1). Can you explain transubstantiation and the Real Presence?
I'll try. . .
Transubstantiation is a philosophical concept the Church uses to explain the Real Presence of Christ in the Eucharist. Trans means change and substance means what a thing is fundamentally. So, we hold that by the prayer and action of the priest, bread and wine are changed into the substance of the Body and Blood of Christ. As an explanation of the Real Presence transubstantiation is not dogmatic.* The Real Presence that results from the process we call transubstantiation is dogmatic.
The term "transubstantiation" comes out of an Aristotelian metaphysics introduced to Catholic theology by Thomas Aquinas. The term predates Thomas in theological use, but he made it popular by teasing out all its philosophical and theological implications. For example, he is able to explain how the substance of bread and wine are changed (what they are) but remain true in their accidents (how they are perceived by the senses).
Probably the most common confusion among Catholics is the use of the word "substance." Even a very quick review of the history of this term will demonstrate that it has had a long and extraordinarily complex history. In modern English, we use the term to mean "stuff" or "materiality." Think of "substance abuse" or "an unidentified substance was found at the crime scene." This is not its meaning in metaphysics. In transubstantiation, "substance" refers to the basic nature of the bread and wine/Body and Blood, i.e. what a thing is most fundamentally. What bread and wine are most fundamentally is changed into what Christ's Body and Blood are most fundamentally.
When we teach the Real Presence of Christ in the Eucharist, we mean that Christ is substantially present under the appearance of bread and wine. Typically, we use the phrase "sacramentally present." In an effort to defend the Real Presence, some have said that "Real Presence" means "physically present," i.e. present in such a way that the consecrated elements can be chemically analyzed to produce DNA or blood type. Rather than being a defense of the Real Presence, this is actually a capitulation to material science. How? By defining the "really Real" as material. There are things in Catholic theology that are real yet not materially verifiable: God, angels, souls, etc. We do not have to surrender the Real to material science in order to understand reality.**It is far greater and more complex than the sum total of the physical objects and processes in nature.
The CCC 1374 teaches: In the most blessed sacrament of the Eucharist "the body and blood, together with the soul and divinity, of our Lord Jesus Christ and, therefore, the whole Christ is truly, really, and substantially contained." "This presence is called 'real' - by which is not intended to exclude the other types of presence as if they could not be 'real' too, but because it is presence in the fullest sense: that is to say, it is a substantial presence by which Christ, God and man, makes himself wholly and entirely present." [The two quotes are from Thomas and Pope Paul VI, respectively.]
When we teach the Real Presence of Christ in the Eucharist, we mean that Christ is substantially present under the appearance of bread and wine. Typically, we use the phrase "sacramentally present." In an effort to defend the Real Presence, some have said that "Real Presence" means "physically present," i.e. present in such a way that the consecrated elements can be chemically analyzed to produce DNA or blood type. Rather than being a defense of the Real Presence, this is actually a capitulation to material science. How? By defining the "really Real" as material. There are things in Catholic theology that are real yet not materially verifiable: God, angels, souls, etc. We do not have to surrender the Real to material science in order to understand reality.**It is far greater and more complex than the sum total of the physical objects and processes in nature.
The CCC 1374 teaches: In the most blessed sacrament of the Eucharist "the body and blood, together with the soul and divinity, of our Lord Jesus Christ and, therefore, the whole Christ is truly, really, and substantially contained." "This presence is called 'real' - by which is not intended to exclude the other types of presence as if they could not be 'real' too, but because it is presence in the fullest sense: that is to say, it is a substantial presence by which Christ, God and man, makes himself wholly and entirely present." [The two quotes are from Thomas and Pope Paul VI, respectively.]
Christ is present in the Eucharist "in the fullest sense." To restrict his presence to the merely physical is to deny the fullest of his true presence. No doubt my sharp commenters will point out that Pope Paul VI goes on to write with regard to the sacred species: ". . .beneath which Christ is present whole and entire in His physical 'reality,' corporeally present. . ." Very true. What is often left out of the quotation is the final phrase that defines what he means by "corporeally present." The rest of the sentence is ". . .although not in the manner in which bodies are in a place" (MF 46). Here the Holy Father is paraphrasing Thomas' teaching found in the Summa (III.76.5).
So, what does it mean for Christ to be corporeally present but not in the way that bodies occupy a place? Thomas writes in the Summa (III.76.1, ad 3): As has been already stated after the consecration of the bread into the body of Christ, or of the wine into His blood, the accidents of both remain. From which it is evident that the dimensions of the bread or wine are not changed into the dimensions of the body of Christ, but substance into substance. And so the substance of Christ's body or blood is under this sacrament by the power of the sacrament, but not the dimensions of Christ's body and blood. IOW, Christ physical presence is located within the spatial dimensions of the sacred species. Imagine your pastor praying the consecration prayer over the paten and chalice at Mass. . .BOOM!. . .now he has a full grown Jesus standing on his altar! This is not what "corporeally present" means. REMEMBER: "Real" is not limited to "material stuff."
We have to avoid two extremes in thinking about the Real Presence. First, we must reject the materialist/physicalist notion that the sacred species can be chemically analyzed to discover human genetic material. This is a failed defense against science that actually adopts the premises of the attackers. Belief based on evidence is not faith. Second, we must reject the "mere symbol" school of thought that reduces Christ's presence to being merely symbolic. As always, the Church takes the middle way: Christ is sacramentally present as a sign (not just a symbol) of God's real presence among us. Signs both point to and make present that which they signify.
* The Council of Trent teaches that the process of achieving the Real Presence of Christ is "suitably and properly called Transubstantiation" (XIII.4). IOW, if you don't like transubstantiation as an explanation for how the Real Presence is achieved, you have to come up with something else that entirely preserves the dogmatic elements of the Real Presence. There are other ways to explain the Real Presence, but they tend to fall short of the ideal. Also, it is important to note: the Church has never dogmatically taught a philosophical doctrine.
** "The presence of Christ's true body and blood in this sacrament cannot be detected by sense, nor understanding, but by faith alone, which rests upon Divine authority" (Summa III.75.1).