Being one of the most controversial figures of the premodern eastern Mediterranean, Şeyh Bedreddin’s (d.1420?) life and deeds constitute a focal point in the historiography on early Ottoman history and Sufism. He was a member of a clandestine network of scholars who called themselves the Brethren of Purity. He has been mostly celebrated as a great revolutionary or a heretic up until now. However, his philosophy and intellectual activities remain poorly studied. This presentation begins with a reevaluation of his ideas based on new findings coming from his unknown or neglected works. The larger aim in doing so is to locate him in his scholarly network not only through his personal or formal networks, but also through his philosophical views —that are, to a large degree, a distilled versions of larger intellectual currents of his time. The second part of the presentation deals with accusations of unbelief, hurūfism and magic directed against him, his master al-Akhlati, and his pupils — especially the accusations coming from the Zayniyya order through the works of ʿAbd al-Latīf al-Qudsī (d. 1452). Among many allegations that al-Qudsī raised against Bedreddin and his peers, the charges related to wujūd are of vital significance to conceptualize the philosophical background of the controversy. Al- Qudsī seems to have distinguished the views of those that he calls wujūdi from the monism of more mainstream Sufis. His descriptions seem rather to be directed against Bedreddin’s more “pantheistic” monism. The presentation will end with the defense written by Bedreddin’s pupil Akşemseddin (d.1459) in order to safeguard monistic ideas and the Sufis who deeply engaged with them. Most of the material in this presentation is obtained from unknown works and manuscripts that help us shed light on a large panorama of intellectual activity within the Mamluk, Ottoman and Timurid worlds in the fifteenth century.