Chapter 8, “The Mystery of the Person of Christ, Part 4”
Genus Idiomaticum and Genus Apotelesmaticum
Note: In this chapter Kilcrease makes numerous reference to Latin words but his usage and spelling is not consistent.
Kilcrease continues to detail God’s gift in Christ as he deals with the way the two natures dwell together in God the Son. This interaction of the divine and human natures involves sharing various attributes, a doctrine called “communicatio idiomatum.” Much of the terminology used in these discussions was borrowed and modified from Greek philosophy. In the modification the terms took on significantly different implications. In the traditional view, the substance of “goodness” (my term) does not change. Neither does the substance of humanness. The two are united into one Christ. Both substances continue. Thus, in Christ, when Jesus does something, he remains fully God and fully man, even in his death and resurrection.
Kilcrease details a number of ways this has been misunderstood. Often there is a separation of the natures. Sometimes one is denied. Sometimes they are mixed, creating something which is neither God nor Man. The Lutheran Reformation tried to hold fast to this historical understanding of the two natures. This was important not only to guard doctrine but because the doctrines mattered in grasping the benefits of Christ’s work on our behalf.
As the chapter ends, Kilcrease gives a detailed example of this protection of doctrine by detailing a number of the arguments of Martin Chemnitz, showing how they applied to various objections current in modern theology.