"Who gave you authority over the ummah [Muslim people]?" the letter asks. "Was it your group? If this is the case, then a group of no more than several thousand has appointed itself the ruler of over a billion and a half Muslims. This attitude is based upon a corrupt circular logic that says: 'Only we are Muslims, and we decide who the caliph is, we have chosen one and so whoever does not accept our caliph is not a Muslim.' "