Explaining the Substantial Change of the Eucharist

The Eucharist might be the strangest of all Catholic beliefs.

For those of us who grew up with the faith, we also experienced our understanding grow from a childlike acceptance of Jesus’ hidden presence to a more mature spiritual insight of the Real Presence. But for those who do not have this upbringing, it can be very hard to understand.

The term for what occurs at the consecration that we Catholics use is “transubstantiation.” The language of transubstantiation is very much rooted in the philosophy of Aristotle. We learn from him that all material substances are a combination of form and matter. A chair, for example, is matter arranged in the the form of a chair. This chair can go through many material changes and still remain a chair. You can paint it, cause wear and tear, or add arms to it and it still remains a chair because its form has not essentially changed, even though the matter has. Think of yourself. You have changed significantly since you were a small child, but you are still the same person because your form (that is, your soul) is still what gives your person its sameness throughout all the changes.

But sometimes things go through substantial changes. If I take a chair and I throw it into the fire where it transforms into ash, then it has gone through a substantial change. It ceases to be a chair and it becomes a new substnace: ash. This is because it has lost its essential form or “chairness” and the matter left behind is now in the form of ash.
This is what occurs in the Eucharist. The form of bread and wine leave the substance and are replaced with Jesus Christ’s Body, Blood, Soul, and Divinity. The material properties all appear to be the same, but the form has changed, thus the change is a substantial change.

I remember back in college I had a discussion with a good friend of mine about the above explanation of transubstantiation. He insisted that a person should not have to become fluent in Aristotelean metaphysics just to come to some understanding of the Eucharist. The average person, he claimed, should not have to get a degree in philosophy in order to see the reason for the belief.

First, it should be said that the Eucharist is a mystery that we will never fully understand. Even a non-Catholic like CS Lewis understood that there was a deep mystery here when he wrote of Christ at the Last Supper, “The command, after all, was Take, eat: not Take, understand.” We will never be able to fully understand the miraculous event that occurs upon every altar at mass.

Second, he was correct in saying that you do not need Aristotle to come to a rational acceptance of the Eucharist. This Aristotelean definition is not found anywhere in the Scriptures. The Apostles and very early Christians all believed in the Real Presence without having to reference the ancient Athenian philosopher. There are many ways to approach some understanding of Eucharist. The Church has adopted much of the language of Aristotle because it has proven to be a useful way to describe the fact of the Eucharistic change.

Have said both of those things, it is still very helpful to know this in order to help non-Catholics understand what we believe about the Eucharist.

Recently I had a student who was having trouble understanding this sacramental mystery.

I said to my class that Catholics do not eat bread or drink wine at mass. The bread and wine cease to be bread and wine and instead turn into the Body, Blood, Soul, and Divinity of Jesus Christ.

“But it’s still just bread and wine, isn’t it?” she asked.

I responded with an explanation similar to the one above about form, matter, and substantial change. But she remained unconvinced.

“So,” she asked, “If I were to examine the Host scientifically, would I find that after the consecration it now has Jesus’ DNA?”

“No,” I replied, “That is not what happens.”

“Then I don’t see how you can say that the Eucharist is Jesus.”

To be perfectly candid, this question about Christ’s DNA in the Eucharist is one that I had never encountered. After years of teaching, I usually have a quick arsenal of answers to the commonly asked questions by my students. But I must admit I wasn’t sure how to answer. So, I did what I always do in situations like this: I prayed to the Holy Spirit. When I’m not sure exactly what to say, I put my trust in Him.

“There is more to you than just the material components of you, isn’t there?” I asked my student. “You are more than your physical parts. You have a soul or a mind don’t you?”


“And the same is true of me. But if I were to die, this material body would become a corpse. But the corpse isn’t me anymore is it?”

“What do you mean?”

“I mean that when someone dies, the body left behind isn’t fully them. We honor their body because of the unity it had with their soul, but the corpse isn’t the person. If it was still the person, we couldn’t bury the body or cremate the body, because we don’t do those things to persons. Does that make sense?”


“But if I die and we were to do a scientific examination of my corpse, whose DNA would it have?”

“Yours,” she replied.

“But even though it has my DNA, that corpse would no longer be me. That is because it is now a different substance because it has gone through a substantial change. My essential, invisible form (or soul) has left the matter. Even though the material body still has the sensible qualities of me, it isn’t me anymore. In the same way, the bread and wine go through a substantial change. All of the sensible qualities of the bread wine remain, but the essential, invisible form have left and been replaced by Christ.”

After a pause, here response was, “Catholicism is whack.”

Leaving aside the fact that I didn’t think anyone still used the word “whack” anymore, I actually couldn’t agree more. As I wrote in my last article, there is an essential strangeness to the Catholic faith that we should embrace. And this strangeness puts us in stark contrast to the world.

As I told this student as we finished this discussion, if Catholics are wrong about the Eucharist, then we are collectively dumber than a bag of hammers. That is because if we are wrong about the Eucharist, then we reverence a piece of bread as God. This would be essentially as ridiculous as worshiping a Ritz cracker.

But if the teacher is correct, then we are blessed beyond words. Because in the Eucharist, He Who the universe cannot contain, humbles Himself to be held in our hands and becomes one with us in Holy Communion. If that substantial change is real then we have a closeness with God that is too wonderful to ever understand.

Copyright 2021, WL Grayson

W.L. Grayson

W.L. Grayson

I am a devoutly Catholic theology teacher who loves a popular culture that often, quite frankly, hates me. I grew up absorbing every movie, TV show, comic book, science fiction novel, etc. I could find. As of today I’ve watched over 2100 movies and tv shows. They take up a huge part of my life. I don’t know that this is a good thing, but it has given me a common vocabulary to draw from in order to illustrate whatever theological point I make in class. I’ve used American Pie the song to explain the Book of Revelation (I’ll post on this some time later) and American Pie the movie to help explain Eucharist (don’t ask). The point is that the popular culture is popular for a reason. It is woven into the fabric of our lives and imaginations, for good or ill. In this blog I will attempt to bring together the things of heaven with the things of earth. Of course this goal may be too lofty for someone like me.

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