Episode 3059: St Thomas Aquinas - Difference of Orthodox and Catholics by Sharon - Part 2

Eucharistic Theology
• Aquinas: Belief in transubstantiation the substance changes, though the accidents remain.
• The East: Often speaks of “mystery” without clear metaphysical explanation.
• Aquinas warns:
“The change which takes place in the Sacrament is one of substance, not of accidents.” (Summa, III, q. 75)
Overview of the Disagreement
At the heart of Eucharistic theology is a question both East and West affirm:
Is Christ truly present in the Eucharist?
Both traditions answer yes but the Western (Latin) and Eastern (Byzantine) traditions differ in how they articulate this presence.
Where the East appeals to mystery, the West, especially through St. Thomas Aquinas, uses precise metaphysical language rooted in Aristotelian philosophy to explain the mechanism of Christ’s Real Presence.
Aquinas: Transubstantiation Substance Changes, Accidents Remain
In Summa Theologiae, Part III, Question 75, St. Thomas Aquinas explains transubstantiation as the unique and miraculous conversion that takes place during the Consecration at Mass:
“The change which takes place in the Sacrament is one of substance, not of accidents.”
— Summa Theologiae, III, q. 75, a. 4
What does this mean?
Aquinas adopts Aristotelian metaphysics, distinguishing between:
• Substance: what a thing is in itself (e.g., the substance of bread is “breadness”)
• Accidents: the outward appearances—what can be perceived by the senses (color, taste, smell, texture, etc.)
In the Eucharist:
• At the moment of consecration, the substance of bread and wine is entirely changed into the substance of the Body and Blood of Christ.
• However, the accidents of bread and wine remain meaning it still looks, smells, and tastes like bread and wine.
This change is called transubstantiation, meaning a change of substance, not merely a symbolic shift or a spiritual indwelling.
Why is this important to Aquinas?
Aquinas stresses that the change must be of substance, because Christ says,
“This is My Body… This is My Blood.” (Luke 22:19–20)
He interprets these words literally, and thus, the change is not metaphorical or partial. Christ is truly, really, and substantially present whole and entire, Body, Blood, Soul, and Divinity under the appearances of bread and wine.
Anything less would undermine:
• The truth of Christ’s words
• The real sacrifice of the Mass
• The objective nature of the sacrament
The Eastern Perspective: Real Presence, but Emphasis on Mystery
The Eastern Orthodox Church affirms the Real Presence of Christ in the Eucharist but generally avoids the term “transubstantiation”, especially in the scholastic sense defined by the Latin West.
Instead, the East emphasizes:
• The mystery of the Eucharist: the change is real, but ineffable it cannot be fully explained or reduced to metaphysical categories.
• The use of terms like "metabole" (Greek for “change”) rather than transubstantiatio.
• A focus on liturgical language: In the Divine Liturgy of St. John Chrysostom, the priest prays:
“Make this bread the precious Body of Thy Christ… and that which is in this chalice the precious Blood of Thy Christ, changing them by Thy Holy Spirit.”
This invocation (epiclesis) is where the East often places the moment of change, in contrast with the West, which sees the change occurring at the words of institution (“This is My Body…”).
Aquinas’ Caution: Doctrine Requires Clarity, Not Ambiguity
While Aquinas acknowledges the mystery of the Eucharist, he insists on doctrinal clarity where divine truth is revealed. For Aquinas, the mystery does not excuse vagueness, especially when it concerns such a central mystery of the faith.
Thus, he warns:
• The Eucharist is not a symbol, nor a mere spiritual presence.
• The change is not a change of appearance (accidents), but a true ontological change a miracle beyond natural power.
• Denying this undermines the reality of Christ’s sacramental presence, the true sacrifice of the Mass, and the doctrine of the priesthood, which depends on the priest’s power to consecrate the Eucharist.
He writes:
“If in this sacrament there were only an accidental change of bread and wine, the body of Christ would not be truly present there, but only figuratively or symbolically… Yet this contradicts the truth of Christ’s words and the faith of the Church.”
— Summa Theologiae, III, q. 75, a. 2
Doctrinal and Liturgical Implications
In the Latin West (guided by Aquinas):
• Eucharistic adoration flourishes based on the certainty of Christ’s presence.
• Corpus Christi processions, tabernacles, and Benediction arise from a clear theological foundation.
• The Council of Trent later affirms Aquinas’ position as dogma, anathematizing those who deny transubstantiation.
In the Byzantine East:
• Mystery is emphasized more than metaphysics.
• There is less focus on adoration outside of the Liturgy.
• The Eucharist is revered, but not consistently approached with the same doctrinal precision as in Thomistic theology.
Mystery and Metaphysics in Harmony
Aquinas’ theology does not deny the mysterious nature of the Eucharist but seeks to safeguard and articulate what the Church definitively believes through the tools of philosophical precision. For him, transubstantiation is the only adequate explanation that both respects the mystery and preserves the truth of Christ’s promise and the Church’s faith.
In short: the mystery must be confessed, but it must also be clarified so that the faithful may believe rightly, worship rightly, and receive Christ worthily.