Aquinas's treatise on
transubstantiation in the Summa Theologica is one of the most famous of his writings,
in part because his analysis of the mystery has had a profound effect on subsequent
official teaching in the Catholic Church. What does it mean to say that in the Mass,
the bread and wine consecrated by the priest truly become the body and blood of Christ?
Aquinas begins his analysis of the Eucharist simply by asking whether the bread and wine truly
become the body and blood of Christ. Should we believe this? He notes first that Christ himself
in the Scriptures teaches that the Eucharist is his true body and blood and that this is the
universal understanding of the Catholic Church from the time of antiquity. In the institution
narrative, Christ says, "This is my body." And likewise in John 6, "Unless you eat my flesh and
drink my blood, you have no life in you."
Aquinas notes that Church Fathers like St. Ambrose of Milan and St. Cyril of Alexandria
are unequivocal in their assertion of the Eucharistic conversion of the bread and wine
into the body and blood of Christ. Furthermore, the teaching was confirmed in Aquinas's own age
by the Fourth Lateran Council, which used the term transubstantiation to describe the mystery.
So St. Thomas then argues that the Eucharistic real presence of Christ is not only something
revealed by God to be believed, but it's also most fitting. Why? Because it permits the Church to
enjoy a perpetual presence of Christ down through history among us that is tangible and concrete
so that we can dwell with Christ and he with us for the duration of our pilgrimage in this world,
both individually and collectively. The Eucharist also allows us to increase in faith
meritoriously, by believing in Christ and in his real presence. Most especially, the Eucharist is
a tremendous wellspring of grace because it is the very body and blood of Christ through which
he gives us a participation in his own charity and in the sacrificial mystery of the cross.
Aquinas then asks the question,
how is Christ present in the Eucharist? What is the kind of presence in question? In his answer,
he notes that there are two ways one can become present in a new way in a particular place.
One way is by a change of place as when one travels from London to New York. So one is
now locally present in New York. The other is when there is a change of substance, as
when you build a fire in a given place, so a new substance or reality is generated like a campfire.
Or when a child is first conceived and there is a presence of a new human being in utero.
The real presence of Christ
in the Eucharist does not derive from a change of place as if Christ were to leave the locality of
heaven and enter into a specific place where Mass is being said, like Tokyo or Seattle. That is an
absurd notion. On the contrary, Christ in glory remains physically unchanged and unaffected in
his glorified body, even as he becomes present in many Masses said around the world each day.
He is perpetually free from being manipulated or altered by what we do in the Mass. Instead then,
we must be talking about a change of substance, as when a fire begins to be present in a place
it was not previously. Of course, this is a mysterious supernatural presence,
not a mere natural reality like building a fire or conceiving a child. And the reality in question,
the glorified body of Christ in heaven, already exists and does not need to come into being.
But it is rendered present to us in a new location through the medium of the sacramental elements
without Christ being altered in himself.
This brings us to the topic of transubstantiation as such, which is the total change of the
substance of bread into the body of Christ and of the wine into the blood of Christ at the time
of the words of consecration. Christ comes to be present like the newly lighted fire you might say.
He's made present where he previously was not.
Aquinas brilliantly argues that transubstantiation is similar to natural generation on the one hand,
and to creation ex nihilo on the other, and also dissimilar from both. It is like natural
generation, where wood changes progressively into fire and ash, since one thing comes to be
where there previously was another. But in this case, the change occurs immediately and at the
very deepest level of the very being and essence of things. It's not a mere change of properties
or of material parts. It is like creation ex nihilo because God causes something to exist
in act by his sheer omnipotence as when God gives existence to the world in creating.
But it is also somewhat dissimilar, because
in creation ex nihilo, God causes something new to be from nothing. While in transubstantiation,
he causes something new to be from something else that previously was there. In other words,
God deploys his almighty power to change one thing into another. He simply changes bread into the
body of Christ. How can God do this? Aquinas notes that God can do it because he has infinite power.
In fact, it is a merely reasonable thing to admit that God can do something like this if he wishes
to. After all, he is omnipotent, so it is feasible for him and there's no logical contradiction
entailed by the action. In fact, it would be unreasonable to say a priori that God simply
cannot do it or that it is impossible.
We only know about the mystery of transubstantiation in faith by grace
enlightening our judgment, but that does not mean that the belief is somehow contrary to reason.
But what about the fact that the host on the alter looks like bread and has the chemical
properties of bread and the taste of bread and so forth? Aquinas notes that there is a real
distinction in all things between the substance and the nature of a given thing on the one hand,
and its properties or accidents, like it's quantity or qualities on the other.
For example, there is a distinction
between a human being as a unified substance, and his size, weight or hair color, which are
inherent properties. Normally a substance is indissociable from its properties, even if some
of them come and go. Can God however, change the very substance of bread into the body of Christ
while leaving the physical properties of quantity and quality of bread present still in the host?
He certainly can if he wishes. The action entails no logical or metaphysical contradiction. There
are no instances of this kind of action in nature, but that is part of the point. The Eucharist is
meant to provide us with a unique form of real presence. Christ's presence substantially under
the appearances or accidents of bread and wine.
In this case, why is the presence of Christ so seemingly hidden or discreet?
Why leave the accidents of bread and wine present and appear under them?
There are several good reasons. First, because the mystery of the Eucharist is accessible to us only
by the grace of faith, discovering his presence in this way has the advantage of nourishing
supernatural life in us. We are saved by grace, not by natural acquisitions of knowledge.
Second,
this mode of presence respects our capacity to engage with God freely. The Eucharistic
presence of Christ does not oblige us to enter into friendship with God against our will.
Finally, the accidents of bread and
wine that remain, symbolize effectively what the Eucharist is spiritually, food for the journey,
and an effective source of perpetual spiritual refreshment. These signs indicate that the
Eucharist is the sacrament of charity. It sustains and nourishes the Church in the love of Christ.
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