I recently received the pleasure of a comment from someone who has been following this blog for a long time, a reader who uses the handle "Orthodox" ("O" for short). O doesn't necessarily represent Eastern Orthodoxy, but he does provide comments against the Reformed position.
O writes: "In too many places to list, Augustine says that the Eucharist IS Christ's body and becomes Christ's body. He doesn't say it becomes Christ's spirit."
Agreed, both as to Augustine saying that (though certainly not in too many places to list) and as to that being what happens. The Eucharist IS Christ's body and blood, and the bread, by being consecrated for the particular purpose, becomes Christ's body, while the cup (or more specifically its contents) become the blood of Christ.
They are not and do not become Christ's spirit and Augustine does not say so (which poses interesting problems for transubstantiation, but since Eastern Orthodoxy doesn't teach transubstantiation, that's not necessarily a problem for O).
Nevertheless, Christ is spiritually (or mystically, if you prefer) present in the sacrament. We don't derive this from the words of institution (this is my body etc.) but from other parts of Scripture. This spiritual presence does not imply any physical change in the elements, nor does it imply that Christ's spirit is somehow contained within the elements. When we feed on Christ (and we do) in the sacrament, it is not through the act of grinding our teeth and digesting the physical substances, but by faith.
O continued: "What would Augustine have to say to convince you, that is the question I have to ask. Anything that could be said in favor of our position, he did say."
As noted previously, there is no particular reason that the Eastern Orthodox view of the mystical presence needs to be set against the Reformed view (and Augustine's view) of the spiritual presence. What Augustine would NOT say if he held to transubstantiation were things like: "Christ deprived them of his bodily presence."
Positively, there are any number of ways that Augustine could have indicated that he meant that Christ was present in more than just a spiritual (or mystical) sense. He did not express himself in those terms, but instead made fairly clear comments to the contrary.
O concluded: "You say the argument is about bodily presence versus spiritual presence. Fine, Augustine says it is Christ's body, so you lose, end of discussion."
This is what I call the "weakest argument against the spiritual presence." As I have noted over and over again, even someone who views the sacrament is merely symbolic could use those expressions.
Even those who hold to a bare symbolic view of the Eucharist affirm that the bread is the body of Christ and the cup is his blood: they simply understand those terms analogically. Perhaps an illustration would help:
Imagine boys playing capture the flag in the woods: there are two teams, the red team and the blue team. The boys from the red team huddle around in a small circle, while their leader draws a map in the dust. "This rock," says the leader, "is Blue's camp. "And this stick," he continued, carefully placing a slender branch next to the rock, "is the creek."
Now, who in their right mind would think that the leader meant that the rock was transubstantiated into the Blue team's base, and who would think that the leader transmogrified the stick into a creek? No one would think that. Everyone would correctly understand that a symbolic sense is intended by the expression "This rock is Blue's camp" and "this stick is the creek." But for some reason (tradition!) people have trouble recognizing the obvious fact that "this is my body" and "this is my blood" were similar statements that shouldn't be understood transubstantially but according to their most obvious sense: representatively and analogically.