Twice in the course of the great discussion, he allowed himself to enter the field of doctrinal controversy, a field foreign to both his nature and his previous practice. One of the topics he dealt with was free will, a crucial question. In his De libero arbitrio diatribe sive collatio (1524), he lampoons the Lutheran view on free will. He lays down both sides of the argument impartially. The "Diatribe" did not encourage any definite action; this was its merit to the Erasmians and its fault in the eyes of the Lutherans. In response, Luther wrote his De servo arbitrio (On the Bondage of the Will) (1525), which attacks the "Diatribe" and Erasmus himself, going so far as to claim that Erasmus was not a Christian. Erasmus responded with a lengthy, two-part Hyperaspistes (1526–27). In this controversy Erasmus lets it be seen that he would like to claim more for free will than St. Paul and St. Augustine seem to allow according to Luther's interpretation. For Erasmus the essential point is that humans have the freedom of choice. The conclusions Erasmus reached drew upon a large array of notable authorities, including, from the Patristic period, Origen, John Chrysostom, Ambrose, Jerome, and Augustine, in addition to many leading Scholastic authors, such as Thomas Aquinas and Duns Scotus. The content of Erasmus' works also engaged with later thought on the state of the question, including the perspectives of the via moderna school and of Lorenzo Valla, whose ideas he rejected.