Phyletism, or ethnophyletism, is the organization or division of the Church primarily according to ethnicity or nationalism in a way that overrides its catholic unity.
Condemnation
A council held at Constantinople in 1872 condemned phyletism amid disputes concerning Bulgarian ecclesiastical organization. The principle has wider significance wherever national identity becomes the controlling basis of church communion or creates parallel rival jurisdictions for the same territory.
Distinction
The condemnation does not erase legitimate languages, cultures, or local traditions. Christianity can sanctify and preserve cultural inheritance. The error arises when nation or ethnicity becomes an ecclesiological absolute and the Church is treated as an instrument of political nationalism.