Besides pieces of his commentaries on books from the Old and New Testament, we have fragments or notices of his writings on various topics. Chief amongst these, and first in point of time, was his treatise in fifteen books, on the Incarnation. According to Gennadius ("de Vir. Ill." 12) it was directed against the Apollinarians and Eunomians, and written while the author was yet a presbyter of Antioch. Gennadius adds an outline of the contents. After a logical and scriptural demonstration of the truth and perfection of each of the natures in Christ, Theodore deals more at length with the Sacred Manhood. In book 14, he discusses the subject of the Trinity and the relation of the creation to the Divine. Large fragments of this treatise have been collected from various quarters. None of the remains of Theodore throw such important light upon his Christology.