like many encyclicals, this one derives its title from its "incipit" or first few words, which are taken from the prayer of jesus in the vulgate translation of the gospel according to john. it deals with the catholic church's relations with the orthodox church and other christian ecclesial communities. this document reiterated that unity of these two "sui juris" churches is essential, as well as further dialogue and unity with the protestant churches. this document shows that the catholic church is officially moved to unity. it has become a common piece of study in ecumenical classes.