The doctrine of transubstantiation has two primary components:
- The real presence of Christ's body and blood
- The real absence of bread and wine.
One theory that attempts to avoid the Real Absence is impanation. Analogously to how Christ became a human, he now becomes bread and wine. But here is a curious fact about impanation. While it does hold that bread and wine exist after consecration, it has to say that the bread and wine cease to exist after consecration. In other words, the particular piece of bread and the particular sample of wine that were present before consecration cease to exist given consecration, and what we have after consecration is a new piece of bread and a new sample of wine. But if this is right, then impanation really doesn't help much with the two objections to Real Absence. We still have cessation of the existence of bread and wine. And while our sense that bread and wine are present is not mistaken, our sense that it's the same bread and wine as before consecration is mistaken. So impanation doesn't offer much of an advantage with respect to the objections.
But am I right? Does impanation imply that the old bread and wine are absent after consecration? I think so. First, consider the analogy with the Incarnation. The thought was that just as Christ came to be a human being, so too Christ came to be bread and wine. But the human being that Christ came to be did not preexist the incarnation. By analogy, the bread and wine that Christ came to be should not preexist the impanation.
Second, let's call the post-impanation bread B, and the pre-impanation bread A. Then B is Christ (just as the post-incarnation human, Jesus, is Christ). But identity is transitive. So if B is Christ, and A is identical with B, then A is Christ. Which is absurd. So the impanationist needs to deny that A is B.
But perhaps my arguments are a misunderstanding of impanation. For maybe the impanationist doesn't say that Christ becomes bread in the same way that Christ becomes human, but that Christ becomes bread in the same way that Christ becomes flesh. When Christ becomes flesh, there isn't a piece of flesh that is Christ. Rather, Christ comes to be a composite of flesh and soul. Now the analogy between impanation and incarnation forces the idea that there be a Y such that Christ comes to be a composite of bread and Y, analogously to his coming to be a composite of flesh and soul. But it is far from clear what Y would be.