For 10 points, name this religious system which supports Ali as the divinely chosen successor of Muhammad, a major branch of Islam along with Sunnism.
One division in this group occurred over whether intellect and consensus can supplement scripture in divine law. That argument between the Usulis and the Akhbaris occurred in a sect of this distinct from that which included the Qarmatians and the Assassins, and from which the Druze split off, the Ismailis. This religious group commemorates the defeat at the Battle of Karbala on the tenth of Muharram, known as Ashura. One sect of this belief system is known as the Twelvers, after the number of imams its adherents accept. For 10 points, name this religious system which supports Ali as the divinely chosen successor of Muhammad, a major branch of Islam along with Sunnism.
One division in this group occurred over whether intellect and consensus can supplement scripture in divine law.
Shi'a Islam [or Shi'ism; accept Twelvers, or Imami Shi'ism, or Ithna'ashariyyah until "distinct"; prompt on "Islam" until "Karbala"]