The Self-Donation of God, chapter 9:
"The genus majestaticum posits that Christ's humanity possesses by communication the fullness of divine attributes when considered in the abstract. Chemnitz describes the genus thus: “so that when we speak of these matters in the schools we can be correct not only in calling Christ a man or saying that the Son of Man makes alive, but also we can then rightly speak in the abstract or in abstract language of the assumed nature as being united with the Logos. We can say that the flesh of Christ, which is united with the Logos, makes alive and that the blood of Christ cleanses from sin.” Vainio comments: “[t]he third genus . . . refers to the supernatural gifts and attributes Christ’s human nature receives in the hypostatic union. Since God’s attributes and essence are inseparable, these supernatural gifts and attributes are God’s essence.”
Gerhard observes that there was a difference between Lutheran theologians of the second generation as to whether one should speak of the glory of God communicated to Christ's human nature in the abstract. Some thought it was proper (notably Chemnitz and Johannes Brenz) others did not (notably Tileman Heshusius). Gerhard comments that this was ultimately a logomachy and not based on any substantive disagreement about the genus. Some claimed that considering the human nature in the abstract entailed thinking of only the essential attributes of his humanity. Therefore, since it was improper to say that divine attributes had been communicated to the human essence (this would entail the heresy of Eutyches, condemned by the fourth ecumenical council), it was not permissible to say that such glory had been communicated to the human nature in the abstract. Others disagreed and stated when a person considers the human nature of Christ in the abstract one must always think about it as it exists in the context of the hypostatic union. To be more exact, because the human nature is anhypostasis, it has never existed and never will exist, except in the concrete unity of the person of the Logos. It therefore follows that it must always be thought of as possessing the fullness of divine glory, because even when considered in the abstract the human nature was still the human nature of the Logos. This latter answer seems more satisfactory for of number reasons. First, terminologically speaking, it creates space for a clearer linguistic distinction between the genus majestaticum and the genus idiomaticum. Secondly, as we shall see below, it more closely replicates the Bible’s own manner of speaking about Jesus. This being said, it should be observed that the other position is technically speaking not incorrect, simply less terminologically precise.
In insisting on the full communication of glory to Christ's humanity, it should be observed that Chemnitz is not positing transmuting of humanity into divinity. Throughout the sixteenth and seventeenth centuries (as it is at present in many circles) this was a common charge of those among the Reformed communions who rejected this genus. As we noted earlier, both Calvin and Zwingli claimed that there was no communication of glory to Christ’s humanity and therefore his body was confined to heaven. From their perspective, since Lutherans believed that Christ’s possessed the fullness of divine glory and could exercise that glory by being present in many places at once (most notably in the Lord’s Supper) they must logically believe in the transmutation of Christ’s humanity into his divinity. Working from Chemnitz’s definitions, it is easy to observe that this charge is utterly without merit. The Lutheran claim is not the human essence is somehow mixed with the divine nature. Rather, the human possesses divine glory by communication within the personal union brought about by the Incarnation."
The Self-Donation of God, chapter 10:
"Although some theologians (notably Werner Elert and Wolfhart Pannenberg) have criticized this schema of the threefold office (triplex munus) first introduced into Lutheranism by Johann Gerhard, it is necessary for understanding the work of Christ. First, as we have shown in our extensive exegesis in the preceding chapters (which we will not repeat here), the threefold office of Christ is thoroughly biblical and is not something arbitrarily imposed on the text of Sacred Scripture. In fact, as we have seen, this schema is used repeatedly not in just a few biblical texts, but is pervasive throughout the New Testament and prophetic writing of the Old Testament. Because of its presence in the Old Testament, the Second Temple Jewish expectation of multiple Messiahs to fulfill these multiple offices makes a great deal of sense. Secondly, because Christ fulfilled the threefold office given to Israel and Adam, the threefold office is also useful for emphasizing the unity of God's works within the new and old creations. Just as God established human vocation in the beginning with Adam as the protological prophet, priest, and king, so too he elected prophets, priests, and kings in biblical Israel. Through the prophets he promised a coming Messiah would fulfill all these roles and that creation would be renewed through him. Finally God sent forth his Son to fulfill these vocations and bring about redemption. Recognizing this unity of divine agency in creation and redemption is useful for staving off the ever present threat of latent Marcionism.
Lastly, humanity is redeemed by Christ's fulfillment of the law through his active and passive righteousness. The law is not an abstract standard, but is fulfilled by human moral agents within concrete vocation within the created order. Therefore in order for the law to be fulfilled, Christ had to take up the human vocation as it had been established at the beginning of creation. Since the law is in fact identical with God's desired structure for the created order, fulfillment of the law by Christ as a divine-human agent is identical with the renewal and recreation of the world. Since the old structure of creation was mangled, it was necessary to recreate the world by a re-actualization of its original narrative and structure. If Christ were merely a man, his activity of fulfilling the law could not do this. Humans are not capable of creating anything by their actions, even if performed in obedience to God’s will. Nevertheless, since the activity and presence of the humanity of Jesus are identical with the divine person of the Logos, his human actions in fulfillment of the law were infused divine power and glory. By this human obedience, he did what only God could do and renewed creation. In order to accomplish this, Christ took over and fulfilled the offices of Adam, the protological prophet, priest, and king."
"Although some theologians (notably Werner Elert and Wolfhart Pannenberg) have criticized this schema of the threefold office (triplex munus) first introduced into Lutheranism by Johann Gerhard, it is necessary for understanding the work of Christ. First, as we have shown in our extensive exegesis in the preceding chapters (which we will not repeat here), the threefold office of Christ is thoroughly biblical and is not something arbitrarily imposed on the text of Sacred Scripture. In fact, as we have seen, this schema is used repeatedly not in just a few biblical texts, but is pervasive throughout the New Testament and prophetic writing of the Old Testament. Because of its presence in the Old Testament, the Second Temple Jewish expectation of multiple Messiahs to fulfill these multiple offices makes a great deal of sense. Secondly, because Christ fulfilled the threefold office given to Israel and Adam, the threefold office is also useful for emphasizing the unity of God's works within the new and old creations. Just as God established human vocation in the beginning with Adam as the protological prophet, priest, and king, so too he elected prophets, priests, and kings in biblical Israel. Through the prophets he promised a coming Messiah would fulfill all these roles and that creation would be renewed through him. Finally God sent forth his Son to fulfill these vocations and bring about redemption. Recognizing this unity of divine agency in creation and redemption is useful for staving off the ever present threat of latent Marcionism.
Lastly, humanity is redeemed by Christ's fulfillment of the law through his active and passive righteousness. The law is not an abstract standard, but is fulfilled by human moral agents within concrete vocation within the created order. Therefore in order for the law to be fulfilled, Christ had to take up the human vocation as it had been established at the beginning of creation. Since the law is in fact identical with God's desired structure for the created order, fulfillment of the law by Christ as a divine-human agent is identical with the renewal and recreation of the world. Since the old structure of creation was mangled, it was necessary to recreate the world by a re-actualization of its original narrative and structure. If Christ were merely a man, his activity of fulfilling the law could not do this. Humans are not capable of creating anything by their actions, even if performed in obedience to God’s will. Nevertheless, since the activity and presence of the humanity of Jesus are identical with the divine person of the Logos, his human actions in fulfillment of the law were infused divine power and glory. By this human obedience, he did what only God could do and renewed creation. In order to accomplish this, Christ took over and fulfilled the offices of Adam, the protological prophet, priest, and king."