Why is it important to rightly discern the visible and invisible aspects of the Church?

It is of vital importance to rightly discern the visible and invisible aspects of the Church because the Holy Spirit repeatedly warns God’s people about counterfeits of what God has ordained. The Lord speaks of “false prophets” and “false messiahs” (Mat 7:15; 24:24) who would deceive “even the elect”; and the book of Revelation shows the Enemy presenting counterfeits of everything holy, “as Jannes and Jambres opposed Moses, these people also oppose the truth. They are mentally corrupted, and as far as the faith is concerned, disqualified” (2Ti 3:8).

In an age when many gatherings claim to be the Church, one must therefore be on guard against those who create schismatic assemblies or introduce false doctrines and practices into the body of the Church. As the Eastern Patriarchs wrote in 1848:

Moreover, neither Patriarchs nor Councils could ever introduce novelties among us, because the protector of religion is the very body of the Church: the people themselves. (Encyclical of the Eastern Patriarchs, 1848, §17)