Due to an upcoming conference, I've been giving some thought lately to how some of the proposals of Radical Orthodoxy intersect with themes of participation and theosis (or deification) as they arise in earlier Christian thought, particularly in the Eastern church.
I seem to have mislaid my copy of Being Reconciled (which partly explains my lack of posting anything for several days), but there are some sections of Milbank and Pickstock's Truth in Aquinas where they explore these themes as they arise in the thought of the Angelic Doctor.
It's helpful to recall that Milbank and Pickstock do not read Aquinas so much as the Aristotelian natural theologian that has come down to us in popular regard. Rather, they interpret him as deeply entwined within and emergent from traditions of Christian neo-platonism (which was a platonism more Proclean than Plotinian and already revised in light of Aristotle), in line with Augustine and Pseudo-Dionysius and, thereby, resonating with various other figures, even earlier Eastern ones such as Gregory of Nyssa.
While the topic of Truth in Aquinas is that of knowledge and truth, these notions are so deeply theological for Aquinas--indeed trinitarian and christological--that the entire theme of human participation in the divine is interwoven with them. This is, in large part, because Aquinas' theory of knowledge offers us less an epistemology as it does an ontology of knowledge.
Milbank and Pickstock go on to note, "the leading characteristic of this ontology is a grasp of creation in the light of grace, as itself graced or supplemented, and so as a preparation for human deification" (51). This assertion arises in the context of a problem of knowledge handed down from Plato: how is it that we seek to know what is unknown since, if it were wholly unknown, we would not know to seek it and if it were already fully known, there would be nothing to seek. And this problem, in turn, comes into Christian thought as eschatological tension between present knowledge and the beatific vision.
Aquinas' discussion of fides (faith) and ratio (reason) operates against this eschatological background, positing that both faith and reason are present "dim anticipations of the final vision of glory," which is, in turn, a fuller participation in the very life of God himself (36). While this problematizes the relationship between faith and reason (and makes any absolute distinction impossible), it is, for Aquinas, merely a reflection upon the doctrine of creation.
In the Summa Theologiae, as Milbank and Pickstock point out, Aquinas proceeds from his discussion from God's being, simplicity, and goodness into a discussion of God's presence to his creatures. He quotes Dionysius that, while there is nothing "outside" of God, God somehow exists "outside of himself," present to himself, thereby, in this impossibility, externally pre-containing space for a creation that is both absolutely "other" than God, but also participating in God. Elsewhere Aquinas explicates this further in terms of the eternal uttering of the divine Logos by the Father in the Spirit.
Aquinas also states that the presence of God to his creatures--a presence that is God himself--is most intensely present to the intellect where "he dwells as if in his own temple," only by grace. As Milbank and Pickstock interpret this, Aquinas is suggesting that "all creatures subsist by grace in the sense that they only subsist in their constant 'return' to full divine self-presence, while intellect simply is the consciousness of this return," grounding thereby the specifically human eschatology of deification as an ascent to God within an eternal divine descent and return (37-38).
There is much more to be said here. For Aquinas this basic theological notion of return within God--which is our deification through participation--only comes to be unfolded in light of the Trinity, history, Incarnation, atonement, liturgy, and sacraments. And it is here that Christ can be seen as "the realization of the human telos which is only here shown, beyond humanity" (59). But more on that later.
I suspect these points also intersect with our earlier discussions of forgiveness and reconciliation, particularly in connection with participation and atonement. David Bentley Hart had a remarkable essay on Anselm's atonement theology in this light, entitled "A Gift Exceeding All Debt" and which appeared in Pro Ecclesia. Perhaps this can also enter into the discussion.