§ 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.’”
When the priest consecrates the bread and wine their appearance remains the same but their substance changes. Each species is no longer bread or wine but becomes in substance, which is to say in reality, Rabbi Yeshua’s body and blood, soul and divinity. This transformation of substance is called transubstantiation.
Transubstantiation indicates that through the consecration of the bread and the wine there occurs the change of the entire substance of the bread into the substance of the Body of Christ, and of the entire substance of the wine into the Blood of Christ—even though the appearances or “species” of bread and wine remain.
Father Hardon tells us, “A being whose essence requires that it exist in itself, an ens per se (a being by itself) or ens in se (a being in itself). It is commonly distinguished from an accident, whose essence is to exist in another, that is, in a substance.”
§ 245 The apostolic faith concerning the Spirit was confessed by the second ecumenical council at Constantinople (381): “We believe in the Holy Spirit, the Lord and giver of life, who proceeds from the Father.” By this confession, the Church recognizes the Father as the source and origin of the whole divinity. But the eternal origin of the Spirit is not unconnected with the Son’s origin: The Holy Spirit, the third person of the Trinity, is God, one and equal with the Father and the Son, of the same substance and also of the same nature. Yet he is not called the Spirit of the Father alone, but the Spirit of both the Father and the Son. The Creed of the Church from the Council of Constantinople confesses: “With the Father and the Son, he is worshipped and glorified.”
Let’s talk about substance. A paper napkin has a substance we might call “napkin-ness.” It exists to wipe our faces during or after a meal. A linen napkin also has the substance of napkin-ness. If a hostess invites us to dinner and puts at our place setting either a paper napkin or a linen napkin, both have the substance of napkin-ness so we accept either as appropriate. Now let’s introduce a paper towel. A paper towel has much more in common with a paper napkin than a linen napkin does. The paper towel and paper napkin are both used for wiping up food, and both are disposable. But if the hostess sets our table by putting a paper towel at our place setting we find it inappropriate. The paper towel can do the job but it doesn’t have the substance of napkin-ness.
Now let’s imagine that we “sacrifice” a paper napkin and a paper towel by setting each one on fire. Within a few moments both will become ashes. No one would wipe his face with the ashes, so we can say that both have completely lost their substance of napkin-ness. Now both have the same substance, which we may call “ash-ness.”
But where the ashes have lost all value by being transformed in their substance, the Holy Eucharist becomes of infinite value. There is no more bread. No more wine. Only 100 percent pure Rabbi Yeshua’s glorified body!
“Things whose essence naturally requires that they exist in another being. Accidents are also called the appearances, species, or properties of a thing. These may be either physical, such as quantity, or modal, such as size or shape. Supernaturally, accidents can exist, in the absence of their natural substance, as happens with the physical properties of bread and wine after Eucharistic consecration.”