Aimee Milburn, who writes the smart and generally excellent blog Historical Christian has been on a hiatus recently because of coursework, but she’s back with a great post on the unity of the Church:

A Protestant reader lately has written to ask about unity, an issue that bothers him as a Protestant, and that bothered me also when I was a Protestant.  All Christians are concerned about unity, because Christ told us to be one on his last night on earth as an important part of our witness for him, so the world may know him and believe in him.

The question is, why is unity, oneness, so important for witnessing and believing that Christ made it a command on his last night on earth?  Why must we be one in order for Christ to be seen and believed in?  In dialoguing with my reader, something came clear, several different strands of theology that I’ve been studying coalesced, that I shared with him and also want to share here: the meaning and significance of unity, of visible oneness for the Church. 

It came together in my mind this way: it is important because it is the nature of God Himself, the nature of creation, the nature of the Church, and the reason for existence itself.  Simply put, the Church must be one because God is One, and the Church is His Body.  It must be unified, though composed of many members, because God is unified, three Persons in perfect harmony as one: the Trinity – and Jesus prayed that we, though many, would be perfectly one (Jn 17:23).  We are created in His image and likeness, so must show forth His image and likeness, which in essence is oneness and unity in love, not only in our individuality but also in our plurality, our relationships.

Turns out my reasoning agrees with the Catechism, which says, “The Church is one because of her source . . . the unity, in the Trinity of Persons, of one God.” (CCC 813)

The following is my attempt to explain why that is.

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