The book is a monographic study by a professor of theology at the University of Warsaw on the history of Orthodoxy in Belarus and Ukraine (Western and Southern Russia) in the XIV-XVIII centuries. In the historical fate of the population of these lands, this period is associated with the existence of the Grand Duchy of Lithuania and the Commonwealth. The history of the Orthodox Church of Belarus and Ukraine is considered by the author in parallel with the analysis of the source of official origin - the set of laws of the Commonwealth "Volumine legume."