Chemnitz terms the first genus the genus idiomaticum. This is a genus that very likely could be agreed upon by most post-Chaceldonian Christians. According to this genus, the properties of both natures must be attributed to the total theandric person of Christ. In other words, because within his person Christ unites a divine and human nature, the idioms of both are attributable to his total person when considered in the concrete unity of the hypostatic union. Though Aquinas does not explicitly address the question of the validity of such an attribution, in light of the statements that we have already examined regarding the Incarnation, it appears that he would accept this genus.
The second category, the genus apotelesmaticum, represents the communication of activities within the hypostatic union. Due to the concrete unity of the person of Christ, it is possible to say that when the man Jesus died, the Logos died. Of course, the divine nature when considered in the abstract (that is, in itself, apart from the hypostatic union) can neither suffer nor die. Nevertheless, because of the unity of the person of Christ in the concrete, it is possible to say that things done or suffered by either nature are attributable to the person of Christ. In keeping with this, it is conversely possible to point to the man Jesus and say that he created the universe. Again, although the human nature was not present at the creation of the world, when considered in the concrete, Christ's humanity must properly be thought of from the perspective of its subsistence within the divine person of the Logos, who did create the universe.
Moreover, beyond the mere recognition of the unity of Christ's agency, the genus apotelesmaticum also has significant implications for the doctrine of atonement. Positing the unified agency of both natures within the hypostatic union entails the participation of each nature in the act of redemption. In this regard, Chemnitz states that the work of redemption ". . . pertains to the person of Christ not according to either the divine or the human nature alone but to both. And the person in carrying out these works possesses activities or operations in both natures and not only in one." Therefore, atonement is described as an event in which each nature plays its own particular role in concert with the other. Hence, the divine nature ". . . does not turn away from the suffering but permits the human nature to suffer and die, yet strengthens and sustains it so that it can endure the immeasurable burden of the sins of the world and the total wrath of God, thus making those sufferings precious before God and saving the world." Moreover, without its unity with an infinite, divine person, the human nature in and of itself would not represent a sufficient payment for the sins of the world. Chemnitz writes that ". . . there would not have been an adequate ransom . . . for sin and God's wrath, which are boundless evils. For this reason, therefore, the price is so great and the merit of the suffering and death of Christ [so great] that it is the propitiation for the sins of the whole world." Indeed, ". . . the creature [Christ's human nature] by itself could not have borne the enormous burden of the wrath of God which was owed for the sins of the entire world." For this reason, Chemnitz asserts that Christ is humanity's redemptive mediator according to both natures. Later the Formula of Concord would also reinforce this point.
As noted above, Chemnitz's emphasis on the unity of Christ's theanthropic agency is well in keeping with the tradition of late Greek patristic theology. For example, in On the Unity of Christ, Cyril of Alexandria writes:
Such things [hunger, suffering, etc.] would not be at all fitting to the Word, if we considered him nakedly, as if were, not yet made flesh or before he had descended into the self-emptying. Your thoughts are right on this. But once he is made man and emptied out, what harm can this inflict on him? Just as we say that the flesh became his very own in an economic appropriation according to the terms of the unification. So he is "made like his brethren in all things except sin alone (Heb 2:17).
Standing at the end of the development of Greek patristic Christology, John of Damascus states similarly:
For His flesh did not suffer through the divinity in the same way that the divinity acted through the flesh, because the flesh served as an instrument of the divinity. So, even though from the first instant of conception there was no divisions whatsoever of either form, but all the actions of each form at all times belonged to one Person, we nevertheless in no way confuse these things which were done inseparably . . . Christ acts through each of His natures and in Him each nature acts in communion with the other.
As we will see, in contrast to Chemnitz and the later Greek Fathers, in Aquinas we discover a very heavy accent on duality within Christ's divine-human agency.
 Chemnitz, 62-79; Preus, 171-213. Also see the discussion of the genus in the later Formula of Concord. FC, SD VIII.36 in Kolb and Wengert, 622. See a discussion of the historical development of the genus in the Lutheran scholastics in: Heinrich Schmid, The Doctrinal Theology of the Evangelical Lutheran Church, trans. Charles Hay and Henry Jacobs (Minneapolis: Augsburg Publishing House, 1961), 313-4.
 Chemnitz, 62-4; Preus, 173-4. "Sed proprietas uni naturae conveniens, communicatur seu tribuitur personae in concreto, hoc est, vocabulo non naturas ipsas, sed personam significante."
 Chemnitz, 80-7; Preus, 215-30. See discussion in FC, SD VIII.46-7 in Kolb and Wengert, 624.
 Chemnitz, 80; Preus, 216-7.
 This is consistent with Luther in his rejection of Zwingli's Christology. Luther writes in LW 41:103-104; WA 50:590:
Consequently Christ is God and man in one person because whatever is said of him as man must also be said of him as God, namely, Christ has died, and Christ is God; therefore God died- not the separated God, but God united with humanity . . . [similarly] whatever is said of God must also be said of man, namely, God created the world and is almighty; the man Christ is God, therefore the man Christ created the world and is almighty. The reason for this is that since God and man have become one person, it follows that this person bears the idiomata of both natures.
 Chemnitz, 80; Preus, 217. Chemnitz writes:
Secundo pertinet ad hunc gradum, etiam haec consideratio, Quando una in Christo naturaid, quod sibi proprium est, agit aut quando Christus secundum proprietatem unius naturae aliquid agit, quod tunc in illa actione seu passione, altera natura, non sit ociosa ve vel nihil, vel aliud agat, sed quod et hoc, quod unius naturae proprium est, fiat et agatur in Christo cum communione alterius naturae salva differentia illa, quod cujusque proprium est, vt quando Christus, humana sua natura patitur et moritur, quod et hoc fiat cum communione alterius naturae, non vt divina etiam natura in sese patiatur et moriatur, hoc enim humanae proprium est, Sed quia Divina Christi natura adest personaliter naturae patienti, ac vult illam humanae suae nature passionem, non avertit eam, sed permitit humanitatem suam pati ac mori, corroborat ac sustenteam, ut possit sustinere immensum illud onus peccati mundi, ac totius irae Dei, et efficit passiones illas, coram Deo preciosas, ac mundo salutares.
 Chemnitz, 80; Preus, 216.
 Chemniz, 52; Preus, 148.
 Ibid. The full passage reads:
1. Quia non suisset aequivalens λύτξον pro pecato et ira Dei, quae infinita mala sunt, sed inde ac ideo tantum est precium ac dignitata passionis ac mortis Christi, ut pro peccatis totitus mundi sit propirtiatio, quia filius Dei carne sua passus et mortuus est. 2. Quia nuda creatura non potuisset sustinere immensum onus irae Dei, totius mundi peccatis debitae.
 Chemnitz, 81; Preus, 215. "Ut persona Mediatoris nostri in utraq; natura , per et secundum utramque naturam, operaretur et efficeret ea, quae ad Redemtionem et salutem nostram pertinet."
 FC, SD III.4 in Kolb and Wengert, 562-3.
 Cyril of Alexandria, On the Unity of Christ, trans. John McGuckin (Crestwood, NY: St. Vladimir's Seminary Press, 2000), 107.
 John of Damascus, De Fide Orthodoxa 3.15, in Saint John of Damascus: Writings, trans. Frederic Chase (New York: Fathers of the Church, Inc., 1958), 311. Emphasis added.