What came to be known as Isma'ilis, are those who believed that the Imamate should remain within the line of Isma'il ibn Ja’far. It was believed that the designation went to Isma'il ibn Ja'far, and therefore the Imamate should continue through his lineage. His early supporters initially theorized that Isma'il ibn Ja’far’s death was staged, and he went into hiding out of fear for his life from the Abbasid Caliph al-Mansūr. They refused to acknowledge his death, and some even claimed to have seen him after his funeral. However, most Ismā'īlīs later accepted Isma'il ibn Ja’far’s death, and instead followed his son Muhammad ibn Isma'il as the next Imam, since the Imamate could still be continued through Isma'il ibn Ja’far’s lineage. On a theological level, Ismai'lis refuse to acknowledge Imams outside of the lineage of Ismail ibn Ja’far due to the notion of "naṣṣ" (designation) and "‘ișma" (infallibility). Because Shi’as believe that the Imams are infallible and contain special knowledge of the Divine decree, it is inconceivable that Imam Ja'far al-Sādiq would have incorrectly chosen Imam Isma'il ibn Ja’far as his successor and then retract his original "naṣṣ". This would mean that Imam Ja'far al-Sādiq either made a major mistake which would make him fallible, or later claims regarding other designations were forged narrations.