When it comes to church history, denominations often form because a group of Christians correctly identifies a current error. Then, denominations fall into errors of their own because they are right by too much.
So, the Lutherans were right that salvation is really by faith alone, and they were right by too much to say that this grace is so great, even baptism bestowed on an infant imparts it. The Catholics are right that the church is the unifying factor which brings meaning to all of life, and too right in saying that the Roman church is that One Church. The Presbyterians are right in seeing all of redemptive history as forms and patterns, and too right in forcing passages that don’t work that way into those patterns and forms. The Bereans are right that the books of Revelation and Daniel can’t be reduced to a vague mash-up of symbols, but are too right in thinking that they can be reduced to a fortune-telling newsreel about events in the Middle East. The ecumenical mega churches are right in thinking that we are all brothers and sisters in Christ in spite of our differences, but too right in thinking that our differences are not essential enough to divide us. Mark-Driscoll-type-churches are right in thinking that the church is a place for hipsters and progressives, but too right in thinking that the church should be hip and progressive.
Although this is a mess, the mess of Christendom is a lovely mess – a mess that shows we have a real savior, who is actually purifying His bride, actually making her His crown, and actually her Lord.