How did John Duns Scotus defend the doctrine of the Immaculate Conception?

Blessed John Duns Scotus, a 13th-century Franciscan theologian, pioneered the classical defense of the Immaculate Conception by reconciling the doctrine with the concept of universal redemption.12

Critics of the time argued that if Mary were conceived without original sin, she would not have required Christ’s redemptive grace, thereby challenging the universality of his salvation. Duns Scotus addressed this by proposing that Christ’s mediation was preventative rather than merely curative. He argued that Christ applied his redemptive grace to Mary at the moment of her conception to prevent sin from ever reaching her soul. By framing this as a more perfect form of mediation, he demonstrated that Mary was indeed redeemed by Christ, but in a way that preserved her from the stain of original sin entirely. This brilliant defense marked a significant turning point in the history of the doctrine.31