Perhaps the most influential point of Duns Scotus’ theology was his defense of the Immaculate Conception of Mary. At the time, there was a great deal of argument about the subject. The general opinion was that it was appropriate, but it could not be seen how to resolve the problem that only with Christ’s death would the stain of original sin be removed. The great philosophers and theologians of the West were divided on the subject (indeed, it appears that even Thomas Aquinas sided with those who denied the doctrine, though some Thomists dispute this). The feast day had existed in the East since the seventh century and had been introduced in several dioceses in the West as well, even though the philosophical basis was lacking. Citing Anselm of Canterbury’s principle, “potuit, decuit, ergo fecit” (God could do it, it was appropriate, therefore he did it), Duns Scotus devised the following argument: Mary was in need of redemption like all other human beings, but through the merits of Jesus’ crucifixion, given in advance, she was conceived without the stain of original sin. God could have brought it about (1) that she was never in original sin, (2) she was in sin only for an instant, (3) she was in sin for a period of time, being purged at the last instant. Whatever of these was more excellent should probably be attributed to Mary.[7] This apparently careful statement provoked a storm of opposition at Paris, and suggested the line ‘fired France for Mary without spot’ in the famous poem “Duns Scotus’s Oxford,” by Gerard Manley Hopkins.
Irrefutable!