B. The High Scholastic Doctrine of God: Theologians of the Thirteenth Century
Once scholastic theology has been arranged in a definitive form, such as Peter Lombard’s Sentences became for the thirteenth, fourteenth, and fifteenth centuries, theologians were able to examine more closely the individual subtopics of theology—Lombard’s “distinctions”—together with the issues proposed or adumbrated by those subtopics.
It would be difficult to underestimate the formal significance of Lombard’s work: not only did the Sentences provide the standard format for theological discussion for centuries, it also provided with this standard format a set of topics which, because of their order and coherence in virtually all basic lectures on theology, could be compared, contrasted, and constantly reworked by each succeeding generation of theological teachers.
The tradition of lecturing on the Sentences made possible a tradition of discussion that easily incorporated and brought forward for discussion the insights and problems of the theological tradition, whether ancient, more recent, or contemporary. This internal development of debate was not as apparent in the topics belonging to the prolegomena (including the doctrine of Scripture), granting that Lombard did not develop a preliminary discussion of theology and its principles in and for his Sentences, but it becomes quite apparent in the high scholastic doctrine of God.
Muller, R. A. (2003). Post-Reformation Reformed Dogmatics: The Rise And Development Of Reformed Orthodoxy; Volume 3: The Divine Essence And Attributes (p. 46). Grand Rapids, MI: Baker Academic.
To put Lombard into perspective, Alister McGrath (“Intellectual Origins of the Reformation”, p. 95) notes “in the first edition  of the [Institutes], Calvin tends to identify scholastic theology primarily with the writings of Gratian and Peter Lombard. Thus there are some 35 references to the Lombard in this edition, and no references whatsoever to any theologian of the fourteenth or centuries, irrespective of theological orientation.”
Additionally, Anthony N.S. Lane (“John Calvin: Student of the Church Fathers”, p. 44), says:
If the root cause of the decline of the church lies in the papacy, its theological fruit is to be found in scholasticism. Peter Lombard and Gratian both appear in Calvin’s ‘top ten’, but this does not mean he had any admiration for them. Peter Lombard’s Sentences was the standard textbook for theology and Gratian’s Concordia discordantium canonum played a similar role in canon law. Both were cited for evidence of the Roman teaching. Lombard was ‘eorum coryphaeus’, ‘eorum Pythagoras’ (their chorister, their Pythagoras). He is repeatedly attacked as the spokesman for scholasticism. But Calvin was also aware of the contrast between Peter Lombard and later scholasticism, and noted occasions where Lombard was sounder than his successors.
So Lombard was a focal point, good and bad, for discussions that followed, both in the Medieval years, and the early Reformation.