The Lombard may seem like a bit of an odd choice. He’s certainly not one to be charged with originality. However, no work was more influential in shaping medieval theology than his Sentences. He also serves as a prime example of traditional orthodoxy and is particularly clear and consistent with his terminology. Additionally, I believe the depth of his thought has been underappreciated.
Peter’s key source was Augustine, so there’s a high level of agreement between the two. Particularly noticeable is their unwavering commitment to divine unity, with no subordination and the insistence that all three members of the Trinity participate in every action by any member. The only distinction between persons is in how they relate to one another, with the Son being eternally generated from the Father.
Christology is discussed in a systematic fashion in book 3 of the Sentences. He has major sections on the incarnation, soteriology, and the virtues, presenting a well-rounded doctrine focusing on ontology and activity. At this point we will focus on ontology and in a later paper cover activity more thoroughly. Jesus possessed both divine and human natures, united in partnership from birth. Peter spends a lot of time defending this unity as opposed to a divinization of Jesus’ human nature because he felt that divinization would, in effect, deny the humanity of Jesus or allow one to distinguish between divine and human natures. When the Son took on human nature he took on its defects, but not its faults. This way he could deal with the problem of sin without bearing any guilt. Also, his human nature became enlightened via contact with his divine nature so that he did not fall prey to the fault of ignorance. In the process of making this argument he walks a tightrope because he cannot have the possibility of sin or distraction from God caused by suffering or any other experience in the human body or jeopardize the impassability of God. Thus Christ truly experienced suffering and pain but not to the point where it ever drew him away from communion with God. Human emotions were experienced but not succumbed to. It was something that Christ’s divine nature allowed him to rise above. Jesus’ ultimate exultation is a recognition of the fact that, as a man, he was God (i.e., he possessed divine nature).
There is no extended discussion of Jesus’ status as Messiah or king in the Lombard. We do get a discussion of his role in judgment. In his glorified human form he executes judgment on the last day, as the representative of the triune God. He also seems to imply that a glorified human form is not the ultimate form of the Son. This is a kingly action, and presumably Peter understood it as such, but it is not made explicit.
 If one wants to read up on what I’m skipping, I recommend Uthemann 2007.
 His orthodoxy on the humanity of Christ was challenged, however, I agree with Rosemann 2004 pp. 131-33 and Colish 1994 pp. 423-25 that those challenges were misguided. He doesn’t seem to deviate from traditional orthodoxy. Any difficulties I pose are difficulties for the mainstream Christian tradition as a whole. On his terminological clarity, see the praise of Colish 1994 pp. 398-99.
 Sentences 1.XXV.3, 1.XXXI, 3.IV.1. Rosemann 2004 p. 91.
 Sentences 1.XXVI.2, 3, 1.XXVII.2, 3. Rosemann 2004 pp. 84-85. This extends to Christological titles as well, like Image and Word. They are taken to express how the Son relates to the Father and nothing more. See Sentences 1.XXVII.3, 1.XXXIII Sentences 3.I.2, 3.III.1. Rosemann 2004 pp. 122-26. See also Sentences 3.XIII.1 where the Lombard’s total commitment to full divinity from birth causes him to deny growth in wisdom as Jesus grew. This seems more in line with the portrait of the apocryphal gospels than the canonical ones. This view also subtly differs from Augustine’s theology of mixture of natures. See Colish 1994, p. 418.
 Colish 1994 p. 426.
 Similar to Augustine, Mary’s virginity is important at this point. Sentences 3.III.4.
 Sentences 3.XV.1-4. This assumes that the human and divine natures were both present and united as the divine Son took on flesh. See Sentences 3.V-VII.
 This does lead him to a strange statement in 3.XV.4 where he denies that Christ was sorrowful because of his impending death but claims that Jesus was sorrowful “because of those who were going to be scandalized…” c.f., Mark 14:34. This is one of a few cases where the Lombard’s theology can’t make room for diversity of Scripture and he just explains it away. See Rosemann 2004 p. 136
 Sentences 3.XVIII.3.
 Remember, Father, Son, and Spirit always act in concert. Sentences 4.XLVIII.2. Colish 1994 pp. 712-13.
 Sentences 4.XLVIII.2, Rosemann 2004 p. 187.