The roots of Christian doctrine extend back to God's revelation in the Old and New Testaments. In the early centuries of the church, apologists defended Christian beliefs. Ecumenical councils affirmed the Trinity and theologians fleshed out these beliefs.
True systematic theology owes its origin in large part to Peter Lombard (AD 1100–60). Educated at Rheims and Paris, Lombard rose through the ranks to become professor at the cathedral school of Notre Dame. He came into contact with Hugh of St. Victor and Peter Abelard, leading theologians of that era. Lombard wrote commentaries for classroom instruction that earned him respect among his peers. His reputation as a scholar and teacher led to his becoming bishop of Paris in 1159, shortly before his death.
His earlier commentaries—called glosses—consisted of passages from the Psalms and the Pauline letters interspersed with extensive notes from medieval thinkers. As theological studies developed in the twelfth century, however, scholarly attention went beyond glosses to focus on theological method: how to identify the topics to be studied and how to organize them into a coherent whole; how to utilize reason in conjunction with biblical texts; and how to handle theological authorities (especially when they conflict with one another). While Lombard contributed little in original material, his most famous writing fulfilled the tasks necessary for systematic theology as a discipline. Drawing upon his vast knowledge of earlier theologians—from Augustine in the West and John of Damascus in the East—Lombard compiled his material into a coherent whole in his Four Books of Sentences.
In constructing his Sentences, Lombard confronted a crucial decision. Would he follow the model of Hugh of St. Victor, who constructed a historically ordered theology consistent with the biblical narrative? Or would he venture into the new, speculative territory mapped out by Abelard? Hugh's theological treatment concurred with orthodox teaching extending back to Augustine. Abelard, on the other hand, proved innovative, as indicated by his Sic et Non (Yes and No), wherein he juxtaposed conflicting citations from the fathers, leaving the task of resolving the differences to the reader. At a minimum, Abelard's method sowed seeds of doubt that any genuine unity of thought was possible in Christian doctrine. Though not ignoring Abelard's use of reason, Lombard in the preface of the Sentences decisively anchored his method to the "sacred page" of Scripture. Lombard's arrangement of theological topics would be faithful to the Bible and previous church teaching.
The four books marked four divisions in his theology. Book I dealt with the Trinity—the unity of the Godhead, the distinction and equality of the three persons, and topics such as providence, predestination, and evil. Book II explored creation, including the origin of the universe, the existence of angels, the fall, and the effects of original sin. Book III investigated the incarnation, the hypostatic union, Jesus' redeeming work, and the Christian virtues. Book IV probed the sacraments, the resurrection, and the future judgment.
What distinguished Lombard's work was its sheer bulk and thoroughness— each book was divided into "distinctions" (more than forty in each book); Distinctions, in turn, were divided into chapters. Significantly, Lombard resolved inconsistencies among his sources. He repudiated some previous sources, and his schema proved compatible with biblical texts. Summations arrived at orthodox conclusions consistent with biblical content. In some instances, Lombard did not resolve conflicting opinions and claimed that the matter lay beyond reason's capacity to comprehend. In so doing, he left some issues open for succeeding thinkers.
The Sentences solidified Lombard as the leading theologian of his day. His system was the first to declare seven sacraments. While not all concurred with his formulations, his stature as "Master of the Sentences" led to his work being the standard university text until Thomas Aquinas' Summa Theologica appeared a century later.
Lombard's staying power was manifested by Luther's citation of the Sentences to caution students against speculative philosophy such as Abelard's dialectical method. Calvin cited Lombard more than one hundred times in his Institutes, and W.G.T. Shedd, a nineteenth-century Calvinist, praised Lombard for his systematic method.
Lombard, therefore, established a systematic discipline that not only connected back to the earliest theological reflection of the church but continued to influence theological discourse into modernity.