This monumental effort is based on the writings of Aquinas, Bonaventure and Scotus. Thomas, merely gave his real doctrine and opinion concerning the Immaculate Conception. However, now a favorable opportunity was offered to contribute in loving gratitude to the greater honor and glory of Mary Immaculate and of her glorious defender, D. Scotus, by presenting his doctrine concerning Mary's Immaculate Conception. Now of the three greatest scholastic Doctors, to include Bonaventure, Scotus alone gives Mary the full glory of a real and complete Immaculate Conception. In comparing the three Doctors, those portions of their works will chiefly be used which "ex professo" state and explain their position and opinion regarding this doctrine and other doctrines closely connected with it, for instance, original justice, original sin, conception, sanctification, redemption. This is indeed a pinnacle treatise regarding this issue.