This book reconsiders Iamblichus? Response to Porphyry, Late Antiquity?s seminal work on theurgy, which is often referred to as De Mysteriis. Was this text intended to be more than just a defence of ritualism or a philosophical crossing of metaphysical wits between Porphyry and Iamblichus? This volume examines whether De Mysteriis constituted a manifesto of restoration, a call to resignify and revive a religion that Iamblichus felt was spiralling into barren traditionalism. Through a nuanced examination of Iamblichus? theurgy, this book shows the emergence of a sophisticated philosophico-ritualistic system, one designed to reform religious practice through divine epiphanies and direct communication with the gods. Using a thorough textual analysis, this book uncovers crucial distinctions between theurgy and magic and explores the mechanics of divine illumination during theurgic rituals in the context of Iamblichus intricate hierarchy of spiritual beings. In this system, this book demonstrates, material objects could become vessels of divine power and humans could become interlocutors with the divine itself.