Pieper, Francis. Christian Dogmatics: Volume 2. St. Louis: Concordia Publishing House, 1968.
“Lutherans and Reformed Use the Same Terms of the Third Genus in a Different Sense” Loc. 6014.
Pieper observes that the same terms may be used in different senses. “This is true, especially of such terms as “organ,” “official act,” and “personal union.” (Pieper 1968, Loc. 6014). Pieper begins exploring these terms. Luther began using the word “organ” to describe the human nature of Christ in performing his ἀποτελέσματα. This was the instrument used by God the Son to accomplish his work of salvation. The Lutheran view has been that in Christ the human nature is firmly joined to the divine nature, not like in other humans through whom God works, using a nature not joined to Him. The Reformed (Ibid., Loc. 6026) see “no difference between the organic relation of Christ’s human nature and the organic relation of merely human workers of miracles. “By ‘official act’ the Lutherans understand the joint action, or working, of both natures, so that every redemptive action of Christ is neither purely divine, nor purely human, but always theanthropic (actio). The Reformed, however, allege that the communion pertains not to the action, but to the result of the action” (Ibid., Loc. 6085). Scripture teaches that the activity, not just the result, comes from the divine nature working through the human nature.
Finally, Pieper points out that Reformed concepts of the union of God and Man in Christ is the same as with all believers (Ibid., Loc. 6144). This effectively denies all communication of attributes since it requires Christ to be, in fact, completely human at times and completely divine at times but never both.