This interactive map application presents the most complete dataset of early cases of heresy in the West, ca. 1000–1150, compiled from original Latin sources. It shows locations, heresy cases linked to those locations, and mentions in the sources, on which the description is based. The application allows filtering by time, religious aspects (beliefs and practices), and intervention (type of action against heresy, outcome of the case).

Each case is accompanied by a list of mentions in the sources. Each mention constitutes an independent record, which allows differences in the descriptions of the same case to be assessed, as well as filtering down only to cases (and, through them, locations) where at least one mention meets the query condition. For each mention, a detailed info box can be displayed, which contains the name of the source, a summary of the content, dates, location(s), the names used to describe the heretics and the heresy and those names’ broaderconnotations, the social characterization of people involved in the heresy, a list of beliefs and practices stated in that source, the characterization of the intervention, the outcome, and notes. Under each category, information is given in the order of appearance in the mention.

Year follows the consensus in historiography. If a date in a mention differs from it, this difference is specified in the mention summary or notes.

Names gives a full list of the names used to describe the heresy and its followers in a given mention. Connotations are all the words used to create a negative image of a given heresy and its followers.

Persons lists all persons or groups mentioned in the source. Names in square brackets do not appear directly but are derived from the broader context. If a person is known from multiple sources under different orthographic variants, we use a standardized version.

Religion lists all beliefs and practices ascribed to heretics by a given mention. They are presented either in English or in the original Latin version.

Intervention provides an English typology of action against heresy and the outcome of the case.

The choice of cases was based on literature, especially J. B. Russell’s Dissent and Reform in the Early Middle Ages (1965) with some additions from C. Taylor’s Heresy in Medieval France (2005), M. Zerner’s L’hérétique Henri dans les sources de son temps (1135-1145) (2014) and A. Krawiec’s Eudo de Stella, heretyk bretoński z XII w. i jego zwolennicy (2003). Cases with a political or defamatory use of the word “heresis” with no specific doctrinal grounds were not included, just as cases openly dealing with Symoniac and Nicolaite heresy or over-zealous followers of Gregorian Reforms (which is why the Pataria movement and the case of Ramihrdus of Cambrai are missing). Concerning the Berengarian heresy, the dataset only presents the summaries of synods where the case was discussed. Sermons of Adhemar of Chabannes were not included, in spite of precious information about possible heresies in Aquitaine, as there is no critical edition of all of them available.

• Data source: reading of original sources
• Type of primary source: chronicles, letters, charters, theological treatises, synodal acts, annals, vitae, books of miracles,
           exegetical commentaries, etc.
• Data: Lidia Hinz-Wieczorek
• Map: Peter Ondrejka
• Dataset design and supervision: David Zbíral

Recommended citation: Hinz-Wieczorek, Lidia; Ondrejka, Peter; Zbíral, David (2023). Early heresy: heresy cases in the West, c.1000–c.1150 (v. 0.5.1). Dissident Networks Project (DISSINET). Retrieved July 15, 2025, from https://dissinet.cz/maps/early-heresy.