If you look in the telephone directory, you will find a huge diversity of churches. Even within individual denominations there often exists great variation. Jesus once prayed that His followers would be one (Jn 17). But what we see today is anything but unity. What are we to make of this disunity? Does this not demonstrate that Christianity is hopelessly divided? Perhaps. Then again, there may be another way of looking at it.
It is important to ask whether denominations are a good thing. Denominations generally developed out of churches seeking fellowship with one another and joint `ministry. That is certainly a biblical idea (Ac 11:27-30).
Often denominations began as renewal movements. So the Reformed movements of the sixteenth century arose to restore teachings about justification by faith and God's sovereignty in salvation-teachings that had been eclipsed in the church for a long time. Later, some Presbyterians caved in to the pressures of liberalism and newer conservative Presbyterian groups emerged to preserve the traditions. Other denominations had similar experiences. Baptists came along within the Reformed tradition, contending that the Reformation principles of justification by faith ought to be applied to the church. In the twentieth century Pentecostals and charismatics formed new unions based on their view of the Spirit and spiritual gifts.
So is this diversity among the churches a good thing or a bad thing? It is always vital to avoid false teaching in the church. Often in the NT false teachers were either disciplined or left churches of their own accord (1 Tm 1:19-20; 1 Jn 2:19). In other cases the early church leaders predicted a future time of apostasy when false teachers would gain great influence (2 Tm 3:1-9). In such cases, it might be necessary for genuine Christians to separate themselves from the false church.
That is not to say that all denominational separations have been for the right reasons. The most important thing to do is to examine a church's teaching and practice consistent with Scripture. And finally we have to realize that in this life Christians will not agree on everything.
Extracted from the Apologetics Study Bible.