Theurgia, or Theurgy (Gr.). A communication with, and means of bringing down to earth, planetary spirits and angels—the “gods of Light”. Knowledge of the inner meaning of their hierarchies, and purity of life alone can lead to the acquisition of the powers necessary for communion with them. To arrive at such an exalted goal the aspirant must be absolutely worthy and unselfish.
Theurgist. The first school of practical theurgy (from θεος, god, and εργον work,) in the Christian period, was founded by Iamblichus among certain Alexandrian Platonists. The priests, however, who were attached to the temples of Egypt, Assyria, Babylonia and Greece, and whose business it was to evoke the gods during the celebration of the Mysteries, were known by this name, or its equivalent in other tongues, from the earliest archaic period. Spirits (but not those of the dead, the evocation of which was called Necromancy) were made visible to the eyes of mortals. Thus a theurgist had to be a hierophant and an expert in the esoteric learning of the Sanctuaries of all great countries. The Neo-platonists of the school of Iamblichus were called theurgists, for they performed the so-called “ceremonial magic”, and evoked the simulacra or the images of the ancient heroes, “gods”, and daimonia (δαιμονια, divine, spiritual entities). In the rare cases when the presence of a tangible and visible “spirit” was required, the theurgist had to furnish the weird apparition with a portion of his own flesh and blood—he had to perform the thepæa or the “creation of gods”, by a mysterious process well known to the old, and perhaps some of the modern, Tântrikasand initiated Brahmans of India. Such is what is said in the Book of Evocations of the pagodas. It shows the perfect identity of rites and ceremonial between the oldest Brahmanic theurgy and that of the Alexandrian Platonists.
The following is from Isis Unveiled: “The Brahman Grihasta (the evocator) must be in a state of complete purity before he ventures to call forth the Pitris. After having prepared a lamp, some sandal-incense, etc., and having traced the magic circles taught him by the superior Guru, in order to keep away bad spirits, he ceases to breathe, and calls the fire (Kundalini) to his help to disperse his body.” He pronounces a certain number of times the sacred word, and “his soul (astral body) escapes from its prison, his body disappears, and the soul (image) of the evoked spirit descends into the double body and animates it”. Then “his (the theurgist’s) soul (astral) re-enters its body, whose subtile particles have again been aggregating (to the objective sense), after having formed from themselves an aërial body for the deva (god or spirit) he evoked”. . . . And then, the operator propounds to the latter questions “on the mysteries of Being and the transformation of the imperishable”. The popular prevailing idea is that the theurgists, as well as the magicians, worked wonders, such as evoking the souls or shadows of the heroes and gods, and other thaumaturgic works, by supernatural powers. But this never was the fact. They did it simply by the liberation of their own astral body, which, taking the form of a god or hero, served as a medium or vehicle through which the special current preserving the ideas and knowledge of that hero or god could be reached and manifested. (See “Iamblichus”.)
—Theosophical Glossary (HPB)
Theurgy, divine Magic, or power to work phenomena through Divine aid or by the aid of the “Gods”, or powers of nature. See Magic.
Magic, the science of bringing into visible action forces ordinarily hidden. The ancients recognized three sorts: Theurgia, or White Magic; Goetia, or Black Magic; and Natural Magic. Theurgia had to do with the powers of the soul, the philosopher’s stone, the magic which makes of man a God. Goetia was sorcery, or the communication with the regents of the invisible worlds with evil intent. Natural Magic had dealings entirely with nature, and might be either Black or White according as the Adept whose will called it into action was of the Left- or Right-hand path. The physician who heals with the use of his drugs is as much a natural magician as the necromancer who effects cures by his thaumaturgy; with the difference, however, that the one can give no reason for the effects he produces, while the other can.
—Working Glossary (WQJ)
Theurgist.— From Θεος, god, and εργον, work. The first school of practical theurgy in the Christian period was founded by Iamblichus among the Alexandrian Platonists; but the priests attached to the temples of Egypt, Assyria, and Babylonia, and who took an active part in the evocations of the gods during the Sacred Mysteries, were known by this name from the earliest archaic period. The purpose of it was to make spirits visible to the eyes of mortals. A theurgist was one expert in the esoteric learning of the Sanctuaries of all the great countries. The Neoplatonists of the school of Iamblichus were called theurgists, for they performed the so-called “ceremonial magic,” and evoked the “spirits” of the departed heroes, “gods,” and Daimonia (ϐαιμονια, divine, spiritual entities). In the rare cases when the presence of a tangible and visible spirit was required, the theurgist had to furnish the weird apparition with a portion of his own flesh and blood — he had to perform the theopœa, orthe “creation of gods,” by a mysterious process well known to the modern fakirs and initiated Brahmans of India. This is what is said in the Book of Evocations of the pagodas. It shows the perfect identity of rites and ceremonial between the oldest Brahmanic theurgy and that of the Alexandrian Platonists:
“The Brahman Grihasta (the evocator) must be in a state of complete purity before he ventures to call forth the Pitris.”
After having prepared a lamp, some sandal, incense, etc., and having traced the magic circles taught to him by the superior guru, in order to keep away bad spirits, he “ceases to breathe, and calls the fire to his help to disperse his body.” He pronounces a certain number of times the sacred word, and “his soul escapes from his body, and his body disappears, and the soul of the evoked spirit descends into the double body and animates it.” Then “His (Grihasta’s) soul reënters into his body, whose subtile particles have again been aggregating, after having formed of their emanations an aërial body to the spirit he evoked.”
And now, that he has formed for the Pitri a body with the particles the most essential and pure of his own, the grihasta is allowed, after the ceremonial sacrifice is over, to “converse with the souls of the ancestors and the Pitris, and offer them questions on the mysteries of the Being and the transformations of the imperishable.”
“Then after having blown out his lamp he must light it again, and set at liberty the bad spirits shut out from the place by the magical circles, and leave the sanctuary of the Pitris.”*
The school of Iamblichus was distinct from that of Plotinus and Porphyry, who were strongly against ceremonial magic and practical theurgy as dangerous, though these two eminent men firmly believed in both. “The theurgic or benevolent magic, the Goëtic, or dark and evil necromancy, were alike in preëminent repute during the first century of the Christian era.” But never have any of the highly moral and pious philosophers, whose fame has descended to us spotless of any evil deed, practiced any other kind of magic than the theurgic, or benevolent, as Bulwer-Lytton terms it. “Whoever is acquainted with the nature ofdivinely luminous appearances ( fasmata ) knows also on what account it is requisite to abstain from all birds (animal food), and especially for him who hastens to be liberated from terrestrial concerns and to be established with the celestial gods,” says Porphyry.
Though he refused to practice theurgy himself, Porphyry, in his Life of Plotinus, mentions a priest of Egypt, who, “at the request of a certain friend of Plotinus (which friend was perhaps Porphyry himself, remarks T. Taylor), exhibited to Plotinus, in the temple of Isis at Rome, the familiar daimon, or, in modern language, the guardian angel of that philosopher.”
The popular, prevailing idea was that the theurgists, as well as the magicians, worked wonders, such as evoking the souls or shadows of the heroes and gods, and doing other thaumaturgic works by supernatural powers.
—Glossary from Isis Unveiled (HPB)
Theurgy (Encyclopedic Theosophical Glossary)
Theurgy (Theosophy Wiki)
Iamblichus on The Mysteries of the Egyptians, Chaldeans, and Assyrians, tr. Thomas Taylor