Bringing you the "Good News" of Jesus Christ and His Church While PROMOTING CATHOLIC Apologetic Support groups loyal to the Holy Father and Church's magisterium
Home About
What's New? Resources The Church Family Life Mass and
Ask A Catholic
Knowledge base
AskACatholic Disclaimer
Search the
AskACatholic Database
Donate and
Support our work
Frequently Asked Questions (FAQs)
New Questions
Cool Catholic Videos
About Saints
Disciplines and Practices for distinct Church seasons
Purgatory and Indulgences
About the Holy Mass
About Mary
Searching and Confused
Contemplating becoming a Catholic or Coming home
Homosexual and Gender Issues
Life, Dating, and Family
No Salvation Outside the Church
Sacred Scripture
non-Catholic Cults
Justification and Salvation
The Pope and Papacy
The Sacraments
Relationships and Marriage situations
Specific people, organizations and events
Doctrine and Teachings
Specific Practices
Church Internals
Church History

Frank Bunne wrote:

Hi, guys —

  • What does the Church mean when it refers to the substance of blood?


  { What does the Church mean when it refers to the substance of blood? }

Mike replied:

Hi Frank,

Thanks for the question.

These previous postings and other web pages should answer your question.

If not, just come back:


Frank replied:

Hi Mr. Humphrey!

Thanks for your quick reply. I'm still confused! In one of your links someone wrote:

"The chemical structure of bread is not the substance, it is the accident."

I understand what accidents are, and I understand what the substance isn't, but I do not understand what substance is.

  • If I took away every accident of flesh, I would have the substance of flesh, but what is the substance of flesh?
  • I often hear that when the substance changes, the accidents remain the same, but what is the substance?

Accidents of flesh include its:

  • cells
  • DNA
  • its weight, and
  • its texture, but

  • What is the substance of flesh?
  • What is it exactly that I would be left with if I had a piece of flesh with no accidents at all?



Mike replied:

Hi Frank,

My colleague Paul may have a better answer than I, seeing he is a philosopher. I'm glided more by what the Church teaches and what Church history has told us.

That said, this article from New Advent on Substance may help:

This other article from Wikipedia may help as well:

In my words, the substance is "what keeps the object together".

Maybe Paul can do a better job of explaining this than I can.

The Catechism states:

1376 The Council of Trent summarizes the Catholic faith by declaring: "Because Christ our Redeemer said that it was truly his body that he was offering under the species of bread, it has always been the conviction of the Church of God, and this holy Council now declares again, that by the consecration of the bread and wine there takes place a change of the whole substance of the bread into the substance of the body of Christ our Lord and of the whole substance of the wine into the substance of his blood. This change the holy Catholic Church has fittingly and properly called transubstantiation."

By the way, please don't call me Mr. Humphrey; it make me sound old and I'm not even half way home, age-wise. : )

In my family, I'm called one of three names:

  1. ugly
  2. Uncle Michael, or
  3. Mike

I prefer ugly. : )


Frank replied:

Hi, Mike —

The links you sent were useful for describing what substance is in general, but they don't discuss what specifically the substance of blood is.

  • Doesn't there have to be a difference between the substance of wine and the substance of blood?

The only differences between wine and blood, that I can think of, are all accidents.

  • Blood has animal cells, wine has plant cells
  • blood has plasma, wine has alcohol
  • blood is useful to people needing transfusions, wine is not, etc.

But these differences are all accidental.

  • If I had a container of blood with no accidents, and a container of wine with no accidents, what would I notice that sets them apart from each other?
  • What makes blood different from wine, other than its accidents?
  • Doesn't there have to be a substantial difference?

That's what I mean by the substance of blood. You described substance as:

what keeps the object together.

  • What is it that keeps blood together, and what is the difference between that and what (usually) keeps the wine together?

I know this might be kind of irrelevant, but thanks for all your thoughts,


Paul replied:

Dear Frank,

Substance is an object's essence, what it is — its identity. It is an abstract immaterial concept, not a sensual concrete one.

The substance of blood is simply blood. That is what it is, the identity of the object. You are correct in stating that the accidents are all the attributes that describe or make up blood — its shape, its color, is viscosity, etc.; but substance is not something seen or experienced with the senses. It is simply a thing's whatness. So substance is what an object is while accidents are what it has.

So when transubstantiation occurs, all the accidents stay the same — all the physical traits and attributes of wine remain — but it is literally no longer wine. What it:

  • looks like
  • feels like
  • tastes like

has remained, but what it is has changed.

In our ordinary experience, we are used to the opposite occurring: when substance stays the same while accidents change.

  • When hair turns from black to grey, for example. It is still hair.
  • Or when trees go from being full of green leaves to being bare in the winter.
    It is still a tree.

Suppose you had the supernatural power to turn your brother into a cat. Your brother would walk on all fours, meow, have black fur, and chase mice. Yet, when you point to the cat you'd be pointing to your brother. The accidents are what you would find in a cat, but the substance is your brother.

Likewise with the Eucharist, the substance is Christ while the accidents are those you would find in bread or wine, so in Holy Communion, Catholics consume Jesus Christ, under the appearance of bread and wine.

In the posting Mike referred you to titled:

The key statement in the answer is this:

If we can change qualities without changing substance, God can certainly change substance without changing qualities.

In nature, qualities usually indicate substance but we can see that through a miracle of God, it does not contradict reason that a substance could be different from, or hidden in, the accidental qualities.



Frank replied:

Hi Paul,

I don't totally understand your answer. For one thing you said,

"The substance of blood is simply blood."

but I guess I'm not sure how it answers my question, because then I have to ask:

  • What is blood then?
  • What makes something blood, and what makes something that isn't blood, not blood?

If you can answer my question about what the difference between the substance of blood and the substance of wine is, I think I might get a much clearer picture.

I feel like the answer, the substance of blood is blood whereas the substance of wine is wine, which I thought of in consideration of your answer, is somehow incomplete. It seems to me like even a thing's whatness is accidental.

  • If I ask What is blood?, what would a good answer be? says blood is

  • The red liquid that circulates in the arteries and veins of vertebrate animals.

But all of that is accidental. I can't think of any answer to the question, "What is blood?" that doesn't rely on the accidents of blood.

I was also kind of unclear about your example of being able to turn my brother into a cat: the accidents change but the substance remains, my brother has whiskers and walks on all fours, but is still my brother.

  • Was it just to show the opposite of what is more common, the accidents staying the same but the substance changing?

In that case, if I had a supernatural power of turning my brother into a cat, it would be more like, he still spoke English, knew my mom's maiden name, and wore shoes, but nevertheless was no longer my brother at all, but a cat. That's what I don't get.

  • What is the substance of a cat?
  • If a cat doesn't necessarily have to have cat DNA, or meow, or have whiskers, then what is the difference between something that is a cat and something that isn't a cat?
  • If blood doesn't necessarily have to have a role in blood transfusions, or have plasma, or have blood cells, then what is the difference between something that is blood and something that isn't blood?



Paul replied:

Hello Frank,

If God turned you into a piece of bread you would still demand all the respect that is given to you now. That is because you would still be you, but with all the attributes of bread. This is why we kneel and pray to the Eucharistic Christ who looks like bread; it is His Real Presence.

Substance is the immaterial substratum or essence of an object. In the normality of nature, a substance is indicated by its accidents: if it feels, tastes, and looks like bread, it is probably bread.

If the Second Person of God can allow Himself to be essentially united to the human nature of Jesus, He certainly could intervene in His own creation to enable Christ to be substantially present in the Eucharist. God does not contradict reason (He cannot because, as St. John says in the first Chapter of his gospel, God is [Reason|Logos|Word]), in changing the substance of bread into Christ, while leaving all the accidents in place.

Because of this promise, this miracle, we can be confident that we are in the Real Presence of Christ. The identity of that which looks like bread after consecration is Jesus Christ Risen.


Frank replied:

Dear Paul,

I think I understand now. Thanks for giving my question so much of your focus; it's definitely a pretty multifaceted one, as I've seen.

Thanks a lot for all of your help and ideas.



Please report any and all typos or grammatical errors.
Suggestions for this web page and the web site can be sent to Mike Humphrey
© 2012 Panoramic Sites
The Early Church Fathers Church Fathers on the Primacy of Peter. The Early Church Fathers on the Catholic Church and the term Catholic. The Early Church Fathers on the importance of the Roman Catholic Church centered in Rome.