Ka kammala wannan jumla: Bayan mutuwar annabin Islama, Muhammad, ra'ayi biyu sun fito game da wanda zai gaje shi a matsayin shugaban al'ummar Musulmi. Wasu Musulmai, waɗanda suka gaskata cewa Muhammadu bai taɓa bayyana magajinsa a fili ba, sun yi amfani da al'adar Larabawa na zaɓar shugabansu ta hanyar majalisa na membobin al'umma masu tasiri. Wasu kuma sun yi imanin cewa Muhammadu ya zaɓi dan uwansa da surukinsa Ali ibn Abi Talib ya gaje shi. Wannan rashin jituwa daga bisani ya haifar da
yakin basasa wanda ya jefa magoya bayan Ali a kan magoya bayan wanda ya kafa daular Umayyad Muawiyah, kuma wadannan sansanonin biyu daga baya sun zama sunna da Shia. Ga 'yan Shi'a, Ali da Imamai da suka gaje shi a hankali sun zama ainihin jagorancin Allah, kuma suna da sha'awar jaddada ayyukan addini na khalifanci da kuma nuna rashin amincewar siyasa; Sunni sun fi karkata ga iyakance matsayinta na addini kuma sun fi yarda da matakan da ya dace. Yayin da waɗannan bambance-bambance suka zama masu mahimmanci tare da muhimmancin addini, sun haifar da nau'i biyu na Islama.