For 10 points, name this Catholic doctrine which maintains that the Virgin Mary was free from original sin.
The celebration of this doctrine was advocated in a letter by Peter Comestor in response to one attacking it written by St. Bernard, and this doctrine was defended with the axiom "potuit, decuit, ergo fecit", which originated from Eadmer. A feast celebrating this doctrine takes place on December 8, and in the papal bull Ineffabilis Deus, this doctrine was defined ex cathedra in 1854 by Pius IX. For 10 points, name this Catholic doctrine which maintains that the Virgin Mary was free from original sin.
The celebration of this doctrine was advocated in a letter by Peter Comestor in response to one attacking it written by St. Bernard, and this doctrine was defended with the axiom "potuit, decuit, ergo fecit", which originated from Eadmer.
{Immaculate Conception}