Despite his importance, no substantial study has been devoted to the career of Abū 'l-'Abbās Ahmad b. Idrīs al-Hasanī al-'Arā'ishī al-Fāsī (d. 1837); most accounts of him appear by way of a preface to studies of his pupils. And yet through his teachings, pupils, and family, he was undoubtedly one of the key religious figures of the early 19th century Arab Muslim world. Indeed, his influence, direct and indirect, appears to have stretched from North Africa to Indonesia. Three of his pupils from his immediate circle established major brotherhoods, the Sanūsiyya, Khatmiyya, and Rāshidiyya, from which stemmed several other orders.