Building up the Body - Growing in unity and maturity

Unity is elusive. It is uncommon in much of the world and, unfortunately, also among Christians. Why do we have so many denominations? Perhaps it is because we all think that we are right. Jesus' prayer for us (John 17:20-21) was: I pray also for those who will believe in me through their message, that all of them may be one, Father, just as you are in me and I am in you.