This book redefines our interpretation of Iamblichus' theurgy and religiosity, as revealed in his only complete surviving work, the De Mysteriis. Clarke argues that the existence and operation of the supernatural, or the miraculous, is the sine qua non of this work, and yet this is often overlooked by Iamblichus' philosophical interpreters. The argument is developed through the examination of numerous religious practices described by Iamblichus, most importantly those of animal sacrifice, oracular consultation, divine possession, and the ritual observation of the luminous divine epiphanies. The book seeks to understand Iamblichus' position within the framework of, rather than through the eyes of, other Neoplatonists. Emma Clarke is the chief editor of the only modern English translation of the De Mysteriis, and in this book she breaks new ground in a growing area of interest, Neoplatonism.