Spiritualism and Millenarianism: Reception of the Collegiant Dániel de Breen among the Antitrinitarians in Transylvania The study offers new information about the reception of the collegiant ideas among the Transylvanian Antitrinitarians in the 18th century. The Amica disputatio adversus Judaeos... (1644) and its appendix about the explanation of the Apocalypse, written by Daniel de Breen, one of the founder of the Collegium in Amsterdam, are found in more copies among the Unitarian manuscripts and prints in the Library of Academy in Cluj-Napoca. Moreover, the appendix is reviewed by the History of Transylvanian Unitarian Church. The study introduces the early phase and ideas of the Collegiant movement and its connections with the polish Socinians through the millenarian and spiritualist thoughts and works of De Breen. Besides, it establishes the context of the Arnica disputatio... among the English and Dutch philosemiticmillenarian works from the mid-17111 century, which aimed to convert the Jews before the millennium. De Breen's activity was a part of the spiritualmystical period of the Collegiant movement, so the emergence of the Arnica disputatio... among the Transylvanian Unitarians is appraisable as the Unitarian reception of the spiritualist literature in the 18th century. However, there is no information about its influence on the Unitarian writings yet.