Hans Jonas explores the ancient spiritual movement of Gnosticism, which viewed the material world as flawed and believed in a hidden, divine knowledge (gnosis) as a path to spiritual liberation. Jonas examines Gnostic myths, such as the alien god who seeks to save humanity, and how these ideas influenced early Christianity. By blending history, philosophy, and theology, the book reveals how Gnosticism challenged mainstream beliefs, emphasizing inner enlightenment and the quest to transcend earthly limitations.