(1) The split originated with a caliph named Hakim, a religious reformer who ruled from Cairo at the turn of the 11 th century.(2) One of the earliest and most distinguished of the Arabic mathematicians was the ninth century scholar Abu Ja'far Mohammed ibn Musa Al-Khwarizmi, who was an astronomer to the caliph at Baghdad.(3) Ali, who was the fourth caliph of Sunni Islam and the first Shia imam, disagreed with Umar's decision at the time, as did other leading Sahaba, or companions of the Prophet.(4) Imam Ali is the fourth caliph to the Muslim, to the Sunni Muslims, and he is the first successor of the Prophet according to the Shia Muslims.(5) Abu Bakr, a close companion of Muhammad, is unanimously selected as the first caliph of Islam.(6) Historically, for the Muslim community to act, the leader of that community - the caliph for the Sunnis, the imam for the Shi'ites - had to authorize the action.(7) The difference between a caliph and an imam is that a caliph can be anyone accepted by Muslims, but an imam must hail from the Prophet Mohammed's family and be a recognized religious authority (clergy).(8) In orthodox writings the title caliph generally means deputy or successor to the Prophet Muhammad (as in khalifat rasul Allah - deputy to the Messenger of God).(9) Every non-Muslim people living under the rule of the caliph enjoyed not only peace and security, but complete autonomy as well which lived on in the form of capitulations in the Turkish Empire up to quite recent times.(10) By 1055, the Seljuks had spread across Iran to Iraq, where in Baghdad Seljuk's grandson Tughrul liberated the caliph , the supreme religious leader of the Islamic faith, from the control of another dynasty.(11) Their only source of identity was Islam, for the sultan was the caliph , the successor to Mohammad, and the only legitimate leader of all Muslims.(12) The sultan was also the caliph , the symbol of Islamic unity and piety.(13) In early Islamic history the Shia were a political faction that supported Ali, son-in-law of the prophet Mohammed, who was the fourth caliph , the temporal and spiritual ruler of the Muslim world.(14) The primary difference between the two groups is that Sunni Muslims recognize a caliph , who maintains military and political authority in Muslim societies.(15) The caliphs (successors of The Prophet Muhammad) ruled that couples should not be separate for more than 4 months without permission, and if they were it was grounds for divorce.(16) The Omayyad dynasty of caliphs ruled from Damascus until 750, when Shiite Muslims, who descended from the caliph Ali, massacred the Omayyad family.