Jonathan Seiling is a Fellow of the Pontifical Institute of Mediaeval Studies and has studied the suppression of radical Reformation leaders and groups, particularly Anabaptists in the 1520-1530s. The Catholic controversialist Johann Fabri von Leutkirch (1478-1541) who played a key role in proscribing Anabaptism in the 1520s in the Holy Roman Empire, has been the focus of his postdoctoral research.
Seiling has also been preparing volumes of early modern texts in English translation related to religious dissidence in during the early Reformation. Currently press is a collection of Anabaptist texts concerning violence and nonresistance. Two additional volumes near completion include the apocalyptic writings of Melchior Hoffman in Strasbourg (1529-1530), and a large collection of texts from a range of Reformation writers concerning violence from the years 1510-1540. Stemming from the latter project Seiling has been developing theoretical framework for classifying and comparing early modern texts concerning violence.
In addition to early modern studies Seiling wrote a dissertation on religious dissent in pre-Soviet Russia, focusing on the motif of the Divine Sophia, especially as developed by Sergei N. Bulgakov and the concomitant Spinozist controversies.
Most recently he was named executive editor of a major source edition project, Trials of the Venetian Inquisition against Anabaptists, which is expected to publish ca. 2,000 of materials primarily from the Archivio di Stato di Venezia, Sant’Uffizio. The project was initiated by Dr. Dr. Martin Rothkegel (Berlin) and the editorial board also includes Giovanna Paolin (Trieste), Federica Ambrosini (Padua) and Lothar Vogel (Rome). In connection with this project and others, Seiling is also a Fellow of the Institut für Baptismusstudien des Theologischen Seminars Elstal (Berlin).