As mentioned, theurgy eventually was incorporated into Christian thought. The critical link here is Pseudo-Dionysius the Areopagite.
Tradition describes Dionysius the Areopagite as being the convert of Paul from Acts 17.34: "Some of the people became followers of Paul and believed. Among them was Dionysius, a member of the Areopagus." After his conversion, Dionysius became the Bishop of Athens and is recognized as a saint in the Catholic and Orthodox traditions.
In the early sixth century, a collection of mystical writings called the Corpus Areopagiticum or Corpus Dionysiacum appeared which was pseudepigraphically attributed to Dionysius the Areopagite. The author of these works is unknown and thus is called Pseudo-Dionysius the Areopagite.
Pseudo-Dionysius the Areopagite is an important figure in Christian theology, generally recognized as a seminal voice in the apophatic theological tradition. One could call him "The Father of Apophatic Theology."
Pseudo-Dionysius was deeply influenced by Neoplatonism, so much so he is controversial in some theological circles. Martin Luther, for example, felt Pseudo-Dionysius was too Greek, that Platonic philosophy had compromised his theology. But many theologians have been profoundly influenced by Pseudo-Dionysius, from Maximus the Confessor to Bonaventure. For my part, Pseudo-Dionysius' The Divine Names had a profound impact upon me.
Due to his Neoplatonism, it's not surprising that Pseudo-Dionysius describes theurgy, mentioning it twenty-five times in his Corpus, along with other variants of the word.
Now, how similar is Dionysian theurgy to Iamblichian theurgy? A debate rages about this. Some scholars, wanting to draw a hard line between pagan theurgy and Christian liturgy, see Pseudo-Dionysius as making a break with Iamblichus. Other scholars argue that this hard contrast is being imposed by anxious Christian scholars wanting to quarantine Christian thought from pagan contamination. These scholars see Dionysian theurgy as straightforwardly similar to Iamblichian theurgy only translated into a Christian liturgical context.
For example, Pseudo-Dionysius describes how the divine light of God descends to earth with the goal of raising us up. Here are the opening lines of The Celestial Hierarchy:
Inspired by the Father, each procession of Light spreads itself generously toward us, and, in its power to unify, it stirs us up by lifting us up. It returns us back to the oneness and deifying simplicity of the Father who gathers us in...However, this divine ray can enlighten us only by being upliftingly concealed in a variety of sacred veils which the providence of the Father adapts to our nature as human beings.
These "sacred veils" are Christian symbols and liturgical practices. As Pseudo-Dionysius writes, human beings need "perceptible things to lift us up" toward God:
For it is quite impossible that we humans should, in any material way, rise up to imitate and to contemplate the heavenly hierarchies without the aid of those material means capable of guiding us as our nature requires.
Similar to Iamblichian theurgy, Pseudo-Dionysius describes how, through "material means" and "perceptible things," human beings are lifted up toward God and divinized. For Pseudo-Dionysius these "material means" and "perceptible things" are encountered in the Christian liturgy. Pseudo-Dionysius describes how liturgical participation leads to union and communion with the divine. As Pseudo-Dionysius says, Christian liturgy uses "varied symbolism determined from the realm of perception, symbolism by means of which there is a sacred uplifting to the divine." For example, here is Pseudo-Dionysius describing the Eucharist in theurgic terms:
The hierarch [the priest] speaks in praise of the most sacred works of God, sets about the performance of the most divine acts, and lifts into view the things praised through the sacredly displayed symbols. Having thus revealed the kindly gifts of the works of God, he himself comes into communion with them and exhorts the others to follow him.
The priest "sets about the performance of the most divine acts" and presents before the congregation the "sacred symbols." In doing so the priest "comes into communion" with God and exhorts the congregation to "follow him" into that theurgic union. Through the liturgical symbolism and rites there is "a sacred uplifting to the divine."
The point of this union is divinization. As Pseudo-Dionysius says, “the assimilation to, and union with, God, as far as attainable, is deification." The liturgical rites aren't just ceremonial or symbolic. Through the liturgy we are raised by the divine Light and this effects an ontological change upon us. Liturgy is theurgy, a practice of sacred magic.
If that sounds strange, here's how the theologian John Milbank describes liturgy-as-theurgy in Pseudo-Dionysius:
Thus for Dionysius, as for Iamblichus and Proclus, God is ‘there’ for us not when we ‘look’ at him, but rather when we call upon him and perform actions atuned to him. This ‘higher magic’ is not merely automatic...and it is not possible to influence God, but rather it is possible to atune ourselves and the cosmos to a greater receptivity of the divine. How else are we to understand prayer without reducing it either to a mythical attempt to change God’s mind, or else to mere self-therapy? Clearly liturgical prayer is indeed a kind of higher magic.All this might be a bit too much for some, describing liturgy as "sacred" or "higher" magic. But viewing liturgy as theurgy helps keep worship weird. And by "weird" I mean highlighting an ontological dimension of worship that we've wholly lost track of, or never recognized in the first place.
