The branch of theology that primarily examines issues pertaining to the nature and essence of the Church is called Ecclesiology.
The Holy Metropolis of Oropos and Phyle focuses its attention especially on ecclesiology, since the dogma of the unity and uniqueness of the Church, which is ontologically identical with Orthodoxy, is threatened today by ecumenism
. • The heresies of the past assailed the Church’s Triadology, Christology, and Pneumatology. The heresy of ecumenism is now working counter to the Orthodox Church’s Ecclesiology.