With regard to moral theology, Lehmkhul tells us that in the middle of the eighteenth century there arose a man who was, so to say, a blessing of Divine Providence. Owing to the eminent sanctity which he combined with solid learning, he definitely established the system of moral theology which now prevails in the Church. That man was St. Alphonsus Maria Liguori, who was canonized in 1839, and declared a Doctor of the Church in 1871. In his youth he was imbued with the stricter principles of moral theology, but as he himself confesses, the experience of fifteen years of missionary life and careful study brought him to realize the falseness and the evil consequences of the system in which he had been educated, and the necessity of a change. He, therefore, took the "Medulla" of the Jesuit, Hermann Busembaum, subjected it to a thorough examination, confirmed it by internal reasons and external authority, and then published a work which was received with universal applause, and whose doctrine is entirely on Probabilistic principles. This approval and appropriation of Busembaum's teaching by one who has been made a Doctor of the Church is a sufficient vindication of the doctrine of Probabilism, for which the Society suffered so much, and is at the same time a magnificent tribute to the greatness of Busembaum, "whose book," Lehmkuhl contents himself with saying, "was widely used," whereas forty editions of it had been issued during the author's own life, which happened to be an entire century before the publication of Liguori's great work. Busembaum's "Medulla" was printed in 1645, and Liguori's "Moral Theology" in 1748. Up to 1845, there were 200 editions of Busembaum; that is, one edition for every year of its existence. In the history of moral theology Sánchez, Layman, Azor, Castro Palao, Torres, Escobar also may be cited as leading lights.