Allegedly, Neoplatonic theurgy originated with Julian the theurgist, who lived in the time of emperor Marcus Aurelius. At first sight, theurgy seems to share many characteristics with magic (theory of cosmic sympathy, invocations, animation of statues of gods and demons), but it is, as far as we can judge from the extant sources, clearly different from it. In his De Mysteriis Iamblichus developed a theology of the hieratic rituals from Platonic principles, which clearly sets them apart from the vulgar magical practices. While magic assumes that the gods can be rendered subservient to the magicians, Platonic philosophers consider this impossible. According to Plato's principles of theology (Republic II and Laws X), the gods are immutable, unchangeable, and cannot be bribed by means of sacrifices. Proclus' views on theurgy (of which only some fragments belonging to his treatise On Hieratic Art [i.e., theurgy] survived) are fully in line with these fundamental Platonic axioms. But how, then, does theurgy work? The theurgists take up an old belief, shared also by many philosophers, namely the natural and cosmic ‘sympathy’ (sumpatheia) pervading all reality. As with an organism, all parts of reality are somehow linked together as one. Another way of expressing this idea is in the Neoplatonic principle, going back at least to Iamblichus, that everything is in everything (panta en pasin). According to Proclus, all reality, including its most inferior level, matter, is directed upwards towards the origin from which it proceeds. To say it in the words of Theodorus of Asine, whom Proclus quotes in his Commentary on the Timaeus (I 213.2–3): “All things pray except the First.”
As stated before (cf. 3.3), the human soul contains the principles (logoi) of all reality within itself. The soul carries, however, also sumbola or sunthêmata which correspond to the divine principles of reality. The same symbols also establish the secret correspondences between sensible things (stones, plants, and animals) and celestial and divine realities. Thanks to these symbols, things on different levels (stones, plants, animals, souls) are linked in a ‘chain’ (seira) to the divine principle on which they depend, as the chain of the sun and the many solar beings, or the chain of the moon. Of great importance in the rituals was also the evocation of the secret divine names. In his Commentary on the Cratylus, Proclus compares divine names to statues of the gods used in theurgy (In Crat. § 46), pointing to the fact that also language is an important means in the ascent to the divine.
Proclus evokes the Platonic background of his theurgical beliefs, namely his theory of love (erôs) as expressed in the Symposium and the Phaedrus, in his treatise On Hieratic Art:
Just as lovers move on from the beauty perceived by the senses until they reach the sole cause of all beautiful and intelligible beings, so too, the theurgists (hieratikoi), starting with the sympathy connecting visible things both to one another and to the invisible powers, and having understood that all things are to be found in all things, established the hieratic science. (trans. Ronan, modified)In the wake of an article of Anne Sheppard (1982), scholars usually distinguish between three kinds of theurgy in Proclus. The first kind, as described in the above quoted treatise On Hieratic Art, was mainly concerned with animating statues (in order to obtain oracles or to evoke divine apparitions) or, in general, with activities related to physical phenomena or human affairs (influencing the weather, healing illnesses etc.) (see Life of Proclus § 28–29). As emerges from our sources, it is this kind of theurgy that involved much ritualistic practice, including hymns and prayers. The second kind of theurgy makes the soul capable of ascending up to the level of the hypercosmic gods and the divine intellect. This second kind too operates by means of prayers and invocations and it seems especially characteristic of Proclus' Hymns. And finally, the third kind of theurgy establishes unity with the first principles, that is the One itself. This third kind corresponds to the level of the highest virtues (i.e., ‘theurgic virtues’) in the scale of virtues. It is not clear whether some form of ritual is involved here at all. For this last stage of the Platonic homoiôsis theôi the following elements are of major importance: negative theology (culminating in the negation of the negation), mystic silence and the intriguing notion of faith (pistis), which thus enters with a non-Platonic meaning - though even for the latter notion Proclus will search for confirmation in the Platonic dialogues.
Those who hasten to be conjoined with the Good, do no longer need knowledge and activity, but need to be established and a stable state and quietness. What then is it which unites us to the Good? What is it which causes in us a cessation of activity and motion? What is it which establishes all divine natures in the first and ineffable unity of goodness? […] It is, in short, the faith (pistis) of the Gods, which ineffably unites all the classes of Gods, of daemons, and of blessed souls to the Good. For we should investigate the Good not through knowledge (gnôstikôs) and in an imperfect manner, but giving ourselves up to the divine light, and closing the eyes, to become thus established in the unknown and occult unity of beings. For such a kind of faith is more venerable than cognitive activity, not in us only, but with the Gods themselves. (Proclus, Platonic Theology, I 25, trans. Th. Taylor, modified).<a href="http://plato.stanford.edu/entries/proclus/">http://plato.stanford.edu/entries/proclus/</a>