This work selectively addresses certain events from the historical journey of the Church during the period of the 2nd Millennium. Starting with the tragic event of the Schism of 1054 and the interruption of normal ecclesiastical relations between East and West, it approaches, with the appropriate scientific methodology, the most significant events that contributed to the formation of the modern fragmented Christian world.

It examines the main characteristics of the individual Christian traditions and identifies the differences between them, which have at times been a source of friction and tension, leading to even extreme phenomena of intolerance and fanaticism, especially in the European context.

Particular emphasis is placed on the efforts of the Orthodox to restore ecclesiastical unity with the West and on the institutional functioning of the Ecumenical Patriarchate during the Ottoman period.