This book is an English translation of the award-winning book by Mohammad Ali Amir-Moezzi on the Book of the Proof (Kitab al-Hujja) part of the Sufficient Book (Kitab al-Kafi), authored by one of the most celebrated religious authorities and a foundational figure of Shi'i Islam, Muhammad ibn Ya'qub al-Kulayni (d. ca. 940 CE). The significance of this source for the formation and development of Shi'i beliefs and doctrines cannot be overestimated. Whilst the field of Shi'i studies is still dominated by works focused on legal, political, or theological aspects of Sh'i Islam, Amir-Moezzi's approach to the study of the early Shi'i traditions in this work is characterised by a keen interest in its esoteric, mystical aspects. Complemented by detailed analytical comments, Amir-Moezzi's book demonstrates how al-Kulayni was able to set out an extraordinarily wide-ranging and coherent set of doctrinal and legal traditions derived from the Imams, thus playing a leading role in the unification and, consequently, the consolidation of the Imami faith. More specifically, by elaborating on the nature of the 'Proof', which in Shi'i terminology identifies the central figure, i.e., the guide (imam) of mystical spirituality, Amir-Moezzi's study portrays Shi'i Islam as multifaceted, not merely as the politico-religious ideology of its 'clergy', but above all as an inspirational religion. As Amir-Moezzi himself puts it, 'enriching Muslim thought and spirituality, sometimes with unusual finesse and sophistication'.

Mohammad Ali Amir-Moezzi, professor at the Ecole Pratique des Hautes Etudes/PSL (Sorbonne). Member of the Advisory Board of the Societas Iranologica Europaea, Scientific Consultant of the Encyclopaedia Iranica, Encyclopaedia Islamica and Senior Fellow at the Institute of Ismaili Studies. Also member of the Ambrosian Academy and the scientific committees of numerous journals and reviews. Among his mongraphs: The Divine Guide in Early Shi'ism (State University of New York Press, 1994), The Spirituality of Shii Islam (IIS, I.B. Tauris, 2013), The Silent Quran and the Speaking Quran (Columbia University Press, 2015), La Preuve de Dieu. La mystique shi'ite à travers l'ouvre de Kulayni (Cerf, 2018) and Ali, The Well-Guarded Secret (Brill, 2022). Among the collective works directed by him: Le Dictionnaire du Coran (Robert Laffont, 2007) and le Coran des historiens (Cerf, 2019, co-directed by Guillaume Dye).

Maria De Cillisis a Senior Research Associate at the Institute of Ismaili Studies, where she is also a Series Editor of the Shi?i Heritage Series. She has authored Salvation and Destiny in Islam: The Shi?i Ismaili Perspective of ?amid al-Din al-Kirmani (2018), Free Will and Predestination in Islamic Thought: Theoretical Compromises in the Works of Avicenna, al-Ghazali and Ibn ?Arabi (2014) and has co-edited L'ésotérisme shi?ite, ses racines et ses prolongements/Shi?i Esotericism: Its Roots and Developments (2016).

Orkhan Mir-Kasimov is a Senior Research Fellow at the Institute of Ismaili Studies. He is a Senior Fellow of the Higher Education Academy and teaches on the IIS graduate programmes. Previously, he lectured at the Ecole Pratique des Hautes Etudes and the National Institute for Oriental Languages and Civilisations (INALCO) in Paris and worked at various research centres in France and Germany, including the Institute for Advanced Study of Nantes and the Free University of Berlin. Since 2020, he is the Series Editor of the Ismaili Texts and Translations Series.