Dualism (thanawiyya, also aṣḥāb al-ithnayn and ahl al-tathniya) a term in Islamic heresiography used to denote certain groups said to have espoused dualist beliefs (al-Ashʿarī, 327, 485; al-Bāqillānī, 60). While this term is not found in the Qurʾān and the ḥadīth corpus, refutations of the thanawiyya mentioned in Ibn al-Nadīm’s Fihrist suggest that the term was widely used in the 2nd/8th century. Judging by its contexts, an accusation of dualism was often deployed by Muslim authors as a pejorative term for groups whose beliefs were deemed to contradict the core Islamic doctrine of tawḥī…