Patriarch Kallistos, who died in August 1363, was succeeded once again by Philotheos Kokkinos on February 12, 1364; Kokkinos had been reconciled with John V Palaiologos through the good offices of Demetrios Kydones as part of an agreement restoring Philotheos Kokkinos to the Patriarchy; according to the terms of this agreement, Patriarch Philotheos was to allow those who did not subscribe to the Palamite doctrine to live in peace. But Philotheos, a fervent disciple of Palamas, did not keep his promise for long, and in 1368 he moved to crack down on Demetrios Kydones' own brother Prochoros, a monk and priest at Mount Athos. Prochoros was a formidable adversary to the Palamites. It is to him, and not to Gregory Akindynos that one must ascribe the work "De essentia et operatione", in six books, of which only the first and the beginning of the second have been published (cf. PG 151, 1191–1242). It gives a true summary of Thomistic theology; Barlaam of Seminara himself never wrote anything as plain and forceful. Prochoros also composed other treatises and shorter works, such as "On the light of Tabor," "On the Anti-Barlaamite Synodal Tome of 1351," etc.