The second largest branch of Islam, with between 130 and 190 million adherents across the globe, Shi'i Islam is becoming an increasingly significant force in contemporary politics, especially in the Middle East. This makes an informed understanding of its fundamental spiritual beliefs and practices both necessary and timely. Mohammad Ali Amir-Moezzi is one of the most distinguished scholars of Shi'i history and theology, and in this volume he offers a wide-ranging and engaging survey of the core texts of Shi'i Islam. Examining in turn the origins and later developments of Shi'i spirituality, the author reveals the profoundly esoteric nature of the beliefs which accrued to the figures of the early Imams, and which became associated with their interaction between the material and spiritual worlds. Many of these beliefs have remained much misunderstood even within the wider Muslim world. Furthermore, Western scholarship has tended to follow the lead of the earlier orientalists and critics, viewing Shi'i teachings as marginal. In this study the author shows, by contrast, how central and creative the very nature of spirituality was to the development of Shi'i Islam, as well as to classical Muslim civilisation as a whole. In this comprehensive treatment, the esoteric nature of Shi'i spirituality emerges as an essential phenomenon for understanding Shi'i Islam.