This edition results from an interdisciplinary collaborative research project with the title “Acindynus and Palamas in Dispute on Divine Energies”, funded by the Swiss National Science Foundation. The project was established at the Institute of Historical Theology (Faculty of Theology, University of Bern, Switzerland) and ran from January 2015 through March 2019. The research group was headed by Prof. Dr. Katharina Heyden and included Dr. Theodoros Alexopoulos, Dr. Renate Burri and Carmen Stark. A printed critical edition of the two versions of Gregory Palamas’ Third Letter to Gregory Akindynos (Versions A and B) and the editio princeps of Akindynos’ Refutation of this Letter, accompanied by a German translation, introduction and commentary, will be published in the series Byzantinisches Archiv by De Gruyter in 2021.