One of the more perplexing questions of Christian theology is how, if at all, man is made righteous by the death, resurrection, and ascension of Jesus Christ. Perhaps more than any other issue, this question reveals the fault lines between the Protestant Reformers and everyone else.
For Calvin, the question lurks behind the issue of how man retains the image of God. While critiquing Osiander’s view of the issue, he writes:
“Therefore we must take it to be a fact that souls, although the image of God be engraved upon them, are just as much created as angels are. But creation is not inpouring, but the beginning of essence out of nothing. Indeed, if the spirit has been given by God, and in departing from the flesh returns to him, we must not forthwith say that it was plucked from his substance. And Osiander, while carried away with his own delusions, has in this matter entangled himself in an impious error; he does not recognize the image of God in man apart from essential righteousness, as if God were unable to make us conform to himself by the inestimable power of his Spirit, apart from Christ’s pouring his own substance into us…And when Paul discusses the restoration of the image, it is clear that we should infer from his words that man is made to conform to God, not by an inflowing of substance, but by the grace and power of the Spirit.
Calvin leaves articulating how the Spirit and humans interact to its proper place in the Institutes–Book III, where he deals again with Osiander–which is mildly disappointing given the unclarity surrounding how grace is given. If not a substance, then what?
For Aquinas,the answer is clear:
“Now the gift of grace exceeds every capacity of nature, since it is none other than a participation of the divine nature, which exceeds every other nature. It is therefore impossible for any creature to be a cause of grace. Hence it is just as inevitable that God alone should deify, by communicating a sharing of the divine nature through a participation of likeness, as it is just as impossible that anything save fire alone should ignite.”
I’m going over my head here, but it strikes me that Aquinas’ formulation of grace’s effect on the soul ties the Divine and Human together so closely that the human is nearly negated entirely. Perhaps Aquinas saw this coming: his response to the first objection is an explicit defense of the necessity of Christ’s humanity for salvation.
Regardless, Calvin has no such problem. In the act of salvation, the human remains human and the divine, divine. Calvin’s reference to creation is, I think, telling: the new creation is a (re)forming of an essence by an outside agent (who dwells within), rather than an infusion of a substance. What God has left divided let no man join together.