Excellent essay:
Is Christ Divided?
And two more apostolic questions today's church must answer.
by Timothy George

When Jesus said, "Upon this rock I will build my church, and the gates of hell shall not prevail against it," did he intend that the people called to bear his name in the world would eventually be divided into 37,000 competing denominations? That is the number of separate Christian bodies worldwide, according to missions statistician Todd Johnson of the World Christian Database. Some argue that this number is inflated due to the database's definition of denomination. But even if we were to suppose he is high by one-fourth (not likely), we're still looking at 27,000 separate Christian groups.

Sometimes church division is a tragic necessity, and the call to Christian unity does not mean that we must blend all believers into a single homogenous unit. But neither does it allow us to relax and accept the status quo as God's perfect will. Evangelicals believe in the spiritual oneness of all true Christians-what Augustine of Hippo called the invisible church-but does this mean that we should have no concern for visible church unity?

Our visible disunity causes many unbelievers to stumble. The problem is not only division, but divisiveness, within congregations as well as between (and within) denominations. To jar the Corinthians-a divided church if ever there was one-out of complacency, Paul asked three pointed questions in 1 Corinthians 1:13, questions we need to reconsider today.

Essay: http://www.christianitytoday.com/ct/2005/007/23.31.html