As Jesus is the cornerstone upon which the Church is built, so are his teachings the unifying cornerstone of Christian doctrine.
Conflict between Church Leaders
East and West
When the aggrieved parties are church leaders, unsolvable conflicts can arise. Stubborn unwillingness to make peace on lesser issues has historically been a major cause of division. For instance, the division between east and west was over issues which neither Jesus nor the Apostles commanded. It began with differences in language and culture, Latin versus Greek. It was made worse by Latin political claims of supremacy. While the east honored stylized church art works (icons), the west forbade it. The west added a clause to the Nicene Creed over which the east had not been consulted. The west demanded celibacy of priests while the east did not. These and other lesser issues boiled over to the point where Leo and Michael simultaneously excommunicated each other. In this case, going to the church (Matthew 18:15-20) failed to resolve the dispute.