This chapter introduces the themes and tensions related to historiography on Islam’s fourth caliph, ʿAlī. Anti-ʿAlids (nawāṣib) were Muslims who disliked ʿAlī and his descendants, while ʿAlī's partisans, pro-ʿAlids and Shīʿīs, exalted him and developed doctrines about the nature of his authority. All of these early Muslims transmitted reports about ʿAlī's character, which resulted in portrayals that were diverse and contradictory. Sunnī and Shīʿī writers sifted through such reports not only to construct an image of ʿAlī that they considered authentic, but also to validate their own communal identities and conceptions of religion.