1. Historically, various denominations espouse some version of the real presence. Some denominations (Lutheranism, Roman Catholicism, Eastern Orthodoxy) are committed to it while others (Anglicanism) allow for it.
Some theological traditions attempt to be more specific about how and what is. In Catholicism, Aquinas gave the classic formulation, which was codified at Trent. However, some 20C Catholic theologians (e.g. Karl Rahner, Edward Schillebeeckx) proposed alternatives.
Although traditional Catholics regard them as heretical, their alternative views on the eucharist were never officially censured (to my knowledge).
In Lutheranism, Martin Chemnitz provided the classic formulation in his monograph on The Lord's Supper. For a more up-to-date summary, see David P. Scaer's contribution to Understanding Four Views on the Lord's Supper (Counterpoints: Church Life).
You also have theologians who take a more eclectic, mediating position, viz. Myk Habets, Theosis in the Theology of Thomas Torrance.
Conversely, there are Christians who affirm the real presence, but resist detailing the mechanics. They relegate that to mystery and miracle.
Whether that's successful I'll address momentarily.
In this post I'm not going to evaluate historical positions. I just mention them for background.
2. Just as a matter of logical options, it seems to me that the real presence reduces to one of two different claims:
i) The (consecrated0 communion elements are the body of Jesus
ii) The (consecrated) communion elements contain the body of Jesus
Put another way:
i) The (consecrated) communion elements are other than bread and wine
ii) The (consecrated) communion elements are more than bread and wine
According to (i), the communion elements cease to be bread and wine. According to (ii), the communion elements remain intact, but there is now something over and above the communion elements.
I think models of the real presence come down to variations on either of these two claims.
3. There are roughly two components to the real presence:
i) A dichotomy between appearance and reality
ii) The underlying reality
According to the real presence, the appearance of the bread and wine is illusory, in part or in whole. By "appearance," I don't merely mean visually, or what we can see with the naked eye.
I mean in reference to the primary and secondary properties generally. The true body is empirically indetectable, whether by sight, taste, chemical analysis, &c.
As such, the theory of the real presence requires God to create an illusion. In principle, there are different ways this could be produced. Take science fiction scenarios about telepathic aliens who make people imagine things that aren't there, or fail to perceive things that are there.
BTW, I'm not being facetious. I'm taking the implications of the real presence seriously. This is what an adherent is committed to. It has an illusory dimension.
I think this component of the real presence is coherent. It's possible for God to do that. That's because this aspect of the real presence concerns perception rather than reality. The more challenging aspect of the real presence concerns the stipulated reality. Which brings me to:
4. In reference to the real presence, what is the "true body" of Jesus? What do the communion elements either become or contain?
Since the real presence stands in contrast to symbolic interpretations, since proponents accentuate literality, I think this must have reference to the physical body of Jesus. A complete human body.
This means that when a communicant consumes the wafer or sips the wine, he's ingesting the brain, teeth, eyes, ribs, liver, bladder, intestines, penis, hair, toenails, &c., of Jesus.
I'm not being sarcastic when I say that. That's what their theory requires of them. There's not much wiggle room. It boils down to two alternatives: either a "true body" or symbolism. Since proponents deny that Jesus is "spiritually" present, since they reject the symbolic interpretation, the "true body" must be the physical body of Jesus. A complete human body. What else could it be–given the demands of the theory?
I think some proponents make the real presence more palatable (pardon the pun) by studied vagueness.
5. This, in turn, determines what must happen at communion. What the theory amounts to. There are at least two metaphysical components:
How can a wafer be the body of Jesus, or contain the body of Jesus? If we take the claim seriously (it's a true body), then that suggests a process of miniaturization. After all, the dimensions of a wafer are far smaller than a human body. And the shape is completely different. A wafer is a small, flat, round object.
How can the wafer be the body of Jesus, or contain his body, unless his body is miniaturized?
In a way, it's even more daunting to ask how a liquid (communion wine in the chalice) can be, or contain, the body of Jesus. Are bodies of Jesus, in miniature, in the wine–like complex molecules?
I'm not making fun of the claim. I'm unpacking the claim. If it doesn't mean that, then in what respect is it the true body of Jesus?
I'm the moment I'm not discussing how that's possible. Rather, I'm discussing what is said to happen.
If a priest distributes communion to 200 worshipers, doesn't that entail 200 bodies of Jesus? Each wafer is (or contains) the body of Jesus.
Likewise, if one communicant after another sips the wine, is a body Jesus replicated anew each time the next communicant sips the wine? Are there an infinite number of true bodies swimming around inside the chalice? Might you inadvertently imbibe more than one?
Or is the true body duplicated one at a time for each communicant?
Once again, I'm not being flippant. The theory of the real presence simultaneously affirms something and denies something. What is the claim?
It seems as though the real presence entails the reincarnation of Christ. The repeated reincarnation of Christ. His body is multiplied every time the Eucharist is celebrated. If two communicants receive his body, then it can't be the numerically same body in each case, can it? Rather, it has to be copies.
6. From what I've read, adherents of the real presence ground it in one of two events:
i) Made possible by virtue of the Incarnation
ii) Made possible by virtue of the Resurrection
According to (i), the human nature acquires the divine attribute of ubiquity via the hypostatic union.
That's subject to two objections:
a) Divine omniscience doesn't mean God has literal spatial extension. It doesn't mean he's diffused through space. That he exists in every part of space. Rather, it's a picturesque metaphor for divine omniscience and omnipotence.
b) To say divine attributes are transferrable to the human nature is pantheistic. It erases the categorical distinction between the creature and the Creator.
According to (ii), the glorified body of Christ is hyperdimensional.
That's subject to three objections:
i) It rests on exegetically dubious inferences
ii) Adding spacial dimensions fails to solve the problem it posed for itself. The problem is not that his body has too few dimensions, but too many. It's a problem of scale. A 3D human body is too big for another human to swallow whole. To say the glorified body has even more dimensions aggravates rather than alleviates the problem.
iii) A hyperdimensional body isn't recognizably human. That's not what Scripture means by a human body.
7. At this point, adherents retreat into pious appeals to mystery and miracle. And that appeal has a legitimate place in Christian theology. But it's not unqualified.
i) On a classic definition of miracle, God can produce naturally impossible results by circumventing nature. If, however, God is working through a natural medium, then that limits the divine field of action. If God uses a natural medium, then he can only do what's naturally possible. He can do what's naturally impossible by simply bypassing the natural medium. But so long as the natural medium is instrumental to the result, that imposes a restriction on what he can do with it. Nature is finite. It has in-built constraints.
ii) According to the real presence, the communicant is receiving something essentially natural. The body of Jesus is a natural object. A physical organism. If it were supernatural, it wouldn't be a true body.
So you can't invoke a miracle to make the real presence go through.
iii) In theory, you could invoke a miracle of replication (see above). But that wouldn't solve the problem of scale.
In theory, you could invoke a miracle of miniaturization. But that's problematic on several grounds:
a) Consuming tiny bodies of Jesus is cannibalistic. Adherents of the real presence deny that communion is cannibalism.
b) To miniaturize a human body, you must shrink everything down. Everything must be scaled up or down to match everything else, viz. the heart in relation to cells, &c. You'd have to miniaturize cells.
But body systems designed to function at one scale can't naturally function at a very different scale. Consider the difference between insects and humans. Because insects are so much smaller, they have systems which work at their scale that couldn't work for a much larger organism, or vice versa. Take the circulatory system or oxygenation. The scale of an organism affects what is feasible, from an engineering standpoint.
You end up with a makeshift explanation that isn't consistently natural or supernatural.