Includes studies in English, German and French. Preface; Part I Shi'a:'Abd Allah b. Abbas and Shi'ite law; Shi'ism in the age of the rightly-guided caliphs.; Part II Zaydiyya: Zu einigen Werken des Imams Abu Talib an-Natiq bi I-Haqq; Imam al-Qasim ibn Ibrahim and Mu'tazilism; Al-Qasim ibn Ibrahim and Christian theology; Zaydi attitudes to Sufism.; Part III Isma'iliyya: Das Imamat in der fruhen ismailitischen Lehre; Abu Ya'qub al-Sijistani and metempsychosis; Abu Ya'qub al-Sijistani and the seven faculties of the intellect; The Fatimids and the Qarmatis of Bahrayn; Hamdan Qarmat and the Da'i Abu'Ali; The religious policy of the Fatimids toward their Sunni subjects in the Maghrib; A treatise on the Imamate of the Fatimid caliph al-Mansur bi-Allah; An Ismaili interpretation of Ibn Sina's Qasidat al-Nafs; Shahriyar b. al Hasan: a Persian Isma'ili da'l Muhammad b. Ahmad al-Nasafi; Addenda and Corrigenda; Index.