Here’s an astute quote on church unity from Karl Barth, as quoted by Volf in After Our Likeness: The Church As the Image of the Trinity.

If a man can acquiesce in divisions, if he can even take pleasure in them, if he can be complacent in relation to the obvious faults and errors of others and therefore his own responsibility for them, then that man may be a good and loyal confessor in the sense of his own particular denomination, he may be a good Roman Catholic or Reformed or Orthodox or Baptist, but he must not imagine that he is a good Christian.