I think some beliefs from the Catholic Church stuck with Calvin throughout his life. How could it not? One, as we've discussed, is the perpetual virginity of Mary. Even though there is overwhelming scripture that says otherwise, Calvin insisted on the Catholic interpretation. For one who put together such an elegant theology, his arguments are weak on this point. The Body and Blood of Christ in communion is another area where his past Catholicism stuck with him.
While all doctrine is important, to me some of these are "lower level" discussions than others. Far more important in my mind is understanding man's depravity and how we are totally lost without God's grace. Man is incapable of coming to a knowledge of God unless God so grants it. And God does not grant it to everyone, something that should give us pause.
But going back to the Body and Blood of Christ, I heard an interesting sermon by Sproul yesterday in which he stated some in the church believe blasphemy of the Holy Spirit is taking communion unworthily. Since I have never found a satisfactory answer for what precisely is blasphemy of the Holy Spirit, and I've never heard this before, I found it intriguing. Sproul pointed to Corinthians as his reference where people actually died for taking communion in an unworthy manner. I wondered if Calvin might have thought the same thing.
I thought that was rather interesting and underscores your point that, no matter what precisely the elements do or how/if they change, communion is to be taken reverently.
Calvin believed, as Presbyterians believe, that the Lord's Supper was more than simply a memorial; he believed that Christ was spiritually present in the sacrament which seems clear from Scripture. How could any Christian deny this?
But in no way did Calvin assert it was anything like what the Romanists believe. Far, far from it.
This perverse opinion, after it was once received, engendered numerous other superstitions. First of all comes that carnal adoration which is mere idolatry. For to prostrate ourselves before the bread of the Supper, and worship Jesus Christ as if he were contained in it, is to make an idol of it rather than a sacrament. The command given us is not to adore, but to take and eat. That, therefore, ought not to have been presumptuously attempted...43. OTHER ABUSES ARISING OUT OF AN IMAGINARY BODILY PRESENCE.