The Eucharist and Divine Simplicity?

Q. 58: How can the Catholic doctrine of Transubstantiation be explained in a way that safeguards divine simplicity and fits a relational ontology?

There are two levels to the answer here. The first level offers a practical and theologically grounded response that can be shared without diving into advanced metaphysics. The second level outlines the deeper metaphysical grammar required for a fully systematic treatment. I’m not providing that full treatment here. Time and I don’t have bandwidth right now to go as in depth as the subject requires, it’s daunting. But the framework below gives the core distinctions and theological checkpoints that would guide such a deeper exploration. If someone wants to take up that task, the grammar is there to support a rigorous and faithful account.

First-Level Answer

At the moment of consecration, Christ “re-utters” His one, undivided divine-human act, and not as a repetition, but as a liturgical expression of the same self-giving that is always alive in Him as the Son. In this act, the substance of bread and wine is changed into His Body and Blood. The appearances, or accidents, remain so that our senses have a point of contact. Because God is simple, the communicant doesn’t receive a piece or fragment of Christ, but the whole Christ—Body, Blood, Soul, and Divinity.

The distinction between Person and Nature tells us it is the one divine Person of the Son whom we receive, in both His natures. The distinction between Substance and Accidents explains why the elements still look, taste, and feel like bread and wine, allowing for full, embodied participation without falling into physical cannibalism. So Transubstantiation doesn’t bypass simplicity or sidestep relational ontology. It gives visible, liturgical form to both.

This is simplicity, because in the Eucharist, the Son gives Himself as He eternally is: the full manifestation of the one simple divine essence, personally possessed and perichoretically realized without division. This is why the Eucharist isn’t a theological workaround. It is the concrete sacramental manifestation of a God who gives Himself entirely, without parts, without division, without ceasing to be who He eternally is.

Second-Level Framework: The Grammar of a Full Answer

A more thorough answer would need to show how a change of substance without a change of accidents coheres with:

(a) divine simplicity
(b) the classical metaphysical grammar (especially substance/accidents)
(c) the givenness of God’s relational selfhood

The theological distinctions that form the grammar for such a full answer include:

Substance/Accidents – As Trent teaches, the substance of the bread and wine truly vanishes, while the accidents remain. This keeps the Eucharist perceptible and participatory.
Form/Matter – The matter, what underlies sensible appearance, stays, but the form, what makes it bread, is replaced with Christ’s Body, which is already hypostatically united to the Logos.
Essence/Existence – Christ’s presence in the Eucharist is not a second instance of existence for the Logos, but the same divine-human essence now present sacramentally.
Creator/Creature and Act/Potency – Only God, as Pure Act, can effect this kind of transformation. Bread has no potency in itself to become God. The change is entirely wrought by divine initiative.
Divine Simplicity – Ensures that Christ is fully present under every particle. God does not divide Himself. He gives Himself entirely, because He is entirely simple.
Person/Nature – Clarifies who is present (the one divine Person of the Son) and what is present (His full divine and human natures).
Relation (Subsistent Relations) – Receiving the Eucharist is real personal communion. Through the Son, we are drawn into His relation to the Father in the Spirit.
Nature/Grace – Grace does not override nature here. Instead, ordinary food becomes the vessel through which divine life is offered to the communicant.
Analogy – The terms “Body” and “Blood” are real in substance but must be understood analogically. Christ is truly present, but not in a crude, physicalist sense.

To put this all together: the Eucharist reveals, not violates, divine simplicity. Christ’s self-gift is not a new act tacked onto His divine life but a sacramental form of the very same act He eternally is. The retained accidents function as a kind of bridge, as St. Catherine of Siena put it: “This is that tavern, which I mentioned to you, standing on the Bridge, to provide food and comfort for the travelers and the pilgrims, who pass by the way of the doctrine of My Truth, lest they should faint through weakness. This food strengthens little or much, according to the desire of the recipient, whether he receives sacramentally or virtually” (see her Dialogue, ch. 26).

Chalcedon’s formula, “without confusion, without division,” guarantees that Christ’s humanity is never separated from His divinity. So when we say He is present under the appearance of bread, we are not speaking poetically or symbolically. We mean that His full personal reality, human and divine, is truly there, under sacramental signs. That only makes sense if God is simple, not pieced together, not compounded, not subject to time. It is precisely this simplicity that allows Him to be wholly present, without remainder, wherever He gives Himself.

Act and potency, form and matter, substance and accident all help explain how this can be. But relation is what shows us why. Because the Son is eternally given by the Father and eternally gives Himself back, and because this giving can be extended into the created order, the Eucharist becomes the concrete site where divine simplicity and relational self-gift meet and are offered to us for participation.