Isidore of Seville is one of the dominant contributors to the development of medieval Catholic theology. Sententiae, his major theological work, is arranged in three divisions or books. The first is a dogmatic part, presenting the doctrinal assertions of the Catholic faith. This is followed by two additional books, developing the moral principles and correct behavior necessary to attain eternal union with God, the highest good—summum bonum—who is the subject of the first assertion of faith in Book 1. The work presents a marvelously holistic view of faith and action, developing the relationship between the intellectual and moral, the individual and social life of the Christian believer, all in the context of eternal life. †