Certain differences should not create division in the body of Christ. While that unity will only be perfectly realized in the invisible church, the visible church ought to strive for it. There is, therefore, a biblical call and necessity for unity in the church. Unity in the visible church is clearly a good. This unity then gives warrant for two or more churches to exist under the same government. We see this unity expressed in the government which oversaw the early church in the book of Acts, specifically the Jerusalem Council in Acts 15.
Presbyterian churches are deliberative bodies. When decisions are made, they are determined through voting and majority rule. This process is biblical. This process maintains the unity of the church. This process has worked through the history of the church. This process is beneficial for the church today. And this process lays certain obligations upon the members of that body when decisions are made.
It should be fairly apparent that the church is more than the local congregation. One of the signs of a cult is to view one’s particular local body as the totality of the church. It should be, therefore, no radical statement to say that the visible church is larger than the local church. If that is true, then there must be some manner in which the visible church can govern herself at the numerically larger levels. The question is not if she does, but how she comes to decisions regarding the larger body. There must be some process for the government of the larger church. This government necessitates a type of union among particular church bodies.
This isn’t to say that the church everywhere is to look and feel identical. The church is one. This is clearly confessed in the Apostles’ Creed when “a holy catholic church” is affirmed. But uniformity within the church is not necessarily a good. Uniformity is not the same as unity.