticae.
J. à Royas, De Haereticis.
Bernard of Como, Lucerna Inquisitorum haereticae pravitatis.
Arnaldo Albertini, Tractatus de agnoscendis assertionibus Catholicis et haereticis.
Zanchino Ugolini, De Haereticis.
All these, among other similar tracts, are included in Zilettus, Tractatus Universi Juris (Venice, 1633), vol. xi, pt. ii.
See also Ludovico à Paramo, De origine et progressu officii Sanctae Inquisitionis (Madrid, 1598).
Umberto Locati, Opus judiciale inquisitorum (Rome, 1572).
F. Peña, Inquirendorum haereticorum lucerna (Madrid, 1598).
Carena, Tractatus de officio Sanctae Inquisitionis (Lyons, 1669).