"A monk of the Church of the East" on his conversion to Orthodoxy

This article presents two unpublished letters by Father Lev Gillet ("A Monk of the Eastern Church"), discovered in the archives of the Greek Catholic metropolis of Lviv and addressed to the Ukrainian metropolitan Andreas Szeptitsky between April and June 1928. Elisabeth Behr-Sigel introduces and contextualizes them in a biographical and theological study. These letters shed light on Lev Gillet's conversion to Orthodoxy, precipitated by the publication of the papal encyclical *Mortalium animos* (1928), which condemned the nascent ecumenical movement. They reveal that this decision stemmed from a rigorous ecclesiological conviction — the rejection of the Roman conception of Petrine primacy — rather than from political circumstances, thus contradicting earlier hypotheses. The article provides previously unpublished documentary insight into Gillet's spiritual journey and into the tensions between Roman unionism and Orthodoxy in the early twentieth century.