This book offers a comprehensive exploration of Gnosticism, its historical development, theological concepts, and lasting influence on early Christianity and Western thought. Beginning with an in-depth examination of the origins of Gnostic thought in the Hellenistic world, the book traces the emergence of Gnostic ideas within the diverse religious landscape of the Roman Empire. It analyzes the distinct cosmology, soteriology, and Christology that characterized Gnostic traditions, particularly their dualistic view of the material world and their emphasis on salvation through hidden knowledge (gnosis). The work further delves into the relationship between Gnosticism and early Christianity, examining the theological struggles that led to the classification of Gnosticism as heretical by the early Church Fathers, such as Irenaeus, Tertullian, and Hippolytus. It highlights key theological debates, particularly concerning the nature of salvation, the material world, and the role of Christ. The book also assesses the political and social implications of Gnostic ideas, especially their challenge to the authority of the Church and their critique of established religious and political structures.