TEURGIA (θεουργία). — From θεός “god” and ἔργον “work,” it means “divine operation,” almost always of a magical nature, performed by one invested with divine power, that is, by the theurgist, an epithet first assumed by a certain Giuliano, son of the Chaldean Giulino, who lived in the time of Marcus Aurelius and is presumed to have been the author of the Chaldaean Oracles, a composition in verse in which the mystical-astral doctrines of Babylonian science are fused with the philosophical doctrines of Greece.
While Neoplatonism, with Plotinus and in part with his disciple Porphyry, had remained within a noble sphere of mystical philosophy, with Iamblichus, Porphyry’s disciple and author of the De mysteriis Aegyptorum, it descended to the level of magic. He claimed to achieve union with the supreme Being through magical means, supplied above all by sacrifice, which was capable of raising man toward the One despite his moral inferiority, and by divination, both divine, which takes place through a sacred sleep, and demonic, which is effected by means of amulets and talismans.
The theurgist can free himself from every bond with matter, making himself insensible to fire or wounds; he can rise into the air, transform his appearance, and read the future. In short, the theurgist, thanks to his commerce with the divine world, can command the things of the world without limitation (Iamblichus, De myst., 7, 4; 96, 9). The theurgist adopted this epithet to distinguish himself from the magician, since he considered himself the confidant of celestial spirits and claimed that his miracles “took place through simple faith and trust in God, and not through the spells and incantations of a sinful curiosity, which they call magic, or, by a more detestable name, Goetia” (St. Augustine, De civ. Dei, X, 9). By this word (γοετελκ from γοδα = “I groan, I lament”) were understood the mournful incantations that preceded the operations of diabolical magic.