ʿIṢMAH. The Arabic term ʿiṣmah means "immunity" from sin or error. ʿIṣmah is discussed by the Sunnīs in relation to the Prophet Muḥammad and other prophets, and by the Shīʿah in relation to not only the prophets but, most importantly, the imāms, the charismatic descendants of ʿAlī ibn Abī Ṭālib who stand at the center of Shīʿī piety. The paths taken by Sunnīs and Shīʿah with regard to ʿiṣmah throw much light on the different development and character of the two traditions.

The idea of immunity is latent in the tendency of Homo religiosus to attribute outstanding qualities to special persons. This tendency was already evident in the first centuries of Islam in efforts to dissociate Muḥammad from polytheism in his early life and Ṣūfī and Sh...