In reading Augustine we accompany the author on a private journey to a solution which he often finds by making a pioneering expedition into the territory, and where he sometimes strikes the unexpected. Gregory the Great was not a thinker of Augustine's sort. His mind was practical. He wanted to teach men how to live and to pray, and his theology is presented within a framework of spiritual and pastoral instruction. But in his way, Gregory presents us with something altogether more finished. His own theological and philosophical position is so clear and settled for him that he is able to assume it in his writing and preaching and direct his efforts to the task of teaching his flock to live a better Christian life on assumptions he holds to be absolute.

Augustine's struggle with the problems he discusses has borne fruit in a set of settled opinions for Gregory; his threads have become a closely-woven fabric. Much besides Augustine's achievement went into Gregory's picture of things: the decisions of the Council of Chalcedon (451) in particular gave him confidence that things were, doctrinally speaking, settled for all Christians for all time.