EN
The aim of this article is to make a thorough study of the idea of the union of the Catholic and the Orthodox Churches at the beginning of the 1590s in the Commonwealth of Poland and Lithuania. As early as in 1590 it took the form of many secret internal meetings and consultations. Their subject was a more or less specified idea of the union between the two Churches. We have analysed two fundamental documents: unification declaration of the Orthodox episcopate formulated on the 24th June 1590 and the answer to it in the form of the official document issued twice by king Sigismund III Chancellery – on the 18th March 1592 and 18th May 1592. They were concentrated mainly on differently comprehended ideas of the union with Rome. That was the idea of the universal union which would not mean the break of the Orthodox with the Patriarch of Constantinople.