Justo L. Gonzalez quotes:

The eastern part of the Roman Empire spoke mostly Greek, and the western parts spoke mostly Latin. So very soon, you begin getting different emphases between the Eastern church and the Western church.

A person wearing tinted glasses can avoid the conclusion that the entire world is tinted only by being conscious of the glasses themselves.

It's a matter of each of the two churches being very deeply enculturated in its own setting and having difficulty understand the other.

The Church must be one because a fragmented church is not much help to a fragmented world.