Ivo was a prolific writer but is most known for his canonical works: the "Decretum" of seventeen books; the "Tripartita", of very substantial material, divided in three parts, and attributed to him; and the "Panormia" of eight books attributed to him. All three are primarily works of canon law and center on the principle of "caritas", that is, the Catholic theological virtue of charity, as taught by Paul of Tarsus. His works are replete with treatments of charity and dispensation in a pastoral manner regarding the Holy See. He thought that "caritas" was the solution for sin, and not harsh punishment without contrition. This theme is most evident in his Prologus, which is most often compared to the teachings of the Church Fathers than those of the scholars of his day. Paul's message of loving one's fellow man as one would himself is particularly prevalent in Ivo's works: "He was called to teach. His lesson was love. It was all that mattered.".